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There are currently no known predictors of myelodysplastic syndrome (MDS)/myeloproliferative overlap neoplasm (MPN) patients’ response to hypomethylating agents (HMA). Forty-three patients with MDS/MPN who were treated with HMA during chronic phase and had next-generation sequencing using the established 63-genes panel were identified. Complete and partial remission and marrow response were assessed based on the MDS/MPN International Working Group response criteria. On univariate analysis, younger age, higher number of mutations, and mutations in SETBP1, RUNX1, or EZH2 were associated with no response. Multivariable analysis for modeling response were conducted via least absolute shrinkage and selection operator logistic regression approach, and showed that mutations in SETBP1, RUNX1, or EZH2 predict lack of HMA response. While limited by sample size, our findings suggest that genomic land-scape can potentially identify MDS/MPN patients with lower likelihood of response to HMA.

Introduction Mutations in the IDH1 or IDH2 genes are detected in approximately 20% of cases of acute myeloid leukemia (AML). Few studies have examined the impact of IDH mutations in AML on allogeneic bone marrow transplant (alloBMT) outcomes. Patients and methods In this single center study, alloBMT outcomes for 61 patients with IDH-mutated (mIDH) AML were compared to those for 146 patients with IDH-wildtype (wtIDH) AML. Results Patients with mIDH AML had a 2-year overall survival (OS) of 85% (95% CI 76%-95%), 2-year relapse free survival (RFS) of 71% (95% CI 59%-85%), 1-year cumulative incidence of relapse (CIR) of 14% (95% CI 5%-23%) and a 1-year cumulative incidence of transplant related mortality (CITRM) of 3% (95% CI 0%-8%). Patients with wtIDH had a 2-year OS of 61% (95% CI 53%-70%), 2-year RFS of 58% (95% CI 50%-67%), 1-year CIR of 27% (95% CI 20%-35%), and a 1-year CITRM of 9% (95% CI 5%-14%). In a univariate analysis cox-proportional hazard model, mIDH was associated with significantly better OS (HR 0.52, 95% CI 0.29-0.96) and a trend toward better RFS (HR 0.60, 95% CI 0.35-1.01). After controlling for donor age, diagnosis, and ELN risk category, mIDH was associated with a nonsignificantly improved OS (HR 0.54, 95% CI 0.29-1.01) and RFS (HR 0.67, 95% CI 0.39-1.15). Conclusion Among patients with mIDH AML, patients who received a peritransplant IDH inhibitor had improved OS (P = .03) compared to those who did not, but there was no detectable difference for RFS (P = .29).

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Immune suppression, exhaustion, and senescence are frequently seen throughout disease progression in acute myeloid leukemia (AML). We conducted a phase II study of high-dose cytarabine followed by pembrolizumab 200 mg i.v. on day 14 to examine whether PD-1 inhibition improves clinical responses in relapsed/refractory (R/R) AML. Overall responders could receive pembrolizumab maintenance up to 2 years. Among 37 patients enrolled, the overall response rate, composite complete remission (CRc) rate (primary endpoint), and median overall survival (OS) were 46%, 38%, and 11.1 months, respectively. Patients with refractory/early relapse and those receiving treatment as first salvage had encouraging outcomes (median OS, 13.2 and 11.3 months, respectively). Grade ≥3 immune-related adverse events were rare (14%) and self-limiting. Patients who achieved CRc had a higher frequency of progenitor exhausted CD8+ T cells expressing TCF-1 in the bone marrow prior to treatment. A multifaceted correlative approach of genomic, transcriptomic, and immunophenotypic profiling offers insights on molecular correlates of response and resistance to pembrolizumab.Significance:Immune-checkpoint blockade with pembrolizumab was tolerable and feasible after high-dose cytarabine in R/R AML, with encouraging clinical activity, particularly in refractory AML and those receiving treatment as first salvage regimen. Further study of pembrolizumab and other immune-checkpoint blockade strategies after cytotoxic chemotherapy is warranted in AML.See related commentary by Wei et al., p. 551.This article is highlighted in the In This Issue feature, p. 549

Patients ≥55 years-old with acute lymphoblastic leukemia (ALL) fare poorly with conventional chemotherapy with 5-year overall survival of ∼20%. Tyrosine kinase inhibitors and novel B-cell targeted therapies improve outcomes, but rates of relapse and death in remission remain high. Allogeneic blood or marrow transplantation (AlloBMT) provides an alternative consolidation strategy, and post-transplantation cyclophosphamide (PTCy) facilitates HLA-mismatched transplants with low rates of non-relapse mortality (NRM) and graft-versus-host disease (GVHD).The transplant database at Johns Hopkins was queried for patients ≥ 55 years old who received alloBMT for ALL using PTCy.The database included 77 such patients. Most received reduced-intensity conditioning (RIC) (88.3%), were in first remission (CR1) (85.7%), and had B-lineage disease (90.9%). For the entire cohort, 5-year relapse-free survival (RFS) and overall survival (OS) were 46% (95% CI 34-57) and 49% (95% CI 37-60). Grade 3-4 acute GVHD occurred in only 3% of patients and chronic GVHD in 13%. In multivariable analysis, myeloablative conditioning led to worse RFS (HR 4.65, p=0.001); while transplant in CR1 (HR 0.30, p=0.004), and transplant for Ph+ ALL vs. T ALL (HR 0.29, p=0.03) improved RFS. Of the 54 patients who received RIC alloBMT in CR1 for B ALL, 5-year RFS and OS were 62% (95% CI 47-74) and 65% (95% CI 51-77), respectively, with a 5-year relapse incidence of 16% (95% CI 7-27) and NRM of 24% (95% CI 13-36).RIC AlloBMT with PTCy in CR1 represents a promising consolidation strategy for B ALL patients ≥ 55 years old.NIH grants P01 CA225618 and P30 CA06973.

Immune suppression, exhaustion, and senescence are frequently seen throughout disease progression in acute myeloid leukemia (AML). We conducted a phase II study of high-dose cytarabine followed by pembrolizumab 200 mg i.v. on day 14 to examine whether PD-1 inhibition improves clinical responses in relapsed/refractory (R/R) AML. Overall responders could receive pembrolizumab maintenance up to 2 years. Among 37 patients enrolled, the overall response rate, composite complete remission (CRc) rate (primary endpoint), and median overall survival (OS) were 46%, 38%, and 11.1 months, respectively. Patients with refractory/early relapse and those receiving treatment as first salvage had encouraging outcomes (median OS, 13.2 and 11.3 months, respectively). Grade ≥3 immune-related adverse events were rare (14%) and self-limiting. Patients who achieved CRc had a higher frequency of progenitor exhausted CD8+ T cells expressing TCF-1 in the bone marrow prior to treatment. A multifaceted correlative approach of genomic, transcriptomic, and immunophenotypic profiling offers insights on molecular correlates of response and resistance to pembrolizumab. Significance: Immune-checkpoint blockade with pembrolizumab was tolerable and feasible after high-dose cytarabine in R/R AML, with encouraging clinical activity, particularly in refractory AML and those receiving treatment as first salvage regimen. Further study of pembrolizumab and other immune-checkpoint blockade strategies after cytotoxic chemotherapy is warranted in AML. See related commentary by Wei et al., p. 551. This article is highlighted in the In This Issue feature, p. 549

Allogeneic blood or marrow transplantation (alloBMT) is standard of care for adults with Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph+ ALL) in first complete remission (CR1). The routine pretransplant and posttransplant use of tyrosine kinase inhibitors (TKIs) has dramatically improved outcomes, but the optimal conditioning regimen, donor type, and TKI remain undefined. The bone marrow transplant database at Johns Hopkins was queried for adult patients with de novo Ph+ ALL who received alloBMT using posttransplantation cyclophosphamide (PTCy) as a component of graft-versus-host disease (GVHD) prophylaxis from 2008 to 2018. Among transplants for Ph+ ALL, 69 (85%) were performed in CR1, and 12 (15%) were performed in second or greater remission (CR2+). The majority of transplants (58%) were HLA haploidentical. Nearly all patients (91.4%) initiated TKI posttransplant. For patients in CR1, the 5-year relapse-free survival (RFS) was 66%. The use of nonmyeloablative conditioning, absence of measurable residual disease (MRD) according to flow cytometry at transplant, and the use of dasatinib vs imatinib at diagnosis were associated with improved overall survival (OS) and RFS. Neither donor type nor recipient age ≥60 years affected RFS. When analyzing all transplants, alloBMT in CR1 (vs CR2+) and the absence of pretransplant MRD were associated with improved RFS. Most relapses were associated with the emergence of kinase domain mutations. The cumulative incidence of grade 3 to 4 acute GVHD at 1 year was 9%, and moderate to severe chronic GVHD at 2 years was 8%. Nonmyeloablative alloBMT with PTCy for Ph+ ALL in an MRD-negative CR1 after initial treatment with dasatinib yields favorable outcomes.

Background: Reduced-intensity induction (RII) with imatinib yields comparable outcomes to HyperCVAD with imatinib with fewer induction deaths and an improved CR rate in Ph+ ALL (Chalandon. Blood. 2015). Dasatinib with steroids also produces excellent responses with little toxicity (Foa. Blood. 2011). Allogeneic bone marrow transplant (AlloBMT) remains the goal of therapy in Ph+ ALL based on contemporary trials with TKIs demonstrating improved survival in patients transplanted in CR1, and we have shown that transplant following induction with dasatinib yields better outcomes than with imatinib. Thus we implemented RII with dasatinib for the treatment of Ph+ ALL and compared to patients who received HyperCVAD with a 2nd generation TKI. Methods: Patients with newly diagnosed Ph+ ALL admitted to Johns Hopkins Hospital from September 2017-June 2020 underwent a 4-week RII with: vincristine 2 mg/d weekly, dexamethasone 40 mg PO weekly on days 1 and 2, and dasatinib 100 mg PO daily. CNS prophylaxis with IT MTX was given on day 8. Dexamethasone and vincristine were reduced by 50% for patients over age 70. Filgrastim was started on day 15 for patients without ANC recovery. Patients who received HyperCVAD with dose adjustments for age (Rausch et al. Cancer. 2020) from July 2011-June 2020 were included for comparison. Dasatinib 100 mg PO daily or nilotinib 400 mg PO BID were given with HyperCVAD at the discretion of the treating physician. Rituximab 375 mg/m^2 on days 1 and 8 was given based on CD20 status. Subsequent therapy after induction was not specifically mandated. Results: 21 patients received RII and 24 received HyperCVAD. The cohorts were comparable in terms of gender (38.1% female vs. 50%, p=0.55), age (median 49.8 vs. 50.3, p=0.33), age >60 (33.3% vs. 29.2%, p>0.99), median WBC at diagnosis (19 vs. 23.5, p=0.56), and the presence of decompensated DIC (fibrinogen 0.99). Among the patients treated with HyperCVAD, 15 received dasatinib (62.5%) and 9 received nilotinib (37.5%). Rituximab use was balanced between the cohorts (61.9% vs. 58.3%, p>0.99). Table 1 compares the time to ANC recovery >500, transfusion requirements within 30 days of chemotherapy initiation, rates of decompensated DIC following treatment initiation, and the duration of inpatient hospitalization for induction. While the rates of decompensated DIC were similar in each cohort, patients treated with RII required fewer platelet and pRBC transfusions. ANC recovery was faster following RII, and only 5 patients (23.8%) received growth factor support. All patients achieved a hematologic response. There was one induction death with HyperCVAD (4.2%). Most patients received a subsequent cycle of high-dose (HD) MTX and Ara-C with TKI (76.2% following RII and 91.7% following HyperCVAD). The remaining patients treated with RII subsequently received HD MTX (14.2%) or blinatumomab (9.5%) with TKI due to co-morbidities. Among those patients treated with HD MTX and Ara-C, blinatumomab was given with TKI to 6 patients (37.5%) who initially received RII and 1 patient (4.5%) after HyperCVAD (p=0.03) due to persistent MRD. As shown in Figure 1, the incidence of MRD-negativity by multi-color flow cytometry (MFC) with a sensitivity of 10-4 at day 120 after treatment initiation was similar for RII (85.4%, 95% CI 64.8-97.1) versus HyperCVAD (86.7%, 95% CI 69.8-96.6). Among patients subsequently treated with HD MTX and Ara-C, 62.5% proceeded to alloBMT after RII with an additional 12.5% currently undergoing transplant evaluation, while 86.4% proceeded to alloBMT after HyperCVAD. The 1-year RFS and OS following RII were 87.9% (95% CI 59.6-96.8) and 100% compared to 87.5% (95% CI 66.1-95.8) and 95.8% (95% CI 73.9-99.4) following HyperCVAD. Conclusion: RII with dasatinib results in fewer transfusions and less myelosuppression compared to HyperCVAD with a 2nd generation TKI. More patients treated with RII received blinatumomab following high-dose MTX and Ara-C, but the rates of MRD-negativity were comparable between the two regimens. Thus RII with dasatinib followed by MRD-guided follow-up therapy facilitates MRD negative remissions with less toxicity than HyperCVAD. The vast majority of fit patients were able to proceed to alloBMT following either regimen. Transplant outcomes following dasatinib with induction are presented in our concurrent abstract demonstrating a 5-year RFS of 83% (95% CI 59.8-93.5). Disclosures Webster: Amgen: Consultancy; Pfizer: Consultancy. Jain:Bristol Myer Squibb: Other: for advisory board participation; CareDx: Other: Advisory Board; Takeda: Consultancy, Honoraria. Dalton:AbbVie: Research Funding; Eli Lilly: Research Funding. DeZern:Abbvie: Consultancy; Astex: Research Funding; Celgene: Consultancy, Honoraria; MEI: Consultancy. Gojo:Genentech: Research Funding; Amphivena: Research Funding; Merck: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding. Bolanos-Meade:Incyte: Other: DSMB Fees. Luznik:WindMil Therapeutics: Patents & Royalties: Patent holder; AbbVie: Consultancy; Merck: Research Funding, Speakers Bureau; Genentech: Research Funding. Ali:Celgene: Membership on an entity's Board of Directors or advisory committees. Borrello:Celgene: Research Funding; Aduro: Patents & Royalties; WindMIL Therapeutics: Other: Founder , Research Funding. Wagner-Johnston:ADC Therapeutics, Regeneron, CALIB-R, Verastem: Membership on an entity's Board of Directors or advisory committees. Smith:Jazz: 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; Celgene: 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; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Levis:Menarini: Honoraria; Amgen: Honoraria; Daiichi-Sankyo: Honoraria; FujiFilm: Honoraria, Research Funding; Astellas: Honoraria, Research Funding.

An immunosuppressive microenvironment promoting leukemia cell immune escape plays an important role in the pathogenesis of AML. Through its interaction with cereblon, a substrate receptor for the E3 ubiquitin ligase complex, pomalidomide leads to selective ubiquitination of transcription factors Aiolos and Ikaros thereby promoting immune modulation. In this phase I trial, 51 newly diagnosed non-favorable risk AML and high-risk MDS patients were enrolled and treated with AcDVP16 (cytarabine 667 mg/m(2)/day IV continuous infusion days 1–3, daunorubicin 45 mg/m(2) IV days 1–3, etoposide 400 mg/m(2) IV days 8–10) induction therapy followed by dose- and duration-escalation pomalidomide beginning at early lymphocyte recovery. Forty-three patients (AML: n = 39, MDS: n = 4) received pomalidomide. The maximum tolerated dose of pomalidomide was 4 mg for 21 consecutive days. The overall complete remission (CR + CRi) rate, median overall survival, and disease-free survival were 75%, 27.1 and 20.6 months, respectively. Subset analyses revealed 86% CR/CRi rate in AML patients with unfavorable-risk karyotype treated with pomalidomide. Pomalidomide significantly decreased Aiolos expression in both CD4(+) and CD8(+) peripheral blood and bone marrow T cells, promoted T cell differentiation, proliferation, and heightened their cytokine production. Finally, pomalidomide induced distinct gene expression changes in immune function-related ontologies in CD4(+) and CD8(+) T cells.

