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Myeloid leukemia in children with Down syndrome (ML-DS) is associated with young age and somatic GATA1 mutations. Because of high event-free survival (EFS) and hypersensitivity of the leukemic blasts to chemotherapy, the prior Children’s Oncology Group protocol ML-DS protocol (AAML0431) reduced overall treatment intensity but lacking risk stratification, retained the high-dose cytarabine course (HD-AraC), which was highly associated with infectious morbidity. Despite high EFS of ML-DS, survival for those who relapse is rare. AAML1531 introduced therapeutic risk stratification based on the previously identified prognostic factor, measurable residual disease (MRD) at the end of the first induction course. Standard risk (SR) patients were identified by negative MRD using flow cytometry (

Bortezomib (BTZ) was recently evaluated in a randomized phase 3 clinical trial by the Children’s Oncology Group (COG) that compared standard chemotherapy (cytarabine, daunorubicin, and etoposide [ADE]) vs standard therapy with BTZ (ADEB) for de novo pediatric acute myeloid leukemia (AML). Although the study concluded that BTZ did not improve outcome overall, we examined patient subgroups benefiting from BTZ-containing chemotherapy using proteomic analyses. The proteasome inhibitor BTZ disrupts protein homeostasis and activates cytoprotective heat shock responses. Total heat shock factor 1 (HSF1) and phosphorylated HSF1 (HSF1-pSer326) were measured in leukemic cells from 483 pediatric patients using reverse phase protein arrays. HSF1-pSer326 phosphorylation was significantly lower in pediatric AML compared with CD34+ nonmalignant cells. We identified a strong correlation between HSF1-pSer326 expression and BTZ sensitivity. BTZ significantly improved outcome of patients with low-HSF1-pSer326 with a 5-year event-free survival of 44% (ADE) vs 67% for low-HSF1-pSer326 treated with ADEB (P = .019). To determine the effect of HSF1 expression on BTZ potency in vitro, cell viability with HSF1 gene variants that mimicked phosphorylated (S326A) and nonphosphorylated (S326E) HSF1-pSer326 were examined. Those with increased HSF1 phosphorylation showed clear resistance to BTZ vs those with wild-type or reduced HSF1-phosphorylation. We hypothesize that HSF1-pSer326 expression could identify patients who benefit from BTZ-containing chemotherapy.

B-cell lymphoma 6 (BCL6) is a transcription repressor and proto-oncogene that plays a crucial role in the innate and adaptive immune system and lymphoid neoplasms. However, its role in myeloid malignancies remains unclear. Here, we explored the role of BCL6 in acute myeloid leukemia (AML). BCL6 was expressed at variable and often high levels in AML cell lines and primary AML samples. AMLs with higher levels of BCL6 were generally sensitive to treatment with BCL6 inhibitors, with the exception of those with monocytic differentiation. Gene expression profiling of AML cells treated with a BCL6 inhibitor revealed induction of BCL6-repressed target genes and transcriptional programs linked to DNA damage checkpoints and downregulation of stem cell genes. Ex vivo treatment of primary AML cells with BCL6 inhibitors induced apoptosis and decreased colony-forming capacity, which correlated with the levels of BCL6 expression. Importantly, inhibition or knockdown of BCL6 in primary AML cells resulted in a significant reduction of leukemia-initiating capacity in mice, suggesting ablation of leukemia repopulating cell functionality. In contrast, BCL6 knockout or inhibition did not suppress the function of normal hematopoietic stem cells. Treatment with cytarabine further induced BCL6 expression, and the levels of BCL6 induction were correlated with resistance to cytarabine. Treatment of AML patient-derived xenografts with BCL6 inhibitor plus cytarabine suggested enhanced antileukemia activity with this combination. Hence, pharmacologic inhibition of BCL6 might provide a novel therapeutic strategy for ablation of leukemia-repopulating cells and increased responsiveness to chemotherapy. Key Points: • Primary human AML cells with higher levels of BCL6 expression displayed sensitivity when exposed to BCL6 inhibitors. • BCL6 induction contributed to cytarabine resistance, and inhibition of BCL6 in AML cells decreased leukemia stem cell activity.

