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Patients with refractory or relapsed and refractory myeloid malignancies have a poor prognosis. Allogeneic hematopoietic cell transplantation (HCT) with myeloablative conditioning (MAC) in patients with active, chemotherapy-refractory myeloid disease is historically associated with high rates of relapse and nonrelapse mortality (NRM). A MAC regimen combining clofarabine with busulfan (Clo/Bu4) has been reported to exhibit antileukemic activity with acceptable toxicity in patients age ≤70 years. Here we describe the clinical outcomes of a real-world population of patients with active myeloid malignancies undergoing allogeneic HCT with Clo/Bu4 MAC. In a single-center retrospective descriptive analysis, we identified patients who underwent HCT for myeloid malignancies not in remission using Clo/Bu4 MAC between 2012 and 2020. We report event-free survival (EFS) and overall survival (OS), cumulative incidences of relapse and NRM, and the incidence and severity of acute and chronic graft-versus-host disease (GVHD). We identified 69 patients with a median age of 60 years (range, 22 to 70 years). Most patients had relapsed/refractory or primary refractory acute myelogenous leukemia (AML; n = 55) or refractory myelodysplastic syndrome (MDS; n = 12); 1 patient had chronic myelogenous leukemia, and 1 patient had a blastic plasmacytoid dendritic cell neoplasm. Fifty patients (72.5%) had complete remission at day 100 post-transplantation. Two-year EFS and OS were 30% (95% confidence interval [CI], 20% to 44%) and 40% (95% CI, 29% to 54%), respectively. Patients with AML had a 2-year EFS and OS of 28% (95% CI, 18% to 44%) and 38% (95% CI, 27% to 54%), respectively; those with MDS had a 2-year EFS and OS of 47% (95% CI, 25% to 88%) and 56% (95% CI, 33% to 94%), respectively. The cumulative incidence of relapse at 2 years was 39% (95% CI, 27% to 51%) for all patients, including 45% (95% CI, 31% to 58%) in the patients with AML and 18% (95% CI, 2% to 45%) in those with MDS. NRM at 2 years was 31% (95% CI, 20% to 42%), including 27% (95% CI, 15% to 39%) in patients with AML and 35% (95% CI, 10% to 63%) in those with MDS. The total incidence of acute GVHD (aGVHD) of any severity was 80%, and the incidence of grade III-IV aGVHD was 22%. In patients who achieved remission, those who required systemic immunosuppression for aGVHD (58%) had poorer 2-year EFS (29% versus 54%; P = .05) and 2-year OS (39% versus 70%; P = .04) compared to those who did not. The 2-year cumulative incidence of chronic GVHD was 44% (95% CI, 28% to 58%). Clo/Bu4 MAC followed by allogeneic HCT for patients with active myeloid malignancies is an effective transplantation strategy for patients up to age 70, particularly those with advanced MDS. The high incidence of and poor outcomes associated with aGVHD highlight the importance of optimizing preventative strategies.

The fms-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib improved the survival of patients with relapsed or refractory (R/R) FLT3-mutated acute myelogenous leukemia (AML) in the phase 3 ADMIRAL trial. In this study, we assessed survival and relapse rates of patients in the ADMIRAL trial who underwent hematopoietic stem cell transplantation (HSCT), as well as safety outcomes in patients who received post-transplantation gilteritinib maintenance therapy. ADMIRAL was a global phase 3 randomized controlled trial that enrolled adult patients with FLT3-mutated R/R AML. Patients with R/R AML who harbored FLT3 internal tandem duplication mutations in the juxtamembrane domain or D835/I836 point mutations in the tyrosine kinase domain were randomized (2:1) to gilteritinib (120 mg/day) or to preselected high- or low-intensity salvage chemotherapy (1 or 2 cycles). Patients in the gilteritinib arm who proceeded to HSCT could receive post-transplantation gilteritinib maintenance therapy if they were within 30 to 90 days post-transplantation and had achieved composite complete remission (CRc) with successful engraftment and no post-transplantation complications. Adverse events (AEs) during HSCT were recorded in the gilteritinib arm only. Survival outcomes and the cumulative incidence of relapse were assessed in patients who underwent HSCT during the trial. Treatment-emergent AEs were evaluated in patients who restarted gilteritinib as post-transplantation maintenance therapy. Patients in the gilteritinib arm underwent HSCT more frequently than those in the chemotherapy arm (26% [n = 64] versus 15% [n = 19]). For all transplantation recipients, 12- and 24-month overall survival (OS) rates were 68% and 47%, respectively. Despite a trend toward longer OS after pretransplantation CRc, post-transplantation survival was comparable in the 2 arms. Patients who resumed gilteritinib after HSCT had a low relapse rate after pretransplantation CRc (20%) or CR (0%). The most common AEs observed with post-transplantation gilteritinib therapy were increased alanine aminotransferase level (40%), pyrexia (43%), and diarrhea (40%); grade ≥3 AEs were related primarily to myelosuppression. The incidences of grade ≥III acute graft-versus-host disease and related mortality were low. Post-transplantation survival was similar across the 2 study arms in the ADMIRAL trial, but higher remission rates with gilteritinib facilitated receipt of HSCT. Gilteritinib as post-transplantation maintenance therapy had a stable safety and tolerability profile and was associated with low relapse rates. Taken together, these data support a preference for bridging therapy with gilteritinib over chemotherapy in transplantation-eligible patients.

Background: Gilteritinib is approved for the treatment of relapsed/refractory (R/R) AML and FLT3-mutation (FLT3mut+). However, the gilteritinib phase 3 ADMIRAL study (Perl et al NEJM 2019) enrolled prior to widespread adoption of either midostaurin as a component of standard intensive induction and consolidation or post-transplant FLT3inhibitor (FLT3i) maintenance. Some mechanisms of drug resistance can be shared across FLT3i's, suggesting response to gilteritinib might differ in patients treated with frontline FLT3i. A better understanding of how prior therapy modulates response to gilteritinib is necessary to clarify this novel agent's role in the current FLT3-mutated AML treatment algorithm. Methods: This is an ongoing multi-institutional analysis from 13 US centers identifying patients who received gilteritinib alone or as combination therapy for the treatment of R/R FLT3mut+ AML. Patients who received gilteritinib as a part of an ongoing trial were excluded. Response criteria were identical to the ADMIRAL trial. For patients with available data and a composite complete remission (CRc), we defined clinically measurable residual disease (cMRD) negative status by bone marrow flow cytometry using a cutoff of Results: 72 patients treated with prior FLT3i exposure received gilteritinib for treatment of R/R FLT3mut+ AML. Patient characteristics are presented in table-1 with 46 (64%) previously receiving midostaurin, 19 (26%) sorafenib, and 7 (10%) other FLT3i. 8 (11%) received more than one prior TKI. NGS at diagnosis were available in 66 patients (92%) and co-mutations in DNMT3A, NPM1 and NRAS were observed in more than 10% of patients. Average duration of gilteritinib therapy was 5.7 months (range: 0.2-25 months). 27 (37.5%) received stem cell transplant (SCT) before gilteritinib and 15 (21%) underwent SCT after gilteritinib. The composite CR rate (CRc, defined as CR + CRi + CRp) was 51.4% (n= 37 patients). With regard to specific FLT3i's, we found no significant difference in median survival (7.1 months and 6.4 months for midostaurin and sorafenib, respectively) or remission rates (CRc 54% and 47% for prior midostaurin and sorafenib, respectively). The CRc rate for patients who received only prior 7+3 and midostaurin with or without consolidation was 58% with a median survival of 7.8 months. A trend toward higher CRc rate was noted in patients treated with gilteritinib in combination regimens rather than as a single agent (64% vs 43%, respectively, p=0.09 using Chi-square test). No survival advantage for combination therapy was seen over single agent. Survival was longest in patients who obtained a CR, particularly a cMRD negative response; this remained significant after censoring at the time of SCT (figures 1&2). Patients who received SCT after gilteritinib had significantly longer survival than non-transplanted patients (9.3 months vs 5.6 months, respectively, HR 0.44, 95% CI 0.2-0.8)(figure-3). Patients with concurrent mutations of NPM1/DNMT3A had a trend toward a higher CRc compared to FLT3 mutation alone (71% vs 50%, p= 0.2) but similar survival. With regard to mutations associated with drug resistance to other FLT3i's, patients with both FLT3-ITD and FLT3-D835 mutation had similar response and survival to FLT3-ITD alone. However, patients with MAPK pathway activating mutations (e.g. NRAS and PTPN11) had lower CRc (37.5% vs 59.5%) and poorer median survival than other patients (3.3 months vs 7.5 months) (HR 2.2- 95% CI 1.1-4.4) p value Conclusions: In this multi-center, retrospective analysis, gilteritinib remains a clinically active agent after treatment failure of prior FLT3i's (midostaurin or sorafenib). Mutations activating MAPK pathway have been implicated in secondary gilteritinib resistance but are seldom co-mutated at initial FLT3mut+ AML diagnosis. While further study is required, we hypothesize that their detection after frontline FLT3i therapy may represent treatment-emergent clones with propensity for pan-FLT3i resistance. Disclosures Zeidan: Cardiff Oncology: Consultancy, Honoraria, Other; Trovagene: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Otsuka: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Celgene / BMS: Consultancy, Honoraria, Research Funding; Jazz: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; BeyondSpring: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Taiho: Consultancy, Honoraria; Cardinal Health: Consultancy, Honoraria; Acceleron: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Aprea: Research Funding; ADC Therapeutics: Research Funding; MedImmune/Astrazeneca: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Ionis: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria; Astex: Research Funding; CCITLA: Other; Leukemia and Lymphoma Society: Other; Agios: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding. Yilmaz:Pint Pharma: Honoraria; Pfizer: Research Funding; Daicho Sankyo: Research Funding. Foran:Agios: Honoraria, Research Funding; H3Biosciences: Research Funding; Xencor: Research Funding; Trillium: Research Funding; Takeda: Research Funding; Kura Oncology: Research Funding; Aptose: Research Funding; Aprea: Research Funding; Actinium: Research Funding; Boehringer Ingelheim: Research Funding; Abbvie: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Revolution Medicine: Consultancy. Daver:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Fate Therapeutics: Research Funding; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees. Perl:Novartis: Honoraria, Other, Research Funding; Agios: Consultancy, Honoraria, Other; Biomed Valley Discoveries: Research Funding; Jazz: Honoraria, Other; FORMA Therapeutics: Consultancy, Honoraria, Other; Syndax: Consultancy, Honoraria; Actinium Pharmaceuticals Inc: Consultancy, Honoraria, Research Funding; AbbVie Inc: Consultancy, Honoraria, Other, Research Funding; Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Consultancy, Honoraria, Other; Bayer HealthCare Pharmaceuticals: Research Funding; New Link Genetics: Honoraria, Other; Astellas: Consultancy, Honoraria, Other: writing/editorial support, travel costs for meeting presentations related to study, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other: Writing/editorial support, travel costs for meetings, Research Funding; Leukemia & Lymphoma Society, Beat AML: Consultancy; Arog Pharmaceuticals Inc: Other: uncompensated consulting, travel costs for meetings; FUJIFILM Pharmaceuticals USA, Inc: Research Funding; Takeda: Honoraria, Other: Travel costs for meeting. Altman:Kartos: Research Funding; Celgene: Research Funding; Boehringer Ingelheim: Research Funding; ImmunoGen: Research Funding; Amgen: Research Funding; Aprea: Research Funding; Amphivena: Research Funding; Genentech: Research Funding; Novartis: Consultancy; Syros: Consultancy; Janssen: Consultancy; Immune Pharmaceuticals: Consultancy; ASH: Consultancy; Bristol-Myers Squibb: Consultancy; Glycomimetics: Other: Data safety and monitoring committee; Daiichi Sankyo: Other: Advisory Board - no payment but was reimbursed for travel; Kura Oncology: Other: Scientific Advisory Board - no payment accepted, Research Funding; BioSight: Other: No payment but was reimbursed for travel , Research Funding; AbbVie: Other: advisory board, Research Funding; Agios: Other: advisory board, Research Funding; Theradex: Other: Advisory Board; Astellas: Other: Advisory Board, Speaker (no payment), Steering Committee (no payment), Research Funding; PrIME Oncology: Consultancy; PeerView: Consultancy; Cancer Expert Now: Consultancy; France Foundation: Consultancy; Fujifilm: Research Funding. OffLabel Disclosure: Some of the patients we are reporting on received gilteritinib in combination with other agents which is off-label use.

Background: The FMS-like tyrosine kinase 3 (FLT3) inhibitor gilteritinib (Gilt) improves survival compared with standard salvage chemotherapy in relapsed/refractory (R/R) FLT3-mutated (FLT3mut+) acute myeloid leukemia (AML); however, relapses are common and long-term survival remains poor. Combination therapies of FLT3 tyrosine kinase inhibitors (TKIs) with agents that induce apoptosis have demonstrated preclinical synthetic lethality and enhanced cytotoxicity against FLT3mut+ clones. This may delay or prevent drug resistance. We present updated data from the dose-escalation and expansion cohorts of an ongoing, multicenter, open-label, Phase 1b trial (NCT03625505) of Gilt in combination with B-cell lymphoma 2 (BCL-2) inhibitor venetoclax (Ven) in patients (pts) with R/R FLT3mut+ AML. Methods: Pts with R/R AML with ≥1 prior line of therapy and Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 were eligible. The expansion cohort required FLT3mut+ R/R AML at enrollment. Pts received the recommended Phase 2 dose (RP2D) of Ven 400 mg in combination with Gilt 120 mg daily in 28-day cycles, following a 3-day ramp-up of Ven. Pts with prior Gilt were excluded from expansion, and none were enrolled in dose escalation; prior Ven or other FLT3 inhibitor was permitted. Concurrent use of moderate or strong CYP3A4 inhibitor was allowed. Interruptions of Ven or both drugs simultaneously were permitted for management of adverse events (AEs), and subsequent cycles could include dose adjustments to minimize myelosuppression or other drug-related AEs. The primary endpoint was modified composite complete remission (mCRc; complete response [CR] + CR with incomplete platelet recovery [CRp] + CR with incomplete blood count recovery [CRi]) + morphologic leukemia-free state (MLFS). Responses were graded by the International Working Group (IWG) for AML criteria (with adapted CRi criteria as presented in the ADMIRAL trial) for comparison with composite CR (CRc) used in Gilt development. All criteria for response used by IWG were maintained in these response definitions. Secondary endpoints included CR + CR with partial hematologic recovery (CRh) and duration of response (DOR) of mCRc. Results: At data cutoff, April 15, 2020, 39 R/R pts started therapy at the RP2D (internal tandem duplications [ITD] only [n=32]; tyrosine kinase domain [TKD] mutation only [n=5]; both TKD and ITD [n=2]). Median age was 63 years (range 23-85) and the majority had an ECOG status of 1-2 (87.2%). Most pts (n=29; 74.4%) had received ≥2 prior lines of therapy, including ≥1 FLT3 TKI (n=25, 64.1%; midostaurin, n=19; sorafenib, n=5; crenolanib, n=1). Twelve pts (30.8%) had prior stem-cell transplant (SCT); 3 (7.7%) had received prior Ven. Grade ≥3 treatment-emergent AEs (TEAEs) were reported in 37 pts (94.9%), and 28 (71.8%) reported serious AEs. The only Grade 3/4 nonhematologic TEAE reported in >20% of pts was febrile neutropenia (48.7%). Four pts (10.3%) experienced a fatal AE, including colitis, disease progression, multiple organ dysfunction syndrome, and bronchopulmonary aspergillosis (all n=1). AEs leading to Ven and Gilt interruptions occurred in 19 pts (48.7%) and 18 pts (46.2%), respectively, and AEs leading to dose reductions occurred in 2 pts (5.1%) for each treatment. Six pts (15.4 %) and 5 pts (12.8%) discontinued Ven and Gilt, respectively, owing to AEs. mCRc was achieved by 83.8% of pts (n=31/37; Table). With median duration of follow-up of 2.9 (range 0.8−11.0) months in all pts, median event-free survival was 5.1 (95% confidence interval: 2.8, 8.3) months but administrative censoring after short follow-up for a large number of recently enrolled patients limits interpretation; median DOR has not been reached. Eight pts (21.6%), all ITD only, proceeded to SCT. CR + CRh was achieved by 7 pts (18.9%). Conclusions: Ven plus Gilt achieved a very high overall rate of marrow and blood blast elimination and mCRc rate (84%) in this expansion cohort of heavily pretreated FLT3mut+ pts, the majority of whom had prior FLT3 TKI exposure. Using similar response assessment criteria, the high mCRc rate here suggests substantially greater antileukemic activity from Ven plus Gilt compared with single-agent Gilt. Cytopenias were prominent but manageable with dose interruption/modification on subsequent cycles. Nonhematologic toxicities were modest, and the combination was well tolerated. Disclosures Daver: Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Fate Therapeutics: Research Funding; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Altman:AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Fujifilm: Research Funding; Astellas: Other: Advisory Board, Speaker (no payment), Steering Committee (no payment), Research Funding; Agios, Theradex, Abbvie: Other: Advisory Board; Astellas, Agios: Honoraria, Research Funding; Glycomimetics: Other: Data safety and monitoring committee; Daiichi Sankyo: Other: Advisory Board - no payment but was reimbursed for travel; Kura Oncology: Patents & Royalties: Scientific Advisory Board - no payment accepted; Biosight: Other: No payment but was reimbursed for travel . Levis:Menarini: Honoraria; Amgen: Honoraria; FujiFilm: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria; Astellas: Honoraria, Research Funding. Ritchie:Abbvie: Honoraria; Sierra Oncology: Honoraria; Incyte: Speakers Bureau; Novartis: Honoraria; Jazz pharmaceuticals: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding. McCloskey:Amgen: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Jazz: Consultancy, Honoraria. Smith:Abbvie: Other: Research Support, Research Funding; Sanofi: Honoraria; Astellas Pharma: Honoraria, Other: Research Support, Research Funding; FujiFilm: Other: Research support, Research Funding; Revolution Medicines: Other: Research Support, Research Funding; Daiichi Sanyko: Consultancy, Honoraria. Schiller:Johnson & Johnson: Current equity holder in publicly-traded company; Novartis: Consultancy, Research Funding; Sangamo: Research Funding; Tolero: Research Funding; Trovagene: Research Funding; Kaiser Permanente: Consultancy; Genentech-Roche: Research Funding; Geron: Research Funding; DeltaFly: Research Funding; Deciphera: Research Funding; Celator: Research Funding; FujiFilm: Research Funding; Ariad: Research Funding; Constellation: Research Funding; Cyclacel: Research Funding; Jazz Pharmaceuticals: Research Funding; Karyopharm: Research Funding; Kite Pharma: Research Funding; Mateon: Research Funding; MedImmune: Research Funding; Astellas Pharma: Honoraria, Research Funding; Actinium: Research Funding; Gamida: Research Funding; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; Daiichi Sankyo: Research Funding; Abbvie: Research Funding; Stemline: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Ono Pharma: Consultancy; Forma: Research Funding; Incyte: Consultancy, Research Funding, Speakers Bureau; Gilead: Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Onconova: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; Regimmune: Research Funding; Samus: Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Sanofi: Speakers Bureau. Bradley:AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Speakers Bureau. Tiu:Astellas Pharma Global Development: Current Employment; Eli Lilly & Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Hong:F. Hoffmann-La Roche: Current equity holder in publicly-traded company; Genentech, Inc.: Current Employment. Tong:AbbVie, Inc.: Current Employment, Other: may hold stock or other options. Qin:AbbVie: Current Employment, Other: may hold stock or other options. Dilley:AbbVie Inc.: Current Employment, Other: may hold stock or stock options. Perl:Leukemia & Lymphoma Society.: Other; AbbVie Inc, Astellas, Actinium, Bayer HealthCare Pharmaceuticals, Daiichi Sankyo Inc, FUJIFILM Pharmaceuticals USA Inc: Research Funding; AbbVie Inc, Actinium Pharmaceuticals Inc, Astellas, Daiichi Sankyo Inc, FORMA Therapeutics, Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company, NewLink Genetics: Other; AbbVie Inc, Arog Pharmaceuticals Inc, Astellas, Daiichi Sankyo Inc: Consultancy; Astellas, AbbVie Inc, Daiichi Sankyo, Actinium, Forma, Syndax, Loxo: Consultancy, Honoraria. OffLabel Disclosure: Venetoclax is a B-cell lymphoma 2 inhibitor approved in combination with azacitidine, or decitabine, or low-dose cytarabine for the treatment of newly-diagnosed acute myeloid leukemia (AML) in adults who are age 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy. Gilteritinib is a kinase inhibitor indicated for the treatment of adult patients who have relapsed or refractory acute myeloid leukemia (AML) with an FLT3 mutation as detected by an FDA-approved test.

The natural history of FLT3-mutated AML is changing after the approval of midostaurin for frontline therapy and gilteritinib for relapsed or refractory patients. Recently reported, positive randomized trials of the drugs gilteritinib, quizartinib, and sorafenib predict even wider use of FLT3 inhibitors going forward. FLT3 inhibitors now emerge as an important, if not indispensable, part of therapy for a large subset of high-risk patients.