Relapse is the most common cause of treatment failure following allogeneic blood or marrow transplantation (alloBMT) for AML or MDS. Post-transplant maintenance therapies may prevent relapse. We conducted a phase II trial combining azacitidine (AZA) with GM-CSF in non-relapsed, post-transplant patients with AML or MDS. Patients received escalating doses of AZA to a maximum of 75 mg/m2 for 5 days per cycle for up to 12 cycles. GM-CSF was given on days 1-10 of each cycle. Eighteen patients were treated following non-myeloablative (17) and myeloablative (1) alloBMT for AML (61.1%), MDS (27.7%), or therapy-related myeloid neoplasm (11.1%). The majority of patients (72%) received their graft from an HLA-haploidentical donor. The treatment was well-tolerated with rare grade 3-4 hematologic toxicities. One patient suffered an exacerbation of GVHD. The 24-month relapse-free and overall survivals were 47 and 57%, respectively, with a median of 18.6 and 29 months.

7053 Background: Mutations in isocitrate dehydrogenase 1 ( IDH1) occur in ̃3% of patients (pts) with MDS and are associated with increased transformation to acute myeloid leukemia (AML). Ivosidenib (IVO), an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme, is FDA approved for m IDH1 R/R AML and m IDH1 newly diagnosed AML in pts ≥75 years old or with comorbidities precluding the use of intensive induction chemotherapy. In the first-in-human study of IVO in pts with m IDH1 advanced hematologic malignancies (NCT02074839), 12 pts with R/R MDS received IVO 500 mg once daily (QD). Based on encouraging safety and efficacy findings, including an investigator-assessed overall response rate (ORR) of 75%, with median response duration of 21.4 months, the FDA granted Breakthrough Therapy designation to IVO in m IDH1 R/R MDS and the study was amended to enroll additional pts. We report updated results. Methods: This substudy of the single-arm, open-label study of IVO evaluated pts with R/R MDS after documented failure or relapse following prior standard therapy including intensive chemotherapy and hypomethylating agents. Other key eligibility criteria included: high disease burden based on IPSS or IPSS-R risk at baseline; an Eastern Cooperative Oncology Group performance status score of 0–2; and no prior IDH1 inhibitor therapy. Pts received IVO 500 mg QD orally on days 1–28 of 28-day cycles. Results: As of 08May2021, 16 pts with R/R MDS were enrolled: 5 (31%) pts remained on treatment and free from leukemic transformation; 11 (69%) had discontinued including 6 for disease progression, 1 for allogeneic stem cell transplantation, and 1 owing to an adverse event (AE) of sepsis (the only fatal AE; reported by investigator as not related to IVO). AEs are summarized in the Table. 2 pts each experienced differentiation syndrome (grade 2) and QTcF prolongation (grade 1 and 2). 7/16 pts achieved complete response (CR, 44%; 95% CI, 20%, 70%), 1 achieved partial response (6%), and 5 achieved marrow CR (31%), resulting in an ORR of 81% (95% CI, 54%, 96%). Hematologic improvement in ≥1 lineages was achieved by 11/16 (69%) pts. The Kaplan-Meier estimate of duration of CR+PR at 12 months was 60%. 3 pts experienced CRs lasting 24.0, 63.7, and 65.4 months, which remain ongoing. 5/7 pts (71%) who were transfusion dependent at baseline became independent of red blood cell or platelet transfusions for 56 or more consecutive days on treatment. Additional translational data are being analyzed. Conclusions: In pts with m IDH1 R/R MDS, IVO monotherapy was tolerable and induced durable remissions and transfusion independence. These findings support the role of IVO as an effective, oral, targeted treatment for pts with m IDH1 R/R MDS. Clinical trial information: NCT02074839. [Table: see text]

Mutations in the gene encoding isocitrate dehydrogenase 1 ( IDH1) occur in 6 to 10% of patients with acute myeloid leukemia (AML). Ivosidenib (AG-120) is an oral, targeted, small-molecule inhibitor of mutant IDH1.We conducted a phase 1 dose-escalation and dose-expansion study of ivosidenib monotherapy in IDH1-mutated AML. Safety and efficacy were assessed in all treated patients. The primary efficacy population included patients with relapsed or refractory AML receiving 500 mg of ivosidenib daily with at least 6 months of follow-up.Overall, 258 patients received ivosidenib and had safety outcomes assessed. Among patients with relapsed or refractory AML (179 patients), treatment-related adverse events of grade 3 or higher that occurred in at least 3 patients were prolongation of the QT interval (in 7.8% of the patients), the IDH differentiation syndrome (in 3.9%), anemia (in 2.2%), thrombocytopenia or a decrease in the platelet count (in 3.4%), and leukocytosis (in 1.7%). In the primary efficacy population (125 patients), the rate of complete remission or complete remission with partial hematologic recovery was 30.4% (95% confidence interval [CI], 22.5 to 39.3), the rate of complete remission was 21.6% (95% CI, 14.7 to 29.8), and the overall response rate was 41.6% (95% CI, 32.9 to 50.8). The median durations of these responses were 8.2 months (95% CI, 5.5 to 12.0), 9.3 months (95% CI, 5.6 to 18.3), and 6.5 months (95% CI, 4.6 to 9.3), respectively. Transfusion independence was attained in 29 of 84 patients (35%), and patients who had a response had fewer infections and febrile neutropenia episodes than those who did not have a response. Among 34 patients who had a complete remission or complete remission with partial hematologic recovery, 7 (21%) had no residual detectable IDH1 mutations on digital polymerase-chain-reaction assay. No preexisting co-occurring single gene mutation predicted clinical response or resistance to treatment.In patients with advanced IDH1-mutated relapsed or refractory AML, ivosidenib at a dose of 500 mg daily was associated with a low frequency of grade 3 or higher treatment-related adverse events and with transfusion independence, durable remissions, and molecular remissions in some patients with complete remission. (Funded by Agios Pharmaceuticals; ClinicalTrials.gov number, NCT02074839 .).

Context: Mutations in isocitrate dehydrogenase 1 (IDH1) occur in ~3% of patients with MDS and are associated with increased transformation to acute myeloid leukemia (AML). IVO is an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme and is FDA-approved for mIDH1 R/R AML and mIDH1 newly diagnosed AML in patients ≥75 years old or with comorbidities precluding the use of intensive induction chemotherapy. In the first-in-human, phase 1 study of IVO in patients with mIDH1 advanced hematologic malignancies (NCT02074839), 12 patients with R/R MDS, with median age 72.5 years (range 52–78), received IVO 500 mg once daily (QD). All patients received prior MDS treatment. Investigator-assessed ORR (CR + PR + marrow CR, per IWG 2006) was 75% (95% CI 43–95), with median duration of response of 21.4 months (95% CI 2.3–NE). Nine (75%) patients were transfusion-independent for ≥56 days during treatment. No dose-limiting toxicities or adverse events leading to treatment discontinuation were reported among patients with MDS. Based on these encouraging data, the FDA granted Breakthrough Therapy Designation to IVO in mIDH1 MDS; the study was amended to enroll additional patients with mIDH1 R/R MDS. Objective: To evaluate safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of IVO in patients with mIDH1 R/R MDS. Design: A sub-study of the single-arm, open-label, phase 1 dose escalation and expansion study of IVO in mIDH1 advanced hematologic malignancies, evaluating patients with R/R MDS. Patients must have R/R disease after prior standard therapy; high disease burden based on cytopenia and/or transfusion dependence at baseline; an Eastern Cooperative Oncology Group performance status score of 0–2; and be amenable to bone marrow aspirate and/or core biopsy at specified study timepoints. Patients with documented AML are not eligible. IVO 500 mg QD orally on days 1–28 of 28-day cycles. Results: Study is open; enrollment of ~23 patients from the US and France planned. Results not yet available. Conclusions: This sub-study will provide additional insights into safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of treatment with IVO in patients with mIDH1 R/R MDS. Funding: Agios; Servier.

Background: The benefit of allogeneic blood or marrow transplantation (alloBMT) following myeloablative conditioning (MAC) in first complete remission (CR1) compared to chemotherapy has been demonstrated in a randomized trial for adults with acute lymphoblastic leukemia (ALL). Persistence of measurable residual disease (MRD) prior to alloBMT confers an increased risk of relapse. Blinatumomab eradicates persistent or recurrent MRD at levels ≥10 -3 in 78% of B ALL. However, post-hoc analyses of patients who have undergone alloBMT following blinatumomab for MRD demonstrate non-relapse mortality (NRM) of 36.5%. NRM following nonmyeloablative (NMAC) alloBMT with high-dose post-transplantation cyclophosphamide (PTCy) is just 11%. Given broadly similar outcomes between HLA-matched MAC alloBMT and HLA-haploidentical NMAC alloBMT following PTCy, we have shifted to using exclusively NMAC alloBMT with PTCy and sought to explore outcomes depending on receipt of pre-transplant blinatumomab. Methods: The bone marrow transplant database at Johns Hopkins was queried for adult patients with Ph-negative B-ALL who received NMAC alloBMT in CR1 using PTCy between January 2008 and July 2020. Characteristics of patients were summarized and compared using the student's T test for continuous variables and Fisher's exact test for categorical variables. Estimators of OS and RFS were reported using the Kaplan-Meier method. Differences in time-to-event outcomes were estimated using Cox proportional hazards model for OS and RFS, and Fine and Gray's model for cumulative incidence of relapse (CIR)/NRM considering competing events. Results: Among the 50 identified patients undergoing 1 st transplant in CR1 with NMAC, all received conditioning with fludarabine and cyclophosphamide followed by total body irradiation (TBI). In addition to PTCy, all patients received mycophenolate mofetil and either tacrolimus or sirolimus as GVHD prophylaxis. Sixteen patients (32%) received blinatumomab in CR1 or achieved CR1 following blinatumomab and proceeded to transplant without intervening therapy, while 34 patients (68%) did not. At the time of treatment with blinatumomab; 3 patients had >5% blasts after chemotherapy, 8 had persistent or recurrent MRD >10 -4 after chemotherapy, and 5 had no evidence of MRD at a sensitivity of 10 -4. Among the 5 MRD- patients treated with blinatumomab; 1 had been refractory to their first course of chemotherapy (67% blasts), 3 had MRD >10 -4 at the first MRD response assessment following chemotherapy, and 1 had CNS involvement at diagnosis. The demographics of these two groups are presented in Table 1 and separated by pre-transplant blinatumomab status. The groups were well balanced in terms of gender, age, WBC at diagnosis, CNS involvement at diagnosis, and donor type. Patients who received blinatumomab were more likely to have been refractory to their initial course of chemotherapy and were transplanted later after their initial diagnosis than those who did not. All patients who received blinatumomab were MRD-negative at a sensitivity of 10 -4 prior to their transplant, while 11.8% of patients who did not receive blinatumomab were MRD-positive. Relapse-free and overall survival, cumulative incidence of relapse, and non-relapse mortality by receipt of blinatumomab prior to transplant are shown in Figure 1. Non-relapse mortality was not increased among patients who received pre-transplant blinatumomab (HR=1.06, p=0.94). The causes of non-relapse mortality included GVHD (1) and secondary malignancy (1) in patients who received blinatumomab; and infection (1), bleeding (1), secondary malignancy (1), and other (1) in patients who did not receive blinatumomab. Receipt of pre-transplant blinatumomab was associated with a decreased cumulative incidence of relapse (HR=0.15, p=0.07) and improved relapse-free survival (HR=0.32, p=0.07). Overall survival (HR=0.63, p=0.5) between the two groups was similar, likely reflecting the efficacy of salvage therapies such as CD19 CAR T cells; blinatumomab; and inotuzumab in the relapsed, post-transplant population. Conclusions: Treatment with blinatumomab prior to NMAC alloBMT with PTCy in CR1 for Ph-negative B ALL did not increase NRM and produced a 3-year RFS of 81%. The low CIR and NRM of NMAC alloBMT in an MRD-negative CR1 following blinatumomab suggest it could be a viable alternative to MAC. Figure 1 Figure 1. Disclosures Webster: AmGen: Consultancy; Pfizer: Consultancy. DeZern: Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: 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. Levis: Takeda: Honoraria; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Astellas and FujiFilm: Research Funding; Amgen, Astellas Pharma, Daiichi-Sankyo, FujiFilm, and Menarini: Honoraria; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Ghiaur: Syros Pharmaceuticals: Consultancy; Menarini Richerche: Research Funding. Hourigan: Sellas: Research Funding. Jain: Syneos Health: Research Funding; CTI Biopharma: Research Funding; CareDx: Other: for advisory board participation; Bristol Myers Squibb: Other: for advisory board participation; Targeted Healthcare Communications: Consultancy. Ali: Janssen: Consultancy; BMS: Consultancy; Oncopeptides: Consultancy; Sanofi: Consultancy; Amgen: Consultancy; Aduro: Consultancy; Poseida: Research Funding; Aduro: Research Funding; BMS: Research Funding.

Timed sequential therapy (TST) aims to improve outcomes in acute myelogenous leukemia (AML) by harnessing drug-induced cell cycle kinetics of AML, where a second drug is timed to coincide with peak leukemia proliferation induced by the first drugs. We analyzed outcomes in 301 newly diagnosed AML patients treated from 2004–2013 with cytarabine, anthracycline, and etoposide TST induction. Median age was 52 (range 20–74) and complete remission rate 68%. With median follow-up 5.8 years, 5-year DFS and overall survival (OS) were 37% (95% CI 31–45%) and 32% (95% CI 27–38%), respectively. In multivariate analysis, older age, unfavorable cytogenetics, and WBC ≥ 50 × 109/L resulted in worse OS. Among patients not undergoing blood and marrow transplant, a propensity score analysis, which reduces imbalance in baseline characteristics, showed consolidation with TST compared with 1 or more cycles high-dose cytarabine trended toward lower DFS and post-remission survival with hazard ratio (HR) 1.9 (95% CI 0.9–4.0), and 1.6 (95% CI 0.7–3.6), respectively. Our results demonstrate the efficacy and feasibility of TST induction for newly diagnosed patients with AML, with results comparable to that seen in clinical trials with other TST therapies and 7 + 3.

Background Changes in adaptive immune cells after chemotherapy in adult acute myeloid leukemia (AML) may have implications for the success of immunotherapy. This study was designed to determine the functional capacity of the immune system in adult patients with AML who have completed chemotherapy and are potential candidates for immunotherapy. Methods We used the response to seasonal influenza vaccination as a surrogate for the robustness of the immune system in 10 AML patients in a complete remission post-chemotherapy and performed genetic, phenotypic, and functional characterization of adaptive immune cell subsets. Results Only 2 patients generated protective titers in response to vaccination, and a majority of patients had abnormal frequencies of transitional and memory B-cells. B-cell receptor sequencing showed a B-cell repertoire with little evidence of somatic hypermutation in most patients. Conversely, frequencies of T-cell populations were similar to those seen in healthy controls, and cytotoxic T-cells demonstrated antigen-specific activity after vaccination. Effector T-cells had increased PD-1 expression in AML patients least removed from chemotherapy. Conclusion Our results suggest that while some aspects of cellular immunity recover quickly, humoral immunity is incompletely reconstituted in the year following intensive cytotoxic chemotherapy for AML. The observed B-cell abnormalities may explain the poor response to vaccination often seen in AML patients after chemotherapy. Furthermore, the uncoupled recovery of B-cell and T-cell immunity and increased PD-1 expression shortly after chemotherapy might have implications for the success of several modalities of immunotherapy. Electronic supplementary material The online version of this article (doi:10.1186/s12967-017-1252-2) contains supplementary material, which is available to authorized users.