The prognosis for infants with acute lymphoblastic leukemia (ALL), particularly those with KMT2A gene rearrangement (KMT2A-r), is dismal. Continuous efforts have been made in Japan to investigate the role of hematopoietic stem cell transplantation (HSCT) for infants with KMT2A-r ALL, but improvement in outcome was modest. In the Japanese Pediatric Leukemia/Lymphoma Study Group MLL-10 trial, infants with ALL were stratified into 3 risk groups (low risk [LR], intermediate risk [IR], and high risk [HR]) according to KMT2A status, age, and presence of central nervous system leukemia. Children’s Oncology Group AALL0631 modified chemotherapy with the addition of high-dose cytarabine in early intensification was introduced to KMT2A-r patients, and the option of HSCT was restricted to HR patients only. The role of minimal residual disease (MRD) was also evaluated. Ninety eligible infants were stratified into LR (n = 15), IR (n = 19), or HR (n = 56) risk groups. The 3-year event-free survival (EFS) rate for patients with KMT2A-r ALL (IR + HR) was 66.2% (standard error [SE], 5.6%), and for those with germline KMT2A (KMT2A-g) ALL (LR), the 3-year EFS rate was 93.3% (SE, 6.4%). The 3-year EFS rate was 94.4% (SE, 5.4%) for IR patients and 56.6% (SE, 6.8%) for HR patients. In multivariable analysis, female sex and MRD ≥0.01% at the end of early consolidation were significant factors for poor prognosis. Risk stratification and introduction of intensive chemotherapy in this study were effective and were able to eliminate HSCT for a subset of infants with KMT2A-r ALL. Early clearance of MRD seems to have translated into favorable outcomes and should be incorporated into risk stratifications in future trials. This trial was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as #UMIN000004801.

Metabolic alterations in cancer represent convergent effects of oncogenic mutations. We hypothesized that a metabolism-restricted genetic screen, comparing normal primary mouse hematopoietic cells and their malignant counterparts in an ex vivo system mimicking the bone marrow microenvironment, would define distinctive vulnerabilities in acute myeloid leukemia (AML). Leukemic cells, but not their normal myeloid counterparts, depended on the aldehyde dehydrogenase 3a2 (Aldh3a2) enzyme that oxidizes long-chain aliphatic aldehydes to prevent cellular oxidative damage. Aldehydes are by-products of increased oxidative phosphorylation and nucleotide synthesis in cancer and are generated from lipid peroxides underlying the non–caspase-dependent form of cell death, ferroptosis. Leukemic cell dependence on Aldh3a2 was seen across multiple mouse and human myeloid leukemias. Aldh3a2 inhibition was synthetically lethal with glutathione peroxidase-4 (GPX4) inhibition; GPX4 inhibition is a known trigger of ferroptosis that by itself minimally affects AML cells. Inhibiting Aldh3a2 provides a therapeutic opportunity and a unique synthetic lethality to exploit the distinctive metabolic state of malignant cells.