Oropharyngeal mucositis (OPM) is common following conditioning for allogeneic hematopoietic cell transplantation (alloHCT) and results in pain, functional status decline, need for nutritional support, infections, and prolonged length of stay (LOS). Methotrexate (MTX) graft-versus-host disease (GVHD) prophylaxis exacerbates OPM and slows hematopoietic engraftment, which may prolong LOS. Previous studies have demonstrated reduced OPM and more rapid engraftment when leucovorin (LCV) is added following MTX GVHD prophylaxis, yet this practice is controversial. The primary objective of this study was to determine if the routine addition of LCV to MTX GVHD prophylaxis impacted the duration of grade 2 to 4 OPM. Secondary objectives included determination of the incidence of grade 2 to 4 and grade 3 to 4 OPM, time to engraftment, ability to receive all four planned MTX doses, use of total parenteral nutrition (TPN), use of patient-controlled analgesia (PCA), LOS, incidence of acute or chronic GVHD, relapse-free survival (RFS), and overall survival (OS). This single-center, retrospective cohort study compared alloHCT outcomes for 46 adult patients who received MTX 15 mg/m2 day +1; MTX 10 mg/m2 days +3, +6, and +11 (15-10-10-10); and LCV following days +3, +6, and +11 MTX compared to historical controls who did not. Patients who received myeloablative conditioning (MAC) and matched related donor (MRD) or matched unrelated donor (MUD) alloHCT were included. The addition of LCV resulted in significant reductions in the duration of grade 2 to 4 OPM (median, 6 days versus 10.5 days; P = .0004), duration of TPN (7 days versus 16 days; P = .001), PCA use (16% versus 39%; P = .0001), time to neutrophil engraftment (median, 18 versus 20 days; P = .008), and LOS (median, 27.5 versus 31 days; P = .017) compared to historical controls. Patients who received routine LCV had similar incidences of grade 2 to 4 acute GVHD (30% versus 28%; relative risk [RR], 1.08; 95% confidence interval [CI], .57 to 2.03; P = 1.0), grade 3 or 4 acute GVHD (2% versus 7%; RR, .33; 95% CI, .04 to 3.09; P = .62) and chronic GVHD (37% versus 30%; RR, 1.21; 95% CI, .67 to 2.16; P = .66) compared to historical controls. Graft failure occurred in 2% of patients in each group. In a multivariable logistic regression analysis, RFS was similar in the LCV group compared to historical controls (HR, .86; 95% CI, .24 to 1.2; P = .13); however, OS was improved in patients who received LCV (HR, .33; 95% CI, .13 to .83; P = .01). In patients undergoing MAC MRD/MUD alloHCT with four planned doses of MTX GVHD prophylaxis (15-10-10-10), LCV was associated with reduced duration of grade 2 to 4 OPM, faster neutrophil engraftment, reduced utilization of TPN and PCA, and shortened LOS compared to historical controls not receiving routine LCV. These benefits were apparent without an increased risk of acute or chronic GVHD or adverse effect on RFS. LCV improved OS; however, it is unclear if this was due to the intervention or an unmeasured confounder. A randomized, prospective trial of LCV prophylaxis in patients receiving MAC alloHCT and MTX 15-10-10-10 GVHD prophylaxis is warranted to confirm our findings.

The interaction of menin (MEN1) and MLL (MLL1, KMT2A) is a dependency and provides a potential opportunity for treatment of NPM1-mutant (NPM1(mut)) and MLL-rearranged (MLL-r) leukemias. Concomitant activating driver mutations in the gene encoding the tyrosine kinase FLT3 occur in both leukemias and are particularly common in the NPM1(mut) subtype. In this study, transcriptional profiling after pharmacological inhibition of the menin-MLL complex revealed specific changes in gene expression, with downregulation of the MEIS1 transcription factor and its transcriptional target gene FLT3 being the most pronounced. Combining menin-MLL inhibition with specific small-molecule kinase inhibitors of FLT3 phosphorylation resulted in a significantly superior reduction of phosphorylated FLT3 and transcriptional suppression of genes downstream of FLT3 signaling. The drug combination induced synergistic inhibition of proliferation, as well as enhanced apoptosis, compared with single-drug treatment in models of human and murine NPM1(mut) and MLL-r leukemias harboring an FLT3 mutation. Primary acute myeloid leukemia (AML) cells harvested from patients with NPM1(mut) FLT3(mut) AML showed significantly better responses to combined menin and FLT3 inhibition than to single-drug or vehicle control treatment, whereas AML cells with wild-type NPM1, MLL, and FLT3 were not affected by either of the 2 drugs. In vivo treatment of leukemic animals with MLL-r FLT3(mut) leukemia reduced leukemia burden significantly and prolonged survival compared with results in the single-drug and vehicle control groups. Our data suggest that combined menin-MLL and FLT3 inhibition represents a novel and promising therapeutic strategy for patients with NPM1(mut) or MLL-r leukemia and concurrent FLT3 mutation.

Despite the substantial clinical activity of fms-related tyrosine kinase 3 (FLT3) inhibitors in relapsed or refractory (R/R) FLT3-ITD‒positive acute myelogenous leukemia (AML), durable remissions and prolonged survival in this population require allogeneic hematopoietic stem cell transplantation (allo-HSCT). Quizartinib, a once-daily oral, highly potent, and selective FLT3 inhibitor, significantly prolonged overall survival (OS) and improved clinical benefit compared with salvage chemotherapy (median OS, 6.2 months versus 4.7 months; hazard ratio [HR], .76; 95% confidence interval [CI], .58 to .98; P = .018; composite complete remission [CRc] rate, 48% versus 27%; median duration of CRc, 2.8 months versus 1.2 months; mortality rate, .8% versus 14% by day 30, 7% versus 24% by day 60) in patients with R/R FLT3-ITD AML in the phase 3 QuANTUM-R trial. In this post hoc analysis, we described the characteristics of and clinical outcomes in patients who underwent on-study HSCT in QuANTUM-R at the investigator's discretion and institutional practices. Of 367 randomized patients, 78 (32%) in the quizartinib arm and 14 (11%) in the salvage chemotherapy arm underwent on-study allo-HSCT without any intervening therapy for AML after quizartinib or study-specified salvage chemotherapy. Pooled data of patients from both treatment arms showed a longer median overall survival (OS) in transplant recipients versus those treated without allo-HSCT (12.2 months versus 4.4 months; HR, .315; 95% CI, .233 to .427). Pooled data also showed a longer median OS in patients with a last recorded response of CRc before allo-HSCT versus patients without a CRc (20.1 months versus 8.8 months; HR, .506; 95% CI, .296 to .864). By treatment arm, the median OS was 25.1 months with quizartinib and 20.1 months with salvage chemotherapy in patients with a last recorded response of CRc before allo-HSCT. Forty-eight patients in the quizartinib arm continued quizartinib treatment after allo-HSCT. In the 31 patients with a last recorded response of CRc before allo-HSCT who continued quizartinib after allo-HSCT, the median OS was 27.1 months. Continuation of quizartinib after allo-HSCT was tolerable, and no new safety signals were identified. These results suggest that post-transplantation survival following salvage chemotherapy and quizartinib treatment are similar. However, quizartinib response occurs more frequently than with salvage chemotherapy, potentially allowing more patients to undergo transplantation and achieve durable clinical benefit. In addition, post-transplant quizartinib was found to be tolerable and may be associated with prolonged survival in some patients, highlighting its potential value in the management of patients with FLT3-ITD R/R AML.

This randomized, open-label, phase 2b study (NCT01565668) evaluated the efficacy and safety of 2 dosing regimens of quizartinib monotherapy in patients with relapsed/refractory (R/R) FLT3-internal tandem duplication (ITD)-mutated acute myeloid leukemia (AML) who previously underwent transplant or 1 second-line salvage therapy. Patients (N = 76) were randomly assigned to 30- or 60-mg/day doses (escalations to 60 or 90 mg/day, respectively, permitted for lack/loss of response) of single-agent oral quizartinib dihydrochloride. Allelic frequency of at least 10% was defined as FLT3-ITD-mutated disease. Coprimary endpoints were composite complete remission (CRc) rates and incidence of QT interval corrected by Fridericia's formula (QTcF) of more than 480 ms (grade 2 or greater). Secondary endpoints included overall survival (OS), duration of CRc, bridge to transplant, and safety. CRc rates were 47% in both groups, similar to earlier reports with higher quizartinib doses. Incidence of QTcF above 480 ms was 11% and 17%, and QTcF above 500 ms was 5% and 3% in the 30- and 60-mg groups, respectively, which is less than earlier reports with higher doses of quizartinib. Median OS (20.9 and 27.3 weeks), duration of CRc (4.2 and 9.1 weeks), and bridge to transplant rates (32% and 42%) were higher in the 60-mg groups than in the 30-mg group. Dose escalation occurred in 61% and 14% of patients in the 30- and 60-mg groups, respectively. This high clinical activity of quizartinib at the evaluated doses is consistent with previous reports with an improved safety profile. Need to dose-escalate more than half of patients who received quizartinib 30 mg also supports further investigation of treatment with quizartinib 60 mg/day.

Introduction Increasingly clinicians face the choice between CPX-351 (NCT01696084) and venetoclax and azacitadine (ven/aza, NCT02993523) in front-line acute myeloid leukemia (AML), especially for frailer older adults with comorbidities. Given no prospective data, we examined retrospective observational survival outcomes for patients with newly diagnosed AML receiving either CPX-351 or ven/aza as initial therapy. Methods After local Institutional Review Board approval, we included patients from both the University of Pennsylvania ("HUP", n=111) and the Flatiron Health electronic health record (EHR) derived, de-identified database with a first incident AML diagnosed between January 2017 and 2021, and with documented receipt of CPX-351 or venetoclax and azacitadine as initial therapy (n=548). Given a total of 219 patients received CPX-351 and 440 received ven/aza, there was 90% power to detect a hazard ratio (HR) of 0.77 or smaller with alpha 0.05. Overall Survival (OS) was analyzed by the Kaplan-Meier method and compared between arms using the log-rank test. Pre-planned sensitivity analyses included restriction and multiple imputation (MI) to address missingness with inverse-probability of treatment weighting (IPTW) to balance baseline covariates with treatment effect estimates from each imputed dataset combined via Rubin's rules. Results For all patients, baseline covariates showed patients receiving ven/aza were older (75 vs 65 years old median age), more likely to have Medicare (29% vs 20%), have de-novo AML vs secondary or therapy-related disease (52% vs 29%) and be treated in the community rather than an academic center (66% vs 52%). All other baseline covariates-including ELN cytogenetic risk groups, high risk mutations (TP53, ASXL1, RUNX1), FLT3, IDH, HCT-comorbidity index-were not statistically significant different between groups (table 1). Missing values in the HUP dataset was Median OS (mOS) was 12 months for all patients and 13 months for CPX-351 versus 11 months for ven/aza (HR 0.87, 95% CI 0.70-1.07, p-value 0.184, Fig 1a). There was no clear subset with improved OS with CPX-351 vs ven/aza (Fig 1b); in multi-variate analysis controlling for all covariates with univariate p-value < 0.20 induction choice did not affect overall survival (limited to complete cases n=133, HR 0.63, p-value 0.73). Restricting to only the population eligible for CPX-351 pivotal trial, there was no significant difference in OS (CPX-351 n=160 mOS=10, ven/aza n=181 mOS=12 HR 0.86 p-value 0.33). After MI and IPTW, survival remained similar with HR 0.95 p-value 0.77 (Fig 1c). Adjusting further for variables with absolute standardized difference >10% after MI and IPTW (baseline HCT-comorbidity index, race and insurance status), multivariable Cox model gave similar results (HR 0.93, p-value 0.70). Regarding safety outcomes, early mortality was similar. However, documented diagnosed infections were higher in CPX-351 patients and within the HUP cohort, rates of febrile neutropenia and culture positive infection were also higher (Fig 1d). Length of stay, including any admission prior to next cycle of therapy, was more than twice as long for CPX-351 in the HUP cohort. Additional analyses, including detailed assessment of baseline covariates, multivariate analysis with transplant as a time-varying dependent covariate, event free survival, disease free survival also available for presentation. Conclusion In this multi-center real word dataset with over 600 patients, there was no statistically significant difference in overall survival between induction with CPX-351 and ven/aza. This large retrospective dataset is limited by missingness in covariates, risk of misclassification bias and lack of power for formal equivalence testing. However, a consistent lack of superiority for CPX-351 or ven/aza within a robust, manual chart-review of an academic institution, a large national real world database and combined analyses of these cohorts supports clinical equipoise. Given the apparent lack of a large survival benefit further work is needed. Prospective studies to confirm similar effectiveness with careful attention to side effects, quality of life and impact on transplant outcomes may help clinicians decide between these therapies. Figure 1 Figure 1. Disclosures Perl: Syndax: Consultancy; Loxo: Consultancy; Forma: Consultancy; AbbVie: Consultancy, Research Funding; Roche: Consultancy; Actinium: Consultancy; Genentech: Consultancy; Astellas: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Fujifilm: Research Funding; BMS/Celgene: Consultancy; Arog: Research Funding; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Frey: Kite Pharma: Consultancy; Novartis: Research Funding; Sana Biotechnology: Consultancy; Syndax Pharmaceuticals: Consultancy. Gill: Interius Biotherapeutics: Current holder of stock options in a privately-held company, Research Funding; Carisma Therapeutics: Current holder of stock options in a privately-held company, Research Funding; Novartis: Other: licensed intellectual property, Research Funding. Hexner: Blueprint medicines: Membership on an entity's Board of Directors or advisory committees, Research Funding; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees; Tmunity Therapeutics: Research Funding. Porter: American Society for Transplantation and Cellular Therapy: Honoraria; ASH: Membership on an entity's Board of Directors or advisory committees; DeCart: Membership on an entity's Board of Directors or advisory committees; Genentech: Current Employment, Current equity holder in publicly-traded company; Incyte: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Unity: Patents & Royalties; Wiley and Sons Publishing: Honoraria. Stadtmauer: Oncopeptides: Consultancy; Amgen: Consultancy; BMS Celgene: Consultancy; GSK: Consultancy; Janssen: Consultancy; AbbVie: Consultancy, Research Funding. Maillard: Regeneron: Research Funding. Margolis: Pfizer: Consultancy; Leo: Consultancy; Sanofi: Consultancy; National Eczema Association: Membership on an entity's Board of Directors or advisory committees. Pratz: Abbvie: Consultancy, Honoraria, Research Funding; Agios: Consultancy; BMS: Consultancy, Honoraria; Novartis: Consultancy; Astellas: Consultancy, Honoraria, Research Funding; Cellgene: Consultancy, Honoraria; Millenium: Research Funding; University of Pennsylvania: Current Employment.

Gilteritinib (Gilt), a FLT3 tyrosine kinase inhibitor (TKI), is approved for the treatment of relapsed/refractory (R/R) FLT3-mutated (FLT3 +)acute myeloid leukemia (AML). However, long-term survival is limited by the development of drug resistance mutations in persistent FLT3 + clones. Combination regimens may deepen response and improve outcomes. Venetoclax (Ven), a BCL-2 inhibitor, is approved in combination with hypomethylating agents for newly diagnosed AML not suitable for standard induction therapy. FLT3 + AMLhas been associated with clinical resistance to Ven. Still, FLT3 TKIs + Ven have demonstrated synthetic lethality in preclinical models, prompting this multicenter, open-label, phase 1b trial (NCT03625505) to evaluate Ven + Gilt for R/R AML. Here, we report final response and survival endpoints, and molecular clearance among patients (pts) treated at the recommended phase two dose (RP2D). The study design has been previously described (Daver, et al. ASH 2020, Abstract 333). Pts in the dose expansion cohort received Ven 400 mg + Gilt 120 mg (RP2D) daily in 28-day cycles, following Ven ramp-up. The primary endpoint was mCRc (complete response [CR] + CR with incomplete platelet recovery [CRp] + CR with incomplete blood count recovery [CRi] + morphologic leukemia-free state) to align with the ADMIRAL phase III trial (Perl, et al. NEJM 2019). Baseline co-mutations and serial FLT3 internal tandem duplications (ITD) allelic burden were assessed using the MyAML panel (Invivoscribe, San Diego, CA) and FLT3-ITD MRD assay with sensitivities of 5% and 0.001%, respectively. As of the data cut off of January 31, 2021, 54 pts were treated at the RP2D. Fifty-two pts (as assessed locally) had FLT3 +AML; 41 had FLT3-ITD only, 8 had tyrosine kinase domain only, 3 had both mutations, and 2 were FLT3 wild type (wt). Additional baseline characteristics are in Table 1. Grade 3 or 4 AEs occurred in 51 (94.4%) pts, and 39 (72.2%) pts had serious AEs. Grade 3 or 4 cytopenias occurred in 43 (79.6%) pts. AEs of special interest included tumor lysis syndrome (2 [3.7%]) and QT prolongation (1 [1.9%]). AEs leading to dosing interruptions (Ven, 27 [50%]; Gilt, 26 [48.1%]), reductions (Ven, 3 [5.6%]; Gilt, 4 [7.4%]), and discontinuation (Ven, 7 [13%]; Gilt, 7 [13%]) were reported for both study drugs. There was 1 treatment-emergent death of typhlitis. Among FLT3 + pts with post-baseline assessments (51/52), mCRc was achieved by 38 pts (74.5%; CR/CRp/CRi, 19 [37.3%] pts), with a median follow-up time of 12 mo (range: 0.8 - 20.1). The mCRc in pts with prior TKI (32) or prior Ven (10) use were 78.1% and 60%, respectively. The mOS among all FLT3 +pts was 10 mo (95%CI: 6.6, NE), with a median DoR (mDoR) of 5.4 mo (95% CI: 3.3, 6.6). Pts with FLT3-ITD had a mOS of 10.5 mo (95%CI: 6.8, NE), and a mDoR of 5.6 mo (95% CI: 3.3, 8.3). For the 14 pts who had a transplant, the mOS was not reached (95%CI: 10.0, NE) vs 6.89 mo (95%CI: 3.0, 10.5) for those who did not have a transplant (37). The mOS for pts with prior TKI or Ven was 9.6 (95% CI: 4.3, NE) and 10.5 mo (95% CI: 2.0, NE), respectively, with a mDoR of 9.6 (95% CI: 4.3, NE) and 6.2 mo (95% CI: 2.6, NE), respectively. The 60-day mortality rate was 11.8% (95% CI: 4.4, 23.9). The mCRc for NPM1 + and NPM1wt were 92.3% and 61.1%, respectively. mCRc for DNMT3A + and DMNT3A wt pts were 82.4% and 64.3%, respectively. WT1 + and WT1 wt mCRc were 66.7% and 77.3%, respectively. The mCRc for NPM1 + and DNMT3A + co-mutated pts was 100%. In a post hoc analysis of the 30 analyzable mCRc pts with at least one follow-up MRD assessment, 17 (56.7%) achieved molecular clearance defined as FLT3 allelic burden < 10 -2. The mOS of pts achieving mCRc with FLT3 allelic burden of < 10 -2 vs mCRc with FLT3 allelic burden ≥ 10 -2 (Figure 1) was not reached (95% CI: 9.76, NE) vs 6.83 mo (4.21, NE). Ven + Gilt achieved high mCRc in patients with R/R FLT3 + AML, with or without prior TKI exposure, and an encouraging mOS. FLT3 mutation clearance was seen in a majority of patients and associated with longer OS. Encouraging remission rates were observed across many genotypes and were particularly high among pts with NPM1 + +/- DNMT3A co-mutation. Cytopenias were common but manageable with appropriate Ven or Gilt dosing modifications. Serial NGS molecular data, as well as updated survival data will be presented at the meeting. Figure 1 Figure 1. Disclosures Daver: Hanmi: Research Funding; Abbvie: Consultancy, Research Funding; Trillium: Consultancy, Research Funding; Trovagene: Consultancy, Research Funding; Novimmune: Research Funding; FATE Therapeutics: Research Funding; Glycomimetics: Research Funding; Amgen: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Sevier: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; ImmunoGen: Consultancy, Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy, Other: Data Monitoring Committee member; Dava Oncology (Arog): Consultancy; Celgene: Consultancy; Syndax: Consultancy; Shattuck Labs: Consultancy; Agios: Consultancy; Kite Pharmaceuticals: Consultancy; SOBI: Consultancy; STAR Therapeutics: Consultancy; Karyopharm: Research Funding; Newave: Research Funding. Perl: Actinium: Consultancy; Genentech: Consultancy; Roche: Consultancy; Astellas: Consultancy, Research Funding; Forma: Consultancy; Syndax: Consultancy; Loxo: Consultancy; Fujifilm: Research Funding; Arog: Research Funding; BMS/Celgene: Consultancy; AbbVie: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Levis: Amgen, Astellas Pharma, Daiichi-Sankyo, FujiFilm, and Menarini: Honoraria; Astellas and FujiFilm: Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Jazz: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Ritchie: Astellas: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria; Celgene/BMS: Consultancy, Other: travel support, Speakers Bureau; Bristol Myers Squibb: Consultancy, Research Funding; NS Pharma: Research Funding; Incyte: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria; Jazz: Consultancy, Research Funding; Protaganist: Consultancy, Honoraria; ARIAD Pharmaceuticals: Ended employment in the past 24 months, Speakers Bureau; Pfizer: Consultancy, Research Funding. Litzow: Astellas: Research Funding; Omeros: Other: Advisory Board; Pluristem: Research Funding; AbbVie: Research Funding; Amgen: Research Funding; Actinium: Research Funding; Jazz: Other: Advisory Board; Biosight: Other: Data monitoring committee. McCloskey: Jazz: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Smith: AbbVie: Research Funding; Revolutions Medicine: Research Funding; Daiichi Sankyo: Consultancy; FUJIFILM: Research Funding; Astellas Pharma: Consultancy, Research Funding; Amgen: Honoraria. Schiller: Takeda: Research Funding; Trovagene: Research Funding; Tolero: Research Funding; Ono: Consultancy; Novartis: Consultancy, Research Funding; ASH foundation: Other: Chair-unpaid; Pfizer: Current equity holder in publicly-traded company, Research Funding; Incyte: Consultancy; Sanofi: Honoraria, Research Funding, Speakers Bureau; Ariad: Research Funding; Stemline Therapeutics, Inc.: Honoraria, Research Funding, Speakers Bureau; Ono-UK: Consultancy, Research Funding; Karyopharm: Research Funding; Kite/Gilead: Honoraria, Research Funding, Speakers Bureau; Onconova: Research Funding; Mateon: Research Funding; Sangamo: Research Funding; Samus: Research Funding; Regimmune: Research Funding; PrECOG: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Kaiser Permanente: Consultancy; Cyclacel: Research Funding; MedImmune: Research Funding; Ambit: Research Funding; Agios: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Research Funding, Speakers Bureau; Jazz: Consultancy, Honoraria, Research Funding, Speakers Bureau; Elevate: Research Funding; Bio: Research Funding; Pharma: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Biomed Valley Discoveries: Research Funding; Eli Lilly: Research Funding; Sellas: Research Funding; Geron: Research Funding; Genentech-Roche: Research Funding; Gamida Cell Ltd.: Research Funding; FujiFilm: Research Funding; Forma: Research Funding; Delta-Fly: Research Funding; Deciphera: Research Funding; Daiichi-Sankyo: Research Funding; Constellation Pharmaceuticals: Research Funding; Celator: Research Funding; BMS/Celgene: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Astellas: Honoraria, Research Funding, Speakers Bureau; Arog: Research Funding; Actuate: Research Funding; Actinium Pharmaceuticals, Inc: Research Funding; Abbvie: Research Funding; Leukemia & Lymphoma Society: Research Funding; Bluebird Bio: Research Funding; Boehringer-Ingleheim: Research Funding; Cellerant: Research Funding; CTI Biopharma: Research Funding; Janssen: Research Funding; Kura Oncology: Research Funding; Pharmacyclics: Honoraria, Speakers Bureau; Millennium: Research Funding; National Marrow Donor Program: Research Funding; NIH: Research Funding; Onyx: Research Funding; Pharmamar: Research Funding; UC Davis: Research Funding; UCSD: Research Funding; Evidera: Consultancy; NCI: Consultancy; Novartis: Speakers Bureau. Bradley: AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Tiu: Astellas Pharma: Current Employment; Eli Lilly and Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Naqvi: Genentech/Roche: Current Employment, Current holder of stock options in a privately-held company. Dail: Genentech/Roche: Current Employment, Current equity holder in publicly-traded company. Siddani: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Wang: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Chyla: AbbVie: Current Employment, Current equity holder in publicly-traded company. Lee: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Altman: Astellas: Consultancy, Other: Advisory Board, Research Funding; AbbVie: Consultancy, Other: Advisory Board, Research Funding; Biosight: Consultancy, Other: Travel fees, Research Funding; Daiichi Sankyo: Consultancy; Kura Oncology: Consultancy; Syros: Consultancy; Theradex: Consultancy, Other: Advisory boards; GlycoMimetics: Other: Participation on an advisory board; ALZ Oncology: Research Funding; Amgen: Research Funding; Aprea: Research Funding; BMS: Research Funding; Boehringer Ingelheim: Research Funding; Fujifilm: Research Funding; Immunogen: Research Funding; Kartos: Research Funding; Kura: Research Funding. OffLabel Disclosure: Venetoclax is a B-cell lymphoma 2 inhibitor approved in combination with azacitidine, or decitabine, or low-dose cytarabine for the treatment of newly-diagnosed acute myeloid leukemia (AML) in adults who are age 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy. Gilteritinib is a kinase inhibitor indicated for the treatment of adult patients who have relapsed or refractory acute myeloid leukemia (AML) with an FLT3 mutation as detected by an FDA-approved test.