Background: Somatic mutations in isocitrate dehydrogenase 1 (IDH1) are reported in 6-10% of patients (pts) with acute myeloid leukemia (AML), resulting in production of the oncometabolite D-2-hydroxyglutarate. Ivosidenib (IVO) is an oral, potent, targeted inhibitor of mutant IDH1 (mIDH1) and is FDA-approved for the treatment of mIDH1 relapsed or refractory (R/R) AML and mIDH1 newly diagnosed (ND) AML in adults ≥ 75 years of age or with comorbidities precluding intensive induction chemotherapy. In a phase 1 study (NCT02074839), durable remissions in pts with mIDH1 ND AML (n = 33) were achieved with IVO, with a complete remission (CR) plus CR with partial hematologic recovery (CRh) rate of 42.4%, and median overall survival of 12.6 months (mo), as of 02Nov2018. The most frequent co-occurring mutations at baseline were ASXL1, DNMT3A, RUNX1, SRSF2, TET2, and NRAS. Aim: To characterize the longitudinal evolution of gene mutations in pts with mIDH1 ND AML treated with IVO 500 mg once daily, including relapse mechanisms and depth of molecular response for mIDH1 and co-occurring mutations. Methods: The mIDH1 variant allele frequency (VAF) was assessed in bone marrow mononuclear cells (BMMCs), peripheral blood mononuclear cells (PBMCs), and neutrophils using BEAMing digital polymerase chain reaction (PCR) technology (Sysmex Inostics, Inc.), which has a lower limit of detection for mIDH1 of 0.02-0.04%. Deep IDH1 mutation clearance (MC) was defined as reduction in mIDH1 VAF to below the limit of detection for ≥ 1 on-treatment timepoint. Baseline and longitudinal co-occurring mutation profiling was conducted on BMMC or PBMC samples by next-generation sequencing (NGS; detection sensitivity of 1-5%). Single-cell targeted DNA sequencing (DNA-seq) was performed on PBMCs using a microfluidic platform (Tapestri®). The clinical data cut-off for this analysis was 02Nov2018. Results: In pts who achieved a best response of CR or CRh, the IDH1-MC rate in BMMCs was 64.3% (9/14), and 72.7% (8/11) in both PBMCs and neutrophils, by sensitive digital PCR (Table). Median time to IDH1-MC was 7.4 mo (BMMCs), 6.9 mo (PBMCs), and 5.1 mo (neutrophils) in pts achieving CR or CRh. IDH1-MC was significantly associated with a best response of CR or CRh (p < 0.001, Table). Overall survival at 12 mo was 88.9% (95% CI 43.3, 98.4) for pts with IDH1-MC in BMMCs (n = 9), as compared with 38.5% (95% CI 17.7, 59.0) for pts who did not achieve IDH1-MC (n = 21). The longitudinal evolution of mIDH1 and co-occurring mutations during IVO treatment was profiled by NGS in 27 pts. In 13 pts who achieved a best response of CR/CRh and with available data, non-DTA (DNMT3A, TET2, ASXL1) gene mutation clearance was observed for IDH1 (11/13), RUNX1 (2/4), SRSF2 (2/3), and NPM1 (2/2). One pt had all co-occurring mutations (IDH1, FLT3, and NPM1) cleared by IVO monotherapy, and maintained CR for 30.2 mo as of the data cut-off. The most frequent mutations acquired at relapse or disease progression following IVO treatment were mutations in receptor tyrosine kinase (RTK) pathway genes (38.5%; 5/13), followed by mutations in chromatin remodeling (15.4%; 2/13) and IDH2 (7.7%; 1/13; Table). No IDH1 second-site mutations were observed in this cohort by NGS; however, emergence of an IDH1 R119P second-site mutation was observed in 1 pt using a single-cell DNA-seq assay. Conclusions: IDH1-MC across examined cell types (BMMCs, PBMC, and neutrophils) suggests that IVO can alter the biology of mIDH1 ND AML via reduction of the primitive mIDH1 cells. Similar to previous findings in R/R AML, the observed trend of improved overall survival in pts with deep molecular remission (ie, IDH1-MC) warrants further investigation in a larger pt cohort. Relapse is mediated by diverse emergent mutations, most frequently in RTK pathway genes, chromatin remodeling genes, and IDH2. Clonal architecture and evolution in ~ 20 pts revealed by single-cell DNA-seq analysis will be presented. Disclosures Choe: Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Wang:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Roboz:Array BioPharma: Consultancy; MEI Pharma: Consultancy; Helsinn: Consultancy; Epizyme: Consultancy; Jasper Therapeutics: Consultancy; Cellectis: Research Funding; Trovagene: Consultancy; Takeda: Consultancy; Otsuka: Consultancy; Bayer: Consultancy; Celltrion: Consultancy; Eisai: Consultancy; Jazz: Consultancy; Roche/Genentech: Consultancy; Sandoz: Consultancy; Abbvie: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Astex: Consultancy; Amphivena: Consultancy; Agios: Consultancy; Orsenix: Consultancy; AstraZeneca: Consultancy; Daiichi Sankyo: Consultancy; Astellas: Consultancy; Argenx: Consultancy; Actinium: Consultancy. DiNardo:Agios: Consultancy, Honoraria, Research Funding; Jazz: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; ImmuneOnc: Honoraria; Syros: Honoraria; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Novartis: Consultancy; Notable Labs: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Calithera: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; MedImmune: Honoraria. Stein:Syros: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Syndax: Consultancy, Research Funding; Amgen: Consultancy; Abbvie: Consultancy; PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Biotheryx: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Mims:Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Novartis: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy. Watts:Pfizer: Consultancy; Celgene: Consultancy; Jazz: Consultancy, Speakers Bureau; Takeda: Research Funding. Fan:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Nejad:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Zhang:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Liu:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Attar:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Wu:Agios Pharmaceuticals: Current Employment, Current equity holder in private company. Stone:Takeda: Consultancy; Arog: Research Funding; Argenx: Consultancy, Other: Data and safety monitoring board; Agios: Consultancy, Research Funding; Actinium: Consultancy; Novartis: Consultancy, Research Funding; Jazz: Consultancy; AbbVie: Consultancy, Research Funding; Gemoab: Consultancy; Elevate: Consultancy; Daiichi-Sankyo: Consultancy; Stemline: Consultancy; Syndax: Consultancy; Syntrix: Consultancy; Hoffman LaRoche: Consultancy; Macrogenics: Consultancy; Janssen: Consultancy; Syros: Consultancy; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy; Biolinerx: Consultancy; Celgene: Consultancy, Other: Data and safety monitoring board; Trovagene: Consultancy; Pfizer: Consultancy; Otsuka: Consultancy.

Ivosidenib (AG-120) is an oral, targeted agent that suppresses production of the oncometabolite 2-hydroxyglutarate via inhibition of the mutant isocitrate dehydrogenase 1 (IDH1; mIDH1) enzyme. From a phase 1 study of 258 patients with IDH1-mutant hematologic malignancies, we report results for 34 patients with newly diagnosed acute myeloid leukemia (AML) ineligible for standard therapy who received 500 mg ivosidenib daily. Median age was 76.5 years, 26 patients (76%) had secondary AML, and 16 (47%) had received ≥1 hypomethylating agent for an antecedent hematologic disorder. The most common all-grade adverse events were diarrhea (n = 18; 53%), fatigue (n = 16; 47%), nausea (n = 13; 38%), and decreased appetite (n = 12; 35%). Differentiation syndrome was reported in 6 patients (18%) (grade ≥3 in 3 [9%]) and did not require treatment discontinuation. Complete remission (CR) plus CR with partial hematologic recovery (CRh) rate was 42.4% (95% confidence interval [CI], 25.5% to 60.8%); CR 30.3% (95% CI, 15.6% to 48.7%). Median durations of CR+CRh and CR were not reached, with 95% CI lower bounds of 4.6 and 4.2 months, respectively; 61.5% and 77.8% of patients remained in remission at 1 year. With median follow-up of 23.5 months (range, 0.6-40.9 months), median overall survival was 12.6 months (95% CI, 4.5-25.7). Of 21 transfusion-dependent patients (63.6%) at baseline, 9 (42.9%) became transfusion independent. IDH1 mutation clearance was seen in 9/14 patients achieving CR+CRh (5/10 CR; 4/4 CRh). Ivosidenib monotherapy was well-tolerated and induced durable remissions and transfusion independence in patients with newly diagnosed AML. This trial was registered at www.clinicaltrials.gov as #{"type":"clinical-trial","attrs":{"text":"NCT02074839","term_id":"NCT02074839"}}NCT02074839.

Context: IVO is an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme, approved in the US for the treatment of AML with a susceptible IDH1 mutation in adults with newly diagnosed AML ≥75 years of age or having comorbidities precluding intensive induction chemotherapy, and in adults with R/R AML. In a phase 1 dose escalation and expansion study of IVO in mIDH1 advanced hematologic malignancies ( NCT02074839 ), 12 patients with R/R MDS received IVO 500 mg once daily (QD). Median age was 72.5 years (range 52–78). All patients had received prior treatment for MDS, with 3 (25.0%) and 1 (8.3%) having received 2 or ≥3 prior therapies, respectively. Investigator-assessed ORR (CR + PR + marrow CR) per International Working Group 2006 criteria was 75.0% (95% CI 42.8%, 94.5%) with a median duration of 21.4 months (95% CI 2.3, not estimable). Nine patients (75.0%) were transfusion independent for ≥56 days during study treatment. Based on these data, the FDA recently granted a Breakthrough Therapy Designation status for IVO monotherapy in this indication, and the study has been amended to enroll additional mIDH1 R/R MDS patients. Objective: To assess safety, tolerability, clinical activity, pharmacokinetics, and pharmacodynamics of IVO in patients with mIDH1 R/R MDS. Design: This is a sub-study of the phase 1 study of IVO in mIDH1 advanced hematologic malignancies to evaluate patients with mIDH1 R/R MDS. Patients must have R/R disease after treatment with standard agents indicated for MDS and high disease burden based on cytopenia and/or transfusion dependence at baseline. IVO will be administered at a dose of 500 mg QD orally on Days 1–28 of 28-day cycles. Results: The study is open and will enroll ∼23 patients from the US and France; results not yet available. Conclusions: The favorable efficacy and safety of IVO in the small population of patients with mIDH1 R/R MDS in the phase 1 clinical study supports further evaluation in this MDS sub-study. This sub-study will provide additional insights into safety, tolerability, clinical activity, and pharmacokinetics/pharmacodynamics of treatment with IVO in patients with mIDH1 R/R MDS. Funding: Agios.

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematopoietic stem cell malignancies. Currently, approved drugs are given with non-curative intent as the only known cure is allogeneic bone marrow transplantation, which relies on the donor's immune system driving an allogeneic effect. Previous efforts to harness the endogenous immune system have been less successful. We present the results of a pilot study of K562/GM-CSF (GVAX) whole-cell vaccination in MDS patients. The primary objective of safety was met as there were no serious adverse events. One patient had a decrease in transfusion requirements and another demonstrated hematologic improvement suggesting a signal for clinical activity. In vitro correlative studies indicated biological effects on immune cells following vaccination. Although only a pilot study, results are encouraging that an immunotherapeutic approach with a whole-cell vaccine may be feasible in MDS patients.

Purpose Recent advances in nonmyeloablative (NMA), related HLA-haploidentical blood or marrow transplantation (haplo-BMT) have expanded the donor pool. This study evaluated the effect of age on NMA haplo-BMT outcomes in patients age 50 to 75 years. Patients and Methods A retrospective analysis was performed of 271 consecutive patients with hematologic malignancies, age 50 to 75 years, who received NMA, T-cell–replete haplo-BMT with high-dose post-transplantation cyclophosphamide. Results The median age was 61 years, with 115 patients (42%) age 50 to 59, 129 (48%) age 60 to 69, and 27 (10%) age 70 to 75 years. Overall, 84% of patients had intermediate- or high-/very high–risk disease. The 6-month probabilities of grade 3 or 4 acute graft-versus-host disease (GVHD) and nonrelapse mortality (NRM) were 3% and 8%, respectively. Patients in their 50s, 60s, and 70s had 6-month NRM probabilities of 8%, 9%, and 7%, respectively (P = .20). With a median follow-up of 4 years, corresponding 3-year progression-free survival probabilities were 39%, 35%, and 33% (P = .65), and corresponding 3-year overall survival probabilities were 48%, 45%, and 44% (P = .66). Three-year progression-free survival probabilities were 40% in acute myeloid leukemia (n = 65), 39% in aggressive non-Hodgkin lymphoma (n = 83), and 37% in indolent or mantle-cell lymphoma (n = 65). Older patient age was associated with a significantly higher risk of grade 2 to 4 acute GVHD but not grade 3 to 4 acute or chronic GVHD. No statistically significant associations were found between older age (relative to age 50 to 59 years or as a continuous variable) and NRM, relapse, or survival. Conclusion NMA haplo-BMT with post-transplantation cyclophosphamide has encouraging safety and survival outcomes in patients age 50 to 75 years. In patients otherwise fit for BMT, the results support consideration of this approach despite advanced age.

Related HLA-haploidentical blood or marrow transplantation (BMT) with high-dose posttransplantation cyclophosphamide (PTCy) is being increasingly used because of its acceptable safety profile. To better define outcomes of nonmyeloablative (NMA) HLA-haploidentical BMT with PTCy, 372 consecutive adult hematologic malignancy patients who underwent this procedure were retrospectively studied. Risk-stratified outcomes were evaluated using the refined Disease Risk Index (DRI), developed to stratify disease risk across histologies and allogeneic BMT regimens. Patients received uniform conditioning, T-cell–replete allografting, then PTCy, mycophenolate mofetil, and tacrolimus. Six-month probabilities of nonrelapse mortality and severe acute graft-versus-host disease were 8% and 4%. With 4.1-year median follow-up, 3-year probabilities of relapse, progression-free survival (PFS), and overall survival (OS) were 46%, 40%, and 50%, respectively. By refined DRI group, low (n = 71), intermediate (n = 241), and high/very high (n = 60) risk groups had 3-year PFS estimates of 65%, 37%, and 22% (P < .0001), with corresponding 3-year OS estimates of 71%, 48%, and 35% (P = .0001). On multivariable analyses, the DRI was statistically significantly associated with relapse, PFS, and OS (each P < .001). This analysis demonstrates that the DRI effectively risk stratifies recipients of NMA HLA-haploidentical BMT with PTCy and also suggests that this transplantation platform yields similar survivals to those seen with HLA-matched BMT.