Treatment-related mortality is common among children with acute lymphoblastic leukemia (ALL) treated in poor-resource settings. We applied a simplified flow cytometric assay to identify patients with precursor B-cell ALL (B-ALL) at very low risk (VLR) of relapse and treated them with a reduced-intensity treatment plan (RELLA05). VLR criteria include favorable presenting features (age ≥ 1 and < 10 years), white blood cell count of

The BCL-2 inhibitor venetoclax combined with hypomethylating agents or low-dose cytarabine represents an important new therapy for older or unfit patients with acute myeloid leukemia (AML). We analyzed 81 patients receiving these venetoclax-based combinations to identify molecular correlates of durable remission, response followed by relapse (adaptive resistance), or refractory disease (primary resistance). High response rates and durable remissions were typically associated with NPM1 or IDH2 mutations, with prolonged molecular remissions prevalent for NPM1 mutations. Primary and adaptive resistance to venetoclax-based combinations was most commonly characterized by acquisition or enrichment of clones activating signaling pathways such as FLT3 or RAS or biallelically perturbing TP53. Single-cell studies highlighted the polyclonal nature of intratumoral resistance mechanisms in some cases. Among cases that were primary refractory, we identified heterogeneous and sometimes divergent interval changes in leukemic clones within a single cycle of therapy, highlighting the dynamic and rapid occurrence of therapeutic selection in AML. In functional studies, FLT3 internal tandem duplication gain or TP53 loss conferred cross-resistance to both venetoclax and cytotoxic-based therapies. Collectively, we highlight molecular determinants of outcome with clinical relevance to patients with AML receiving venetoclax-based combination therapies.

Myeloid leukemia in children with Down syndrome (ML-DS) is associated with young age and somatic GATA1 mutations. Because of high event-free survival (EFS) and hypersensitivity of the leukemic blasts to chemotherapy, the prior Children’s Oncology Group protocol ML-DS protocol (AAML0431) reduced overall treatment intensity but lacking risk stratification, retained the high-dose cytarabine course (HD-AraC), which was highly associated with infectious morbidity. Despite high EFS of ML-DS, survival for those who relapse is rare. AAML1531 introduced therapeutic risk stratification based on the previously identified prognostic factor, measurable residual disease (MRD) at the end of the first induction course. Standard risk (SR) patients were identified by negative MRD using flow cytometry (

Background: Alvocidib is an investigational cyclin-dependent kinase-9 (CDK9) inhibitor that can suppress RNA polymerase II-mediated transcription of genes implicated in leukemia cell survival, including myeloid leukemia cell-1 (MCL-1). MCL-1 is an anti-apoptotic BCL-2 family member that is a key mediator of apoptosis in AML. Alvocidib combined in a timed-sequential regimen with cytarabine and mitoxantrone (ACM) has shown clinical activity in newly diagnosed and relapsed/refractory (R/R) AML through Phase I and II clinical trials. Analysis of bone marrow samples from newly diagnosed AML patients (pts) treated with ACM showed an association of complete remission (CR) with MCL-1 dependence by a BH3 profiling biomarker assay. Zella 201 was initiated based on the hypothesis that ACM may have preferential clinical activity in pts with MCL-1 dependence. We report the findings from an exploratory cohort of newly diagnosed high-risk (NDHR) AML pts with MCL-1 dependence treated with ACM. Methods: Zella 201 is a biomarker-driven Phase II study of ACM in R/R AML patients with MCL-1 dependence. Stage 1 included a cohort of R/R AML pts with various levels of MCL-1 dependence and an exploratory cohort of NDHR AML with MCL-1 dependence >40%, as determined by a BH3 profiling assay. Eligibility criteria for the NDHR cohort included pts 18-65 years with high-risk AML defined as one of the following: A) treatment-related AML, B) AML from preexisting MDS/MPN, C) adverse-risk by ELN 2017 criteria. Induction therapy consisted of alvocidib 30 mg/m2 as a 30 minute IV bolus followed by 60 mg/m2 over 4 hours on Days (D) 1-3, cytarabine 667 mg/m2/D by continuous IV infusion D6-8, and mitoxantrone 40 mg/m2 IV on D9. Up to 3 additional