Background: Genetically modified T cells expressing an anti-CD19 murine chimeric antigen receptor (CAR) result in response rates of up to 90% in patients with relapsed or refractory (r/r) B cell acute lymphoblastic leukemia (ALL). Durable remissions are limited by relapses of both CD19+ disease, correlating with loss of persistence, and CD19- disease, due to target antigen loss. The use of humanized CAR T products with improved persistence and dual antigen targeting are strategies that may improve relapse free survival. Methods: Adult patients with r/r ALL were co-administered two humanized autologous CAR T cell products, one targeted to CD19 (huCART19) and the other to CD22 (CART22-65s) after fludarabine and cyclophosphamide lymphodepletion. A three day fractionated adaptive dosing scheme was used in which the second or third huCART19 and CART22-65s infusions could be held for early signs of cytokine release syndrome (CRS). Total planned dose was 2.0x10 6 CART22-65sf2 cells/kg and 2.0x10 6 huCART19 cells/kg. Safety of the novel combination was the primary endpoint of the study; feasibility and efficacy were key secondary endpoints. Results: Of 13 treated patients (median age 46 (range 28-71)), two had received prior murine CART19 cells, 8 had prior blinatumomab, 8 had prior inotuzumab and 10 had a prior allogeneic stem cell transplant (SCT). The two products had distinct peak expansions which correlated with two clinically distinct episodes of CRS in some patients. The median time to peak huCART19 expansion was 9 days versus 16 days for CART22-65s. Eleven patients experienced CRS, all Grade 1 or 2. Two patients had immune effector cell-associated neurotoxicity syndrome (ICANS), one of which was grade 4. Two patients died within 30 days of infusion, one from complications of treatment (Grade 4 ICANS and sepsis) and one from rapidly progressive disease. One patient developed hemophagocytic lymphohistiocytosis-like syndrome that was clinically and temporally distinct from a CRS event; this was characterized by delayed pancytopenia, transaminase elevation and hypofibrinogenemia, similar to events reported in other trials of CART22. This syndrome was refractory to IL6 and IL1beta inhibition but ultimately responded to ruxolitinib. Of the 11 patients evaluable for response, 100% achieved CR with unmeasurable residual disease (uMRD) one month after infusion. One of the 11 had molecular recurrence 9 months post infusion. The other 10 patients are alive and remain in an uMRD remission with a median follow up of 6.2 months (range 0.2 to 25 months) and none have proceeded to consolidative SCT. Three months after infusion, 9/11 patients had detectable huCART19 and 8/11 patients had detectable CART22-65s. At 6 months, 7/8 evaluable patients had detectable huCART19 cells and 4/8 patients had detectable CART22-65s. All three patients with 12 months follow-up had detectable huCART19 and CART22-65s. Conclusion: Co-administration and adaptive dosing of CART22-65s with huCART19 in adult patients with r/r ALL is feasible and effective. The two different products demonstrated differential expansion and persistence kinetics. Despite prior exposure to CD19- and/or CD22-specific immunotherapies, all evaluable patients achieved CR with uMRD; we continue to monitor CAR T cell persistence and its impact on durability of response. Disclosures Frey: Novartis: Research Funding; Sana Biotechnology: Consultancy; Syndax Pharmaceuticals: Consultancy; Kite Pharma: Consultancy. Gill: Interius Biotherapeutics: Current holder of stock options in a privately-held company, Research Funding; Novartis: Other: licensed intellectual property, Research Funding; Carisma Therapeutics: Current holder of stock options in a privately-held company, Research Funding. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Pratz: Abbvie: Consultancy, Honoraria, Research Funding; Novartis: Consultancy; BMS: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding; University of Pennsylvania: Current Employment; Agios: Consultancy; Cellgene: Consultancy, Honoraria; Millenium: Research Funding. Perl: AbbVie: Consultancy, Research Funding; Roche: Consultancy; Astellas: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Fujifilm: Research Funding; Arog: Research Funding; BMS/Celgene: Consultancy; Genentech: Consultancy; Actinium: Consultancy; Forma: Consultancy; Syndax: Consultancy; Loxo: Consultancy; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Ruella: viTToria biotherapeutics: Research Funding; Tmunity: Patents & Royalties; AbClon: Consultancy, Research Funding; BMS, BAYER, GSK: Consultancy; Novartis: Patents & Royalties. Brogdon: Novartis Institutes for Biomedical Research: Current Employment. Engels: Novartis: Current Employment, Current equity holder in publicly-traded company. Levine: In8bio: Membership on an entity's Board of Directors or advisory committees; Ori Biotech: Membership on an entity's Board of Directors or advisory committees; Vycellix: Membership on an entity's Board of Directors or advisory committees; Immusoft: Membership on an entity's Board of Directors or advisory committees; Tmunity Therapeutics: Other: Co-Founder and equity holder; Immuneel: Membership on an entity's Board of Directors or advisory committees; Avectas: Membership on an entity's Board of Directors or advisory committees; Akron: Membership on an entity's Board of Directors or advisory committees. June: Tmunity, DeCART, BluesphereBio, Carisma, Cellares, Celldex, Cabaletta, Poseida, Verismo, Ziopharm: Current equity holder in publicly-traded company; Novartis: Patents & Royalties; AC Immune, DeCART, BluesphereBio, Carisma, Cellares, Celldex, Cabaletta, Poseida, Verismo, Ziopharm: Consultancy. Porter: American Society for Transplantation and Cellular Therapy: Honoraria; Incyte: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; Genentech: Current equity holder in publicly-traded company, Ended employment in the past 24 months; DeCart: Membership on an entity's Board of Directors or advisory committees; ASH: Membership on an entity's Board of Directors or advisory committees; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Tmunity: Patents & Royalties; Wiley and Sons Publishing: Honoraria. Hexner: Tmunity Therapeutics: Research Funding; Blueprint medicines: Membership on an entity's Board of Directors or advisory committees, Research Funding; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: This trial reports outcomes from investigational products delivered as part of a clinical trial.

Background Pharmacologic immunosuppression and incomplete immune reconstitution after allogeneic stem cell transplant (alloSCT) may impair a patient's ability to mount an immune response to vaccines, including currently available COVID-19 vaccines. Since immunocompromised patients are susceptible to severe COVID-19 and likely to respond poorly to vaccination, we sought to characterize SARS-CoV-2 antibody responses after vaccination in alloSCT patients to determine predictors of serologic response, which may inform timing of vaccine administration. Methods This retrospective analysis included adult patients who underwent alloSCT at the University of Pennsylvania between 1/1/2019 and 1/1/2021. Chart review identified patients who had received COVID-19 vaccines and had post-vaccination antibody titers drawn by July 2021 as part of routine care (n=63). Antibodies to SARS-CoV-2 spike protein receptor binding domain were detected using an assay developed at the Hospital of the University of Pennsylvania. Variables analyzed include interval between transplant date and initial vaccination, active GVHD, concurrent immunosuppressive therapy, absolute CD4 count greater than or equal to 200 cells/mm3 peri-vaccination, and total IgG greater than or equal to 400 mg/dL peri-vaccination. Immunosuppressive therapy was defined as tacrolimus, rituximab, ruxolitinib, prednisone 10 mg daily or greater, or extracorporeal photopheresis. Predictors of positive antibody response were assessed using a multivariate, binary logistic regression. Results Median transplant to vaccine interval was 458 days (range 125 to 813) for the 63 vaccinated patients with serologies available. GVHD was present in 23/63 (37%), and 19/63 (30%) were receiving immunosuppressive therapies at the time of vaccination. CD4 count greater than 200 cells/mm3 was observed in 49 patients (78%), and total IgG greater than 400 mg/dL was observed in 51 patients (81%). In total, 50/63 patients (79%) were positive for SARS-CoV-2 IgG antibodies. Positive serologies were observed in 41/49 (84%) with CD4 counts greater than 200 cells/mm3, compared to 9/14 (64%) with CD4 less than 200 cells/mm3. Our model found that peri-vaccination CD4 count greater than 200 cells/mm3 was a significant predictor of positive SARS-CoV-2 IgG serologies in this population (OR 2.14, 97.5% CI = 0.7 to 3.8, p= 0.005). Transplant to vaccine interval, total IgG levels, GVHD status, and immunosuppressive therapies were not significant predictors of serologic response. As of July 2021 no patients had developed COVID-19 after vaccination, regardless of serologic response. Conclusions This retrospective observational study demonstrates that the majority of alloSCT patients vaccinated against COVID-19 within 2 years of transplant, including those with active GVHD and on immunosuppressive therapies, can mount serologic responses. CD4 count greater than 200 cells/mm3 is a significant predictor of positive serologic response, though even among patients with CD4 counts under 200 cells/mm3 over 60% developed SARS-CoV-2 IgG antibodies. Disclosures Perry: Incyte: Consultancy, Speakers Bureau; Abbvie,: Speakers Bureau; Kadmon: Consultancy. Pratz: University of Pennsylvania: Current Employment; Abbvie: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Cellgene: Consultancy, Honoraria; Novartis: Consultancy; BMS: Consultancy, Honoraria; Agios: Consultancy; Millenium: Research Funding. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Perl: Astellas: Consultancy, Research Funding; Loxo: Consultancy; AbbVie: Consultancy, Research Funding; Syndax: Consultancy; BMS/Celgene: Consultancy; Roche: Consultancy; Fujifilm: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Forma: Consultancy; Arog: Research Funding; Genentech: Consultancy; Actinium: Consultancy; Onconova: Consultancy; Sumitomo Dainippon: Consultancy. Porter: ASH: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; DeCart: Membership on an entity's Board of Directors or advisory committees; Genentech: Current equity holder in publicly-traded company, Ended employment in the past 24 months; American Society for Transplantation and Cellular Therapy: Honoraria; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Tmunity: Patents & Royalties; Wiley and Sons Publishing: Honoraria. Hexner: Blueprint medicines: Membership on an entity's Board of Directors or advisory committees, Research Funding; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees; Tmunity Therapeutics: Research Funding. Frey: Sana Biotechnology: Consultancy; Kite Pharma: Consultancy; Syndax Pharmaceuticals: Consultancy; Novartis: Research Funding.

Philadelphia chromosome (Ph)-like B-cell acute lymphoblastic leukemia (Ph-like ALL) is associated with activated JAK/STAT, Abelson kinase (ABL), and/or phosphatidylinositol 3-kinase (PI3K) signaling and poor clinical outcomes. PI3K pathway signaling inhibitors have been minimally investigated in Ph-like ALL. We hypothesized that targeted inhibition of PI3Kα, PI3Kδ, PI3K/mTOR, or target of rapamycin complex 1/2 (TORC1/TORC2) would decrease leukemia proliferation and abrogate aberrant kinase signaling and that combined PI3K pathway and JAK inhibition or PI3K pathway and SRC/ABL inhibition would have superior efficacy compared to inhibitor monotherapy. We treated 10 childhood ALL patient-derived xenograft models harboring various Ph-like genomic alterations with 4 discrete PI3K pathway protein inhibitors and observed marked leukemia reduction and in vivo signaling inhibition in all models. Treatment with dual PI3K/mTOR inhibitor gedatolisib resulted in near eradication of ALL in cytokine receptor-like factor 2 (CRLF2)/JAK-mutant models with mean 92.2% (range, 86.0%-99.4%) reduction vs vehicle controls (P < .0001) and in prolonged animal survival. Gedatolisib also inhibited ALL proliferation in ABL/platelet-derived growth factor receptor (PDGFR)-mutant models with mean 66.9% (range, 42.0%-87.6%) reduction vs vehicle (P < .0001). Combined gedatolisib and ruxolitinib treatment of CRLF2/JAK-mutant models more effectively inhibited ALL proliferation than either inhibitor alone (P < .001) and further enhanced survival. Similarly, superior efficacy of combined gedatolisib and dasatinib was observed in ABL/PDGFR-mutant models (P < .001). Overall, PI3K/mTOR inhibition potently decreased ALL burden in vivo; antileukemia activity was further enhanced with combination inhibitor therapy. Clinical trials testing combinations of kinase inhibitors in Ph-like ALL patients are indicated.

Characterization of pathogenic alterations in acute myeloid leukemia (AML) has led to development of promising targeted therapies, including FLT3 (FLT3i) and IDH1/2 inhibitors (IDHi), with several approved for use; midostaurin (MIDO), gilteritinib, enasidenib (ENA), and ivosidenib (IVO). A proportion of patients (pts) have concurrentFLT3andIDHmutations at diagnosis or develop a second mutation during therapy.FLT3mutations, in particular, are associated with poor response rates to IDHi therapy, and treatment-emergentFLT3mutations also appear to confer therapeutic resistance to these agents. There is therefore growing interest to study combined therapies that target multiple pathways, but the clinical experience with combined IDHi and FLT3i therapy has not yet been reported. We performed a retrospective data collection and analysis at 5 institutions (Massachusetts General Hospital, University of Pennsylvania, Johns Hopkins University, University of California San Francisco, and MD Anderson). Using de-identified information from institutional databases, pts treated with concurrent IDHi and FLT3i were identified. Collected data included demographic data, date of initial diagnosis, number of prior therapies, prior hematopoietic cell transplant (HCT), prior targeted therapy, type ofIDHandFLT3mutation, concurrent mutations and cytogenetics, duration of concurrent therapy, therapy-related toxicity, best response, toxicities, and vital status. We identified 12 pts who received concurrent IDHi and FLT3i therapy, 11 of which had relapsed/refractory (R/R) AML. Median age was 57 (range 31-84) and 9 (75%) were male. 7 (58%) were Caucasian, 3 (25%) African American, and 2 (17%) Asian. All pts had intermediate-risk cytogenetics.IDH1R132 mutations were detected in 3 (25%), andIDH2R140 mutations in 9 (75%) pts. OneIDH2mutation arose at relapse. All pts hadFLT3-ITDmutations, and for 3 (38%), this mutation was known to have emerged at relapse. Common concurrent mutations includedDNMT3A(75%) andNPM1(58%). Median number of prior lines of therapy was 2 (range 0-6), and 4 pts (33%) had underwent prior HCT. Six pts (50%) had received FLT3i monotherapy in a prior line of treatment; 4 sorafenib, 1 gilteritinib, 1 MIDO, and 1 with FF-10101 (one pt had 2 prior lines of FLT3i). Six pts were initiated on concurrent therapy in simultaneous fashion, and the remainder were sequential; 2 pts (17%) were on IDHi therapy to which the FLT3i was added, and 4 (33%) had been on FLT3i with subsequent IDHi addition. Four pts (33%) received concurrent gilteritinib and ENA, 3 (25%) received gilteritinib and IVO, 3 (25%) received sorafenib and ENA, and 2 (17%) MIDO and ENA. Three pts received hypomethylating therapy concurrent with combined FLT3i/IDHi therapy; 2 received azacitidine (AZA) with ENA/MIDO, and 1 received AZA with ENA/gilteritinib. Pts were on concurrent therapy for a median of 75 days (range 9-343). Two pts had rash attributable to sorafenib, leading to temporary treatment pause in one and discontinuation in the other. No other toxicities were thought to be related to concurrent treatment. Four pts (33%) achieved CR or CRi (2 CR, 2 CRi), all with persistence of molecular residual disease (MRD). The median duration of remission for these pts was 310 days (range 85-326), and 3 have since relapsed. One pt experienced MLFS, 1 had peripheral blast reduction and 1 had improvement in platelets. An additional pt had MRD(+) CR (byNPM1PCR) on gilteritinib prior to addition of ENA, and then achieved MRD(-) CR with dual therapy. The 4 remaining pts did not respond to concurrent treatment. Two pts (17%) were effectively bridged to HCT following dual therapy. Five pts (42%) remain alive. In this retrospective analysis, a notable proportion of pts benefitted from concurrent FLT3i and IDHi therapy. Composite remission rate was 33%, and overall response rate (CR+CRi+MLFS) was 42% among a largely R/R patient cohort, the majority of whom had received IDHi or FLT3i monotherapy in a prior line of treatment. An additional pt in MRD(+) CR cleared MRD following concurrent treatment. Concurrent therapy appeared to be largely well-tolerated. These response rates are particularly intriguing, given the presence ofFLT3/ITDmutations, alterations thought to confer resistance to IDHi monotherapy. Larger, prospective studies are needed to fully assess the promise of concurrent FLT3i and IDHi therapy in co-mutated pts with AML. Disclosures Fathi: Amphivena:Consultancy;Astellas:Consultancy;Trillium:Consultancy;Amgen:Consultancy;Seattle Genetics:Consultancy, Research Funding;Abbvie:Consultancy;Pfizer:Consultancy;Newlink Genetics:Consultancy;Forty Seven:Consultancy;Trovagene:Consultancy;Kite:Consultancy;BMS/Celgene:Consultancy, Research Funding;Novartis:Consultancy;Daiichi Sankyo:Consultancy;Kura Oncology:Consultancy;Blueprint:Consultancy;PTC Therapeutics:Consultancy;Agios:Consultancy, Research Funding;Takeda:Consultancy, Research Funding;Jazz:Consultancy;Boston Biomedical:Consultancy.Perl:Arog Pharmaceuticals Inc:Other: uncompensated consulting, travel costs for meetings;Astellas:Consultancy, Honoraria, Other: writing/editorial support, travel costs for meeting presentations related to study, Research Funding;AbbVie Inc:Consultancy, Honoraria, Other, Research Funding;Syndax:Consultancy, Honoraria;Takeda:Honoraria, Other: Travel costs for meeting;Leukemia & Lymphoma Society, Beat AML:Consultancy;Novartis:Honoraria, Other, Research Funding;Actinium Pharmaceuticals Inc:Consultancy, Honoraria, Research Funding;Daiichi Sankyo:Consultancy, Honoraria, Other: Writing/editorial support, travel costs for meetings, Research Funding;FUJIFILM Pharmaceuticals USA, Inc:Research Funding;New Link Genetics:Honoraria, Other;Bayer HealthCare Pharmaceuticals:Research Funding;Biomed Valley Discoveries:Research Funding;Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company:Consultancy, Honoraria, Other;Jazz:Honoraria, Other;Agios:Consultancy, Honoraria, Other;FORMA Therapeutics:Consultancy, Honoraria, Other.Levis:Menarini:Honoraria;Amgen:Honoraria;FujiFilm:Honoraria, Research Funding;Daiichi-Sankyo:Honoraria;Astellas:Honoraria, Research Funding.Smith:Daiichi Sanyko:Consultancy, Honoraria;Abbvie:Other: Research Support, Research Funding;FujiFilm:Other: Research support, Research Funding;Astellas Pharma:Honoraria, Other: Research Support, Research Funding;Revolution Medicines:Other: Research Support, Research Funding;Sanofi:Honoraria.Brunner:Forty-Seven Inc:Membership on an entity's Board of Directors or advisory committees;AstraZeneca:Research Funding;Takeda:Research Funding;Celgene:Membership on an entity's Board of Directors or advisory committees, Research Funding;Novartis:Research Funding;Jazz Pharmaceuticals:Membership on an entity's Board of Directors or advisory committees.Amrein:Amgen:Research Funding;AstraZeneca:Consultancy, Research Funding;Takeda:Research Funding.Hobbs:Merck:Research Funding;Constellation:Honoraria, Research Funding;Incyte:Research Funding;Bayer:Research Funding;Celgene/BMS:Honoraria;Novartis:Honoraria;Jazz:Honoraria.Narayan:Sanofi-Genzyme:Other: Current Spouse employment ;Takeda:Other: Prior Spouse employment within 24 months;Genentech:Other: Prior Spouse employment within 24 months and prior spouse equity divested within past 24 months.Daver:Pfizer:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Karyopharm:Research Funding;Servier:Research Funding;Daiichi Sankyo:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Genentech:Research Funding;AbbVie:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Astellas:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Novimmune:Research Funding;Gilead:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Amgen:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Trovagene:Research Funding;Fate Therapeutics:Research Funding;ImmunoGen:Research Funding;Novartis:Consultancy, Membership on an entity's Board of Directors or advisory committees;Celgene:Consultancy, Membership on an entity's Board of Directors or advisory committees;Jazz:Consultancy, Membership on an entity's Board of Directors or advisory committees;Trillium:Consultancy, Membership on an entity's Board of Directors or advisory committees;Syndax:Consultancy, Membership on an entity's Board of Directors or advisory committees;Amgen:Consultancy, Membership on an entity's Board of Directors or advisory committees;KITE:Consultancy, Membership on an entity's Board of Directors or advisory committees;Agios:Consultancy, Membership on an entity's Board of Directors or advisory committees;Bristol-Myers Squibb:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.DiNardo:Calithera:Research Funding;Celgene:Consultancy, Honoraria, Research Funding;Agios:Consultancy, Honoraria, Research Funding;Syros:Honoraria;Daiichi Sankyo:Consultancy, Honoraria, Research Funding;Notable Labs:Membership on an entity's Board of Directors or advisory committees;Jazz:Honoraria;ImmuneOnc:Honoraria;Takeda:Honoraria;MedImmune:Honoraria;Novartis:Consultancy;AbbVie:Consultancy, Honoraria, Research Funding. OffLabel Disclosure: Midostaurin for relapsed/refractory AML Sorafenib for relapsed/refractory AML