Background: Mutations in isocitrate dehydrogenase 1 (IDH1) occur in ~3% of individuals with myelodysplastic syndrome (MDS) and have been associated with increased transformation to acute myeloid leukemia (AML). Ivosidenib (AG-120) is an oral, potent, targeted inhibitor of the mutant isocitrate dehydrogenase 1 enzyme (mIDH1) and is approved in the US for the treatment of newly diagnosed AML with a susceptible IDH1 mutation in patients ≥75 years of age or who have comorbidities that preclude the use of intensive induction chemotherapy, and in adult patients with relapsed or refractory (R/R) AML. The first-in-human, phase 1 dose escalation and expansion study of ivosidenib (NCT02074839) enrolled adults with mIDH1 advanced hematologic malignancies, including R/R MDS, and the study is ongoing. In the initial phase of the study (DiNardo et al. N Engl J Med 2018), the 12 patients with R/R MDS received 500 mg ivosidenib once daily and were characterized as follows: 75% were male, median age was 72.5 years (range 52-78), and 42% were ≥75 years of age; median number of prior therapies was 1 (range 1-3). Adverse events (AEs) of any grade, irrespective of causality, occurring in ≥20% of the 12 patients were diarrhea, fatigue, back pain, rash (n=4 each, 33.3%), anemia, urinary tract infection, decreased appetite, hypokalemia, arthralgia, dyspnea, pruritus, and hypotension (n=3 each, 25.0%). No AEs led to permanent discontinuation of treatment. Response was assessed according to International Working Group 2006 criteria for MDS. According to investigators, five of 12 patients achieved complete remission (CR) (41.7%; 95% CI 15.2%, 72.3%); median duration of CR was not estimable for these patients (95% CI 2.8 months, not estimable). Nine of 12 patients were transfusion independent for at least 56 days during study treatment. Mutation clearance was observed in one of the 5 CR patients. Here we report the design of a new sub-study of this trial, which is being undertaken to further assess the safety, tolerability, and clinical activity of treatment with ivosidenib in patients with R/R MDS. Methods: This sub-study is evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and clinical activity of ivosidenib. Adults with R/R MDS with an IDH1 mutation will be enrolled in the MDS sub-study. These individuals must have R/R disease after treatment with standard agents indicated for MDS. Eligible patients must have a platelet count of ≥20,000/μL, and adequate hepatic function (total bilirubin ≤1.5 × upper limit of normal [ULN]; aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase ≤3.0 × ULN) and renal function (serum creatinine ≤2.0 × ULN or creatinine clearance >40 mL/min). Additional key inclusion criteria are bone marrow blasts >5% and/or transfusion dependence. Ivosidenib is to be administered at a dose of 500 mg once daily orally on Days 1 to 28 of 28-day cycles. The addition of the MDS sub-study to this phase 1 clinical study in patients with hematological malignancies will provide additional insights into the use of ivosidenib for the treatment of mIDH1 R/R MDS. Disclosures Foran: Agios: Honoraria, Research Funding. DiNardo:notable labs: Membership on an entity's Board of Directors or advisory committees; medimmune: Honoraria; daiichi sankyo: Honoraria; abbvie: Consultancy, Honoraria; agios: Consultancy, Honoraria; jazz: Honoraria; celgene: Consultancy, Honoraria; syros: Honoraria. Watts:Takeda: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Stein:Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas Pharma US, Inc: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo, Inc.: Membership on an entity's Board of Directors or advisory committees; Bioline: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees. De Botton:Daiichi Sankyo: Consultancy; Astellas: Consultancy; Bayer: Consultancy; AbbVie: Consultancy; Syros: Consultancy; Forma: Consultancy, Research Funding; Janssen: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Servier: Consultancy; Pierre Fabre: Consultancy; Celgene: Consultancy, Speakers Bureau; Agios: Consultancy, Research Funding. Fathi:Amphivena, Kite, Jazz, NewLink Genetics,: Honoraria; Agios, Astellas, Celgene, Daiichi Sankyo, Novartis, Takeda, Amphivena, Kite, Forty Seven,Trovagene, NewLink genetics, Jazz, Abbvie, and PTC Therapeutics: Consultancy. Stein:Stemline: Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau. Stone:AbbVie, Actinium, Agios, Argenx, Arog, Astellas, AstraZeneca, Biolinerx, Celgene, Cornerstone Biopharma, Fujifilm, Jazz Pharmaceuticals, Amgen, Ono, Orsenix, Otsuka, Merck, Novartis, Pfizer, Sumitomo, Trovagene: Consultancy; Argenx, Celgene, Takeda Oncology: Other: Data and Safety Monitoring Board/Committee: ; Novartis, Agios, Arog: Research Funding. Patel:France Foundation: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dava Oncology: Honoraria. Tallman:UpToDate: Patents & Royalties; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; BioLineRx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Rigel: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cellerant: Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Delta Fly Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Nohla: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Research Funding; Tetraphase: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orsenix: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Biosight: Research Funding; Oncolyze: Consultancy, Membership on an entity's Board of Directors or advisory committees; KAHR: Consultancy, Membership on an entity's Board of Directors or advisory committees. Choe:Agios: Employment, Equity Ownership; Agios: Employment, Equity Ownership. Wang:Agios: Employment, Equity Ownership. Zhang:Agios: Employment, Equity Ownership; Agios: Employment, Equity Ownership. Fan:Agios: Employment, Equity Ownership. Yen:Agios: Employment, Equity Ownership. Oluyadi:Agios: Employment, Equity Ownership. Winkler:Agios: Employment. Hickman:Agios: Employment, Equity Ownership. Agresta:Agios: Employment, Equity Ownership. Liu:Agios: Employment, Equity Ownership. Wu:Agios: Employment, Equity Ownership. Attar:Aprea Therapeutics: Employment; Agios: Employment, Equity Ownership. Kantarjian:Astex: Research Funding; Takeda: Honoraria; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Immunogen: Research Funding; AbbVie: Honoraria, Research Funding; Jazz Pharma: Research Funding; Agios: Honoraria, Research Funding; Ariad: Research Funding; Amgen: Honoraria, Research Funding; Cyclacel: Research Funding; BMS: Research Funding; Daiichi-Sankyo: Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding. OffLabel Disclosure: Ivosidenib (AG-120) is an IDH1 inhibitor indicated for the treatment of AML with a susceptible IDH1 mutation as detected by an FDA-approved test in: 1) adult patients with newly-diagnosed AML who are more than 75 years old or who have comorbidities that preclude use of intensive induction chemotherapy and 2) adult patients with relapsed or refractory AML. It is being evaluated in clinical trials for mutant IDH1 advanced hematologic malignancies.

Background: AlloBMT can be curative as consolidation for high risk B ALL and NHL. However, long term survival is limited by transplant-related toxicity and particularly by disease relapse. Post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis limits GVHD and facilitates the use of alternative allograft sources. Moreover, following PTCy, cellular immune reconstitution is favorable for the integration of strategies to augment anti-tumor immunity. Blina, a CD19/CD3 bispecific T cell engager antibody construct, is effective in the treatment of CD19+ ALL and NHL. Blina leads to T cell activation that may enhance established posttransplant tumor-specific T cell responses, leading to a more potent graft-versus-tumor effect. Thus, we have undertaken a phase Ib trial to assess the tolerability and preliminary efficacy of blina as post-alloBMT remission maintenance in B-cell ALL and NHL. Methods: Patients ³18 years-old with high risk CD19+ B ALL or NHL who underwent alloBMT using PTCy were eligible including those with prior blina exposure. Patients had to be 60-180 days from transplant with documented count recovery and no evidence of disease progression. Patients had to be off all post-transplant immunosuppression including steroids for the treatment of GVHD for ≥4 weeks prior to treatment initiation, and without a history of grade ≥3 acute GVHD or severe chronic GVHD. Patients could receive two cycles of blina if they had evidence of disease (including MRD) at their pre- and/or post-transplant evaluations but otherwise received only one cycle. Blina was given as a continuous infusion at 9 mcg/day on C1D1-7 and 28 mcg/day on C1D8-28 and C2D1-28. Results: As of July 23, 2019, 12 adults (10 males/2 females) have enrolled including 4 patients with B ALL and 8 patients with NHL. Among the B ALL patients, two with known TP53 mutations were transplanted in CR1, while two with relapsed disease were transplanted in CR3. Among the NHL patients, five had large cell transformation (3 from follicular and 2 from CLL); one had relapsed primary CNS lymphoma (PCNSL); one had relapsed mantle cell lymphoma (MCL); and one had diffuse large B cell lymphoma (DLBCL). The median age was 53 (range, 30-73). All patients underwent alloBMT using a conditioning regimen of fludarabine, cyclophosphamide, and total body irradiation (TBI). Eight patients received allografts from haploidentical donors, three from matched-unrelated donors, and one from a matched-related donor. Five patients received peripheral blood allografts, and seven bone marrow. Two patients were enrolled after a second alloBMT, and 3/4 ALL patients previously received blina. Baseline characteristics are presented in Figure 1. Patients started blina a median of 144 days post-transplant (range, 90-180). One patient stopped treatment on day 5 due to a grade 2 tremor, and one patient required dose reduction on day 25 due to grade 4 neutropenia. Toxicities were otherwise mild and are presented in Figure 2. There were no exacerbations of GVHD. At a median follow-up of 13.7 months after BMT (range 3.8-23 months), ten patients remain in remission, while one patient suffered a third CNS relapse of ALL at 20.6 months after his 2nd transplant and another had relapse of his transformed lymphoma. Data on biomarkers including changes in T cell subpopulations in both BM and PB, and co-signaling molecule expression will be presented. Conclusions: Post-alloBMT maintenance therapy with blina is feasible with minimal toxicity. 83% of the very high risk patients treated on study remain in CR at a median of 13.7 months post-transplant. Based on promising safety and efficacy data from the phase IB, the plan is to proceed to the phase II portion of the study. Disclosures Webster: Amgen: Consultancy; Genentech: Research Funding; Pfizer: Consultancy. Wagner-Johnston:Jannsen: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Membership on an entity's Board of Directors or advisory committees. Luznik:Merck: Research Funding, Speakers Bureau; Genentech: Research Funding; AbbVie: Consultancy; WindMiL Therapeutics: Patents & Royalties: Patent holder. Gojo:Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Merck: Research Funding; Jazz: Consultancy, Honoraria; Amgen Inc: Consultancy, Honoraria, Research Funding; Juno: Research Funding; Amphivena: Research Funding. OffLabel Disclosure: Blinatumomab is not labeled for use as post-transplant maintenance therapy or for use in the non-Hodgkin lymphoma.

Background: Despite recent advances in the therapeutic armamentarium for AML, outcomes remain dismal for patients (pts) with relapsed/refractory (R/R) AML. Response rates with high dose cytarabine (HiDAC) salvage chemotherapy are approximately 20%. Multiple immune aberrations in AML lead to immune suppression, exhaustion, and senescence. Programmed Death-1 (PD-1), a co-inhibitory receptor (IR) on immune cells, suppresses immune activation and is exploited by leukemic cells to evade immune surveillance. PD-1 and other IRs are up-regulated during disease progression. We hypothesized that pembrolizumab, a monoclonal antibody targeting PD-1, after HiDAC would stimulate a T-cell mediated anti-leukemic immune response. Methods: Eligibility for this study included R/R AML 18-70 years, ECOG PS 0-1 and adequate organ function. Treatment consisted of HiDAC (60 years: 1.5 gm/m2 IV Q12hours days 1-5) followed by pembrolizumab 200 mg IV on day 14. The primary objective of this study was to estimate the overall complete remission (CR + CRi) rate. Secondary objectives included assessment of safety, durability of CR, overall survival (OS) and biomarker correlates of response. Overall responders were eligible to receive maintenance phase pembrolizumab 200 mg IV Q3weeks for up to 2 years until progression. Allogeneic stem cell transplant (alloSCT) was permissible before or after maintenance phase. Results: Thirty-seven pts were enrolled and evaluable (Table 1). Sixteen (43%) pts had refractory disease and 16 (43%) pts had relapsed AML with CR1 duration 3: n=1), AST elevation (32%; Grade >3: n=1), fatigue (27%), alkaline phosphatase elevation (24%), and maculopapular rash (19%; Grade >3: n=2). Grade >3 immune-related adverse events (iRAE) were rare (maculopapular rash: n=2, AST/ALT increase: n=2, right upper quadrant pain with lymphocytic infiltrate in liver: n=1) and self-limiting. Five (14%) pts required steroid administration for grade 2 hyperbilirubinemia (n=1), grade 3 ALT elevation (n=1), grade 3 AST elevation with liver biopsy revealing no evidence of iRAE (n=1), grade 3 bilirubin subsequently deemed to be a delayed hemolytic transfusion reaction (n=1), and grade 3 systolic dysfunction without evidence of myocarditis by endomyocardial biopsy or cardiac MRI (n=1). Sixty-day mortality was 3% (1/37) due to progressive AML. Median time to full neutrophil (>1x109/L) and platelet (>100x109/L) recovery was 32 and 31 days, respectively. The overall response (ORR: CR+CRi+PR+MLFS) and composite CR (CR+CRi) rates were 46% [29%,63%] and 38% [22%,55%], respectively, meeting the primary endpoint of the study. Notably, 13/28 (46%) pts receiving HiDAC + pembrolizumab as their first salvage regimen achieved CR/CRi. Two pts refractory to HiDAC (administered within past 6 months) achieved CR including one pt who was refractory to HiDAC salvage 1 month prior to enrollment and ultimately achieved CR without evidence of minimal residual disease. Nine (24%) pts received an alloSCT. There were no instances of Grade >3 acute GVHD or veno-occlusive disease post-alloSCT. Nine (24%) pts received maintenance phase pembrolizumab (median # of cycles = 3; range: 1-12) for CR (n=8) or PR (n=1). Seven out of 9 pts relapsed/progressed after maintenance phase. Median follow-up among survivors, and median OS, event-free survival and disease-free survival was 7.8 months, 8.9 months [6.0,13.1], 6.9 months [4.2,11.5], and 5.7 months [1.9,7.3], respectively. Conclusions: Pembrolizumab can be safely administered after HiDAC salvage in R/R AML. Severe iRAE's were uncommon despite administration after cytotoxic chemotherapy. The addition of pembrolizumab to HiDAC led to an encouraging overall CR rate meeting the primary endpoint of the study. Immunogenomic biomarker analyses consisting of B cell receptor amplicon sequencing, RNA-seq of blasts and CD8+ T cells, CD8+ T cell receptor repertoire, whole exome sequencing and flow cytometry analyses are ongoing to determine predictors of response. These results warrant further investigation of IR blockade and other immunomodulatory therapeutic strategies after intensive cytotoxic chemotherapy in AML. Disclosures Zeidner: Takeda: Research Funding; Merck: Research Funding; AsystBio Laboratories: Consultancy; Pfizer: Honoraria; Tolero: Honoraria, Research Funding; Daiichi Sankyo: Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Agios: Honoraria; AbbVie: Honoraria. Vincent:Pharmacyclics: Research Funding; Merck: Research Funding. Foster:Bellicum Pharmaceuticals: Research Funding; Macrogenics: Research Funding; Celgene: Research Funding; Daiichi Sankyo: Consultancy. Coombs:Dedham Group: Consultancy; Covance: Consultancy; Cowen & Co.: Consultancy; Octopharma: Honoraria; H3 Biomedicine: Honoraria; Loxo: Honoraria; Pharmacyclics: Honoraria; Medscape: Honoraria. Webster:Pfizer: Consultancy; Amgen: Consultancy; Genentech: Research Funding. DeZern:Astex Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy. Smith:Jazz: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Agios: Consultancy. Levis:Amgen: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria. Luznik:Merck: Research Funding, Speakers Bureau; Genentech: Research Funding; AbbVie: Consultancy; WindMiL Therapeutics: Patents & Royalties: Patent holder. Serody:Merck: Research Funding; GlaxoSmithKline: Research Funding. Gojo:Amphivena: Research Funding; Amgen Inc: Consultancy, Honoraria, Research Funding; Juno: Research Funding; Merck: Research Funding; Jazz: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. OffLabel Disclosure: Pembrolizumab is investigational for AML.