cycles of the same regimen (with or without mitoxantrone) were permitted in responders. The primary endpoint was CR/CRi. Key secondary endpoints were overall survival (OS), relapse-free survival (RFS), overall response rate and safety. Results: Thirteen NDHR pts were treated and evaluable in this cohort (Table 1). One pt received alvocidib on days 1-3 and withdrew from the study on day 6 due to grade 4 diarrhea, cytokine release syndrome, and acute kidney injury. This pt was excluded from the efficacy analysis. Median MCL-1 score was 56% (Range: 42-70%). This cohort was influenced by the following poor risk categories: secondary AML (n= 9; 69%), adverse-risk by ELN (n=8; 62%) and TP53 mutations (n=6; 46%). The most common ≥Grade 3 treatment-emergent non-hematologic AEs (n=14) were diarrhea (29%); TLS, hypocalcemia, sepsis, hypotension (21%), pneumonia, colitis, hyperglycemia, anorectal infection, dyspnea, and left ventricular dysfunction (all 14%). Overall, CR/CRi was 62% with 7 (54%) pts responding following 1 cycle of therapy and another pt achieving CR after a second cycle. Two of six pts with TP53 mutation achieved CR. Although all pts included in this cohort were determined to be MCL-1 dependent, there was no association of CR with increasing MCL-1 dependence. Six (46%) pts went on to an allogeneic stem cell transplant (SCT). Sixty-day mortality was 0%. Median follow-up, OS, and RFS were 8.0, 8.5, and 6.1 months, respectively. Five of 8 (68%) CR/CRi pts have relapsed, and 10 pts (77%) have expired to date. The three pts still alive all received a post-study SCT. Conclusion: ACM has clinical activity in a limited cohort of NDHR AML pts with MCL-1 dependence scores >40% in a biomarker assay. Despite observed CR rates, duration of CR was modest and overall outcomes were poor. These results are comparable to historical controls with conventional chemotherapy regimens given the high-risk subset (62% of pts had adverse-risk and 46% had TP53 mutations). Further study is warranted to better define subgroups of ND AML pts who may benefit from alvocidib-containing induction regimens. Disclosures Zeidner: AsystBio Laboratories: Consultancy; AROG: Research Funding; Forty-Seven: Other: Travel Reimbursement, Research Funding; Merck: Research Funding; Sumitomo Dainippon Pharma Oncology, Inc.: Research Funding; Daiichi Sankyo: Honoraria; Genentech: Honoraria; Pfizer: Honoraria; Takeda: Consultancy, Honoraria, Other: Travel Reimbursement, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; AbbVie: Honoraria, Other: Independent Review Committee; Agios: Honoraria. Lee:Sumitomo Dainippon Pharma Oncology, Inc.: Research Funding; Novartis: Research Funding; Genentech: Research Funding; Forty Seven: Research Funding; Bayer: Research Funding; AbbVie: Research Funding; Celgene: Consultancy. Fine:Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Wang:Bristol Meyers Squibb (Celgene): Consultancy; Jazz Pharmaceuticals: Consultancy; Abbvie: Consultancy; Pfizer: Speakers Bureau; Genentech: Consultancy; Stemline: Speakers Bureau; PTC Therapeutics: Consultancy; Macrogenics: Consultancy; Astellas: Consultancy. Bhatt:Incyte: Consultancy, Research Funding; Oncoceutics: Other; National Marrow Donor Program: Research Funding; Jazz: Research Funding; Partnership for health analytic research: Consultancy; Takeda: Consultancy; Omeros: Consultancy; Agios: Consultancy; Rigel: Consultancy; Tolero: Research Funding; Pfizer: Research Funding; Abbvie: Consultancy, Research Funding. Kolibaba:Verastem: Honoraria; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Compass Oncology: Ended employment in the past 24 months; Seattle Genetics: Research Funding; Atara Biotech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sumitomo Dainippon Pharma Oncology, Inc.: Consultancy, Other: Travel, Accommodations, Expenses Paid; Genentech: Research Funding; Gilead: Research Funding; Janssen: Research Funding; Celgene: Research Funding; AbbVie: Research Funding; Acerta: Research Funding; McKesson Life Sciences: Consultancy; Cell Therapeutics: Research Funding; Pharmacyclics: Research Funding. Anthony:Sumitomo Dainippon Pharma Oncology, Inc.: Current Employment; Exact Sciences: Consultancy. Bearss:Sumitomo Dainippon Pharma Oncology, Inc: Current Employment. Smith:Jazz: 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; Pfizer: 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.