Background: Gilteritinib is a FLT3 inhibitor with demonstrated efficacy and safety in patients with FLT3-mutated relapsed or refractory (R/R) AML. The efficacy of gilteritinib in patients with prior tyrosine kinase inhibitor (TKI) therapy is not clearly defined. The phase 1/2 CHRYSALIS trial demonstrated the safety and antileukemic activity of gilteritinib in a FLT3-mutation-enriched R/R AML population (Perl AE, et al. Lancet Oncol. 2017). The phase 3 ADMIRAL trial demonstrated the superiority of gilteritinib to salvage chemotherapy (SC) in FLT3-mutated patients based on longer median overall survival (OS) with gilteritinib (9.3 vs 5.6 months; hazard ratio [HR]=0.64 [95% CI: 0.49, 0.83]; P Methods: We retrospectively analyzed clinical outcomes in patients with R/R AML previously treated with TKIs midostaurin or sorafenib, before receiving 120- or 200-mg gilteritinib in the CHRYSALIS trial, or before receiving 120-mg gilteritinib in the ADMIRAL trial. Patients randomized to SC in the ADMIRAL trial were also assessed. Patients in the CHRYSALIS trial had received at least one line of prior AML therapy; patients in the ADMIRAL trial received only one line of prior AML therapy. Results: Of the 145 FLT3-mutation-enriched patients who received 120- or 200-mg gilteritinib in the CHRYSALIS trial, 33 (23%; 120 mg, n=15; 200 mg, n=18) had received a prior TKI (all received sorafenib). Baseline characteristics among patients who received (n=33) or did not receive prior TKIs (n=112) were similar; median age was 56 and 61 years, respectively. Across both dose groups, FLT3 mutation types in prior TKI-treated and non-treated patients were: FLT3-ITD (88% vs 84%, respectively), FLT3-TKD (0 vs 8%, respectively), FLT3-ITD and -TKD (12% vs 6%, respectively), and unknown or missing (0 vs 2%, respectively). Rates of composite complete remission (CRc) were similar in patients who received prior TKIs (42%; n=14/33) and in those who did not (43%; n=48/112). Among patients who received prior TKIs, rates of CRc were 53% (n=8/15) in the 120-mg dose group and 33% (n=6/18) in the 200-mg dose group (Table 1); rates of CRc in patients who did not receive prior TKIs were similar across both the 120- and 200-mg dose groups (44% [n=18/41] and 42% [n=30/71], respectively). Among patients treated with prior TKIs across the 120- or 200-mg dose groups (n=33), most (73%; n=24) had received ≥3 lines of any prior AML therapy. In the phase 3 ADMIRAL trial, 31 of 247 (13%) R/R FLT3-mutated AML patients in the gilteritinib arm and 14 of 124 (11%) patients in the SC arm had received prior TKIs. Demographic and baseline characteristics were well balanced between treatment arms and were also similar between prior TKI-treated (n=45) and non-treated patients (n=326); median age was 57 and 62 years, respectively. Among prior TKI-treated and non-treated patients, FLT3 mutation types in gilteritinib and SC arms were: FLT3-ITD (71% vs 93% and 89% vs 91%, respectively), FLT3-TKD (16% vs 7% and 7% vs 8%, respectively), and FLT3-ITD and -TKD (13% vs 0 and 1% vs 0, respectively). FLT3 mutation type was unconfirmed in 5 of 326 (2%) patients who did not receive prior TKIs (gilteritinib vs SC, 2% vs 1%, respectively). In the gilteritinib arm, CRc rates were comparable in patients who received (48%; n=15/31) and did not receive prior TKIs (55%; n=119/216); lower CRc rates were observed in the SC arm in both TKI-treated and non-treated groups (21% [n=3/14] and 22% [n=24/110], respectively) (Table 2). Median OS in patients treated with prior TKIs, albeit not statistically significant, remained high in patients treated with gilteritinib compared with those treated with SC (6.5 vs 4.7 months, respectively; HR=0.671 [95% CI: 0.328, 1.376]) (Table 2). In patients who did not receive prior TKIs, median OS was 9.6 months in the gilteritinib arm and 6.0 months in the SC arm (HR=0.625 [95% CI: 0.474, 0.824]). Conclusions: Patients with R/R AML who received prior TKIs (midostaurin or sorafenib) were able to achieve remission with gilteritinib. High response rates with gilteritinib were observed in heavily pre-treated FLT3-mutation-enriched patients in the CHRYSALIS trial who received prior TKIs. Higher response rates with gilteritinib than with SC were observed in prior TKI-treated patients with FLT3 mutations in the ADMIRAL trial. Disclosures Perl: Takeda: Honoraria, Other: Travel costs for meeting; Syndax: Consultancy, Honoraria; Leukemia & Lymphoma Society, Beat AML: Consultancy; Agios: Consultancy, Honoraria, Other; FUJIFILM Pharmaceuticals USA, Inc: Research Funding; AbbVie Inc: Consultancy, Honoraria, Other, Research Funding; Astellas: Consultancy, Honoraria, Other: writing/editorial support, travel costs for meeting presentations related to study, Research Funding; Novartis: Honoraria, Other, Research Funding; Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Consultancy, Honoraria, Other; Arog Pharmaceuticals Inc: Other: uncompensated consulting, travel costs for meetings; Actinium Pharmaceuticals Inc: Consultancy, Honoraria, Research Funding; New Link Genetics: Honoraria, Other; Bayer HealthCare Pharmaceuticals: Research Funding; FORMA Therapeutics: Consultancy, Honoraria, Other; Daiichi Sankyo: Consultancy, Honoraria, Other: Writing/editorial support, travel costs for meetings, Research Funding; Jazz: Honoraria, Other; Biomed Valley Discoveries: Research Funding. Altman:Cancer Expert Now: Consultancy; ASH: Consultancy; PeerView: Consultancy; Bristol-Myers Squibb: Consultancy; Fujifilm: Research Funding; AbbVie: Other: advisory board, Research Funding; BioSight: Other: No payment but was reimbursed for travel , Research Funding; Theradex: Other: Advisory Board; Immune Pharmaceuticals: Consultancy; Syros: Consultancy; Janssen: Consultancy; Kartos: Research Funding; Celgene: Research Funding; Boehringer Ingelheim: Research Funding; ImmunoGen: Research Funding; Amgen: Research Funding; Aprea: Research Funding; Amphivena: Research Funding; Genentech: Research Funding; Novartis: Consultancy; Kura Oncology: Other: Scientific Advisory Board - no payment accepted, Research Funding; Daiichi Sankyo: Other: Advisory Board - no payment but was reimbursed for travel; Agios: Other: advisory board, Research Funding; Glycomimetics: Other: Data safety and monitoring committee; Astellas: Other: Advisory Board, Speaker (no payment), Steering Committee (no payment), Research Funding; PrIME Oncology: Consultancy; France Foundation: Consultancy. Montesinos:Celgene, Pfizer, Abbvie: Consultancy; Pfizer, Abbvie, Daiichi Sankyo: Research Funding; Astellas, Novartis, Janssen: Speakers Bureau. Podoltsev:Blueprint Medicines: Consultancy, Honoraria; Astellas Pharma: Research Funding; AI Therapeutics: Research Funding; Samus Therapeutics: Research Funding; Novartis: Consultancy, Honoraria; Bristol-Myers Squib: Consultancy, Honoraria; Alexion: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Agios Pharmaceuticals: Consultancy, Honoraria; Daiichi Sankyo: Research Funding; Genentech: Research Funding; CTI biopharma: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Boehringer Ingelheim: Research Funding; Sunesis Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding; Incyte: Consultancy, Honoraria; Kartos Therapeutics: Research Funding; Arog Pharmaceuticals: Research Funding. Martinelli:Celgene: Consultancy, Speakers Bureau; Amgen: Consultancy; AbbVie: Consultancy, Research Funding; Janssen: Consultancy; Roche: Consultancy; Pfizer: Consultancy, Research Funding, Speakers Bureau; Daichii Sankyo: Consultancy, Research Funding; Incyte: Consultancy; Jazz: Consultancy. Smith:FujiFilm: Other: Research support, Research Funding; Abbvie: Other: Research Support, Research Funding; Revolution Medicines: Other: Research Support, Research Funding; Daiichi Sanyko: Consultancy, Honoraria; Sanofi: Honoraria; Astellas Pharma: Honoraria, Other: Research Support, Research Funding. Levis:Amgen: Honoraria; Menarini: Honoraria; FujiFilm: Honoraria, Research Funding; Astellas: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria. Röllig:Abbvie, Novartis, Pfizer: Consultancy, Research Funding; Amgen, Astellas, BMS, Daiichi Sankyo, Janssen, Roche: Consultancy. Groß-Langenhoff:Astellas: Current Employment. Hasabou:Astellas Pharma: Current Employment. Lu:Astellas: Current Employment. Tiu:Astellas Pharma Global Development: Current Employment; Eli Lilly & Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months.

Background: Gilteritinib is approved for patients (pts) with relapsed/refractory (R/R) FLT3-mutated acute myeloid leukemia (AML), based on findings from the phase 3 ADMIRAL trial (Perl AE, et al. N Engl J Med. 2019). A phase 3 trial, QuANTUM-R, demonstrated the benefit of quizartinib in pts with R/R AML with FLT3 internal tandem duplication (FLT3-ITD) mutations (Cortes JE, et al. Lancet Oncol. 2019). Although eligibility criteria across both studies were similar, QuANTUM-R was more stringent as to prior therapy intensity and remission duration, which potentially enriched for higher-risk pts. We sought to describe outcomes from ADMIRAL among pts who otherwise met eligibility for QuANTUM-R. Methods: In this post-hoc analysis, a subset of pts from ADMIRAL were matched with R/R FLT3-ITD+ AML pts from QuANTUM-R on the basis of baseline characteristics and prior treatment criteria. Matched pts were either refractory to initial anthracycline-based chemotherapy or had relapsed ≤6 mos after achieving composite complete remission (CRc) with an anthracycline-based regimen. Results: Overall, 218 pts with R/R FLT3-ITD+ AML in the ADMIRAL trial (gilteritinib, n=140; salvage chemotherapy [SC], n=78) were matched with the QuANTUM-R intention-to treat (ITT) population (N=367; quizartinib, n=245; SC, n=122). Proportions of pts preselected for high-intensity SC were 66% (n=143/218) in the matched ADMIRAL ITT population and 77% (n=281/367) in the QuANTUM-R ITT populations. Demographic and baseline characteristics of the matched ADMIRAL ITT population and QuANTUM-R ITT population were similar. Median durations of exposure to gilteritinib and quizartinib were 3.8 mos and 3.2 mos, respectively, and median number of treatment cycles received were five and four, respectively. Rates of hematopoietic stem cell transplantation (HSCT) were similar in pts treated with gilteritinib (35%; n=49/140) or quizartinib (32%; n=78/245), as were the proportions of pts who resumed gilteritinib (23%; n=32/140) or quizartinib (20%; n=48/245) therapy post-HSCT. Median overall survival (OS) in pts treated with gilteritinib or quizartinib was longer than that observed with SC. After a median follow-up of 17.4 mos, median OS was 10.2 mos with gilteritinib versus 5.6 mos with SC (hazard ratio [HR]=0.573 [95% CI: 0.403, 0.814]; one-sided nominal P=0.0008). After a median follow-up of 23.5 mos, median OS with quizartinib was 6.2 mos versus 4.7 mos with SC (HR=0.76 [95% CI: 0.58-0.98]; one-sided P=0.02). After censoring for HSCT, median OS was 9.3 mos with gilteritinib versus 5.5 mos with SC (HR=0.525 [95% CI: 0.356-0.775]; nominal one-sided P=0.0005), and 5.7 mos versus 4.6 mos with quizartinib versus SC, respectively (HR=0.79 [95% CI: 0.59, 1.05]; one-sided P=0.05). In both QuANTUM-R and matched ADMIRAL populations, the survival benefits of quizartinib and gilteritinib compared with SC were maintained across multiple subgroups, including high FLT3-ITD allelic ratio subsets. Compared with SC, high CRc rates were observed in pts treated with either gilteritinib (57%; n=80/140) or quizartinib (48%; n=118/245). The complete remission (CR) rate with gilteritinib was 23% (n=32/140), whereas the CR rate with quizartinib was 4% (n=10/245) (Table). Median time to achieve CRc was 1.8 mos with gilteritinib and 1.1 mos with quizartinib, median duration of CRc was 5.5 mos with gilteritinib and 2.8 mos with quizartinib. The safety profiles of gilteritinib and quizartinib were generally similar, though aspartate or alanine aminotransferase elevations (any grade) were more frequent with gilteritinib (41-44%) than quizartinib (≤13%), whereas neutropenia (14% vs 34%, respectively), fatigue (24% vs 39%, respectively), and prolonged QT intervals (9% vs 27%, respectively) were more frequent with quizartinib. Conclusions: In pts with R/R FLT3-ITD+ AML and similar baseline characteristics, both gilteritinib and quizartinib were generally well tolerated and associated with improved survival and treatment response compared with SC. Responses to gilteritinib and quizartinib, as measured by CRc, were similar; blood count recovery varied between the two FLT3 inhibitors. Although cross-study comparisons have substantial limitations, the findings suggest that while remission is achieved faster with quizartinib, response may be more durable and survival potentially longer with gilteritinib. Disclosures Perl: Syndax: Consultancy, Honoraria; Leukemia & Lymphoma Society, Beat AML: Consultancy; Novartis: Honoraria, Other, Research Funding; Agios: Consultancy, Honoraria, Other; Jazz: Honoraria, Other; FORMA Therapeutics: Consultancy, Honoraria, Other; Daiichi Sankyo: Consultancy, Honoraria, Other: Writing/editorial support, travel costs for meetings, Research Funding; FUJIFILM Pharmaceuticals USA, Inc: Research Funding; New Link Genetics: Honoraria, Other; Arog Pharmaceuticals Inc: Other: uncompensated consulting, travel costs for meetings; Actinium Pharmaceuticals Inc: Consultancy, Honoraria, Research Funding; Biomed Valley Discoveries: Research Funding; Astellas: Consultancy, Honoraria, Other: writing/editorial support, travel costs for meeting presentations related to study, Research Funding; Bayer HealthCare Pharmaceuticals: Research Funding; AbbVie Inc: Consultancy, Honoraria, Other, Research Funding; Takeda: Honoraria, Other: Travel costs for meeting; Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Consultancy, Honoraria, Other. Lu:Astellas: Current Employment. Fan:Astellas Pharma: Current Employment. Hasabou:Astellas Pharma: Current Employment. Berrak:Astellas: Current Employment. Tiu:Eli Lilly & Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Astellas Pharma Global Development: Current Employment.

Background: Gilteritinib, an oral FMS-like tyrosine kinase 3 (FLT3) inhibitor, demonstrated antileukemic responses in patients with FLT3-mutated (FLT3mut+) relapsed/refractory acute myeloid leukemia (AML). We report final results from a phase 1 study of once-daily oral gilteritinib plus intravenous (IV) chemotherapy in patients with newly diagnosed AML. Methods: This 4-part, open-label, phase 1 study (NCT02236013) assessed the safety/tolerability and antileukemic effects of gilteritinib plus 7+3 induction and high-dose cytarabine consolidation chemotherapy, and as single-agent maintenance therapy in adults with newly diagnosed AML. In part 1, successive cohorts of 3-6 patients received 40-200 mg/d gilteritinib (Days 4-17) and ≤2 cycles of induction (cytarabine 100 mg/m2/d IV, Days 1-7; idarubicin 12 mg/m2/d IV, Days 1-3). In part 2, patients (n=33, of which at least 15 were FLT3mut+) received the recommended 120 mg/d gilteritinib expansion dose and ≤2 cycles of the part 1 induction schedule. In part 3, patients were stratified into 2 cohorts: one receiving treatment from part 2 (n=7) and the other receiving treatment that replaced idarubicin with daunorubicin (90 mg/m2/d IV, Days 1-3; n=7). In part 4, patients (n=12) received the same induction as the part 3/daunorubicin cohort (with a reduction in cycle 2 to daunorubicin 45 mg/m2/d). During consolidation, patients received ≤3 cycles of cytarabine (1.5 g/m2 every 12 hours; Days 1, 3, and 5) and gilteritinib (Days 1-14 for parts 1-3; Days 1-56 for part 4) at the induction dose. Gilteritinib was given once daily in 28-day cycles for up to 26 cycles as maintenance therapy (maintenance phase is still ongoing). Patients achieving composite complete remission (CRc) or partial remission could undergo hematopoietic stem cell transplant (HSCT) and resume maintenance gilteritinib treatment post-HSCT. Results: As of 23 June 2020, 80 patients were allocated to treatment (safety analysis set, n=79); median age was 59.0 y (range, 23-77) and most were male (62.0%). Median follow-up for overall survival (OS) was 35.8 mo. Dose-limiting toxicities are provided in Table 1. The maximum tolerated dose was 120 mg/d. Serious treatment-related adverse events (AEs) and AEs leading to discontinuation of gilteritinib occurred in 12.7% (n=10) and 5.1% (n=4) of patients, respectively. One (1.3%) death occurred across all treatment phases. Grade ≥3 nonhematologic AEs (≥10% of patients) were increased alanine aminotransferase (13.9%), pneumonia (13.9%), sepsis (11.4%), and bacteremia (11.4%). At the end-of-induction time point, there were 44 (55.7%) total FLT3mut+ patients across all dose groups and 38 (48.1%) patients who received gilteritinib 120 mg/d. Investigator-reported CRc was achieved by 81.8% of patients across all dose groups (n=36) and 81.6% among patients who received gilteritinib 120 mg/d (n=31; Table 2). Anthracycline choice had no clear impact on CRc rate, although the number of patients in these cohorts was low. In FLT3mut+ patients who achieved CRc in any dose group, median (95% CI) duration of CRc and disease-free survival were 14.1 (4.0-29.9) and 15.3 (9.8-not reached) mo, respectively. Median OS for FLT3mut+ patients has not been reached. The survival probability (95% CI) in all FLT3mut+ patients at weeks 8, 12, 26, 52, and 104 were 97.7% (84.6%-99.7%), 95.3% (82.5%-98.8%), 92.9% (79.6%-97.7%), 83.1% (67.7%-91.5%), and 71.8% (54.6%-83.4%), respectively. In patients with FLT3 internal tandem duplication (ITD)-positive AML achieving CRc, mutational clearance (summed FLT3 ITD signal ratio of ≤10-4 after induction or consolidation) was achieved by 70% (n/N=16/23) of patients receiving a gilteritinib dose of ≥120 mg. HSCT occurred in 30.4% of the total population (n/N=24/79). Analysis of plasma inhibitory activity and pharmacokinetics of gilteritinib will be available at presentation. Conclusions: Gilteritinib plus induction and consolidation chemotherapy is well tolerated in patients with newly diagnosed AML. Favorable antileukemic responses were observed in FLT3mut+ patients regardless of anthracycline type or gilteritinib administration schedule, with a mutational clearance rate of 70.0%. Based on these results, randomized clinical trials of induction and consolidation chemotherapy plus gilteritinib vs midostaurin in FLT3mut+ AML patients have been initiated. Disclosures Pratz: AbbVie: Other: Scientific Advisory Board, Research Funding; Astellas: Other: Scientific Advisory Board, Research Funding; Boston BioMedical: Consultancy; Celgene: Other: Scientific Advisory Board; Agios: Other: Scientific Advisory Board, Research Funding; Jazz Pharmaceutical: Consultancy; Millennium: Research Funding; Daiichi Sankyo: Research Funding. Cherry:Pfizer: Other: Advisory Board; BMS: Other: Advisory Board; Kite: Other: Advisory Board. Altman:PeerView: Consultancy; ASH: Consultancy; Syros: Consultancy; Janssen: Consultancy; Genentech: Research Funding; Amphivena: Research Funding; Amgen: Research Funding; Aprea: Research Funding; ImmunoGen: Research Funding; Celgene: Research Funding; Boehringer Ingelheim: Research Funding; PrIME Oncology: Consultancy; Immune Pharmaceuticals: Consultancy; Novartis: Consultancy; Glycomimetics: Other: Data safety and monitoring committee; Daiichi Sankyo: Other: Advisory Board - no payment but was reimbursed for travel; Kura Oncology: Other: Scientific Advisory Board - no payment accepted, Research Funding; Kartos: Research Funding; AbbVie: Other: advisory board, Research Funding; Fujifilm: Research Funding; BioSight: Other: No payment but was reimbursed for travel , Research Funding; Bristol-Myers Squibb: Consultancy; Astellas: Other: Advisory Board, Speaker (no payment), Steering Committee (no payment), Research Funding; Cancer Expert Now: Consultancy; Agios: Other: advisory board, Research Funding; Theradex: Other: Advisory Board; France Foundation: Consultancy. Cruz:Takeda: Speakers Bureau. Jurcic:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Research Funding; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Arog Pharmaceuticals: Research Funding; Astellas: Research Funding; Forma Therapeutics: Research Funding; Genentech: Research Funding; Kura Oncology: Research Funding; PTC Therapeutics: Research Funding; Syros Pharmaceuticals: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Levis:Menarini: Honoraria; Amgen: Honoraria; FujiFilm: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria; Astellas: Honoraria, Research Funding. Lin:Pfizer: Research Funding; Bio-Path Holdings: Research Funding; Abbvie: Research Funding; Seattle Genetics: Research Funding; Tolero Pharmaceuticals: Research Funding; Ono Pharmaceutical: Research Funding; Prescient Therapeutics: Research Funding; Incyte: Research Funding; Genetech-Roche: Research Funding; Gilead Sciences: Research Funding; Aptevo: Research Funding; Celyad: Research Funding; Celgene: Research Funding; Astellas Pharma: Research Funding; Mateon Therapeutics: Research Funding; Jazz: Research Funding; Trovagene: Research Funding. Perl:Bayer HealthCare Pharmaceuticals: Research Funding; Syndax: Consultancy, Honoraria; Jazz: Honoraria, Other; Arog Pharmaceuticals Inc: Other: uncompensated consulting, travel costs for meetings; Biomed Valley Discoveries: Research Funding; Agios: Consultancy, Honoraria, Other; FUJIFILM Pharmaceuticals USA, Inc: Research Funding; AbbVie Inc: Consultancy, Honoraria, Other, Research Funding; Loxo Oncology Inc, a wholly owned subsidiary of Eli Lilly & Company: Consultancy, Honoraria, Other; Takeda: Honoraria, Other: Travel costs for meeting; Astellas: Consultancy, Honoraria, Other: writing/editorial support, travel costs for meeting presentations related to study, Research Funding; Leukemia & Lymphoma Society, Beat AML: Consultancy; New Link Genetics: Honoraria, Other; Daiichi Sankyo: Consultancy, Honoraria, Other: Writing/editorial support, travel costs for meetings, Research Funding; FORMA Therapeutics: Consultancy, Honoraria, Other; Actinium Pharmaceuticals Inc: Consultancy, Honoraria, Research Funding; Novartis: Honoraria, Other, Research Funding. Podoltsev:Arog Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding; Sunesis Pharmaceuticals: Research Funding; Boehringer Ingelheim: Research Funding; Daiichi Sankyo: Research Funding; Astellas Pharma: Research Funding; CTI biopharma: Consultancy, Honoraria, Research Funding; Bristol-Myers Squib: Consultancy, Honoraria; Genentech: Research Funding; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Samus Therapeutics: Research Funding; Agios Pharmaceuticals: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria; Blueprint Medicines: Consultancy, Honoraria; Alexion: Consultancy, Honoraria; Kartos Therapeutics: Research Funding; AI Therapeutics: Research Funding. Schiller:Abbvie: Research Funding; Actinium: Research Funding; Ariad: Research Funding; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Incyte: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding; Ono Pharma: Consultancy; Kite Pharma: Research Funding; Stemline: Speakers Bureau; Gilead: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Sanofi: Speakers Bureau; Agios: Consultancy, Research Funding, Speakers Bureau; DeltaFly: Research Funding; Deciphera: Research Funding; Daiichi Sankyo: Research Funding; Cyclacel: Research Funding; Constellation: Research Funding; Celator: Research Funding; Astellas Pharma: Honoraria, Research Funding; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; Forma: Research Funding; FujiFilm: Research Funding; Gamida: Research Funding; Genentech-Roche: Research Funding; Geron: Research Funding; Jazz Pharmaceuticals: Research Funding; Karyopharm: Research Funding; Mateon: Research Funding; MedImmune: Research Funding; Onconova: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; Regimmune: Research Funding; Samus: Research Funding; Sangamo: Research Funding; Tolero: Research Funding; Trovagene: Research Funding; Kaiser Permanente: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company. Hill:Targeted Molecular Diagnostics: Patents & Royalties: US7862995; Astellas: Current Employment; Ligacept, LLC: Current equity holder in publicly-traded company, Patents & Royalties: US9051388, US9683222. James:Astellas: Current Employment. Lu:Astellas: Current Employment. Tiu:Astellas Pharma Global Development: Current Employment; Eli Lilly & Company: Current equity holder in publicly-traded company, Ended employment in the past 24 months. OffLabel Disclosure: New Indication