Background: Patients with acute myeloid leukemia (AML) presenting with hyperleukocytosis have frequent complications and early mortality. Pulmonary, central nervous system, and cardiovascular complications are common. Attempts to improve outcomes in the 10% of AML patients arriving with hyperleukocytosis have included leukapheresis. No prospective randomized study has supported the use of leukapheresis, and retrospective reports have revealed persistently poor outcomes as well as emerging concerns of acquired coagulopathy and worsening hypoxemia after leukapheresis. While many centers use a leukapheresis protocol processing two blood volumes, Johns Hopkins protocol routinely processes three-five blood volumes. This study aimed to assess coagulopathy, hypoxemia, and mortality with large volume leukapheresis. Methods: 32 patients with newly diagnosed AML treated with large volume leukapheresis for WBC depletion are included in this report. Demographic, clinical, laboratory, and apheresis-related data were collected. Coagulopathy and hypoxemia-related metrics were evaluated within 6 hours before leukapheresis and within 6 hours of completion of leukapheresis. Descriptive and inferential statistics (chi square and Mann-Whitney U test) were used to compare pre and post-leukapheresis findings and assess clinical outcomes. Results: Twenty-nine of 32 (93.8%) patients presented with symptomatic leukostasis (with pulmonary and/or CNS symptoms in 26/29). Median blood volume processed was 14.8 liters (range 4-23.4L). Mean platelet count decreased from 60x109/L to 37x109/L after leukapheresis (p Conclusions: Patients with AML presenting with hyperleukocytosis have a very high mortality, particularly when complicated by symptomatic leukostasis. Similar to Van de Louw's report, we observed worsening coagulopathy and a subgroup with increased oxygen requirements after leukapheresis. While our sample size is too small to draw broad conclusions, we were not able to identify a group clearly benefiting from leukapheresis. We did not find evidence that larger volume leukapheresis decreased complications or mortality. These results should lead to caution when considering leukapheresis for patients with newly diagnosed AML, particularly in those presenting with a severe coagulopathy. Table Disclosures Webster: Pfizer: Consultancy; Amgen: Consultancy; Genentech: Research Funding. Gojo:Amphivena: Research Funding; Amgen Inc: Consultancy, Honoraria, Research Funding; Juno: Research Funding; Merck: Research Funding; Jazz: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. Pratz:Boston Biomedical: Consultancy; Millenium/Takeda: Research Funding; Agios: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding. Smith:Celgene: Consultancy; Jazz: Consultancy; Pfizer: Consultancy; Agios: Consultancy; Novartis: Consultancy. DeZern:Astex Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy. Levis:Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria.

Expression of putative targets of immunotherapy in acute myeloid leukemia and healthy tissues

Since the bone marrow is both the site of disease in most hematologic malignancies and a reservoir of tumor specific T cells, we hypothesized that MILs collected after alloBMT in patients treated with PTCy could be a source of tumor-specific T cells for adoptive immunotherapy. We report results of a first-in-human study of ddMILs, i.e., engrafted allogeneic T cells harvested from the patients' marrow. The primary objectives of this study is to determine feasibility of expanding ddMILs from patients relapsing after alloBMT and the incidence of ddMILs induced grade III-IV acute GVHD. Engrafted patients with relapse after HLA-matched or haploBMT with PTCy as GVHD prophylaxis; at least 6 months post-transplant and without active grade GVHD were eligible. BM was harvested (200 ml) from relapsed patients under ambulatory conscious sedation. Dose-escalated ddMILs were expanded ex-vivo and infused following salvage chemotherapy using pre-determined dosing schedules. A total of 17 patients were harvested and expanded (AML (5), MM (8), CLL (3) and CML (1)) with anti-CD3/CD28 magnetic beads for 10 days. Patients had a medium 22.3 (1.8-104.3)-fold expansion, except the initial 3 AML patients with a high blast counts and low lymphocyte contents which prompted a modification to enrollment criteria requiring 500/µl. Following this modification, we effectively expanded all subsequent patient products. 14 patients received ddMILs: 4 HLA-matched patients (3 patients received 1 × 107 CD3+cells/kg and 1 patent was treated at escalated dose of 5 × 107) and 10 HLA-haploBMT (5 at 1 × 106, 3 at 5 × 106 and 2 at 1 × 107 CD3+T cells/kg). The median time post-transplant at time of MILs infusion was 28 months. Following salvage chemotherapy and MILs infusion, absolute neutropenia (ANC 500 was 7 days. For patients who initially responded and then progressed, intra-patient dose-escalation was done upon retreatment. Overall, no cases of GVHD were observed. Two patients with MM sustained a PR for 9 months at lower doses of ddMILs and 1 MM patient who received 5 × 106 HLA-mismatched ddMILs is in CR >12 months post-infusion (overall response of 30%). One haplo AML patient treated initially with 1 × 106 CD3+T cells/kg progressed and was retreated with 5 × 106 CD3+T cells/kg after salvage chemotherapy. This patient achieved a second CR lasting 9 months. Three patients with relapsed CLL after alloBMT were put on ibrutinib with minimal response and then received ddMILs: two patients are showing no signs of disease progression. In this ongoing phase 1 study, ddMILs has shown promising efficacy in adult patients with relapsed malignancies after alloBMT. The excellent safety profile, the absence of GVHD, and early evidence of clinical activity at low doses suggests a potentially more active, less toxic alternative to the traditional DLI.

Background: Blinatumomab, a CD19/CD3 bispecific T cell engager antibody construct, leads to improved outcomes in patients with R/R CD19+ ALL compared to standard chemotherapy. However, most adults fail to achieve complete remission (CR) with blinatumomab, and the median duration of remission is only 7.3 months. Preclinical studies have shown significantly increased PD-L1 expression on leukemic blasts in patients who are refractory to or relapse after response to blinatumomab. Additionally, expression of the exhaustion markers PD-1 and TIM-3 on bone marrow (BM) CD3+ T cells is significantly higher among ALL patients than controls. The addition of PD-1 blockade +/- CTLA-4 blockade to blinatumomab and ALL blasts in vitro leads to increased T cell proliferation and enhanced blinatumomab-mediated cytotoxicity (Feucht et al, Oncotarget 2016). Thus, blockade of co-inhibitory pathways represents a viable strategy to enhance blinatumomab efficacy. We describe early results of a multi-center phase I study combining blinatumomab with monoclonal antibodies targeting PD-1 (nivolumab) +/- CTLA-4 (ipilimumab) in R/R CD19+ ALL. Methods: This phase I dose-escalation study evaluates the safety and tolerability (MTD) of blinatumomab in combination with nivolumab +/- ipilimumab using a 3+3 design. Patients ≥16 years-old with R/R CD19+ Pre-B ALL or MPAL are eligible including those with prior blinatumomab and/or prior allogeneic transplant (allo-SCT). Patients ≥60 years may be untreated and those 16-21 must be R/R to ³2 lines of therapy. The trial started at dose level (DL) A1 (Fig. 1). Upon determining the MTD for the combination of blinatumomab and nivolumab, dose escalation will add ipilimumab (DLB1). Patients may receive up to 5 cycles of blinatumomab and 1 year of nivolumab/ipilimumab. Patients achieving CR may proceed to allo-SCT. Patients removed from the study during the blinatumomab lead-in (days 1-10) will be replaced. Results: As of July 31, 2018, 8 adults (4 males/4 females) had enrolled at DLA1. The median age was 55 (range, 25-75) and baseline BM blast percentage was 73% (range, 8-98%). Baseline characteristics are presented in Figure 2. Seven patients received cytoreduction before treatment (6 steroids only and 1 steroids + Cytoxan). Two patients previously treated with blinatumomab were withdrawn from the study during the blinatumomab lead-in (1 for G3 pericardial effusion 2/2 disease progression and 1 for G3 hyperbilirubinemia). Among the 5 patients who received nivolumab to date, drug-related non-hematologic AEs of grade ≥3 included elevated AST (20%), ALT (20%), amylase (20%), and lipase (G4, 20%); hypophosphatemia (20%); rash (20%); infusion-related reaction (G4, 20%); and hypotension (20%). The elevated AST, ALT, amylase and lipase occurred prior to nivolumab dosing and resolved. One patient was removed from the study for a G4 infusion-related reaction following the 2nd dose of nivolumab that was considered a DLT. One patient in CR developed G4 neutropenia in cycles 2 + 3 but recovered spontaneously. Among the 5 evaluable patients, 4 (80%) achieved CR without MRD (2 after 1 cycle and 2 after 2 cycles of blinatumomab) with 3 ongoing remissions (median f/u 5 months) and 1 extramedullary relapse at day 125. Data on biomarkers including changes in T cell subpopulations in both BM and PB, and co-signaling molecule expression will be presented. Conclusions: Combination therapy with blinatumomab and nivolumab in R/R ALL with is feasible with acceptable toxicity. The MRD-negative CR rate was (80%) despite heavily pre-treated patients with significant baseline disease burden. The last patient treated at DLA1 is undergoing treatment before dose escalation to include ipilimumab. Disclosures DeAngelo: Shire: Honoraria; ARIAD: Consultancy, Research Funding; Takeda: Honoraria; BMS: Consultancy; Amgen: Consultancy; Blueprint Medicines: Honoraria, Research Funding; Pfizer Inc: Consultancy, Honoraria; Glycomimetics: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Luznik:WIndMIL Therapeutics: Equity Ownership, Patents & Royalties. Gojo:Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Merck inc: Research Funding; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

BACKGROUND: Recurrent mutations in isocitrate dehydrogenase 1 (IDH1) are observed in approximately 4% of patients with myelodysplastic syndrome (MDS) and have been linked with increased transformation to acute myeloid leukemia. Ivosidenib (AG-120), an oral, potent, targeted, small-molecule inhibitor of the mutant IDH1 protein (mIDH1), is a therapeutic candidate for the treatment of patients with mIDH1 MDS. Through inhibition of mIDH1, ivosidenib suppresses the production of the oncometabolite 2-hydroxyglutarate (2-HG), leading to clinical responses via differentiation of malignant cells. AIM: To report safety and efficacy data from patients with relapsed or refractory (R/R) MDS enrolled in the first-in-human, phase 1, dose escalation and expansion study of ivosidenib in patients with mIDH1 advanced hematologic malignancies (NCT02074839). METHODS: This ongoing study is evaluating the safety, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and clinical activity of ivosidenib. Trial enrollment was completed on 08May2017. In dose escalation, patients received single-agent ivosidenib orally once daily (QD) or twice daily in 28-day cycles. The MTD was not reached and 500 mg QD was selected as the dose to be tested in expansion. Expansion Arm 3 enrolled patients with mIDH1 advanced hematologic malignancies, including MDS. The overall response rate (ORR) for MDS was defined as complete remission (CR) + partial remission + marrow CR. Exploratory biomarker assessments included baseline co-occurring mutations (next-generation sequencing panel for hematologic malignancies) and mIDH1 variant allele frequency (VAF) in bone marrow mononuclear cells (BEAMing Digital PCR; lower limit of detection for mIDH1, 0.02-0.04%). Here, we present safety and efficacy data for patients with MDS in expansion Arm 3 and in dose escalation whose starting dose was 500 mg QD. RESULTS: In all, 258 patients (78 in dose escalation, 180 in expansion) received ivosidenib, including 12 patients with MDS (9 from expansion and 3 from escalation) whose starting dose was 500 mg QD. Baseline characteristics for these 12 patients were: 9 men/3 women; median age, 72.5 years (range, 52-78) and 42% were ≥75 years of age; median number of prior therapies, 1 (range, 1-3). As of 10Nov2017, 7 of 12 (58.3%) patients remained on treatment and 5 (41.7%) had discontinued (one for allogeneic stem cell transplantation). The median duration of exposure to ivosidenib was 11.0 months (range, 3.3-31.1). The most common adverse events (AEs) of any grade, irrespective of causality, occurring in ≥20% of the 12 patients were back pain (n=4, 33.3%) and anemia, decreased appetite, diarrhea, dyspnea, fatigue, hypokalemia, pruritus, and rash (n=3, 25.0% each). The majority of these AEs were grade 1-2 and reported as unrelated to treatment. No AEs led to permanent discontinuation of treatment. IDH differentiation syndrome (IDH-DS) was observed in 2 of 12 (16.7%) patients; the events were grade 1 and 2, respectively. Of the 12 patients with MDS receiving ivosidenib 500 mg QD, 5 achieved CR (41.7%; 95% CI 15.2%, 72.3%) and 6 achieved marrow CR (50.0%), resulting in an ORR of 91.7% (95% CI 61.5%, 99.8%). The median durations of CR and overall response were not estimable at the time of the data cutoff. The percentages of patients who remained in CR and response at 12 months were 60.0% and 61.4%, respectively. Among 5 patients who were transfusion dependent at baseline, 4 became transfusion independent for at least 56 days on treatment. Baseline co-occurring mutations and changes in mIDH1 VAF levels on ivosidenib therapy will be presented. CONCLUSION: In patients with mIDH1 R/R MDS, ivosidenib monotherapy was well tolerated and induced durable remissions and transfusion independence. These findings support the role of ivosidenib as an effective, oral, targeted treatment for patients with mIDH1 R/R MDS. Disclosures DiNardo: Karyopharm: Other: Advisory role; Medimmune: Other: Advisory role; Celgene: Other: Advisory role; Bayer: Other: Advisory role; Agios: Consultancy, Other: Advisory role; AbbVie: Consultancy, Other: Advisory role. Watts:Jazz Pharma: Consultancy, Speakers Bureau; Takeda: Research Funding. Stein:Celgene: Consultancy; Daiichi Sankyo: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Bayer: Consultancy. de Botton:Agios: Research Funding; Celgene: Honoraria, Research Funding. Fathi:Takeda: Consultancy, Honoraria; Jazz: Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Boston Biomedical: Consultancy, Honoraria; Astellas: Honoraria; Seattle Genetics: Consultancy, Honoraria; Agios: Honoraria, Research Funding. Stein:Amgen: Speakers Bureau; Celgene: Speakers Bureau. Foran:Agios: Research Funding; Xencor, Inc.: Research Funding. Stone:AbbVie: Consultancy; Agios: Consultancy, Research Funding; Cornerstone: Consultancy; Orsenix: Consultancy; Fujifilm: Consultancy; Sumitomo: Consultancy; Pfizer: Consultancy; Celgene: Consultancy, Other: Data and Safety Monitoring Board, Steering Committee; Ono: Consultancy; Novartis: Consultancy, Research Funding; Otsuka: Consultancy; Jazz: Consultancy; Merck: Consultancy; Astellas: Consultancy; Arog: Consultancy, Research Funding; Argenx: Other: Data and Safety Monitoring Board; Amgen: Consultancy. Patel:France Foundation: Honoraria; Dava Oncology: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Tallman:Cellerant: Research Funding; BioSight: Other: Advisory board; ADC Therapeutics: Research Funding; AbbVie: Research Funding; Daiichi-Sankyo: Other: Advisory board; AROG: Research Funding; Orsenix: Other: Advisory board. Choe:Agios: Employment, Equity Ownership. Wang:Agios: Employment, Equity Ownership. Zhang:Agios: Employment, Equity Ownership. Dai:Agios: Employment, Equity Ownership. Fan:Agios: Employment, Equity Ownership. Yen:Agios: Employment, Equity Ownership. Kapsalis:Agios: Employment, Equity Ownership. Hickman:Agios: Employment, Equity Ownership. Agresta:Agios: Employment, Equity Ownership. Liu:Agios: Employment, Equity Ownership. Wu:Agios: Employment, Equity Ownership, Patents & Royalties. Attar:Agios: Employment, Equity Ownership.