Background Addition of the BCL2 inhibitor venetoclax to lower intensity therapy improved survival (OS) for older and unfit patients with newly diagnosed AML. We have previously reported the safety and efficacy of the nucleoside analogue cladribine combined with high dose ara-C and idarubicin (ida) as an intensive induction regimen (CLIA) in patients with newly diagnosed AML. Here, we report the results of the combination of venetoclax with the CLIA regimen for younger, fit patients with newly diagnosed AML. Methods Patients < 65 years of age with newly diagnosed AML or high-risk MDS were enrolled (NCT02115295). Induction was cladribine 5 mg/m2 IV on D1-5, ara-C 1.5 g/m2 IV on D1-5, and idarubicin 10 mg/m2 IV on D1-3; venetoclax was given at an effective dose of 400mg PO on D2-8 without ramp up with every cycle. Consolidation consisted of 3d of CLIA (2d of ida). AML patients with FLT3-ITD or FLT3 point mutations could receive midostaurin on D6-19 or gilteritinib on D1-14 for induction, and continuously thereafter. Venetoclax dose modifications for CYP3A4 inhibitors were made. All patients underwent baseline next generation sequencing and MRD testing by multiparameter flow cytometry at the time of response. Results A total of 31 patients have been enrolled. The median age was 48 years (range, 18-64). Baseline characteristics are shown in Table 1. Median follow up is 8.8 months. All patients were evaluable for response, with 28 of 31 (90%) achieving a remission, including 23 (74%) complete remission (CR) and 5 (16%) CR with incomplete count recovery (CRi) (Table 1). Of the 2 patients that did not respond, one was ELN adverse risk with TP53 mutation and complex karyotype, the other was ELN favorable risk with a t(8;21) translocation and mutations in IDH1 and JAK2. At time of initial response assessment 19 of 30 (63%) had undetectable MRD, with another 4 patients (77%) becoming MRD negative overall. Median cycles until response was 1 (range: 1 - 2), and patients have received a median of 2 cycles (range: 1 - 5). Median time to absolute neutrophil count ≥ 1000/µL was 32 days (range: 18 - 49) and platelet count ≥ 50k and 100k/µL were 29 days (range: 17 - 61) and 32 days, respectively after induction. 8 patients received FLT3 inhibition (FLT3i) in addition to CLIA and venetoclax, 7 (88%) with gilteritinib and 1 (12%) with midostaurin. Within this subset, there were 6/8 (75%) CR and 1 CR (12%) (Table 2). Median overall survival (OS) for those receiving FLT3i is not yet reached (95% CI: 0.79 - NE months). Median duration of response for the entire cohort is not reached. At 6 and 12 months 87% of responders had an ongoing response (SE=9%). 18 of 28 (64%) of responders received an allogeneic stem cell transplant. Median OS has not been reached, with 6- and 12-month rates of OS 93% (SE=5%) and 81% (SE=9%), respectively (Figure 1). Median OS in all ELN risk categories has not yet been reached, with 6 month OS of 91% (SE=9%), 100% (SE=NA), and 83% (SE=15%) in favorable, intermediate, and adverse risk groups, respectively (Figure 2). Median event free survival (EFS) has not been reached, with 6- and 12-month rates of EFS are 90% (SE=5%) and 79% (SE=9%), respectively. Overall the regimen was well tolerated, with an acceptable toxicity profile. Tumor lysis syndrome was not seen. The most common Grade >/= 3 adverse events were neutropenic fever, pneumonia, nausea, and liver transaminitis. There was one induction death in the FLT3i cohort and none with CLIA + venetoclax. Conclusion Venetoclax added to CLIA was safe and highly effective in newly diagnosed pts with AML and high risk MDS, including patients with FLT3-mutated AML and adverse risk by ELN or IPSS-R. The addition of FLT3i may be associated with delayed count recovery. CLIA plus venetoclax provided high rates of durable MRD negative remissions and encouraging event-free and overall survival across prognostic subgroups. Disclosures Kantarjian: BMS: Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive biotechnologies: Honoraria; Aptitute Health: Honoraria; BioAscend: Honoraria; Daiichi-Sankyo: Honoraria, Research Funding; Immunogen: Research Funding; Jazz: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Sanofi: Research Funding; Delta Fly: Honoraria; Ascentage: Research Funding; Janssen: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Oxford