Genomic studies have revealed significant branching heterogeneity in cancer. Studies of resistance to tyrosine kinase inhibitor therapy have not fully reflected this heterogeneity because resistance in individual patients has been ascribed to largely mutually exclusive on-target or off-target mechanisms in which tumors either retain dependency on the target oncogene or subvert it through a parallel pathway. Using targeted sequencing from single cells and colonies from patient samples, we demonstrate tremendous clonal diversity in the majority of acute myeloid leukemia (AML) patients with activating FLT3 internal tandem duplication mutations at the time of acquired resistance to the FLT3 inhibitor quizartinib. These findings establish that clinical resistance to quizartinib is highly complex and reflects the underlying clonal heterogeneity of AML.

Introduction: In the phase 3 QuANTUM-R trial, once-daily, oral, highly potent and selective FLT3 inhibitor Q improved clinical benefits vs SC (median overall survival [mOS], 6.2 vs 4.7 mo [HR, 0.76 (95% CI, 0.58-0.98); P = .02]; composite complete remission [CRc], 48% vs 27%; median duration of CRc, 12.1 vs 5.0 wk) in 367 pts with R/R FLT3-ITD AML (Cortes et al. Lancet Oncol, 2019; NCT02039726). Prior to randomization, 25% (Q) and 23% (SC) of pts had 1 prior HSCT. An OS sensitivity analysis, with censoring at the time of any subsequent HSCT during QuANTUM-R, was supportive (mOS, 5.7 vs 4.6 mo [HR, 0.79 (95% CI, 0.59-1.05)]; P = .05). Post hoc analyses of characteristics and clinical outcomes in pts who underwent subsequent HSCT in QuANTUM-R are reported. Methods: Pts aged ≥ 18 y with FLT3-ITD R/R AML receiving Q (60 mg [30-mg lead-in]) or 1 of 3 prespecified high- or low-intensity SC regimens and underwent subsequent HSCT as part of the open-label, randomized QuANTUM-R trial were analyzed. Pts receiving HSCT in the Q arm could resume maintenance Q 30-100 days after HSCT. Decisions to proceed to HSCT and resume Q after HSCT were made per investigator discretion/institutional policies. Results: Of 367 randomized pts, 85 in the Q arm underwent any subsequent HSCT (allogenic HSCT [allo-HSCT], 84 [6 with and 78 w/o additional AML therapy]; autologous HSCT, 1) and 19 in the SC arm underwent any HSCT (5 with and 14 w/o additional AML therapy]). Median age (range) was lower in pts with any HSCT (Q, 49 [19-71] y; SC, 44 [23-67] y) vs pts w/o (Q, 58 [19-81] y; SC, 59 [18-78] y). Q + SC pooled data showed a longer mOS (95% CI) in 104 pts with any HSCT vs 263 w/o (12.2 [10.0-24.1] vs 4.4 [4.1-4.9] mo; P < .0001; Fig 1); 1-year OS probabilities (95% CI) were 50% (40%-60%) vs 13% (9%-18%). Among pts preselected for high-intensity therapy (Q [n = 188] + SC [n = 93]), mOS in the pooled high-intensity group was 11.9 (10.0-24.0) mo with any HSCT vs 4.6 (4.1-5.4) mo w/o. Among pts preselected for low-intensity therapy, 13/57 in the Q arm and 0/29 in the SC arm underwent any HSCT; mOS in the pooled low-intensity group was 32.4 (6.2-NA) mo with any HSCT vs 4.1 (2.7-4.6) mo w/o. In pts with CRc (last recorded response prior to allo-HSCT), mean time (range) to allo-HSCT was 13.3 (5.9-26.9) wk with Q and 12.1 (6.3-28.6) wk with SC. Q + SC pooled data showed that mOS (95% CI) was longer in pts with a CRc prior to allo-HSCT vs pts w/o CRc (20.1 [11.7-NA] vs 8.8 [7.0-11.4] mo). Survival outcomes by treatment were similar regardless of study treatment, with longer mOS in pts with any HSCT vs pts w/o (Q, 11.9 [10.2-25.1] vs 4.5 [4.1-5.4] mo; SC, 12.7 [6.1-NA] vs 4.0 [2.7-5.0] mo); respective 1-year OS probabilities (95% CI) were 50% (39%-60%) vs 13% (8%-20%) and 51% (26%-70%) vs 12% (6%-21%). In the Q arm, mOS (95% CI) was longer in pts with a best response of CRc who resumed Q after allo-HSCT (27.1 [18.2-NA] mo) vs pts not resuming Q (5.4 [4.7-11.4] mo; Fig 2). In 48 pts (62%) in the Q arm resuming Q after allo-HSCT, median time (range) from allo-HSCT to Q resumption was 65 (30-106) d. Four pts (5%) in the Q arm died < 30 days after allo-HSCT. As of 2/22/2018, 46 of 78 pts in the Q arm (59%) and 9 of 14 pts in the SC arm (64%) with allo-HSCT w/o additional AML therapy died, primarily due to AML disease progression (Q, 31 [40%]; SC, 7 [50%]). The frequency of treatment-emergent adverse events (TEAEs) was mostly lower in pts resuming Q after allo-HSCT than in the overall Q population (Table 1); TEAEs of interest were similar. Long-term survivor data will be presented. Conclusions: Independent of HSCT, Q improved survival vs SC in pts with FLT3-ITD R/R AML in QuANTUM-R. Q + SC pooled analyses showed longer survival in pts with HSCT vs pts w/o and in pts with CRc prior to allo-HSCT. Importantly, survival post-HSCT was similar in the Q and SC arms, indicating that pts eligible for HSCT were appropriately transplanted, and the higher HSCT rate in the Q arm was beneficial to pts. More pts treated with Q underwent HSCT, likely due to a higher rate and duration of CRc with Q vs SC and better overall fitness. In pts preselected for low-intensity SC at study entry, 13 were able to undergo HSCT after Q treatment. Resumption of Q after HSCT was associated with better survival outcomes and was tolerable. These data illustrate the value of using Q to target the FLT3-ITD mutation as a part of the overall treatment sequence in pts with FLT3-ITD R/R AML. Disclosures Ganguly: Seattle Genetics: Speakers Bureau; Janssen: Honoraria, Other: Advisory Board; Kite Pharma: Honoraria, Other: Advisory Board; Daiichi Sankyo: Research Funding. Cortes:Bristol-Myers Squibb: Consultancy, Research Funding; BiolineRx: Consultancy; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; Merus: Consultancy, Honoraria, Research Funding. Krämer:Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Bayer: Research Funding. Levis:Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Daiichi Sankyo Inc: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; FUJIFILM: Consultancy, Research Funding. Martinelli:Daiichi Sankyo: Consultancy, Honoraria; Pfizer: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Amgen: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Novartis: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant. Perl:Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau. Arunachalam:Daiichi Sankyo: Employment. Gammon:Daiichi Sankyo: Consultancy. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Mires:Daiichi Sankyo: Employment. Namuyinga:Daiichi Sankyo: Employment. Zhang:Daiichi Sankyo: Employment. Khaled:Omeros: Consultancy; Daiichi Sankyo: Other: Travel support; Alexion: Consultancy, Speakers Bureau.

Background: Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk subtype occurring in 15-40% of older children, adolescents, and adults with B-ALL and is associated with high relapse rates and poor survival. Approximately 50% of Ph-like ALL cases have CRLF2 (cytokine receptor-like factor 2 rearrangements (CRLF2-R), often with concomitant JAK2 point mutations. We and others have shown that targeted inhibition of JAK/STAT and PI3K/AKT signaling in CRLF2-rearranged Ph-like ALL only partially inhibits leukemia proliferation. Our preliminary data indicates that modified B cell receptor signaling results in ERK activation and Ph-like ALL cell growth that appears independent of CRLF2-activated signaling. This study aimed to define the extent to which BCR signaling mediates drug resistance in Ph-like ALL after cytokine receptor signaling inhibition and to develop novel combinatorial treatment strategies. Methods and Results: We first validated high basal levels of JAK/STAT and PI3K pathway phosphoproteins via immunoblotting of cell lysates from >20 primary childhood and adult Ph-like ALL samples and patient-derived xenograft (PDX) models. Despite lack of B-cell receptor (BCR) μ heavy chain on Ph-like ALL cells by flow cytometry analysis, we detected high expression levels of the BCR-associated proteins CD79A, CD79B, and BLNK. We further identified constitutive phosphorylation of downstream BCR-associated signaling molecules, including SRC family kinases (SFKs), BTK, and ERK. Given these new observations, we then sought to delineate more precisely alternative pathways in Ph-like ALL (beyond JAK/STAT and PI3K) that may contribute to adaptive signaling regulation and confer resistance to kinase inhibitor monotherapy. We hypothesized that JAK inhibitor (JAKi) resistance is mediated by compensatory activation of PI3K/AKT/mTOR through 'BCR-like' signaling via CD79/CD19/SRC/BTK/ERK. To test this hypothesis, we treated CRLF2-R Ph-like ALL cells in vitro with selective inhibitors of JAK1/2 (ruxolitinib) or PI3Kd (INCB050465) and assessed effects upon signaling via immunoblotting. We observed i) effective dephosphorylation of STAT5 and moderate dephosphorylation of AKT with full reactivation within 72h following JAKi or PI3Kdi monotherapy, respectively, ii) combined JAKi and PI3Kdi prevented PI3K pathway, reactivation, and iii) JAKi and PI3Kdi had no effects upon ERK signaling. These results suggested that oncogene-independent activation of BCR and PI3K pathway signaling occurs in Ph-like ALL. We then performed immunofluorescence analysis and detected distinct clustering and homodimerization of CD79B at the cell membrane of Ph-like ALL cells, as well as physical proximity of CD79B and CD19, suggesting that CD19 could be phosphorylated by SRC/SFKs independently of an activated BCR. Interestingly however, CRISPR-mediated deletion of CD19 or CD79B resulted in hyperactivation of ERK signaling. Finally, we tested if triple inhibition of JAK/STAT, PI3K, and SRC/SFKs signaling is sufficient to eradicate Ph-like ALL. Strikingly, combined JAKi (ruxolitinib), PI3Kdi (INCB050465), and SRCi (dasatinib) silenced STAT5, PI3K, and ERK signaling and induced near-complete cytotoxicity in vitro and in vivo in Ph-like ALL cell lines and patient-derived xenograft (PDX) models. While triple inhibitor treatment appeared well-tolerated in mice, we also assessed dual kinase inhibition of JAK2 and PI3K with dexamethasone (a known repressor of BCR signaling) as a more clinically relevant combinatorial strategy. We observed similarly robust inhibition of signaling pathways and leukemia eradication in vitro and in vivo in our Ph-like ALL cell lines and PDX models. Conclusions: Children and adults with Ph-like ALL have a >60% risk of relapse despite maximally intensive chemotherapy, demonstrating need for alternative therapeutic approaches. While earlier studies by our group and others have reported partial anti-leukemia activity of JAKi and PI3Ki monotherapies, our new data provide compelling evidence that three essential cooperating signaling pathways are required for Ph-like leukemogenesis. We postulate that triple JAK, PI3K, and SRC inhibition or dual kinase inhibition with chemotherapy can overcome innate compensatory mechanisms of signaling resistance and may in fact be necessary to eradicate Ph-like ALL in patients. Disclosures Perl: Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding. Carroll:Astellas Pharmaceuticals: Research Funding; Incyte: Research Funding; Janssen Pharmaceuticals: Consultancy. Tasian:Gilead Sciences: Research Funding; Incyte Corportation: Research Funding; Aleta Biotherapeutics: Membership on an entity's Board of Directors or advisory committees.

BACKGROUND: The FLT3 tyrosine kinase inhibitor (TKI) gilteritinib improves the survival of patients with relapsed/refractory (R/R) FLT3 mutated (FLT3mut+) acute myeloid leukemia (AML) compared to standard salvage chemotherapy; however, single agent TKI therapy is not curative and long-term survival remains low. Combination therapy with agents that induce apoptosis may enhance cytotoxicity against FLT3mut+ and WT clones and potentially delay or prevent drug resistance. Preclinical data demonstrate that the combination of venetoclax with a FLT3 tyrosine kinase inhibitor is highly synergistic, and BCL-2 inhibition by venetoclax directly triggers apoptosis, which may help overcome resistance to FLT3-targeted therapy. Therefore, we sought to define the safety and activity of venetoclax plus gilteritinib in R/R AML. METHODS: This is a multicenter, open-label, phase 1b clinical trial (NCT03625505) evaluating the safety and efficacy of venetoclax in combination with gilteritinib for patients with relapsed or refractory (R/R) AML. Patients had to have R/R AML and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Here, we present data in patients that had either wild type (WT) or mutated FLT3, and were treated with 400 mg venetoclax in combination with 80 mg or 120 mg gilteritinib daily, from the dose escalation portion of the study. For study purposes, gilteritinib was administered alone for one day. On day two venetoclax was initiated in a three-day ramp-up from 100 to 200 to 400 mg; thereafter, target doses of each were administered, daily, in 28-day cycles unless venetoclax was shortened for cytopenia recovery. Interruptions of venetoclax or both drugs simultaneously were permitted for adverse events (AEs). RESULTS: Data cutoff was July 10, 2019. Of 15 patients enrolled and treated, 5 had WT FLT3 and 10 had mutant FLT3 (8 ITD, 1 TKD, and one with both included with the ITD group). The median age for all patients was 58 (range: 23-81). Both patients with WT or mutant FLT3 had a median of 2.0 prior lines of therapy, with ranges of 2-4 and 1-4 prior lines, respectively. Six (60%) of the FLT3 mutant patients had previously received a FLT3 blocking TKI (2 of those receiving both midostaurin and sorafenib), and 5 (50%) had prior stem cell transplant (SCT). None of the patients with WT FLT3 were FLT3 inhibitor-experienced, and one patient had prior stem cell transplant. Key treatment emergent grade ≥3 AEs across all patients were: febrile neutropenia (47%), anemia (27%), thrombocytopenia (7%) and neutropenia (7%). One patient receiving 80 mg of gilteritinib had a protocol-defined dose limiting toxicity of prolonged neutropenia, and one receiving 120 mg of gilteritinib was still within the protocol-defined count recovery period at analysis. Seven (47%) patients had venetoclax interrupted, the majority due to neutropenia; 3 (20%) patients had gilteritinib interrupted. No cases of tumor lysis syndrome were observed. Pharmacokinetic studies showed comparable drug levels to those observed with single agent use of each drug. Key efficacy results are shown in the Table. Fifty percent of patients with mutant FLT3 achieved CRc, and another 40% of patients achieved morphologic leukemia free state, for an ORR of 90% (9/10). The ORR in patients with WT FLT3 was 20% (1/5). 0-32); this patient had WT FLT3. Among the 5 patients who achieved CRc, 2 had relapse after documented CRi (at 2.6 months and 1.6 months). Patient monitoring is ongoing, and enrollment in an expansion cohort has also commenced (FLT3 mutant patients treated with 400 mg venetoclax plus 120 mg of gilteritinib); results will be updated for the presentation. CONCLUSIONS: Venetoclax in combination with gilteritinib was well tolerated and demonstrated blast clearance in 90% of patients with FLT3 mutated AML. The high overall rate of response in patients with FLT3 mutated AML, particularly in patients with previous FLT3 TKI exposure, suggests venetoclax in combination with gilteritinib may be a highly effective treatment option for AML patients with FLT3mut+, even in patients with relapsed/refractory AML. Disclosures Perl: Bayer: Research Funding; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; BioMed Valley Discoveries: Research Funding; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.. Daver:Otsuka: Consultancy; Immunogen: Consultancy, Research Funding; Forty-Seven: Consultancy; Genentech: Consultancy, Research Funding; Agios: Consultancy; Agios: Consultancy; Otsuka: Consultancy; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; BMS: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Servier: Research Funding; Incyte: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Glycomimetics: Research Funding; Astellas: Consultancy; Jazz: Consultancy; Jazz: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; Hanmi Pharm Co., Ltd.: Research Funding; Sunesis: Consultancy, Research Funding; NOHLA: Research Funding; Karyopharm: Consultancy, Research Funding; Celgene: Consultancy; Pfizer: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Hanmi Pharm Co., Ltd.: Research Funding; Forty-Seven: Consultancy; Servier: Research Funding; Genentech: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Immunogen: Consultancy, Research Funding; Glycomimetics: Research Funding; Karyopharm: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; NOHLA: Research Funding; Astellas: Consultancy. Pratz:Astellas Pharma: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Boston Biomedical: Consultancy; Millenium/Takeda: Research Funding. Hong:Genentech Inc.: Employment, Equity Ownership; Roche: Equity Ownership. Bahceci:Astellas: Employment, Patents & Royalties. Tong:AbbVie: Employment, Other: stock or options. Tian:AbbVie, Inc.: Employment, Other: stock or options. Dilley:AbbVie, Inc.: Employment, Other: stock or options.