BACKGROUND: Isocitrate dehydrogenase 1 (IDH1) mutations are seen in 6-10% of patients with acute myeloid leukemia (AML). Ivosidenib (AG-120), an oral, potent, targeted inhibitor of the mutant IDH1 protein (mIDH1), is a therapeutic candidate for mIDH1 AML. Ivosidenib suppresses production of the oncometabolite 2-hydroxyglutarate (2-HG), leading to clinical responses via differentiation of malignant cells. AIM: To determine the safety and efficacy of single-agent ivosidenib in patients with untreated AML enrolled in the first-in-human, phase 1, dose escalation and expansion study of patients with mIDH1 advanced hematologic malignancies (NCT02074839). METHODS: This ongoing study assesses the safety, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and clinical activity of ivosidenib. Enrollment completed on 08May2017. In dose escalation, patients received single-agent ivosidenib orally once daily (QD) or twice daily in 28-day cycles. MTD was not reached; 500 mg QD was selected as the dose for expansion cohorts. Overall response rate (ORR) was defined as complete remission (CR) + CR with incomplete hematologic or platelet recovery + partial response + morphologic leukemia-free state. CR with partial hematologic recovery (CRh) was defined as CR except absolute neutrophil count >0.5 × 109/L [500/µL] and platelet count >50 × 109/L [50,000/µL]). Exploratory biomarker assessments included baseline co-occurring mutations (next-generation sequencing panel for hematologic malignancies) and mIDH1 variant allele frequency (VAF) in bone marrow mononuclear cells (BEAMing Digital PCR; lower limit of detection for mIDH1, 0.02-0.04%). Here, we present data for all patients with untreated AML whose starting dose was 500 mg QD. RESULTS: In all, 258 patients (78 in dose escalation, 180 in expansion) received ivosidenib, including 34 patients with untreated AML (9 from dose escalation, 25 from expansion) who received ivosidenib 500 mg QD. Baseline characteristics for these 34 patients were: 19 male/15 female with median age 76.5 years (range 64-87); 56% were ≥75 years of age; 79% had secondary AML and 53% had prior MDS; 41% had ≥1 hypomethylating agent for antecedent hematologic disorder. As of 10Nov2017, 9 of 34 (26.5%) patients remained on treatment. Three (8.8%) patients discontinued treatment for allogeneic stem cell transplantation. Median duration of exposure to ivosidenib was 4.3 months (range 0.3-29.1). Treatment was well tolerated; the most common adverse events (AEs) (n=34) of any grade, irrespective of causality, occurring in ≥20% of patients were diarrhea (50.0%), fatigue (44.1%), nausea (38.2%), decreased appetite (32.4%), leukocytosis (26.5%), anemia (26.5%), peripheral edema (26.5%), dyspnea (23.5%), thrombocytopenia (23.5%), hypomagnesemia (23.5%), constipation (20.6%), dizziness (20.6%), and insomnia (20.6%). The majority of AEs were grade 1-2 and reported as unrelated to treatment. IDH differentiation syndrome (IDH-DS) was seen in 6 of 34 (17.6%) patients, and was grade ≥3 in 3 (8.8%); ivosidenib was held due to IDH-DS in 3 patients (8.8%), but IDH-DS did not lead to permanent treatment discontinuation or death. CR rate was 26.5% (95% CI 12.9%, 44.4%), CR+CRh rate was 41.2% (95% CI 24.6%, 59.3%), and ORR 58.8% (95% CI 40.7%, 75.4%; 20/34 patients). Median durations of CR, CR+CRh, and overall response were not estimable (lower bound of 95% CI 4.2, 6.5, and 4.2 months, respectively); 12-month durations of response were 75.0%, 56.4%, and 54.3%, respectively. Of patients who were transfusion dependent at baseline, 38.1% became transfusion independent for ≥56 consecutive days on treatment. Longitudinal mIDH1 VAF data were available for 23 patients with untreated AML in expansion: IDH1 mutation clearance was seen in 6 of 11 patients who achieved CR+CRh, including 3 of 7 patients with CR and 3 of 4 with CRh. The relationship between baseline co-occurring mutations and response will be presented. CONCLUSION: Ivosidenib monotherapy was well tolerated in patients with untreated mIDH1 AML, and induced durable remissions and transfusion independence in a molecularly defined, poor prognosis, elderly patient population with high rates of secondary AML, and prior hypomethylating agent exposure. These results support the role of ivosidenib as an effective, oral, targeted treatment for patients with untreated mIDH1 AML who are not eligible for intensive chemotherapy. Disclosures Roboz: Argenx: Consultancy; Orsenix: Consultancy; Jazz Pharmaceuticals: Consultancy; Cellectis: Research Funding; Sandoz: Consultancy; Aphivena Therapeutics: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy; Celgene Corporation: Consultancy; Bayer: Consultancy; Otsuka: Consultancy; Novartis: Consultancy; Orsenix: Consultancy; Pfizer: Consultancy; Celgene Corporation: Consultancy; Celltrion: Consultancy; Otsuka: Consultancy; Novartis: Consultancy; Eisai: Consultancy; AbbVie: Consultancy; Celltrion: Consultancy; Astex Pharmaceuticals: Consultancy; Janssen Pharmaceuticals: Consultancy; Cellectis: Research Funding; Janssen Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Roche/Genentech: Consultancy; Astex Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy; Sandoz: Consultancy; Eisai: Consultancy; Argenx: Consultancy; Bayer: Consultancy; Daiichi Sankyo: Consultancy; AbbVie: Consultancy; Aphivena Therapeutics: Consultancy. DiNardo:Karyopharm: Other: Advisory role; Medimmune: Other: Advisory role; Celgene: Other: Advisory role; Bayer: Other: Advisory role; Agios: Consultancy, Other: Advisory role; AbbVie: Consultancy, Other: Advisory role. Stein:Agios: Consultancy; Bayer: Consultancy; Daiichi Sankyo: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. de Botton:Agios: Research Funding; Celgene: Honoraria, Research Funding. Mims:Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy. Altman:Pfizer: Other: payment to the institution to conduct clinical trial work; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: payment to the institution to conduct clinical trial work; Agios: Other: Payment to the institution to conduct the trial ; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Bayer: Other: payment to the institution to conduct clinical trial work; GSK: Other: payment to the institution to conduct clinical trial work; Epizyme: Other: payment to the institution to conduct clinical trial work; Ariad: Other: payment to the institution to conduct clinical trial work; Boeringer Ingelheim: Other: payment to the institution to conduct clinical trial work; Immune Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Incyte: Other: payment to the institution to conduct clinical trial work; Astellas Pharma: Other; FujiFilm: Other: payment to the institution to conduct clinical trial work; Syros: Membership on an entity's Board of Directors or advisory committees; Cyclacel: Other: payment to the institution to conduct clinical trial work; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celator: Other: payment to the institution to conduct clinical trial work; Genetech: Other: Payment to the institution to conduct clinical trial work. Arellano:Cephalon: Research Funding. Mannis:Agios: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees; NKarta: Membership on an entity's Board of Directors or advisory committees. Pollyea:Gilead: Consultancy; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Curis: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Stein:Celgene: Speakers Bureau; Amgen: Speakers Bureau. Uy:GlycoMimetics: Consultancy; Curis: Consultancy. Watts:Jazz Pharma: Consultancy, Speakers Bureau; Takeda: Research Funding. Fathi:Astellas: Honoraria; Seattle Genetics: Consultancy, Honoraria; Boston Biomedical: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Jazz: Honoraria; Takeda: Consultancy, Honoraria; Agios: Honoraria, Research Funding. Kantarjian:Orsenix: Honoraria; Novartis: Research Funding; Immunogen: Honoraria; BMS: Honoraria, Research Funding; Astex: Research Funding; ARIAD: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Actinium: Honoraria; AbbVie: Honoraria; Pfizer: Honoraria, Research Funding. Tallman:AbbVie: Research Funding; BioSight: Other: Advisory board; AROG: Research Funding; Daiichi-Sankyo: Other: Advisory board; Orsenix: Other: Advisory board; ADC Therapeutics: Research Funding; Cellerant: Research Funding. Choe:Agios: Employment, Equity Ownership. Dai:Agios: Employment, Equity Ownership. Fan:Agios: Employment, Equity Ownership. Wang:Agios: Employment, Equity Ownership. Zhang:Agios: Employment, Equity Ownership. Yen:Agios: Employment, Equity Ownership. Kapsalis:Agios: Employment, Equity Ownership. Hickman:Agios: Employment, Equity Ownership. Liu:Agios: Employment, Equity Ownership. Agresta:Agios: Employment, Equity Ownership. Wu:Agios: Employment, Equity Ownership, Patents & Royalties. Attar:Agios: Employment, Equity Ownership. Stone:Merck: Consultancy; Cornerstone: Consultancy; AbbVie: Consultancy; Orsenix: Consultancy; Ono: Consultancy; Fujifilm: Consultancy; Otsuka: Consultancy; Celgene: Consultancy, Other: Data and Safety Monitoring Board, Steering Committee; Jazz: Consultancy; Astellas: Consultancy; Argenx: Other: Data and Safety Monitoring Board; Arog: Consultancy, Research Funding; Sumitomo: Consultancy; Novartis: Consultancy, Research Funding; Amgen: Consultancy; Agios: Consultancy, Research Funding; Pfizer: Consultancy.

BACKGROUND: Recurrent isocitrate dehydrogenase (IDH) 1 mutations are observed in 6-10% of patients with acute myeloid leukemia (AML). Ivosidenib (AG-120), a potent, selective, oral, small-molecule inhibitor of the mutant IDH1 (mIDH1) protein, is a promising therapeutic candidate for the treatment of patients with mIDH1 AML. Through inhibition of mIDH1, ivosidenib suppresses the abnormal production of the oncometabolite 2-hydroxyglutarate (2-HG), leading to clinical responses via differentiation of malignant cells. AIM: To report safety and efficacy data from the first-in-human phase 1 study of ivosidenib in patients with mIDH1 advanced hematologic malignancies including relapsed/refractory (R/R) AML (NCT02074839). This is the first report of data from the 4 expansion cohorts, with a total of 258 patients treated on study. METHODS: The ongoing phase 1 study assesses the safety, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and clinical activity of ivosidenib in mIDH1 hematologic malignancies. Enrollment was completed on May 8, 2017. During dose escalation, patients received ivosidenib as a single agent orally once daily (QD) or twice daily (BID) in 28-day cycles. The MTD was not reached and 500 mg QD was selected as the recommended dose to be tested in 4 expansion cohorts: R/R AML (Arms 1 and 4, where Arm 1 patients are those with relapse after transplantation, second or later relapse, resistance to initial induction or reinduction treatment, or relapse within 1 year of initial treatment, and Arm 4 patients have R/R AML but are not eligible for Arm 1); untreated AML (Arm 2); and other advanced hematologic malignancies including myelodysplastic syndrome (MDS) (Arm 3). Updated safety data will be presented for all patients. Efficacy outcomes will be presented for all R/R AML patients treated at 500 mg QD across the dose escalation and expansion cohorts who received their first dose of ivosidenib at least 6 months prior to the analysis cut-off date of May 12, 2017, as well as for the poorest prognosis Arm 1 subset. Efficacy data for all treated patients from the other expansion cohorts (untreated AML and other advanced hematologic malignancies including MDS) will also be presented. RESULTS: In all, 258 patients (78 in dose escalation, 180 in expansion) were treated with ivosidenib. As of May 12, 2017, 62 of 258 (24%) patients were continuing on treatment. The median duration of exposure to ivosidenib was 3.5 months (range 0.1-33.5). Twenty-two (8.5%) patients discontinued treatment to proceed to allogeneic stem cell transplantation. Treatment was well tolerated; the most common adverse events (AEs) (n=258) of any grade irrespective of causality occurring in ≥20% of patients were diarrhea (33%), leukocytosis (30%), nausea (30%), fatigue (29%), febrile neutropenia (25%), dyspnea (24%), anemia (23%), QT prolongation (23%), peripheral edema (22%), pyrexia (21%), and decreased appetite (20%). The majority of these AEs were grades 1-2 and reported as unrelated to treatment. Differentiation syndrome (DS) was observed in 29 of 258 (11.2%) patients, including grade ≥3 DS in 14 (5.4%); study drug was held owing to DS in 11 patients (4.3%), and no instances of DS led to permanent treatment discontinuation or death. The primary efficacy endpoint for R/R AML is the CR+CRh rate, i.e., the rate of complete remission (CR according to modified IWG 2003 criteria plus CR with partial hematologic recovery, defined as CR except absolute neutrophil count >0.5 × 109/L [500/µL] and platelet count >50 × 109/L [50,000/µL]). Among 125 Arm 1 R/R AML patients receiving ivosidenib 500 mg QD across dose escalation and expansion who received their first dose at least 6 months prior to the analysis cutoff date, the CR+CRh rate was 30.4% (95% CI 22.5%, 39.3%), including CR in 27 (21.6%) and CRh in 11 (8.8%) patients. Median duration of CR+CRh was 8.2 months (95% CI 5.5, 12.0), and duration of CR was 9.3 months (95% CI 5.6, 18.3). The overall response rate (CR+CRi/CRp+PR+MLFS) was 41.6% (95% CI 32.9%, 50.8%) (52/125 patients). CONCLUSION: Ivosidenib monotherapy is well tolerated in patients with mIDH1 AML and other advanced hematologic malignancies. In a high-risk, molecularly defined R/R AML patient population with unmet medical need, ivosidenib induced durable remissions and improved patient outcomes. These findings support the role of ivosidenib as an effective, oral, targeted treatment for patients with mIDH1 AML. Disclosures DiNardo: Celgene: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. De Botton: Pfizer: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Servier: Honoraria; Agios: Honoraria, Research Funding. Stein: GSK: Other: Advisory Board, Research Funding; Constellation Pharma: Research Funding; Seattle Genetics: Research Funding; Agios Pharmaceuticals, Inc.: Consultancy, Research Funding; Celgene Corporation: Consultancy, Other: Travel expenses, Research Funding; Pfizer: Consultancy, Other: Travel expenses; Novartis: Consultancy, Research Funding. Roboz: AbbVie, Agios, Amgen, Amphivena, Array Biopharma Inc., Astex, AstraZeneca, Celator, Celgene, Clovis Oncology, CTI BioPharma, Genoptix, Immune Pharmaceuticals, Janssen Pharmaceuticals, Juno, MedImmune, MEI Pharma, Novartis, Onconova, Pfizer, Roche Pharmace: Consultancy; Cellectis: Research Funding. Mims: Novartis: Honoraria. Pollyea: Takeda, Ariad, Alexion, Celgene, Pfizer, Pharmacyclics, Gilead, Jazz, Servier, Curis: Membership on an entity's Board of Directors or advisory committees; Agios, Pfizer: Research Funding. Altman: Syros: Consultancy; NCCN: Other: Educational speaker; BMS: Consultancy; Celgene: Consultancy; Astellas: Consultancy; Ceplene: Consultancy; Janssen Pharmaceuticals: Consultancy; Novartis: Consultancy; ASH: Other: Educational speaker. Collins: Celgene Corporation: Research Funding; Agios: Research Funding; Arog: Research Funding; BMS: Research Funding. Mannis: Curis: Honoraria; Juno: Research Funding; Agios: Research Funding; Amgen: Honoraria. Uy: GlycoMimetics: Consultancy; Novartis: Consultancy, Other: Travel Suppport; Boehringer Ingelheim: Consultancy. Fathi: Juno: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Medimmune: 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. Stein: Amgen: Consultancy, Speakers Bureau; Stemline: Consultancy. Erba: Celgene: Consultancy, Other: Chair, Scientific Steering Committee , Speakers Bureau; Incyte: all research support paid to University of Alabama, Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Other: all research support paid to University of Alabama, Research Funding; Daiichi Sankyo: Consultancy, Other: all research support paid to University of Alabama, Research Funding; ImmunoGen: Consultancy, Other: all research support paid to University of Alabama, Research Funding; MacroGen: Consultancy; Ono: Consultancy; Pfizer: Consultancy; Seattle Genetics: Consultancy, Other: all research support paid to University of Alabama, Research Funding; Sunesis: Consultancy; Millennium/Takeda: Consultancy, Other: all research support paid to University of Alabama, Research Funding; Agios: Other: all research support paid to University of Alabama, Research Funding; Juno: Other: all research support paid to University of Alabama, Research Funding; Astellas: Other: all research support paid to University of Alabama, Research Funding; Celator: Other: all research support paid to University of Alabama, Research Funding; Janssen: Other: all research support paid to University of Alabama, Research Funding; Glycomimetics: Other: Chair, Data and Safety Monitoring Committee. Traer: ImmunoGen: Consultancy; Tolero: Consultancy; Notable Labs: Equity Ownership. Stuart: Pharmacyclics LLC, an AbbVie Company: Research Funding; Amgen: Consultancy, Honoraria; Agios: Research Funding; Celator/Jazz: Research Funding; Sunesis: Consultancy, Honoraria, Other: Travel Support, Research Funding; Bayer: Research Funding; Novartis: Research Funding; Incyte: Research Funding; ONO: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Research Funding; MedImmune: Research Funding; Cantex: Research Funding; Astellas: Research Funding. Arellano: Cephalon Oncology: Research Funding. Sekeres: Celgene: Membership on an entity's Board of Directors or advisory committees. Yen: Agios: Employment, Equity Ownership. Kapsalis: Agios: Employment, Equity Ownership. Liu: Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Goldwasser: Agios: Employment, Equity Ownership. Agresta: Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Attar: Agios: Employment, Equity Ownership. Stone: Novartis: Consultancy; Celgene: Consultancy; Amgen: Consultancy; Abbvie: Consultancy; Fuji Film: Consultancy; Jazz: Consultancy; Astellas: Consultancy; Pfizer: Consultancy; Arog: Consultancy; Ono: Consultancy; Agios: Consultancy; Sumitomo: Consultancy. Kantarjian: ARIAD: Research Funding; Bristol-Meyers Squibb: Research Funding; Delta-Fly Pharma: Research Funding; Amgen: Research Funding; Pfizer: Research Funding; Novartis: Research Funding.