Biomedical: Honoraria. Borthakur:Abbvie: Research Funding; BioLine Rx: Consultancy; FTC Therapeutics: Consultancy; BioTherix: Consultancy; Jannsen: Research Funding; GSK: Research Funding; Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy; Argenx: Consultancy; AstraZeneca: Research Funding; Cyclacel: Research Funding; PTC Therapeutics: Consultancy; PTC Therapeutics: Research Funding; Novartis: Research Funding; BioLine Rx: Research Funding; BMS: Research Funding; Incyte: Research Funding; Curio Science LLC: Consultancy; Oncoceutics: Research Funding; Xbiotech USA: Research Funding; Polaris: Research Funding. Yilmaz:Daicho Sankyo: Research Funding; Pint Pharma: Honoraria; Pfizer: Research Funding. DiNardo:ImmuneOnc: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Calithera: Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Notable Labs: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria; Jazz: Honoraria; MedImmune: Honoraria; Syros: Honoraria; Novartis: Consultancy. Andreeff:Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy. Daver:Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Fate Therapeutics: Research Funding; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Jain:Aprea Therapeutics: Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Fate Therapeutics: Research Funding; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Pfizer: Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics: Research Funding; TG Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Cellectis: Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Precision Bioscienes: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Jabbour:Takeda: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; Pfizer: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; Adaptive Biotechnologies: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding. Short:Astellas: Research Funding; Amgen: Honoraria; AstraZeneca: Consultancy; Takeda Oncology: Consultancy, Honoraria, Research Funding. Alvarado:Daiichi-Sankyo: Research Funding; BerGenBio ASA: Research Funding; Tolero Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Research Funding; FibroGen: Research Funding; MEI Pharma: Research Funding; Sun Pharma: Research Funding. Bose:Constellation Pharmaceuticals: Research Funding; Celgene Corporation: Honoraria, Research Funding; CTI BioPharma: Honoraria, Research Funding; Blueprint Medicines Corporation: Honoraria, Research Funding; Pfizer, Inc.: Research Funding; Astellas Pharmaceuticals: Research Funding; NS Pharma: Research Funding; Promedior, Inc.: Research Funding; Incyte Corporation: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kartos Therapeutics: Honoraria, Research Funding. Garcia-Manero:Merck: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; AbbVie: Honoraria, Research Funding; H3 Biomedicine: Research Funding; Amphivena Therapeutics: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acceleron Pharmaceuticals: Consultancy, Honoraria; Onconova: Research Funding; Novartis: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria, Research Funding; Helsinn Therapeutics: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy, Honoraria, Research Funding. Konopleva:Sanofi: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Ablynx: Research Funding; Genentech: Consultancy, Research Funding; Ascentage: Research Funding; Amgen: Consultancy; Agios: Research Funding; AstraZeneca: Research Funding; Eli Lilly: Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Cellectis: Research Funding; Calithera: Research Funding; Kisoji: Consultancy; AbbVie: Consultancy, Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Forty-Seven: Consultancy, Research Funding. Ravandi:Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; AstraZeneca: Consultancy, Honoraria; Xencor: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Orsenix: Consultancy, Honoraria, Research Funding. Kadia:Amgen: Research Funding; Cellenkos: Research Funding; Cyclacel: Research Funding; Genentech: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Novartis: Honoraria; BMS: Honoraria, Research Funding; Astra Zeneca: Research Funding; Celgene: Research Funding; Ascentage: Research Funding; Astellas: Research Funding; Pulmotec: Research Funding; Incyte: Research Funding; Pfizer: Honoraria, Research Funding; JAZZ: Honoraria, Research Funding.