Background: Quizartinib is a once-daily, oral, highly potent and selective FLT3 inhibitor with proven single-agent activity and a manageable safety profile in FLT3-ITD R/R AML. In the global, phase 3 QuANTUM-R study, quizartinib demonstrated a significant survival benefit over salvage chemotherapy(Cortes, et al. Lancet Oncol, 2019; NCT02039726). Additional support for the safety profile of quizartinib at the proposed dosing regimen (60 mg QD with a 30-mg starting dose) is provided by a pooled analysis of over 600 patients with R/R AML. Methods: We pooled data from four studies: one phase 3 (QuANTUM-R), two phase 2, (ACC220-002 and 2689-CL-2004; Cortes, et al. Lancet Oncol, 2018; Cortes, et al. Blood, 2018), and one phase 1 (CP0001: only patients assigned to continuous daily dosing regimens are included in this analysis; Cortes, et al. J Clin Oncol, 2013) to provide an integrated safety summary of quizartinib monotherapy for the treatment of R/R AML. Treatment-emergent adverse events (TEAEs), on-treatment deaths, and adverse events of special interest (AESIs; QT prolongation and potential ventricular arrhythmias, hepatic disorders, and sequelae of cytopenias such as infections and bleeding) with quizartinib were analyzed. Results: The pooled data set included 673 patients; 51% were male, and median age was 59 years. Thirty-eight patients were assigned to quizartinib 30 mg, 277 to 60 mg, and 358 to >60 mg up to 300 mg. Overall, median treatment duration was 79 days (range, 1-1296 days) and was longest in the 60-mg dose group (95 days) vs the >60-mg (70.5 days) and 30-mg (66 days) groups. The overall TEAE profile was consistent with the results from the phase 3 QuANTUM-R study. Most on-treatment deaths (215 of 599 evaluable patients [36%]; defined as taking place between the first dose and ≤30 days after the last dose) were attributed to AML disease progression (130/599 [22%]), followed by TEAEs (83/599 [14%]), which were predominantly respiratory tract infections and events related to sepsis. TEAEs leading to discontinuation of quizartinib occurred in 173/673 patients (26%). In the 60-mg dose group (quizartinib proposed dosing regimen), the only TEAE associated with discontinuation in >2% of patients was pneumonia (6/277 patients [2%]). The most frequently reported grade ≥3 TEAEs were febrile neutropenia (240/673 [36%]), anemia (188/673 [28%]) and thrombocytopenia (182/673 [27%]) in the hematologic category and pneumonia (119/673 [18%]) and sepsis/septic shock (124/673 [18%]) in the nonhematologic category (Table 1A). In the 60-mg dose group, the most frequent AESI was infection (210/277 [76%]; Table 1B). Epistaxis and petechiae, mainly grade 1/2, were the most frequently reported hemorrhage TEAEs. TEAEs in the hemorrhage category occurred more frequently in the >60-mg dose group than the 60-mg dose group (215/358 [60%] and 136/277 [49%], respectively). The most frequent serious hemorrhage TEAEs were gastrointestinal hemorrhages (15/673 [2%]) and intracranial hemorrhage (10/673 [2%]). QTcF prolongation >500 ms (grade 3) occurred in 75/673 patients (11%), mostly in those receiving quizartinib >60 mg (n = 64) (Table 1C). In the 60-mg dose group, QTcF prolongation >500 ms occurred in 9/277 patients (3%). The median time to onset of QTcF prolongation >500 ms was shorter in the >60-mg dose group than in the 60-mg dose group (9 and 46 days, respectively). Arrhythmias potentially related to QTcF prolongation were infrequent; one event of torsade de pointes, and one event of fatal cardiac arrest (both at doses >60 mg) were observed. No dose effects were seen with hepatic disorders, cardiac arrhythmias, or cardiac failure AESI categories. Conclusions: The overall safety profile of quizartinib in this R/R AML pooled analysis is consistent with that observed in QuANTUM-R. A reduction in the incidence of QTcF prolongation was noted with lower doses of quizartinib (30 or 60 mg vs >60 mg). There was also a reduced incidence of gastrointestinal symptoms, infections, and bleeding at lower doses of quizartinib (30 or 60 mg vs >60 mg). Results from this pooled analysis demonstrate that quizartinib is well tolerated at the proposed dosing regimen (60 mg QD with a 30-mg starting dose) in patients with R/R AML. Disclosures Cortes: BiolineRx: Consultancy; Biopath Holdings: Consultancy, Honoraria; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding. Ganguly:Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau; Daiichi Sankyo: Research Funding. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Levis:FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding. Martinelli:Daiichi Sankyo: Consultancy, Honoraria; Amgen: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant; Novartis: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant. Perl:Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau. Choi:Daiichi Sankyo: Employment. Mendell:Daiichi Sankyo, Inc.: Employment. Namuyinga:Daiichi Sankyo: Employment. Pham:Daiichi Sankyo: Employment. Said:Daiichi Sankyo: Employment. Wang:Daiichi Sankyo: Employment. Mitov:Daiichi Sankyo UK Ltd: Employment. Kim:Daiichi Sankyo: Employment. Khaled:Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support; Omeros: Consultancy.

Introduction: Patients (pts) with relapsed/refractory (R/R) acute myeloid leukemia (AML) with FLT3-ITD mutations have a dismal prognosis and limited treatment options. Given the aggressiveness of FLT3-ITD AML, therapies that produce rapid and sustained disease control are needed. Quizartinib (Q), a once-daily, oral, highly potent and selective FLT3 inhibitor, demonstrated a clinically meaningful overall survival (OS) benefit in pts with R/R FLT3-ITD AML vs salvage chemotherapy (SC; 6.2 vs 4.7 mo [HR, 0.76 (95% CI, 0.58-0.98); P = .02]) in the phase 3 QuANTUM-R trial (NCT02039726; Cortes et al. Lancet Oncol, 2019). In this post hoc analysis, we characterize clinical outcomes in pts who achieved a composite complete remission (CRc) in QuANTUM-R, including pts with CR with incomplete hematologic recovery (CRi) and transfusion independence. Methods: Pts aged ≥ 18 years with FLT3-ITD AML R/R after standard AML therapy, with or without hematopoietic stem cell transplant (HSCT), were randomized 2:1 to Q (60 mg [30-mg lead-in]) or 1 of 3 prespecified SC regimens. Pts receiving HSCT in the Q arm could resume Q after HSCT. Response was assessed per modified International Working Group criteria (Table 1). Transfusion dependence at baseline (BL) was defined as any platelet (PLT) or red blood cell (RBC) transfusion within 28 days of first dose. Post-BL transfusion independence was defined as no PLT or RBC transfusions for any consecutive 56-day period on treatment. Results: Of 367 randomized pts, 245 and 122 were randomized to Q and SC, respectively. Median duration of treatment was 97 days with Q (including post-HSCT resumption) and ranged from 5 to 10 days with SC depending on the regimen. Median follow-up was 23.5 mo. In the intent-to-treat population, CRc was consistent across prespecified subgroups (eg, sex, response to prior therapy, FLT3-ITD variant allele frequency). Median time to CRc was 1.1 mo with Q and 0.9 mo with SC; median duration of CRc was 2.8 mo with Q and 1.2 mo with SC (Table 2). Most responses in both arms were CRi, achieved in 99 pts (40%) in the Q arm and 32 pts (26%) in the SC arm. Peripheral blood counts in pts who achieved CRi are shown in Table 3. Of pts with CRi, 45 (Q) and 13 (SC) underwent HSCT. Outcomes with HSCT included engraftment failure in 11% (Q), rejection in 2% (Q), relapse in 33% (Q) and 46% (SC), and successful transplant in 47% (Q) and 46% (SC) and were unknown in 7% (Q) and 8% (SC). Of the 205 pts in the Q arm who were transfusion dependent at BL, 46 (22%) became transfusion independent post-BL (29 with HSCT; 17 without). Mean (SD) duration of post-BL transfusion independence was 255 (216.6) days. By response, 24 of 91 pts (26%) with CRi, 7 of 48 (15%) with a partial response (PR), and 4 of 47 (9%) with no response (NR) became transfusion independent post-BL; respective mean (SD) durations were 297.6 (268.3), 84.6 (21.7), and 211.3 (111.9) days. Of the 36 pts in the Q arm who were transfusion independent at BL, 20 (55.6%) maintained transfusion independence post-BL (12 with HSCT; 8 without; mean [SD] duration, 208 [203.1] days). Transfusion independence could not be assessed in the SC arm. Transfusion data was not collected after the end of treatment, and most pts in the SC arm were treated for < 56 days. In the Q arm, median OS (95% CI) was longer in pts with CRi (7.5 [5.4-9.9] mo) vs pts with PR (6.1 [5.1-7.2] mo) or NR (4.1 [3.3-5.9] mo) (Figure 1); respective medians in the SC arm were 8.8 (6.3-20.8), 7.8 (5.4-28.2), and 3.8 (2.7-4.7) mo. In the 34 pts in the Q arm with a last response of CRi prior to allogeneic HSCT, median OS (95% CI) was 25.1 (9.9-NA) mo; in the SC arm (n = 9), median OS (95% CI) was 20.1 (4.3-NA) mo. In the Q arm, median OS (95% CI) was longer in pts with CRi who became transfusion independent post-BL vs pts who did not (27.1 [10.4-NA] vs 5.3 [4.6-6.4] mo); similarly, median OS (95% CI) was longer in pts who maintained transfusion independence vs pts who did not (25.1 [11.4-NA] vs 9.6 [4.6-NA] mo). Conclusions: Q induced rapid, durable, and consistent tumor control in pts with FLT3-ITD R/R AML irrespective of prior therapy, including HSCT. A high proportion of pts with CRi became eligible for HSCT, the only potential curative treatment option. Moreover, a high proportion achieved durable transfusion independence regardless of HSCT, which is also associated with clinical benefit. These data highlight the clinical benefit of achieving CRi with Q in pts with FLT3-ITD R/R AML, a population with a high unmet need. Disclosures Levis: Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Amgen: Consultancy, Honoraria; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria. Ganguly:Daiichi Sankyo: Research Funding; Seattle Genetics: Speakers Bureau; Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board. Khaled:Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support; Omeros: Consultancy. Krämer:BMS: Research Funding; Bayer: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees. Martinelli:Novartis: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Other: trial grant; Amgen: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant. Perl:BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau. Choi:Daiichi Sankyo: Employment. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Mendell:Daiichi Sankyo, Inc.: Employment. Mires:Daiichi Sankyo: Employment. Zhang:Daiichi Sankyo: Employment. Cortes:Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Sun Pharma: Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; BiolineRx: Consultancy; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Biopath Holdings: Consultancy, Honoraria; Takeda: Consultancy, Research Funding; Immunogen: Consultancy, Honoraria, Research Funding.

Introduction: R/R FLT3-ITD AML is an aggressive hematologic malignancy with a generally poor prognosis and high relapse rate even after allogeneic hematopoietic stem cell transplantation (HSCT). QuANTUM-R (NCT02039726), a large, global, phase 3, randomized, controlled trial, showed that single-agent quizartinib significantly prolonged overall survival (OS) vs salvage chemotherapy (SC) in patients with R/R FLT3-ITD AML after first-line treatment with or without HSCT (Cortes et al, Lancet Oncol 2019). To evaluate both quality and quantity of life for patients with R/R FLT3-ITD AML, we conducted a Q-TWiST analysis of QuANTUM-R data to compare survival between patients receiving quizartinib and SC adjusted for quality of life (QOL). Methods: The primary analysis cohort was the intent-to-treat (ITT) QuANTUM-R population, which included 367 patients (245 patients receiving quizartinib; 122 patients receiving SC). The secondary analysis cohort was the per-protocol analysis set (PPS), which excluded patients randomized but not treated and patients with major protocol violations who would affect assessment of efficacy endpoints (231 patients receiving quizartinib; 88 patients receiving SC). Each patient's OS was partitioned into 3 health states: time with any grade 3/4 treatment-emergent adverse events (TEAEs) before relapse (TOX), time without relapse or grade 3/4 toxicity (TWiST), and time after relapse (REL). Q-TWiST was assessed at 104 weeks (approximate median follow-up of QuANTUM-R) as the mean time spent in each state weighted by its respective QOL, represented by health utility (u; 0.0-1.0). Q-TWiST was calculated as follows: Q-TWiST = u(TWiST) × TWiST + u(TOX) × TOX + u(REL) × REL for which u(TWiST), u(TOX), and u(REL) represent the utilities applied to the restricted mean time in TWiST, TOX, and REL, respectively. Relative Q-TWiST gain (ie, Q-TWIST gain divided by mean OS of salvage chemotherapy) of ≥ 15% was considered clinically important, based on published minimally important difference norms (Revicki et al, Qual Life Res 2006). The base case that assessed the Q-TWiST difference between quizartinib and SC for the ITT population included any grade 3/4 TEAEs and set utilities at commonly assumed values: u(REL) = u(TOX) = 0.5, relative to u(TWiST) = 1.0. A sensitivity analysis was conducted for which u(TOX) and u(REL) were varied from 0.0 to 1.0. The following additional scenarios analyses were conducted: (1) including only treatment-related (TR) grade 3/4 TEAEs, (2) assessing Q-TWiST difference between quizartinib and SC for the PPS cohort, and (3) including only TR grade 3/4 TEAEs for the PPS cohort. 95% CIs were estimated via nonparametric bootstrap. Results: For the ITT population, quizartinib was associated with a mean OS gain of 8.5 weeks vs SC at 104 weeks from randomization (Table). In base case, the mean (95% CI) Q-TWiST gain at 104 weeks for quizartinib vs SC was 6.7 weeks (1.7-12.3; relative gain, 20.3%), which was statistically significant and clinically meaningful (Table). For the sensitivity analysis for which u(TOX) and u(REL) were varied from 0.0 to 1.0, Q-TWiST gains for quizartinib ranged from 5.0 (u[REL] = u[TOX] = 0.0) to 8.5 weeks (u[REL] = u[TOX] = 1.0). The relative Q-TWiST gains for quizartinib vs SC remained clinically important, irrespective of the values for u(TOX) and u(REL) and ranged from 15.2% to 25.5% (Figure). In the scenario analyses (Table), (1) when only TR grade 3/4 TEAEs were included, the Q-TWiST gain for quizartinib was 7.4 weeks (2.2-13.0; relative gain, 22.5%), (2) in the PPS cohort, the mean (95 % CI) Q-TWiST gain for quizartinib was 6.9 weeks (0.8-13.5; relative gain, 20.7%), and (3) when including only TR grade 3/4 TEAEs in the PPS, the Q-TWiST gain for quizartinib was 7.5 weeks (1.5-14.2; relative gain, 22.5%). Conclusions: Quizartinib significantly prolonged quality-adjusted survival vs SC in patients with R/R FLT3-ITD AML after disease control, safety, and QOL were accounted for, providing evidence of meaningful clinical benefit in a patient population with few treatment options. To put these results in perspective, the relative Q-TWiST gains for quizartinib reported herein are larger than nearly 90% of the relative Q-TWiST gains reported in a recent systematic review of 81 Q-TWiST comparisons across 13 cancers (Solem et al, Exp Rev Pharmacoecon Outcomes Res 2018). Disclosures Cortes: Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; BiolineRx: Consultancy; Sun Pharma: Research Funding. Ganguly:Daiichi Sankyo: Research Funding; Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau. Khaled:Omeros: Consultancy; Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Levis:Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding. Martinelli:Janssen: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria; Amgen: Consultancy, Other: trial grant; Novartis: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant. Perl:Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau. Botteman:Pharmerit International: Employment, Equity Ownership; Alnylam Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy, Research Funding. Shah:Merck: Research Funding; Bayer: Research Funding; Pfizer: Research Funding. Luo:Pharmerit International: Employment. Shun:Daiichi Sankyo: Employment. Ray:Daiichi Sankyo: Employment, Equity Ownership.

Background: Quizartinib, a once-daily, oral, highly potent and selective FLT3 inhibitor, demonstrated a significant improvement in survival vs SC in FLT3-ITD-positive R/R AML in the global, randomized, phase 3 QuANTUM-R study (Cortes et al. Lancet Oncol, 2019; NCT02039726). Patients with R/R FLT3-ITD-positive AML were randomized 2:1 to receive single agent quizartinib or investigator's choice of pre-selected SC. We investigated the effects of baseline co-mutations and FLT3-ITD VAF on overall survival (OS) and response (composite complete remission [CRc]) to quizartinib and SC in QuANTUM-R. Methods: We analyzed 37 recurrently mutated genes in AML in baseline bone marrow samples from 304 patients (82.8% of ITT population [N = 367; quizartinib, n = 245; SC, n = 122]) with R/R FLT3-ITD-positive AML using next-generation sequencing and a customized Archer® Core Myeloid panel. Positive mutation status was defined as ≥ 1 mutation detected in the gene region using a VAF cutoff of 2.7%. FLT3-ITD VAF was measured separately by the Navigate BioPharma FLT3 Mutation Assay (polymerase chain reaction-based, VAF cutoff of 3%). Low and high FLT3-ITD VAF were defined as ≤25% and >25%, respectively. Results: In addition to FLT3-ITD, 5 key co-mutations were detected: DNMT3Amut (n = 182/304 [59.9%]), NPM1mut (n = 168/304 [55.3%]), TET2mut (n = 98/304 [32.2%]), IDH1/2mut (n = 49/304 [16.1%]) and CEBPAmut (n = 46/304 [15.1%]). Median OS was numerically longer with quizartinib vs SC in patients with DNMT3Amut, TET2mut, IDH1/2mut and NPM1mut, but not CEBPAmut (Table). CRc rates were numerically higher with quizartinib vs SC for each of the 5 key baseline co-mutations. For single gene mutations, the longest median OS was seen in patients with CEBPAmut treated with quizartinib or SC (37 and 37.6 weeks, respectively). As the majority of NPM1mut patients were also DNMT3Amut (138/168, 82%), we examined various permutations of these two mutations. Patients with NPM1wt/DNMT3Amut had significantly longer median OS with quizartinib vs SC (39.3 vs 19.6 weeks, respectively; HR, 0.239; P = 0.003 [Table]) while NPM1mut/DNMT3Amut patients had lower and similar median OS between the 2 arms (23.6 vs 23.4 weeks, respectively). Quizartinib treatment showed significantly longer median OS vs SC in patients with high FLT3-ITD VAF (23.9 vs 17 weeks respectively; HR, 0.689, P = 0.0148), while the median OS in patients with low FLT3-ITD VAF was similar (34.1 vs 26.6 weeks, respectively; HR, 0.857, P = 0.535). Conclusions: This is the first evaluation of the effect of baseline co-mutations on clinical outcomes in a large trial of R/R AML patients with FLT3-ITD mutations treated with quizartinib. Key co-mutations identified in this analysis were found to potentially impact treatment response and OS with quizartinib, relative to SC. Despite relatively low CRc rates in patients with IDH1/2mut, this group-as well as those with NPM1wt-derived the greatest OS benefit from quizartinib compared with SC on QuANTUM-R. CEBPA mutations were associated with high CRc rates and relatively long median OS, regardless of treatment arm. Patients with NPM1mut had a higher CRc rate with quizartinib vs SC, but this did not translate into longer survival on either arm compared with NPM1wt. A high allelic burden of FLT3-ITD at the time of salvage therapy was associated with relatively poorer median OS; quizartinib significantly improved survival of patients with high FLT3-ITD VAF relative to SC. Although these results require confirmation in an independent dataset, the modulatory effects of baseline co-mutations on treatment response and OS with quizartinib appear to differ from other FLT3 inhibitors. Our results indicate that a subset of R/R AML patients may particularly derive clinical benefit from quizartinib. Table Disclosures Perl: Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding. Cortes:Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; BiolineRx: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding. Ganguly:Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau; Daiichi Sankyo: Research Funding. Khaled:Omeros: Consultancy; Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Martinelli:Novartis: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Janssen: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Amgen: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Ariad: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria. Russell:Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau. Chang:Daiichi Sankyo: Employment. Mires:Daiichi Sankyo: Employment. Kato:Daiichi Sankyo, Inc.: Employment; Celgene: Employment, Equity Ownership. Zhang:Daiichi Sankyo: Employment. Korkhov:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Wang:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Günnel:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Sumi:Daiichi Sankyo, Inc.: Employment. Isoyama:Daiichi Sankyo Co, Ltd: Employment. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Berisha:Daiichi Sankyo: Employment. Dos Santos:Daiichi Sankyo: Employment. Levis:Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria.

Introduction: Clonal selection occurring under the selective pressure of Fms-like tyrosine kinase 3 (FLT3) tyrosine kinase inhibitor (TKI) therapy is not fully understood. To date, the most common mutations found at the time of resistance to potent and selective type II FLT3 TKIs, like quizartinib, are on-target kinase domain (KD) mutations. Activating RAS pathway mutations are a common mechanism of resistance to type I FLT3 TKIs (McMahon et al., 2019 and Zhang et al., 2019). Changes in the acute myeloid leukemia (AML) genetic landscape at relapse on single agent or combination type II FLT3 TKI therapy have not been well-characterized at the single cell (SC) level. Methods: We performed SC sequencing with a novel high-throughput SC DNA sequencing platform, Mission Bio Tapestri, on bone marrow or peripheral blood samples from 11 patients with FLT3-mutant relapsed/refractory (R/R) AML treated with quizartinib. We analyzed 13 samples from 7 patients treated with quizartinib monotherapy and 12 samples from 4 patients treated with a combination of quizartinib and omacetaxine. Results: We analyzed a mean of 6,636 cells/sample (range 2,437-13,538). Each leukemia was made up of an average of 5 clonal sub-populations (range 2-7). 5/10 patients with serial samples demonstrated increased polyclonality at relapse, with a mean of 4 clones pretreatment (range 2-6) and 5 at relapse (range 2-7). All patients had an internal tandem duplication in FLT3 (FLT3-ITD) in at least 1 clone. Using SC sequencing, we visualized distinct clones with both hetero -and homo-zygous FLT3-ITD mutations. At the time of relapse after quizartinib, 7 patients (6 on monotherapy and 1 with combination therapy) developed at least one additional FLT3 KD mutation. These on-target mutations were found either as co-mutations within the FLT3-ITD clone or in a native FLT3 clone without an ITD. 4 of these 7 patients had polyclonal KD mutations (mean 2 distinct KD mutations; range 1-3), most commonly at the D835 locus. In 6/7 patients, each KD mutation was found in separate cellular subclones. However, 1 patient had multiple KD mutations within the same subclone (at the D835 and S838 loci). In 6/7 patients who relapsed with a KD mutation, the KD mutation was the dominant clone at relapse. No clones with on-target KD mutations were present prior to therapy. However, all relapse clones containing off-target mutations, found in 3/11 patients, were present in small subclones prior to clinical relapse. As an example, 1 patient who relapsed with 2 NRAS mutations had 2 distinct pre-existing clonal NRAS mutant populations, without FLT3-ITD co-mutations, detectable at Conclusions: Single cell (SC) sequencing allows for direct measurement of clonality, co-mutational status, zygosity, and clonal evolution, which can only be inferred through traditional bulk NGS. This detail reveals that individual mutations may be present in a number of different combinations and confirms that polyclonality is common even within a single leukemia. From time of diagnosis, knowledge of which mutations co-exist in the same clone can suggest potential mechanisms of resistance and help direct treatment. On therapy, SC sequencing can conclusively demonstrate clonal selection. SC sequencing allows for detection of clones not detectable by bulk NGS. The fact that all 4 patients sequenced at the time of morphologic remission had measurable residual disease (MRD) by SC sequencing suggests the benefit of SC sequencing as a strategy for MRD detection. At the time of relapse, identifying the dominant as well as smaller clonal subsets can help direct appropriate combination targeted therapy. Despite the fact that highly selective type II agents, like quizartinib, have historically been thought to select for on-target resistance, SC sequencing highlights more diverse mechanisms of resistance including off-target mutations. Our data supports the need for effective combination therapy to delay or suppress outgrowth of resistant clones. Disclosures Jacob: Mission Bio Inc.: Employment. Durruthy-Durruthy:Mission Bio Inc.: Employment. Levis:FUJIFILM: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Amgen: Consultancy, Honoraria. Perl:Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; BioMed Valley Discoveries: Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; FujiFilm: Research Funding; Bayer: Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Smith:Astellas Pharma: Research Funding; Abbvie: Research Funding; Revolution Medicines: Research Funding; fujiFilm: Research Funding.