Introduction: AML pts have a poor prognosis with conventional chemotherapy regimens. Early lymphocyte recovery (ELR) following intensive timed sequential therapy (TST) induction is characterized by a dysfunctional immunosuppressive state. Pomalidomide (Pom), a small molecule immunomodulatory agent (IMiD), has direct effects on T cell co-stimulation by promoting the ubiquitination of Aiolos, an IL-2 transcriptional repressor. We hypothesized that the administration of Pom at the time of ELR after induction TST may influence T cell differentiation and enhance an anti-leukemia immune effect. Methods: A multicenter phase 1 dose escalation study was conducted to determine the safety and tolerability of Pom after intensive induction TST in newly diagnosed AML and HR-MDS pts 18-65 years. Core-binding factor AML was excluded. All pts received induction chemotherapy with AcDVP16: cytarabine 667 mg/m2/day IV continuous infusion days 1-3, daunorubicin 45 mg/m2/day IV days 1-3, etoposide 400 mg/m2/day IV days 8-10. Pom was administered at the assigned dose and schedule after day 14 and within 3 days of the total white blood cell count (WBC) reaching >0.2x109/L above nadir, defined as ELR. Three dose levels were planned (2 mg, 4 mg and 8 mg) within 2 cohorts: 10 days of Pom and 21 days of Pom, in a traditional 3+3 dose escalation design. Results: 25 pts were enrolled on this study January 2014-June 2016 across 3 institutions (Table 1). Pom administration occurred at a median of 21 days after AcDVP16 induction. There were no dose-limiting toxicities (DLTs) in the first cohort of Pom x 10 days within each dose level- 2 mg (n=3), 4 mg (n=3) and 8 mg (n=7). There were no DLTs seen at 4 mg x 21 days (n=7). Two DLTs were seen at Pom 8 mg x 21 days (Grade 3 ALT increase and Grade 3 hypoxia, respectively). Thus, Pom 4 mg x 21 days will be further expanded. Nine (36%) pts discontinued Pom early (median duration = 5 days) due to: grade 3 rash (n=3), physician discretion (decreased WBC: n=1, fever and increased creatinine: n=1), grade 3 ALT increase (n=1), grade 3 hypoxia (n=1), disease progression (n=1), and pt preference (n=1). Adverse events (AEs) possibly associated with Pom that were seen in >1 pt included fever (n=8), rash (n=7), AST/ALT increase (grade 1: n=4, grade 3: n=1), mucositis (n=2), and fatigue (n=2). All of these AEs were self-limiting with supportive care and/or discontinuation of Pom. 60-day mortality was 0%. A complete remission (CR) was achieved in 18 pts and 1 achieved CR with incomplete platelet recovery (CRp) with a combined CR + CRp = 19/25 (76%). Among pts with adverse-risk AML, 5/6 (83%) achieved CR. One pt achieved a partial remission and 5 pts were refractory to treatment. Of the 19 CRs, 15 had no evidence of minimal residual disease by cytogenetics, FISH, or flow cytometry. Among pts who completed a course of Pom (10 days or 21 days), 14/16 (88%) achieved CR. As previously reported, a dramatic decrease of Aiolos expression via flow cytometry in T cell subsets was observed in vivo for the duration of POM treatment with doses > 2 mg, but the effect was lost after Pom was stopped. Figure 1 displays the pattern of cytokine production of CD4+ T cells visualized with pie charts, and shows a significantly different subset composition at ELR in Pom-treated pts compared to the same pts at full recovery (p=0.02), and compared to control AML pts at the same time point (p=0.004). Furthermore, there was a significant increase in TNF-α production (p=0.009) and the combination of TNF-α and IL-2 production (p=0.03) in stimulated CD4+ T cells during Pom treatment, which was reduced to baseline values after Pom was discontinued at full recovery (Figure 1: data analysis performed with the SPICE software). Conclusions: Pom can be safely administered at the time of ELR after intensive induction TST. Fever and rash are the most common AEs seen after Pom administration. Inhibition of Aiolos and consequent increase in both IL-2 and TNF-α expression, as measured by flow cytometry, appear to be reliable markers of Pom-induced T cell modulation in vivo. Planned expansion of the cohort of 4 mgx 21 days will allow further evaluation of safety and activity of Pom in AML. Expression of Cytokines in CD4+ T Cells Expression of Cytokines in CD4+ T Cells Disclosures Zeidner: Takeda: Research Funding; Merck: Research Funding; Agios: Honoraria; Otsuka: Consultancy; Tolero: Research Funding. Zeidan:Celgene: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Ariad: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Smith:Celgene: Consultancy, Other: member of DSMB. Levis:Millennium: Consultancy, Research Funding; Daiichi-Sankyo: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding. Foster:Celgene: Research Funding.

FLT3 ITD mutations occur in both cytogenetically normal and abnormal AML. FLT3 ITD mutated AML is associated with genomic instability and clonal evolution (Gourdinet al., Cancer Genet 2014). The most common other molecular abnormality in FLT3 ITD AML, NPM1, has been shown to participate in DNA damage response and base excision repair but its role in clonal evolution in AML is poorly characterized (Polettoet al., Mol Biol of Cell 2014). We set out to describe the characteristics of clonal evolution in FLT3 ITD AML cases treated at Johns Hopkins Hospital (JHH) over the past 15 years to characterize clinical outcomes in these leukemias. 211 patients with FLT3 ITD AML were seen at JHH between 2000 and 2015, including newly diagnosed cases, and those referred for relapsed disease, with diagnostic and response information was available for 162 patients. 132 patients (81.4%) achieved remission, of which 66 subsequently relapsed (50%). 26 (16%) patients were refractory to therapy, 3 (1.8%) patients died during induction therapy, and 1 (0.6%) patient chose supportive care only. Characteristics at diagnosis are described in Table 1. Median relapse free survival was 1.07 year and median overall survival was 1.48 years (Table 2). Relapse free survival (RFS) and overall survival (OS) were longer for patients who were less than 60 years old (p=0.001 and p/=40 bp). Median RFS was nearly twice as long for patients with NPM1 mutations (median 2.11 v 1.06 yrs, p=NS). The 5-year overall survival for the NPM1 positive patients was 49.6%, when compared to 29.4% for NPM1 negative patients. The median allelic burden and ITD length at relapse (49% and 62bp) were similar to those at diagnosis (30% and 56.5bp) and most remained FLT3 ITD mutated at relapse (88%)(Table 3). 50% of relapsed patients were found to have new cytogenetic abnormalities (27/54). Of those with new findings, 26/27 (96%) of those cytogenetic changes were acquired structural abnormalities (26/27). 9/27 (33%) were acquired numerical abnormalities and 8/27 (30%) acquired both structural and numerical abnormalities. Those patients who acquired structural abnormalities had a median RFS of 0.77 years versus those who remained cytogenetically unchanged from diagnosis had a median RFS of 0.62 years(p=NS). Interestingly, patients with abnormal cytogenetics at diagnosis were not statistically more likely to acquire new cytogenetic abnormalities at relapse than patients with normal cytogenetics at diagnosis who relapsed (40% versus 54%, p=NS). Patients with NPM1 mutations at diagnosis appeared to acquire new cytogenetic abnormalities at relapse less often (5/15) than NPM1 negative patients (7/11)(33% versus 64%, p=NS), although this observation did not reach statistical significance (Fishers exact test). Patients who acquired cytogenetic abnormalities had a higher median allelic burden at diagnosis (67.5% versus 24%), although those without cytogenetic evolution had higher allelic burden at relapse (127.5% vs 38.5% median allelic burden). ITD lengths were similar for both groups at diagnosis (58bp and 56.5bp) but patients who acquired cytogenetic abnormalities also had longer median ITD lengths at relapse (67.5 bp versus 57.5 bp). These results suggest that FLT3 ITD AML is a heterogeneous disease with variable clinical outcome linked to age at diagnosis, NPM1 status, FLT3 ITD allelic burden, and transplantation status. Cytogenetic clonal evolution is common in FLT3 ITD AML, irrespective of karyotype at diagnosis and likely reflects ongoing DNA repair and replication deficiencies in the leukemic clone. Further characterization of this deficiency may reveal future therapeutic targets. Disclosures Smith: Celgene: Consultancy, Other: member of DSMB. Levis:Novartis: Consultancy, Honoraria, Research Funding; Millennium: Consultancy, Research Funding; Daiichi-Sankyo: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding.

INTRODUCTION Recurrent somatic mutations in the metabolic enzymes isocitrate dehydrogenase 1 and 2 (IDH1/2) confer gain-of-function activity in cancer cells, resulting in accumulation of the oncometabolite, D-2-hydroxyglutarate (2-HG). High levels of 2-HG result in epigenetic changes and impaired cellular differentiation. IDH mutations have been identified in multiple solid tumors and hematologic malignancies. Approximately 6-10% and 9-13% of adults with acute myeloid leukemia (AML) carry mutations in IDH1 (mIDH1) or IDH2 (mIDH2), respectively. AG-120 is a first-in-class, oral, potent, reversible, selective inhibitor of the IDH1 mutant enzyme under evaluation in multiple ongoing single agent and combination clinical trials [NCT02074839, NCT02073994, NCT02632708, NCT02677922]. This is the first report of IDH1 mutation clearance assessed by variant allele frequency (VAF) analysis using next-generation sequencing (NGS) in patients treated on the dose escalation portion of the first-in-human phase 1 study [NCT02074839]. METHODS Patients with advanced mIDH1-positive hematologic malignancies received AG-120 as a single agent orally once daily (QD) or twice daily (BID) continuously in 28-day cycles. Primary objectives were determination of safety, maximum tolerated dose (MTD), and selection of a dose schedule for expansion cohorts and future studies. Secondary objectives included clinical activity assessed by investigators using modified 2003 International Working Group Criteria in AML. Determination of mIDH1 VAF was performed using the FoundationOne® Heme test on mononuclear cells from the bone marrow or peripheral blood at screening and subsequent time points on study. This NGS assay reports IDH1 mutations for samples with VAF ≥1%, with median coverage 500X. Patients with IDH1 mutational clearance (IDH1-MC) were defined as having mIDH1 at baseline and at least one on-study sample with no reported mIDH1. RESULTS Seventy-eight patients were treated in the dose escalation portion, which is now closed to enrollment. As of the data cut-off of May 12, 2016, the median duration on treatment was 3.2 months and 9 (11.5%) patients remain on treatment, with an additional 8 (10.3%) patients transitioned to stem cell transplant. Doses ranged from 300-1200 mg QD with 1 cohort at 100 mg BID. Though the MTD was not reached, the recommended phase 2 dose was determined to be 500 mg QD. The majority of adverse events (AEs) were grade 1 and 2, the most common (≥30%) being diarrhea, fatigue, and nausea; the most common grade ≥3 AEs (≥15%) were febrile neutropenia, anemia, leukocytosis and pneumonia. The most common serious AEs were febrile neutropenia (16.7%) and pneumonia (12.8%). The overall response rate (ORR) was 38.5% (n=30), with 17.9% (n=14) achieving a complete remission (CR). Longitudinal mIDH1 VAF data were available for 51 patients; of these, 22% (n=11) achieved a CR. IDH1-MC was observed in 27.3% (3/11) patients who achieved CR (Figure 1). In contrast, only 1/40 patients who did not achieve CR experienced IDH1-MC. This occurred in a patient with an initially low mIDH1 VAF who had clinical progression despite IDH1-MC (Figure 1, bottom right). In all 3 patients with CR who achieved IDH1-MC, an initial increase in mIDH1 VAF, or early peak, was observed prior to IDH1-MC, suggesting that early clonal expansion might have occurred as part of the mechanism of action of AG-120. CONCLUSION This is the first demonstration that treatment with single agent AG-120 can result in mIDH1 clearance as determined by NGS. Further analysis of the mutational profiles is planned. AG-120, a potent, selective, oral inhibitor of mIDH1 continues to demonstrate a well-tolerated safety profile in patients with advanced hematologic malignancies, and induced objective single-agent durable responses. The data continue to support the efficacy and safety of single agent AG-120 and provide evidence that the underlying biology of the disease is altered by treatment. Figure 1. VAF analysis using FoundationOne® Heme NGS assay in 4 AML patients with IDH1-MC treated with AG-120 Figure subscript: Y-axis is mIDH1 VAF, x-axis is days on treatment. Text indicates investigator-assessed clinical response. CR, complete remission; CRi, CR with incomplete neutrophil recovery; CRp, CR with incomplete platelet recovery; R/R, relapsed/refractory; SD, stable disease; PD, progressive disease; *post-transplant sample Figure 1. VAF analysis using FoundationOne® Heme NGS assay in 4 AML patients with IDH1-MC treated with AG-120. / Figure subscript: Y-axis is mIDH1 VAF, x-axis is days on treatment. Text indicates investigator-assessed clinical response. CR, complete remission; CRi, CR with incomplete neutrophil recovery; CRp, CR with incomplete platelet recovery; R/R, relapsed/refractory; SD, stable disease; PD, progressive disease; *post-transplant sample Disclosures DiNardo: Daiichi Sankyo: Other: advisory board, Research Funding; Novartis: Other: advisory board, Research Funding; Abbvie: Research Funding; Celgene: Research Funding; Agios: Other: advisory board, Research Funding. de Botton:Novartis: Consultancy; Agios: Consultancy, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Servier: Consultancy; Pierre Fabre: Consultancy. Stein:Agios: Other: advisory board; Celgene: Other: advisory board; Novartis: Other: advisory board. Roboz:Cellectis: Research Funding; Agios, Amgen, Amphivena, Astex, AstraZeneca, Boehringer Ingelheim, Celator, Celgene, Genoptix, Janssen, Juno, MEI Pharma, MedImmune, Novartis, Onconova, Pfizer, Roche/Genentech, Sunesis, Teva: Consultancy. Pollyea:Alexion: Other: advisory board; Pfizer: Other: advisory board, Research Funding; Ariad: Other: advisory board; Glycomimetics: Other: DSMB member; Celgene: Other: advisory board, Research Funding. Fathi:Bexalata: Other: Advisory Board participation; Agios Pharmaceuticals: Other: Advisory Board participation; Seattle Genetics: Consultancy, Other: Advisory Board participation, Research Funding; Merck: Other: Advisory Board participation; Celgene: Consultancy, Research Funding. Altman:Syros: Honoraria; BMS: Honoraria; Janssen Pharmaceuticals: Honoraria; Novartis: Honoraria. Flinn:Janssen: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Gilead Sciences: Research Funding; ARIAD: Research Funding; RainTree Oncology Services: Equity Ownership. Foran:novartis: Honoraria; Millennium Pharmaceuticals, Inc.: Research Funding; karyopharm: Honoraria; medscape: Honoraria; pfizer: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. Pigneux:Sunesis: Consultancy, Honoraria; Agios: Consultancy, Honoraria. Kantarjian:ARIAD: Research Funding; Bristol-Myers Squibb: Research Funding; Amgen: Research Funding; Pfizer Inc: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding. Liu:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Attar:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Sacolick:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Yen:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Hurov:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Choe:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Wu:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Stone:Amgen: Consultancy; Sunesis Pharmaceuticals: Consultancy; Pfizer: Consultancy; Roche: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy; Celator: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy; Novartis: Consultancy; Jansen: Consultancy; ONO: Consultancy; Juno Therapeutics: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Xenetic Biosciences: Consultancy.