INTRODUCTION: The outcome of patients (pts) with relapsed or refractory AML (R/R AML) or MDS after failing hypomethylating agents (HMA) and/or BCL-2 inhibitor combinations is poor. CPX-351 is a liposomal formulation of cytarabine and daunorubicin, approved by the US Food and Drug Administration (FDA) for newly diagnosed therapy related AML or AML with myelodysplastic related changes. GO is a humanized immunoglobulin G4 antibody directed against CD33 and conjugated to the DNA toxin calicheamicin, also approved by the FDA for the treatment of newly diagnosed or R/R CD33-positive AML. We have hypothesized that the combination of CPX-351 and GO could induce superior antitumor efficacy compared to either agent alone for this patient population. GOALS: To determine the safety and efficacy of CPX-351 in combination with GO in relapsed refractory pts with AML and post-HMA failure HR-MDS. METHODS: This is a single arm and single institution, pilot study (NCT03672539) enrolling patients with CD33 positive R/R AML, post-HMA failure High-Risk MDS (>10% blasts), and pts with newly diagnosed secondary AML after receiving HMA therapy. Patients received induction cycle CPX-351 (daunorubicin 44 mg/m2 and cytarabine 100 mg/m2) administered via intravenous (IV) infusion on days 1, 3, and 5. GO was administered at a dose of 3 mg/m2 (capped at one 4.5 mg vial) IV on day 1. Pts not attaining complete remission (CR) or CR with incomplete count recovery (CRi) after 1 cycle, could receive a 2nd induction cycle of CPX-351 at the same dose, but only on days 1 and 3 with GO 3 mg/m2 on day 1. Patients attaining CR/CRi could receive up to 2 consolidation cycles, after a minimum of 4 weeks from the start of the last cycle with CPX-351 (daunorubicin 29 mg/m2 and cytarabine 65 mg/m2) IV on days 1 and 3, and GO at 3 mg/m2 on day 1. GO was only administered during the second consolidation cycle if there was evidence of minimal residual disease (+MRD). GO could also be administered as a single agent for maintenance treatment on day 1 every 6 weeks, in case of persistent detection of MRD. RESULTS: Twenty pts have been enrolled between November 2018 and July 2019. At the time of data cut off 19 pts were evaluable for response, with one patient too early to assess for response. Patient characteristics are summarized on Table 1; of note 14 (70%) pts had previously been treated with venetoclax in different combinations with HMA's and/or chemotherapy. We observed an overall response rate (ORR) of 42% (n=8), including CR (n=5), CRi (n=1) and PR (n=2). Responses are summarized in Table 2. Among the eight responders there were 4 pts with MRD negative (by flow cytometry) remission. One patient who was considered in CR was taken off study on day 40 because of an underlying invasive fungal sinus infection and concerns of myelosuppression. This patient was transitioned to a lower intensity regimen and remains in remission. Four pts completed 2 inductions, 5 pts received consolidation and 2 pts received GO maintenance before progressing. Unfortunately, none could be transitioned to transplantation due to age or comorbidities. Among responders, median time to ANC >500 was 39 days (30-56) and PLT >50k was 40 days (33-46), median time to ANC >1K was 40 days (31-74) and PLT >100K was 43 days (34-53) after induction (Table 3). With a median follow up of 18.6 months, median OS is 9.1 months (Figure 1) and median duration of response was 10.5 months (figure 2). Adverse events regardless of causality (Table 4) were mainly due to infectious complications. We have not observed treatment related grade 3-4 non-hematological toxicity. Thirty-day mortality was 10% (n=2); both pts died from complications of septicemia. Three additional pts (15%) died within 60 days of treatment, including 2 pts with progressive disease and 1 patient on day 58 after withdrawing care due to infections and 2 aplastic bone marrow examinations on days 14 and 46 of treatment, respectively. CONCLUSION: In this preliminary report, the combination of CPX-351 and GO appears to be active with acceptable toxicities in this high-risk disease population. There are concerns for significant myelosuppression and infectious