Introduction: The phase 3 ADMIRAL trial demonstrated that gilteritinib, a novel, potent, oral FLT3 inhibitor, significantly prolonged overall survival and resulted in higher remission rates compared with salvage chemotherapy in patients with FLT3-mutation-positive (FLT3mut+) relapsed/refractory (R/R) acute myeloid leukemia (AML; Perl AE, et al. AACR 2019), even in the presence of common co-occurring AML mutations (DNMT3A, NPM1, and WT1) (Levis MJ, et al. J Clin Oncol. 2019;37[suppl 15]:7000). However, as with other FLT3 inhibitors, patients often develop resistance after an initial response to gilteritinib. Evidence suggests that expansion of leukemic clones containing mutations in Ras/MAPK pathway genes NRAS and KRAS mediates secondary resistance to gilteritinib in patients with FLT3mut+ R/R AML, and confirms that cells with Ras/MAPK pathway mutations are FLT3mut+ (McMahon CM, et al. Cancer Discov. 2019; doi: 10.1158/2159-8290). We evaluated emerging mutations in patients who relapsed while receiving gilteritinib therapy in the ADMIRAL trial. Methods: Blood or bone marrow samples were available for 361 patients at baseline (97.3% of the intention-to-treat population [N=371]) and for 40 patients who relapsed on gilteritinib treatment. Samples were analyzed by next-generation sequencing using the Archer Core Myeloid Panel. Data were analyzed using Archer Analysis software; the variant allele frequency (VAF) cutoff was ≥2.7%. Results: Of 371 patients enrolled in the ADMIRAL trial, 247 were assigned to 120-mg/day gilteritinib and 75 (30.5%) relapsed during the study. Most relapses (n=72/75; 96.0%) occurred ≤4 weeks from the last gilteritinib dose. Forty patients who had samples available at baseline also had samples at relapse for comparison. No samples were available from patients who relapsed on chemotherapy. At relapse, 27/40 patients (67.5%) had new mutations, including mutations in Ras/MAPK pathway genes (n=18), FLT3 (n=6), WT1 (n=3), IDH1 (n=1), and GATA2 (n=1) (Table). Thirteen patients (32.5%) had no new mutations. Of the 18 patients with Ras/MAPK pathway gene mutations at relapse, 11 (61.1%) had >1 new mutation at relapse (range, 2-6). The most frequently mutated Ras/MAPK pathway gene was NRAS (n=11). Patients were also assessed for Ras/MAPK gene pathway mutations prior to gilteritinib therapy. Among all FLT3mut+ patients analyzed for co-mutated genes at baseline (n=361), 25 (6.9%) had Ras/MAPK pathway gene mutations detected (gilteritinib, n=18; salvage chemotherapy, n=7; median VAF, 13% [range, 3.4%-50%]). In contrast to the 12.0% of patients (n=3/25) who had >1 Ras/MAPK pathway gene mutation at baseline, 61.1% (n=11/18) had >1 Ras/MAPK pathway gene mutation at relapse. Notably, a considerable number of gilteritinib-treated patients who had Ras/MAPK pathway gene mutations at baseline achieved remission: the rate of CRc (ie, composite complete remission: complete remission [CR] or CR with incomplete hematologic/platelet recovery) was 38.9% (n=7/18); the rate of CR/CRh (ie, CR or CR with partial hematologic recovery) was 27.8% (n=5/18). Six patients acquired new FLT3 mutations at relapse. Five of these six patients acquired a F691L gatekeeper mutation; one of these five patients also acquired a FLT3 juxtamembrane domain point mutation. Of the three patients who acquired a WT1 mutation at relapse, one also acquired a FLT3 F691L gatekeeper mutation. The acquisition of Ras/MAPK pathway gene mutations and FLT3 F691L gatekeeper mutations at relapse was mutually exclusive. Conclusions: In patients with FLT3mut+ R/R AML who relapsed on gilteritinib therapy, Ras/MAPK pathway gene mutations and FLT3 F691L gatekeeper mutations were the most common mutational events. The presence of a Ras/MAPK pathway gene mutation at baseline did not preclude benefit from gilteritinib therapy, possibly due to fewer Ras/MAPK pathway gene mutations per patient at baseline than at relapse. The acquisition of multiple Ras/MAPK pathway gene mutations at relapse likely mediates continued engagement of Ras/MAPK signaling in patients with FLT3mut+ R/R AML receiving gilteritinib. The frequency of emergent FLT3 F691 gatekeeper mutations at relapse in patients who received 120-mg/day gilteritinib in the ADMIRAL study was similar to that observed in relapsed patients who received 20- to 450-mg/day gilteritinib (Levis MJ, et al. Blood. 2017;130[suppl 1]:2705). Table Disclosures Smith: Revolution Medicines: Research Funding; Astellas Pharma: Research Funding; fujiFilm: Research Funding; Abbvie: Research Funding. Levis:Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Daiichi Sankyo Inc: Consultancy, Honoraria. Perl:Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; BioMed Valley Discoveries: Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding. Martinelli:Daiichi Sankyo: Consultancy, Honoraria; Roche: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant; Janssen: Consultancy, Other: trial grant; Amgen: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Novartis: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant. Berman:Astellas: Membership on an entity's Board of Directors or advisory committees, Research Funding. Montesinos:Karyopharm: Membership on an entity's Board of Directors or advisory committees, Other: Research support; Pfizer: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research support, Speakers Bureau; Teva: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research support, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Research support, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Baer:Abbvie: Research Funding; Astellas: Research Funding; Al Therapeutics: Research Funding; Forma: Research Funding; Incyte: Research Funding; Kite: Research Funding; Takeda: Research Funding. Larson:Celgene: Consultancy; Agios: Consultancy; Novartis: Honoraria, Other: Contracts for clinical trials. Yokoyama:Astellas: Other: Travel expenses. Recher:Incyte: Honoraria; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sunesis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Macrogenics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Yoon:MSD: Consultancy; Kyowa Hako Kirin: Research Funding; Janssen: Consultancy; Genentech, Inc.: Research Funding; Amgen: Consultancy, Honoraria; Yuhan Pharma: Research Funding; Novartis: Consultancy, Honoraria. Hill:Astellas: Employment; Ligacept, LLC.: Other: Stock, Patents & Royalties. Rosales:Astellas: Employment. Bahceci:Astellas: Employment, Patents & Royalties.

Introduction: Older patients with high-risk myeloid malignancies are now eligible for either induction chemotherapy (IC) or novel treatment strategies including liposomal cytarabine and daunorubicin (Vyxeos) or hypomethylating agent (HMA)/venetoclax. Vyxeos and HMA/venetoclax may be associated with less early mortality, but no trials have demonstrated significantly less mortality compared to IC. In this context, we need a better tool to determine a patient's risk of early mortality by strategy in order to inform therapy selection for older patients. The current methods to assess a patient's fitness for IC are the Eastern Cooperative Oncology Group (ECOG) or Karnofsky Performance Status (KPS) assessments, clinician subjective evaluations [i.e. gestalt (CG)], and often age itself (>75-80 years). None of these include objective measures of fitness. The Fried frailty phenotype (FP) uses both subjective (exhaustion and activity level) and objective measures (weight loss, gait speed, and grip strength) of frailty to categorize patients into fit, pre-frail, and frail. We hypothesized that FP would correlate with early mortality in this population and could be used to guide initial treatment selection. Methods: From September, 2018 to June, 2019 we prospectively enrolled 30 patients age 60 years or older with newly diagnosed, untreated acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) on an ongoing institutional review board approved clinical trial. We performed FP, CG, hematopoietic cell transplantation-comorbidity index (HCT-CI), and ECOG assessments on all patients prior to initiation of any therapy for their high grade myeloid disease. The primary endpoints were 60 and 100-day mortality. Results: Median patient age and follow up were 70.9 (range 61-82) years and 111 days, respectively. Patients had high-risk disease features as shown in Table 1, with the vast majority of AML patients being adverse risk by European Leukemia Network criteria and all MDS patients being high or very high-risk by the Revised International Prognostic Scoring System. The most common molecular mutations were TP53, ASXL1, RUNX1, IDH1/2, FLT3, and DNMT3A. IC consisting of either 7+3 or Vyxeos was used in 11 patients, HMA alone or in combination in 16, targeted therapy with enasidenib alone in 1, and best supportive care (BSC) in 2 (Table 1). Four patients who were frail by FP received IC (3 with Vyxeos). By FP assessments, 17% of patients were fit (score 0), 33% were pre-frail (score 1-2), and 50% were frail (score 3-5). In contrast, CG categorized 37% of patients as fit, 30% as pre-frail, and 33% as frail. Seven of 15 frail patients by FP were categorized as pre-frail or fit by CG. FP and ECOG scores also differed with 7 patients having low-risk ECOG scores of 0-1 and a high-risk FP of ≥3 (frail). For entire cohort, 60- and 100-day mortality rates were 15% and 25%, respectively. Frail patients by FP had 60-day and 100-day mortality rates of 32% and 51%, respectively, which was significantly worse than fit and pre-frail patients, all of whom were alive at 100 days (Figure 1/2, p=.016). Of the 6 out of 15 FP frail patients who died, 1 received a HMA alone, 3 HMA with venetoclax, and 2 BSC. In patients with ECOG scores of 0-1 or those categorized as fit by CG, 100-day mortalities were 8% and 10%, respectively. Mortality for patients with HCT-CI scores of 1-2 was unexpectedly higher (34% at both 60 days and 100 days) than for patients with higher risk HCT-CI scores ≥3 (13% and 29%, respectively). Conclusion: In newly diagnosed older patients with advanced myeloid neoplasms, being frail by FP was associated with increased 60 and 100-day mortality, owing to high mortality rates with HMA based therapies. While HCT-CI scores have been significantly associated with mortality after allogeneic transplantation, we observed that these scores were not linearly associated with survival or mortality in newly diagnosed AML and high/very-high risk MDS patients. By ECOG and CG, even the low risk groups contained patient deaths, suggesting that these standard metrics may not capture certain at-risk patients. CG tended to down grade frailty scores, categorizing patients as fitter than they were by FP. As such, FP may be a useful tool to predict early mortality. Further research is warranted to determine whether mortality differs by treatment within a given FP category, which may support the use of FP to select initial therapy. Disclosures Frey: Novartis: . Gill:Novartis: Research Funding; Tmunity Therapeutics: Research Funding; Carisma Therapeutics: Research Funding; Amphivena: Consultancy; Aro: Consultancy; Intellia: Consultancy; Sensei Bio: Consultancy; Carisma Therapeutics: Equity Ownership. Perl:Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding. Maillard:Genentech: Consultancy; Regeneron: Consultancy. Pratz:Millenium/Takeda: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees, Research Funding. Porter:Kite: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Glenmark Pharm: Membership on an entity's Board of Directors or advisory committees; Immunovative: Membership on an entity's Board of Directors or advisory committees; American Board of Internal Medicine: Membership on an entity's Board of Directors or advisory committees; Wiley and Sons: Honoraria; Genentech: Employment. Carroll:Astellas Pharmaceuticals: Research Funding; Incyte: Research Funding; Janssen Pharmaceuticals: Consultancy. Luger:Seattle Genetics: Research Funding; Biosight: Research Funding; Ariad: Research Funding; Agios: Honoraria; Genetech: Research Funding; Daichi Sankyo: Honoraria; Onconova: Research Funding; Kura: Research Funding; Jazz: Honoraria; Celgene: Research Funding; Cyslacel: Research Funding; Pfizer: Honoraria.

Cancer-associated isocitrate dehydrogenase (IDH) mutations produce the metabolite 2-hydroxyglutarate (2HG), but the clinical utility of 2HG has not been established. We studied whether 2HG measurements in acute myeloid leukemia (AML) patients correlate with IDH mutations, and whether diagnostic or remission 2HG measurements predict survival. Sera from 223 de novo AML patients were analyzed for 2HG concentration by reverse-phase liquid chromatography-mass spectrometry. Pretreatment 2HG levels ranged from 10 to 30 000 ng/mL and were elevated in IDH-mutants (median, 3004 ng/mL), compared to wild-type IDH (median, 61 ng/mL) (P.0005). 2HG levels did not differ among IDH1 or IDH2 allelic variants. In receiver operating characteristic analysis, a discriminatory level of 700 ng/mL optimally segregated patients with and without IDH mutations, and on subsequent mutational analysis of the 13 IDH wild-type samples with 2HG levels700 ng/mL, 9 were identified to have IDH mutations. IDH-mutant patients with 2HG levels200 at complete remission had shorter overall survival compared to 2HG ≤200 ng/mL (hazard ratio, 3.9; P = .02). We establish a firm association between IDH mutations and serum 2HG concentration in AML, and confirm that serum oncometabolite measurements provide useful diagnostic and prognostic information that can improve patient selection for IDH-targeted therapies.

Abstract 2600 Background: Older patients diagnosed with acute lymphoblastic leukemia (ALL) receiving intensive induction therapy often suffer from poor outcomes due to therapy-related toxicity and high rates of relapse. We previously reported that patients age ≥60 diagnosed with ALL and treated at our institution with either hyperfractionated cyclophosphamide, vincristine, doxorubicin and dexamethasone alternating with high-dose methotrexate and cytarabine (hyperCVAD) or daunorubicin, vincristine and prednisone (DVP) induction therapies achieved comparable rates of survival. Now with longer follow-up and further analysis, we describe additional outcomes and factors predictive of survival in this patient population. Methods: Thirty-seven patients diagnosed with ALL at age ≥60 and treated at the University of Pennsylvania between July 2003 and June 2011 who received induction therapy with either hyperCVAD (≥1 A+B cycle) or DVP (phase I+II) were analyzed. HyperCVAD was administered as first described at the MD Anderson Cancer Center and DVP per the ECOG 2993/UKALL XII protocol. Therapy adjustments and bone marrow biopsy to confirm remission were performed at the discretion of the treating physician. Almost all Philadelphia chromosome (Ph) positive patients received a tyrosine kinase inhibitor. Event-free survival (EFS) was defined as the time from diagnosis to either relapse or death from any other cause. Results: Table 1 describes baseline characteristics. Table 2 describes outcomes. If achieved, morphologic remission was recognized upon the first bone marrow assessment performed while on therapy, which occurred after a median of 4 (2 A+B) cycles of hyperCVAD and by completion of phase II induction of DVP. EFS and overall survival (OS) trended in favor of DVP. HyperCVAD patients were more likely to complete intensive therapy but less likely to receive maintenance therapy, and more likely to relapse with the majority of relapses occurring off active treatment. Primary reasons for not starting or stopping maintenance therapy were infections and cytopenias. Relapsed disease was the most frequent cause of death. Table 3 describes univariate Cox regression analysis. Receipt of maintenance therapy demonstrated the strongest association with survival (p=0.0001, hazard ratio 0.06 for EFS; p=0.0002, hazard ratio 0.05 for OS). Valid multivariate analysis could not be performed due to small sample size. Conclusions: In older ALL patients treated with aggressive induction therapies and achieving remission, receipt of maintenance therapy appears to be most predictive of EFS and OS. Outcomes in the DVP and hyperCVAD groups were similar although a trend towards prolonged survival in the DVP group was seen, which may be explained by a lower rate of relapse due to a higher likelihood of remaining on therapy over time. Our findings suggest that these patients may benefit from attenuated courses of intensive initial therapy in order to avoid developing toxicities that may prohibit tolerance of prolonged maintenance therapy. Disclosures: No relevant conflicts of interest to declare.

A hallmark of cancer is the disruption of differentiation within tumor cells. Internal tandem duplication mutations of the FLT3 kinase (FLT3/ITD) occur commonly in acute myeloid leukemia (AML) and are associated with poor survival, leading to efforts to develop FLT3 kinase inhibitors. However, FLT3 inhibitors have thus far met with limited success, inducing only a clearance of peripheral blasts with minimal BM responses. Quizartinib is a novel potent and selective FLT3 inhibitor currently being studied in clinical trials. In 13 of 14 FLT3/ITD AML patients with normal karyotype treated with quizartinib, we observed terminal myeloid differentiation of BM blasts in association with a clinical differentiation syndrome. The single patient whose blasts failed to differentiate had a preexisting C/EBPα mutation and another developed a C/EBPα mutation at disease progression, suggesting a mechanism of resistance to FLT3 inhibition. In vitro, in primary blasts cocultured with human BM stroma, FLT3 inhibition with quizartinib induced cell-cycle arrest and differentiation rather than apoptosis. The present study is the first description of terminal differentiation of cancer cells in patients treated with a tyrosine kinase inhibitor. These data highlight the importance of the differentiation block in the patho-genesis of AML.

The proto-oncogene c-Myc paradoxically activates both proliferation and apoptosis. In the pathogenic state, c-Myc–induced apoptosis is bypassed via a critical, yet poorly understood escape mechanism that promotes cellular transformation and tumorigenesis. The accumulation of unfolded proteins in the ER initiates a cellular stress program termed the unfolded protein response (UPR) to support cell survival. Analysis of spontaneous mouse and human lymphomas demonstrated significantly higher levels of UPR activation compared with normal tissues. Using multiple genetic models, we demonstrated that c-Myc and N-Myc activated the PERK/eIF2α/ATF4 arm of the UPR, leading to increased cell survival via the induction of cytoprotective autophagy. Inhibition of PERK significantly reduced Myc-induced autophagy, colony formation, and tumor formation. Moreover, pharmacologic or genetic inhibition of autophagy resulted in increased Myc-dependent apoptosis. Mechanistically, we demonstrated an important link between Myc-dependent increases in protein synthesis and UPR activation. Specifically, by employing a mouse minute (L24+/–) mutant, which resulted in wild-type levels of protein synthesis and attenuation of Myc-induced lymphomagenesis, we showed that Myc-induced UPR activation was reversed. Our findings establish a role for UPR as an enhancer of c-Myc–induced transformation and suggest that UPR inhibition may be particularly effective against malignancies characterized by c-Myc overexpression.

In a randomized trial of therapy for FMS-like tyrosine kinase-3 (FLT3) mutant acute myeloid leukemia in first relapse, 224 patients received chemotherapy alone or followed by 80 mg of the FLT3 inhibitor lestaurtinib twice daily. Endpoints included complete remission or complete remission with incomplete platelet recovery (CR/CRp), overall survival, safety, and tolerability. Correlative studies included pharmacokinetics and analysis of in vivo FLT3 inhibition. There were 29 patients with CR/CRp in the lestaurtinib arm and 23 in the control arm (26% vs 21%; P = .35), and no difference in overall survival between the 2 arms. There was evidence of toxicity in the lestaurtinib-treated patients, particularly those with plasma levels in excess of 20μM. In the lestaurtinib arm, FLT3 inhibition was highly correlated with remission rate, but target inhibition on day 15 was achieved in only 58% of patients receiving lestaurtinib. Given that such a small proportion of patients on this trial achieved sustained FLT3 inhibition in vivo, any conclusions regarding the efficacy of combining FLT3 inhibition with chemotherapy are limited. Overall, lestaurtinib treatment after chemotherapy did not increase response rates or prolong survival of patients with FLT3 mutant acute myeloid leukemia in first relapse. This study is registered at www.clinicaltrials.gov as #NCT00079482.

Background: Older patients (pts) with AML unfit for intense induction chemotherapy have a poor prognosis with a 5 year survival of 6 weeks and 5 CRi patients did not reach an ANC of ≥ 500/µL. Therefore, the activity level was reduced to 1.5 µCi/kg/dose for further evaluation. Methods: This study enrolled older pts with untreated AML who were considered to be unfit for standard induction chemotherapy. Pts aged 60 to 74 years were required to have significant co-morbidities, while all pts ≥ 75 years were eligible. Other eligibility criteria included ECOG PS 0-2, CD33 expression on > 25% of blasts, and a peripheral blast count Results: 18 pts were included in this prespecified Interim Analysis. An additional 9 pts were treated at this dose and will be included in an updated analysis at the ASH meeting. The median age of the 18 pts was 73.5 years (range 60-87) and median ECOG Performance Status was 1 (0 in 3 pts, 1 in 9 pts, & 6 in 2 pts). 11 pts had prior AHDs (6 MDS, 2 CMML, 2 NHL, 1 myelofibrosis), and 9 had prior treatment for AHDs. Of the pts with known cytogenetic and molecular genetic results, 1 had favorable-risk, 3 had intermediate-risk, and 5 had adverse-risk AML using NCCN guidelines. The median baseline BM blast % was 40.5% (range, 22-66%) with a median CD33 expression of 62% (range, 26-100%) of AML cells. Objective responses were seen in 4 pts (22%): 3 complete remissions with incomplete platelet count recovery (CRp) and 1 complete remission with incomplete hematologic recovery (CRi). Among the responders with known cytogenetics, 1 pt had adverse genetics and 1 had Intermediate-risk genetics.Of the pts with remission, 3 had CT genotype for the CD33 splicing polymorphism SNP rs12459419 (including 2 CRp) and 1 had CC genotype. 3 of the responders are in follow up at Days 59, 169 and 266 without further treatment. Myelosuppression was seen in all pts including Grade 4 thrombocytopenia with marrow aplasia for > 6 weeks after the first dose in 4 pts. 1 pt with prior MDS had pancytopenia for > 4 months. The 3 pts with CRp achieved an ANC ≥ 1000/µL at Days 28, 38, and 40 from the first dose of 225Ac-lin. The pt with CRi did not reach an ANC of 500/µL. Non hematologic Grade ≥3 Treatment-Emergent adverse events (AEs) that were at least possibly related were 4 patients with febrile neutropenia, as well as 1 patient each with fungal pneumonia, acute respiratory failure, pulmonary edema, chest pain, sepsis, gastric hemorrhage, generalized muscle weakness, atrial fibrillation with rapid ventricular response and typhilitis. No pts had an infusion-related reaction requiring dose interruption. Veno-occlusive disease did not occur. The 30-day mortality rate was 16.7% (1 cardiac arrest and 2 with multi organ failure). Conclusions: Preliminary data from this Interim Analysis of 225Ac-lin monotherapy in older AML pts unfit for intensive therapy indicate a lower rate of myelosuppression at 1.5 µCi/kg/dose but also a lower response rate than was seen at 2.0 µCi/kg/dose. Although the study met the prespecified response criteria for continuing enrollment, it will be closed to further accrual in recognition that targeted radiation, like other therapies, will likely have the best outcomes when used in combination with other therapies in pts with active AML. An extensive development program in AML, MDS, and multiple myeloma is planned. One study will utilize 225Ac-lin in combination with salvage chemotherapy and another with venetoclax. 225Ac-lin will be used as a single agent for AML postremission therapy. In addition, 225Ac-lin will be used as targeted conditioning prior to hematopoietic stem cell transplant in pts with MDS with a complex karyotype and as a conditioning agent prior to autologous transplant in MM. Table. Table. Disclosures Atallah: Jazz: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Abbvie: Consultancy; BMS: Consultancy. Orozco:Actinium Pharmaceuticals: Research Funding. Craig:Novartis: Research Funding; Actinium Pharmaceuticals: Research Funding; Celgene: Research Funding. Levy:Takeda (Millennium Pharmaceuticals, Inc.): Consultancy. Finn:Ochsner Clinic Foundation: Employment. Perl:NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy; Astellas: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees. Park:Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Consultancy, Research Funding; Shire: Consultancy; AstraZeneca: Consultancy; Adaptive Biotechnologies: Consultancy; Kite Pharma: Consultancy; Pfizer: Consultancy; Novartis: Consultancy. Roboz:Astex Pharmaceuticals: Consultancy; Bayer: Consultancy; Aphivena Therapeutics: Consultancy; Celltrion: Consultancy; Celgene Corporation: Consultancy; Novartis: Consultancy; Celgene Corporation: Consultancy; Pfizer: Consultancy; Argenx: Consultancy; Roche/Genentech: Consultancy; AbbVie: Consultancy; Cellectis: Research Funding; Aphivena Therapeutics: Consultancy; Roche/Genentech: Consultancy; Sandoz: Consultancy; Bayer: Consultancy; Sandoz: Consultancy; Jazz Pharmaceuticals: Consultancy; Otsuka: Consultancy; Astex Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Orsenix: Consultancy; Janssen Pharmaceuticals: Consultancy; AbbVie: Consultancy; Jazz Pharmaceuticals: Consultancy; Argenx: Consultancy; Janssen Pharmaceuticals: Consultancy; Eisai: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Eisai: Consultancy; Orsenix: Consultancy; Cellectis: Research Funding; Daiichi Sankyo: Consultancy; Novartis: Consultancy; Celltrion: Consultancy. Tse:Brown Cancer Center, University of Louisville School of Medicine: Employment; Jazz: Consultancy; Amgen: Consultancy; Amgen: Honoraria; Amgen: Honoraria. Mawad:Swedish Cancer Institute: Employment. Rizzieri:Novartis: Consultancy; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Arog: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Berger:Actinium Pharmaceuticals: Employment, Equity Ownership. Jurcic:Astellas: Research Funding; Daiichi-Sankyo: Research Funding; Incyte: Consultancy; Celgene: Research Funding; AbbVie: Consultancy, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Forma Therapeutics: Research Funding; Syros Pharmaceuticals: Research Funding; Actinium Pharmaceuticals, Inc: Research Funding; Genetech: Research Funding; Kura Oncology: Research Funding.