Background: Concerns have been raised whether immune checkpoint inhibitor therapy in the alloBMT setting will result in graft versus host disease (GvHD) and transplant related mortality (TRM). We report our experience with a variety of checkpoint inhibitors used before or after allogeneic bone marrow transplantation (alloBMT). Our series comprises patients who received T cell-replete hematopoietic stem cells from HLA-haploidentical or -matched donors and is limited to those treated with post-transplant cyclophosphamide (PTCy) as primary GvHD prophylaxis. Patient selection: We retrospectively reviewed the records of alloBMT recipients who received PTCy and received checkpoint inhibitor therapy before or after alloBMT. GvHD was assessed using the CIBMTR GVHD index. Results: Eleven patients received checkpoint inhibitor therapy prior to alloBMT: anti-PD-1: Nivolumab n=6, anti-CTLA4: Ipilimumab n=8 (3 patients received both nivolumab and ipilimumab). These patients received a median of 4 (range 1 - 18) cycles of therapy. The median interval from last checkpoint inhibitor treatment to day of transplant was 43 (range 18-302) days. All patients received nonmyeloablative conditioning; 6 received partially mismatched allografts (5 were HLA haploidentical). Four patients developed Grade II aGvHD: Three patients who had received partially mismatched allografts (haplo-2, 9/10 unrelated-1) experienced stage 3 cutaneous GvHD only; one patient who received a 10/10 unrelated donor allograft developed stage 3 cutaneous GvHD with stage 1 liver involvement. Three patients were on immunosuppression when GvHD developed, the fourth patient with cutaneous and liver GvHD had been taken off tacrolimus on day 68 due to concerns of graft failure. GvHD resolved with treatment in each case. None of these patients developed chronic GvHD and none have died [median follow-up of 0.66 (range 0.91 - 2.0) years post alloBMT]. Nine patients received checkpoint therapy following alloBMT: anti-PD-1: Pembrolizumab n = 1, Nivolumab n= 6, anti-CTLA4: Ipilimumab n= 3 (one patient received nivolumab and ipilimumab). Eight patients had received nonmyeloablative conditioning; 5 received haploidentical allografts. Six received treatment for relapse of their hematologic malignancy, 1 for relapsed pediatric sarcoma, and 2 for newly diagnosed lung cancer. The median time to initiation of checkpoint inhibitor therapy was 1.2 (range: 0.8 - 5.8) years post alloBMT. Patients received a median of 5 (range 1 - 24) cycles of therapy. There was 1 case of Grade II aGvHD; stage 3 cutaneous GvHD when DLI from a 10/10 matched unrelated donor was given for relapsed disease after ipilimumab. This resulted in GvHD which was not accompanied by the desired graft-vs-leukemia effect. There were no other cases of acute or chronic GvHD in this group. There were 4 tumor-related deaths: pediatric sarcoma (1), lung cancer (1), and AML (2). The median follow-up for this group is 2 years (range 0.85 - 8.0) post alloBMT. Conclusions: In this small series, the incidence and severity of GvHD seen in patients who received checkpoint inhibitors was similar to that seen in patients treated with PTCy as GvHD prophylaxis without checkpoint inhibitors. GvHD was seen in patients treated with checkpoint inhibitors prior to alloBMT, but was generally mild and readily controlled and there were no associated deaths. In patients treated with checkpoint inhibitors after alloBMT, the only case of GvHD occurred after the patient received DLI. We caution that use of checkpoint inhibitors in closer temporal proximity to transplant might well be associated with increased risk of GvHD or severity of GvHD. Disclosures Borrello: WindMIL Therapeutics: Equity Ownership, Patents & Royalties, Research Funding; Celgene: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria, Research Funding. Wagner-Johnston:Seattle Genetics: Research Funding. Smith:Celgene: Consultancy, Other: member of DSMB.

The immunotherapy of cancer is arguably the most promising therapy under development, and vaccination against cancer antigens is a promising strategy to stimulate adaptive immune responses against malignant clones. However, the ability of patients treated with chemotherapy to respond appropriately to immune challenge may be suboptimal. This study was designed to determine the functional capacity of the immune system in adult acute myeloid leukemia (AML) patients who have completed chemotherapy and are potential candidates for immunotherapy. We used the response to influenza vaccination as a surrogate for the health of the immune system in AML patients in a complete remission (CR) post-chemotherapy. Ten adult AML patients in CR after completion of intensive chemotherapy were recruited to the clinical protocol J1293. They were on average 37 weeks post-treatment (range 4-148) when receiving the 2012-2013 inactivated seasonal influenza vaccine. Peripheral blood samples were collected at baseline and 30 days post-vaccination. Ten age and sex matched healthy donors (HD) served as baseline controls. Serological response to vaccination was assessed via microneutralization assays; multi-parameter flow cytometry was used to characterize lymphocyte subsets. ELISPOT assays were used to evaluate lymphocyte function, microarrays were used to assess gene expression, and deep sequencing of the B-cell receptor heavy chain (IGH) was performed to determine expansion and clonality of B-cells. Wilcoxon rank-sum tests were used to assess statistical significance. Only 2/10 (20%) patients seroconverted (AML responders, or AML-R) with a four-fold increase or greater in influenza-specific antibody. One responder was 148 weeks post-treatment; the other had acute promyelocytic leukemia (APL) and was 4 weeks post-treatment. Deep immunophenotyping revealed no striking differences in T-cell compartments between AML at baseline and HD, indicating rapid T-cell recovery after chemotherapy. In contrast, we observed a highly atypical B-cell profile. AML non-responders (AML-NR) at day 0 versus HD had significantly reduced frequencies of mature IgA+ (4.5% vs. 11%) and IgG+ (2.4% vs. 5.9%) B-cells (as a percentage of CD19+CD20+). Further dissection exposed markedly higher frequencies of CD10+CD27- transitional B-cells (36% vs. 16%, p Interestingly, functional T-cell assays revealed that of 5 evaluable patients, including the 2 AML-R and 3 AML-NR, 5/5 (100%) patients had an increase in influenza-specific cytokine production (1.24 - 4.40x higher on day 30 over baseline), suggesting a functional T-cell response even with deficient influenza-specific antibody production. Supervised clustering of microarray data identified many upregulated genes in AML-NR related to apoptosis, BCR, IL2, IL-4, IL-8, and IL-12 signaling pathways, indicative of developing B-cells. IGH sequencing demonstrated AML-NR had greater variability in CDR3 length than seen in HD, consistent with an antigen inexperienced B-cell repertoire. These data suggest that while some aspects of cellular immunity recover comparatively quickly, the humoral immune system is incompletely reconstituted in the year following intensive cytotoxic chemotherapy for AML. Abnormal frequencies of transitional and memory B-cells may explain the poor response to vaccination often seen in patients after chemotherapy. Furthermore, the uncoupled recovery of B-cell and T-cell immune capacity observed here might have implications for the success of immunotherapies based on vaccination. Figure 1. Figure 1. Disclosures Noonan: Celgene: Speakers Bureau. Borrello:Celgene: Research Funding.

Transfusion of red blood cells (RBCs) is vitally important for the care of patients (pts) undergoing myelosuppressive therapy for acute leukemia (AL). At diagnosis and before bone marrow recovery, RBCs are given liberally with hemoglobin (Hb) transfusion triggers of 8-9 g/dL or higher, often with two RBC units given at a time. Research in a variety of non-oncologic settings suggests that lower Hb triggers (7-8 g/dL) do not increase mortality whereas higher Hb triggers (9 g/dL) may increase mortality. For pts with hematologic malignancies, the ideal Hb threshold is unknown. Also, there is literature to suggest that higher Hb values force platelets to the periphery of capillaries and reduce bleeding events. A study of red cell triggers in pts with thrombocytopenia (as in AL) is important as we may not be able to rely on trigger data from others in this setting. This feasibility study was designed to determine whether a randomized trial of Hb triggers could be performed and what challenges may be encountered with this select population. In this prospective randomized study, we enrolled adult pts with AL (myeloid and lymphoid) undergoing intensive induction therapy to evaluate both patient and physician tolerance for a transfusion threshold of 7g/dL (LOW) compared to the standard threshold of 8g/dL (HIGH), as well as operationalize transfusion to a single unit per episode. Pts were randomized with a 2:1 ratio of LOW threshold to HIGH threshold. Pts were ineligible if there was clinical concern for acute coronary syndrome or active blood loss. Pts were monitored from the study enrollment date through the next marrow evaluation after completion of induction therapy. Vital status at Day 60, accrual rate, and safety endpoints (mortality, length of stay, infection, fatigue scores, renal, respiratory, thrombotic, bleeding events) were monitored. Total transfusions, length of inpatient stay, and percentage of pts who crossed over to HIGH threshold for symptomatic reasons were also monitored. Between April 15, 2014 and July 23, 2015, 162 acute leukemia pts would have been eligible for this trial. Of the eligible pts, 112 (69%) were approached and 90 (of planned 90) have enrolled to date. Twenty-two pts (19.6%) of those offered the trial declined. Seventy-four pts are currently evaluable for response (13 pts have not been on-study long enough to evaluate and 3 pts are not eligible for data analysis): 51 pts in LOW arm and 23 in HIGH arm. Interim data is shown in Table 1. In the LOW arm, three pts withdrew consent due to self-reported fatigue and one patient was removed by physician due to clinical scenario. Seventeen pts (33%) in the LOW arm and six pts (26%) in the HIGH arm were transfused outside their hemoglobin trigger without meeting criteria to discontinue the study. No deaths were attributable to Hb thresholds in this study. Significant bleeding events (Grade 3 or 4 by CTCAE 4.0) were comparable with 4 in LOW arm and 3 in HIGH arm. More minor bleeding events (Grade 1 or 2 by CTCAE 4.0) were higher in LOW (24 events) than in HIGH arm (15 events). Acute leukemia and its therapies carry a significant mortality risk and it is not clear how transfusion thresholds and number of PRBC units transfused impact this mortality. Furthermore, blood is an expensive and scarce resource. Without a clear benefit of higher Hb thresholds, the added risks and costs of transfusion may not be justified. This pilot study shows that both pts and leukemia physicians will tolerate randomization between Hb thresholds and there is not a signal for harm in either Hb threshold at present. Pts in the LOW arm receive fewer transfusions and do not experience higher fatigue scores nor increased significant bleeding events. Length of hospitalization was similar in both arms. This safety data will serve as a platform for a larger mortality study in leukemia and possibly additional studies in other oncologic diseases. Table 1. LOW HIGH P value Patients (n) 51 (69%) 23 (31%) Gender Male 23 (45%) 11 (48%) Median Age (Years) 58 63 0.35 AML 44 (86%) 18 (78%) ALL 5 (10%) 5 (22%) APL 2 (4%) 0 Patients Alive at Day 60 46 (90%) 21 (91%) Red Cell Transfusions in Units (Median) 8 (IQR: 5) 10 (IQR: 4) 0.008* Platelet Transfusions in Episodes (Median) 9 (IQR: 6.5) 9 (IQR: 5) 0.86 Length of Stay (Median) 35 (IQR: 10) 36 (IQR: 15) 0.72 Fatigue Scale Score (Median) 4.33 (IQR: 1) 4.54 (IQR: 1.25) 0.40 AML: acute myeloid leukemia; ALL: acute lymphoid leukemia; APL: acute promyelocytic leukemia Disclosures No relevant conflicts of interest to declare.

Background: We recently showed that early lymphocyte recovery (ELR) following intensive induction chemotherapy in AML patients (pts) is characterized by complex immune system aberrations. (Blood 117(2):608, 2011) Full characterization of lymphoid T cell dynamics during this period can provide critical insights into their dysfunction and rationale for targeted therapeutic intervention to augment anti-leukemia immunity. Pomalidomide (POM), a small molecule immunomodulatory agent (IMiD), has direct effects on T cell co-stimulation by promoting the ubitiquitination of IL-2 transcriptional repressor Aiolos (IKZF3). (Br J Haematol 164(6):811, 2014) We hypothesized that administration of POM at the time of ELR may influence T cell differentiation and function in vivo. Methods: We serially collected peripheral blood (PB) samples at the time of ELR from 31 AML pts (median age 57, range 29-76 years; 26 de novo and 5 secondary AML) treated with intensive induction chemotherapy (18 with timed-sequential therapy (TST) and 13 with standard 7+3: cytarabine and idarubicin), 11 AML pts (median age 52, range 31-66 years; 6 de novo, and 5 secondary AML) treated on NCI/CTEP#9524 study of TST induction (AcDVP16: cytarabine, daunorubicin, and etoposide) followed by POM given daily for 10 days at ELR at escalating doses: 2mg (3pts)-4mg (3pts)-8mg (5pts) (Figure 1) and 17 healthy controls (HC) (median age 40, range 25-71 years). ELR was defined as absolute white blood cell (lymphocyte) count >200/mm3 above nadir. Using multi-parameter flow cytometry we performed extensive phenotypic characterization of lymphocyte populations, focusing on T cell differentiation status (CD45RA, CCR7), activation/proliferation (Ki-67), expression of POM-target gene Aiolos (IKZF3), and cytokine secretion. Statistical significance was determined using multiple t-tests using GraphPad Prism software. All protocols were IRB approved. Results: Administration of POM at ELR did not affect absolute lymphocyte count (ALC) compared to control pts not receiving POM (P=>0.5). ALC values ranges (both groups): pre-treatment 2538-3645/mm3, ELR 428-525/mm3, and 931-1360/mm3 at full count recovery (FR1), respectively. The percentages and total numbers of CD4+ and CD8+ T cells behaved similarly; however, POM pts had increase in the frequency of CD4+ central memory subset (CD45RA- CCR7+) (P=0.001) at FR1 and decrease in the terminally differentiated effector memory subset (CD45RA+ CCR7-) of CD8+ T cells only for the duration of POM administration at ELR (P=0.04). Tregs (CD4+ FoxP3+ Tcells) increased in control pts during ELR (p=0.004; n=26) but not in POM-treated group (n=5). A dramatic but dose-dependent decrease of Aiolos expression in T cell subsets in vivo (P Conclusions: ELR represents an interesting time period for therapeutic intervention to modulate immunity following chemotherapy in AML pts. POM administration phenotypically and functionally affected several T cell subsets in vivo. Our data suggest that inhibition of Aiolos, an IL-2 transcriptional repressor, is a reliable pharmacodynamic marker of POM activity on T cells in vivo. Further studies with longer POM administration schedules as well as examination of other compartments such as bone marrow are ongoing to better define the role of immune modulation with POM in the treatment of pts with AML. Disclosures Off Label Use: Pomalidomide is not FDA approved for acute myeloid leukemia..