AML (acute myeloid leukemia) is increasingly being treated with precision medicine. To better inform treatment, the mutational content of patient samples must be determined. However, current tumor sequencing paradigms are inadequate to fully characterize many instances of the disease. A major challenge has been the unambiguous identification of potentially rare and genetically heterogeneous neoplastic cell populations, capable of critically impacting tumor evolution and the acquisition of therapeutic resistance. Standard bulk population sequencing is unable to identify rare alleles and definitively determine whether mutations co-occur within the same cell. Single-cell sequencing has the potential to address these key issues and transform our ability to accurately characterize clonal heterogeneity in AML. Previous single-cell studies examining genetic variation in AML have relied upon laborious, expensive and low-throughput technologies that are not readily scalable for routine analysis of the disease. We applied a newly developed platform technology to perform targeted single-cell DNA sequencing on over 140,000 cells and generated high-resolution maps of clonal architecture from AML tumor samples. Marrow and/or peripheral blood samples were collected prior to, during treatment, and at clinical progression to the FLT3 inhibitor gilteritinib given on a clinical trial for relapsed/refractory AML with FLT3 mutation. Single-cell sequencing of multiple patient samples demonstrated that relapse clones acquired oncogenic RAS mutations. We utilized the high-throughput and sensitivity of our single-cell approach to more definitively assess where in the course of treatment these RAS mutated clones were acquired. Oncogenic RAS harboring clones, comprising between 0.4%, and 0.1% of tumor populations, were identified in patient samples either prior to or shortly after onset of treatment. Significantly, these RAS variant alleles were not detectable with targeted bulk sequencing. Throughout the course of treatment with the FLT3 inhibitor gilteritinib, the RAS mutant clones selectively expanded and were responsible for resistance to therapy and relapse. These findings point to the presence of underlying genetic heterogeneity in AML and demonstrate the utility of sensitively assaying clonal architecture to better inform patient stratification and therapy selection. Disclosures Eastburn: Mission Bio, Inc.: Employment, Equity Ownership. Durruthy-Durruthy:Mission Bio, Inc.: Employment, Equity Ownership. Smith:Astellas Pharma: Research Funding. Perl:Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; Arog: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Introduction: Midostaurin was the first multikinase inhibitor approved in combination with daunorubicin and cytarabine induction and high-dose cytarabine (HiDAC) consolidation chemotherapy for the treatment of adults with newly diagnosed FLT3-mutation-positive (mut+) acute myeloid leukemia (AML). Approval was largely based on the results from the phase 3 RATIFY trial; patients who received midostaurin had significantly improved overall and event-free survival than those who received placebo (Stone et al, N Engl J Med, 2017). RADIUS-X (NCT02624570) is an expanded treatment protocol (ETP) designed to provide access to midostaurin during the US Food and Drug Administration's review process and to extend the understanding of the safety and tolerability of midostaurin in patients with newly diagnosed FLT3-mut+ AML. The safety profile of midostaurin in preliminary data from RADIUS-X was consistent with that in the RATIFY study (Roboz et al, Blood, 2017 [abstract 1338]). Here we report updated safety data for midostaurin during induction and consolidation and safety data during the maintenance phase. Methods: In this open-label, single-arm ETP, patients (aged ≥18 years) received 1-2 cycles of induction therapy (cytarabine plus daunorubicin [60-90 mg/m2/day] or idarubicin [12 mg/m2/day]) and up to 4 cycles of HiDAC consolidation chemotherapy plus midostaurin (50 mg twice daily [bid] on days 8-21 of each 28-day cycle), followed by up to 12 months of single-agent midostaurin (50 mg bid on days 1-28). Patients could enroll at any point before completion of a second cycle of consolidation. Patients achieving complete remission (CR) or CR with incomplete hematologic recovery (CRi) after induction proceeded to consolidation; patients who maintained a response were eligible to proceed to maintenance. The primary endpoints were safety and tolerability of midostaurin. Results: Of 111 patients screened, 103 were enrolled in the study: 47 during induction (46%) and 56 during consolidation (54%) (Figure). The median age was 58 y (range, 19-79 y); all patients were FLT3-mut+ (Table). Of 47 patients enrolled during induction, 15 received daunorubicin and 32 received idarubicin as the anthracycline. Of 35 patients who completed consolidation and entered maintenance, 9 had completed the protocol treatment and 3 remained on therapy at the data cutoff date (March 30, 2018). The CR/CRi rate for the induction phase was 74% (57% CR, 17% CRi). The relapse rate was 14% overall. The most common reason for study discontinuation was proceeding to transplant (overall, 52%; induction, 11%; consolidation, 42%; maintenance, 34%). The median duration of midostaurin exposure was 35 days (range, 3-426 days). Dose adjustment or interruption due to adverse events (AEs) occurred in 26 patients, most commonly due to febrile neutropenia (n=9) and gastrointestinal disorders (n=6). No new safety events were observed with longer follow-up. Most patients (99%) experienced ≥1 any-grade AE, mostly during induction and/or consolidation. Due to the timing of patient enrollment (up to the second cycle of consolidation), hematologic AEs were lower than reported in comparable studies. The most common AEs occurring in ≥20% of patients were febrile neutropenia (53%), nausea (42%), diarrhea (37%), anemia (36%), platelet count decreased (31%), fatigue (23%), headache (22%), and vomiting (22%). Serious AEs occurred in 50% of patients overall, most commonly febrile neutropenia (37%). AEs during induction were generally similar, regardless of anthracycline received. Overall, 9 patients discontinued due to AEs: 5 during induction (febrile neutropenia, blood bilirubin increased, electrocardiogram QT prolonged, renal impairment, and respiratory distress), 1 during consolidation (sepsis), and 1 during maintenance (leukocytosis). During maintenance, 16 of 35 patients (46%) reported any-grade AEs with midostaurin monotherapy; the most common any-grade and grade 3/4 AEs occurring in >1 patient were platelet count decrease (11% and 3%), nausea (9% and 0%), and oropharyngeal pain (6% and 0%).The rate of death during the study was low, with 1 death reported (disease progression). Conclusions: Midostaurin continued to demonstrate a manageable safety profile with longer follow-up and was associated with high transplant and low relapse rates. Maintenance therapy with midostaurin was well tolerated; no new safety signals were observed. Disclosures Perl: Daiichi Sankyo: Consultancy; Arog: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees. Sweet:Agios: Consultancy; Novartis: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria; Incyte: Research Funding; Bristol Myers Squibb: Honoraria; Jazz Pharmaceuticals: Honoraria, Speakers Bureau; Celgene: Speakers Bureau. Roboz:Novartis: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Consultancy; Eisai: Consultancy; Janssen Pharmaceuticals: Consultancy; Argenx: Consultancy; Orsenix: Consultancy; Aphivena Therapeutics: Consultancy; Daiichi Sankyo: Consultancy; Roche/Genentech: Consultancy; Orsenix: Consultancy; Celgene Corporation: Consultancy; Celltrion: Consultancy; Jazz Pharmaceuticals: Consultancy; Celltrion: Consultancy; Cellectis: Research Funding; Jazz Pharmaceuticals: Consultancy; Sandoz: Consultancy; Otsuka: Consultancy; Otsuka: Consultancy; Roche/Genentech: Consultancy; Pfizer: Consultancy; AbbVie: Consultancy; Janssen Pharmaceuticals: Consultancy; Bayer: Consultancy; Astex Pharmaceuticals: Consultancy; Eisai: Consultancy; Aphivena Therapeutics: Consultancy; Argenx: Consultancy; Celgene Corporation: Consultancy; AbbVie: Consultancy; Bayer: Consultancy; Novartis: Consultancy; Astex Pharmaceuticals: Consultancy; Cellectis: Research Funding; Sandoz: Consultancy. Strickland:Astellas Pharma: Consultancy; Boehringer Ingelheim: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Baxalta: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sunesis Pharmaceuticals: Consultancy, Research Funding; Tolero Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bonifacio:Novartis: Employment. Haines:Novartis: Employment. Barbera:Novartis: Employment. Purkayastha:Novartis Pharmaceuticals Corporation: Employment.

Introduction: Venous thromboembolism (VTE) is a significant adverse event in adults receiving pegaspargase (PEG) for acute lymphoblastic leukemia (ALL). PEG increases VTE risk by depletion of antithrombin III (AT). Heparin requires adequate AT for anticoagulation. Younger adults with T-cell ALL receiving prednisone may be particularly at risk. Retrospective series (most with L-asparaginase) suggest AT supplementation may decrease VTE, however prospective data in adults beyond induction is limited while the optimal dose of AT remains undefined and varies across series. We reviewed adults at our institution who received PEG for ALL to assess the incidence of VTE within our AT supplementation practice. Laboratory and cost data for AT repletion were also analyzed. Methods: Adults who received PEG for ALL between 11/2015 and 7/2018 were retrospectively identified. Institutional recommendations were to supplement AT if serum AT < 60% following PEG for at least the first 2 courses (induction/consolidation). AT levels were assessed twice weekly until normalized. AT supplementation following additional cycles was recommended for all patients receiving therapeutic anticoagulation. Pharmacists calculated the AT dose using a repletion factor of 80-120%, rounded to the nearest vial. After VTE, patients received therapeutic enoxaparin throughout all remaining PEG doses, with enoxaparin held only if platelets < 50,000/mcL or for procedures. After 3/2018, all patients receiving PEG also received enoxaparin prophylaxis when platelets >30,000/mcL. A retrospective analysis was done to assess the incidence of VTE. Secondary endpoints included an assessment of VTE risk factors, ability to achieve therapeutic AT levels with supplementation and to characterize drug therapy costs with AT supplementation. Results: Thirty-one patients (30 newly diagnosed, 1 in relapse) with ALL received ≥ 1 dose of PEG followed by AT supplementation. Seventeen of 31 patients were adolescent/young adults (AYA) and 13/31 had T cell ALL. Additional patient characteristics are summarized in table 1. The incidence of VTE was 19%, with 7 VTEs identified in 6 patients. Two patients developed CNS thrombosis (1 fatal), 1 had a pulmonary embolism, and the remainder were upper extremity VTE. Six of 7 VTE occurred during the first two courses at a mean of 66 days (range 6-225) following the first PEG dose. Patients with VTE had a median platelet count of 118/mcL (range 34-377) and a mean AT nadir of 53% (36-98) within 72 hours of VTE. Two of 7 events occurred despite enoxaparin prophylaxis. Five of 6 (83%) patients with VTE had T-ALL; which was more common in the VTE vs. no-VTE group (p = 0.01). The incidence of VTE within the T-ALL group was 38%. Patients with VTE were all AYA and were younger than those without VTE (median 31 vs. 42 years, p = 0.06). Patients with VTE received a higher mean PEG dose than patients without VTE (4589 vs. 3504 units, p < 0.0001), reflective of the more aggressive dosing in the AYA regimen. Six of 7 VTEs occurred during a course containing prednisone (p = 0.08 vs. dexamethasone). AT nadirs during cycles with VTE were similar to cycles without VTE. No clinically significant bleeding occurred. Characteristics of patients with VTE are summarized in table 2. Overall the mean time to AT nadir was 11 days. Therapeutic AT (> 60%) following supplementation occurred 56% of the time. Most AT doses (89%) were calculated with a correction factor of 80-89%. The probability of obtaining a therapeutic AT increased when a higher repletion factor (> 90%) was used (76% vs. 52%, p = 0.06). Patients received a mean of 1.9 (0-6) doses of AT per PEG dose, and a mean of 5.9 (1-21) AT doses throughout treatment. The mean AT supplementation cost per PEG dose was $11,663 with 186 doses administered ($3.22/unit). Conclusions: VTE occurred in 19% of patients receiving AT supplementation following PEG, with 2/7 events involving the CNS. The risk of VTE was greatest in younger adults with T-ALL receiving concurrent prednisone and higher doses of PEG. AT levels were low at the time of VTE in most patients, however nadirs were similar compared to courses not complicated by VTE. Routine or augmented VTE prophylaxis and a higher AT repletion goal (> 90%) may further limit VTE risk but given the cost and patient inconvenience, prospective evaluation is needed to confirm the benefit. Disclosures Frey: Servier Consultancy: Consultancy; Novartis: Consultancy. Perl:Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees. Porter:Genentech: Other: Spouse employment; Novartis: Other: Advisory board, Patents & Royalties, Research Funding; Kite Pharma: Other: Advisory board.

Introduction: CPX-351 (liposomal cytarabine and daunorubicin; VYXEOS) improves survival and complete remission rates compared to standard induction chemotherapy (7+3) in patients 60 to 75 years old with newly diagnosed myelodysplastic syndrome (MDS)-associated and therapy-related AML (Lancet et al., JCO 2018) and was approved by the U.S. Food and Drug Administration in August 2017. In addition to patients with a known history of MDS or cytotoxic and/or radiotherapy, patients with de novo AML with WHO-defined MDS-related cytogenetic changes are also eligible for CPX-351. We have implemented a diagnostic clinical pathway for patients with newly diagnosed AML which includes rapid FISH assessment for the most common MDS-defining karyotypes in patients who are potential candidates for CPX-351. We reviewed outcomes after the first year of this diagnostic pathway in our institutional cohort comparing results of chromosome metaphase analysis and rapid FISH. Methods: We performed both rapid MDS-FISH testing (turnaround time < 6 hours) and metaphase analysis on all patients who presented to the University of Pennsylvania from 9/2017 through 6/2018 with newly diagnosed AML who were potential candidates for CPX-351 induction therapy based on age and other clinical factors. Our MDS-FISH panel includes probes for EGR1(5q31)/5p15.2, D7S486(7q31)/CEP7, and TP53(17p13.1)/NF1(17q11.2) (MetaSystems). Results of the limited FISH testing were compared with metaphase chromosome analysis. Demographic and clinical information was abstracted from the electronic medical record. This study was approved by the University of Pennsylvania Institutional Review Board. Results: Twenty-nine patients with newly diagnosed AML from 9/2017 through 6/2018 had both rapid MDS-FISH and karyotype testing performed. Nineteen patients (65.5%) had de novo AML, while 7 (24.1%) had a clinical history of MDS and 3 (10.3%) had a history of prior cytotoxic and/or radiation therapy. Metaphase analysis revealed WHO-defined MDS-related cytogenetic abnormalities in 14/29 patients (48.3%). Of these 14 patients, 11 (78.6%) also had positive MDS-FISH testing in >=1 probe. Of the 3 patients with MDS-related cytogenetic abnormalities that were identified by metaphase analysis but not the FISH panel, 2 had a history of either MDS (n=1) or prior cytotoxic chemotherapy (n=1) and therefore were eligible for CPX-351 based on clinical history alone. Of the 7 patients with de novo AML and MDS-defining cytogenetic abnormalities, 6 (85.7%) were identified by the FISH screen. Conclusions: Rapid FISH testing for MDS-defining cytogenetic changes using probes for abnormalities of chromosomes 5, 7, and 17 efficiently identifies the majority of patients with newly diagnosed de novo AML who do not have a clinical history of MDS or cytotoxic therapy but are eligible for induction therapy with CPX-351 based on the presence of MDS-defining cytogenetic abnormalities. The combination of rapid FISH testing and clinical history has a high sensitivity for identifying patients with MDS-defining karyotypic abnormalities. This diagnostic clinical pathway allows for the expeditious identification of patients eligible for CPX-351. Disclosures Frey: Servier Consultancy: Consultancy; Novartis: Consultancy. Perl:Astellas: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy.

Introduction: Grade 2-4 mucositis is a major complication after myeloablative (MAC) allogeneic hematopoietic transplantation (HCT) in about 90% of patients. Graft-vs-host-disease (GVHD) prophylaxis with methotrexate (MTX) exacerbates mucositis and delays engraftment. Severe mucositis precludes administration of all 4 MTX doses which increases the risk of GVHD and can prolong hospitalization due to infection, pain control, and the use of total parenteral nutrition (TPN). Leucovorin (LCV) prophylaxis following MTX is advised by the EBMT-ELN adult working group, but not universally accepted given the absence of prospective trials. Our group implemented routine LCV prophylaxis following MAC alloHCT with MTX GVHD prophylaxis in 8/2017. We compared the outcomes of these patients with historical controls. Methods: We treated 22 consecutive adults receiving MAC alloHCT with MTX GVHD prophylaxis with LCV 15 mg PO q6h x 4 doses, starting 12 h after the d +3, +6, and +11 MTX doses. Twenty-nine consecutive patients undergoing similar MAC conditioning and MTX GVHD prophylaxis were retrospectively identified as the control. Routine LCV was not given to control patients, but could have been added following d +6 or +11 MTX to limit toxicity at physician discretion. The primary endpoint was the incidence of grade 2-4 mucositis. Secondary endpoints included the duration of grade 2-4 mucositis, time to engraftment, incidence of neutropenic fever (NF) and bacteremia pre-engraftment, duration of antibacterials for NF, ability to receive all MTX doses, incidence and duration of TPN and patient-controlled analgesia (PCA) use, duration of hospitalization, incidence of acute and chronic GVHD, graft failure, and relapse. Results: Baseline characteristics between the two groups were similar (table 1). All patients received tacrolimus and MTX GVHD prophylaxis with the majority receiving Cy/TBI conditioning. Approximately 30% of controls received ≥ 1 dose of LCV (most following d +11 MTX) to limit toxicity. Although the incidence of grade 2-4 mucositis was similar with between groups (82% vs 91%, p = 0.38), a lower incidence of grade 3-4 mucositis was observed with LCV, although this did not reach statistical significance (32% vs. 55%, p = 0.16). The LCV group had a significantly shorter duration of grade 2-4 mucositis (5.6 vs. 9.7 d, p = 0.01) and less frequent PCA use (32% vs. 62%, p = 0.048). The LCV group needed TPN less often (18% vs. 38%, p = 0.21) and when needed, had a shorter duration of TPN (10 vs. 21 d, p = 0.15), although these findings did not reach statistical significance. The LCV group had a significantly shorter duration of hospitalization (28 d vs. 33.7 d, p = 0.03). Platelet engraftment seemed to be more rapid (16.5 vs 22.2 d, p = 0.097) without reaching statistical significance. The addition of LCV did not appear to impact the incidence of acute GVHD (grade 2-4: 23% vs. 14%, p = 0.47; grade 3-4 14 % vs 3%, p = 0.3) by d +100 or chronic GVHD at 1 year (14% vs. 21%, p = 0.44). No differences were observed in the time to neutrophil engraftment, or in the incidence of nephrotoxicity, hepatotoxicity, graft failure, or relapse between the arms. No other obvious practice change was implemented during the study period that would have been anticipated to impact any of these endpoints. Conclusions: The addition of LCV to MAC alloHCT with MTX GVHD prophylaxis resulted in significant reductions in the duration of grade 2-4 mucositis, frequency of PCA use, and duration of hospitalization compared to a similar historical control. We also observed less frequent grade 3-4 mucositis, more rapid platelet engraftment and less TPN use with LCV, but these findings did not reach statistical significance. Our sample size was small, which may have limited our power to detect small differences between the groups. In addition, about 30% of controls received at least 1 dose of LCV which could have biased our results toward the null. There was no increase in acute or chronic GVHD, graft failure, or relapse risk with the addition of LCV; however follow up remains relatively short. LCV prophylaxis following MTX GVHD prophylaxis warrants prospective evaluation to more definitely assess effects on mucositis, engraftment, GVHD and relapse, as well as to clearly determine the impact on resource utilization such as use of TPN, PCA, and length of hospitalization. Disclosures Frey: Novartis: Consultancy; Servier Consultancy: Consultancy. Gill:Extellia: Consultancy, Membership on an entity's Board of Directors or advisory committees; Carisma Therapeutics: Equity Ownership; Novartis: Research Funding. Perl:Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees. Stadtmauer:Celgene: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Takeda: Consultancy. Porter:Novartis: Other: Advisory board, Patents & Royalties, Research Funding; Kite Pharma: Other: Advisory board; Genentech: Other: Spouse employment.