complications. Disclosures Kadia: Cyclacel: Research Funding; Ascentage: Research Funding; Astellas: Research Funding; Novartis: Honoraria; Genentech: Honoraria, Research Funding; JAZZ: Honoraria, Research Funding; Incyte: Research Funding; Celgene: Research Funding; Pulmotec: Research Funding; Cellenkos: Research Funding; Astra Zeneca: Research Funding; Amgen: Research Funding; Pfizer: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Faderl:Jazz Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Sasaki:Pfizer Japan: Consultancy; Otsuka: Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo: Consultancy. Daver:Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Fate Therapeutics: Research Funding; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees. DiNardo:Syros: Honoraria; Agios: Consultancy, Honoraria, Research Funding; MedImmune: Honoraria; Takeda: Honoraria; Notable Labs: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Jazz: Honoraria; Novartis: Consultancy; ImmuneOnc: Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Calithera: Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Jabbour:Adaptive Biotechnologies: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; Takeda: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; Pfizer: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding. Pemmaraju:Stemline Therapeutics: Honoraria, Research Funding; LFB Biotechnologies: Honoraria; Pacylex Pharmaceuticals: Consultancy; Plexxikon: Research Funding; MustangBio: Honoraria; Roche Diagnostics: Honoraria; Samus Therapeutics: Research Funding; DAVA Oncology: Honoraria; Cellectis: Research Funding; Affymetrix: Other: Grant Support, Research Funding; Daiichi Sankyo: Research Funding; AbbVie: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Incyte Corporation: Honoraria; SagerStrong Foundation: Other: Grant Support; Celgene: Honoraria; Blueprint Medicines: Honoraria. Konopleva:AbbVie: Consultancy, Research Funding; Kisoji: Consultancy; Calithera: Research Funding; Amgen: Consultancy; Sanofi: Research Funding; Ascentage: Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Genentech: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Forty-Seven: Consultancy, Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Ablynx: Research Funding; Agios: Research Funding; AstraZeneca: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding. Garcia-Manero:Acceleron Pharmaceuticals: Consultancy, Honoraria; AbbVie: Honoraria, Research Funding; Novartis: Research Funding; Onconova: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy; H3 Biomedicine: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amphivena Therapeutics: Research Funding; Helsinn Therapeutics: Consultancy, Honoraria, Research Funding; Merck: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding. Andreeff:Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Amgen: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding. Kantarjian:Jazz Pharma: Research Funding; Novartis: Research Funding; Agios: Honoraria, Research Funding; Ariad: Research Funding; Amgen: Honoraria, Research Funding; Takeda: Honoraria; AbbVie: Honoraria, Research Funding; BMS: Research Funding; Pfizer: Honoraria, Research Funding; Astex: Research Funding; Daiichi-Sankyo: Research Funding; Immunogen: Research Funding; Cyclacel: Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ravandi:Amgen: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Orsenix: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Astellas: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding. Alvarado:MEI Pharma: Research Funding; Sun Pharma: Research Funding; FibroGen: Research Funding; BerGenBio ASA: Research Funding; Tolero Pharmaceuticals: Research Funding; Daiichi-Sankyo: Research Funding; Jazz Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding.

BACKGROUND: CNS directed chemotherapy (chemo) reduces the risk of CNS relapse of ALL, but the optimal way to measure baseline CNS involvement is controversial. Baseline CSF testing can provide risk stratification and often dictates CNS prophylaxis (ppx) during initial treatment. Despite advances, up to 10% of adults still suffer CNS relapse (Blood 2008;112:1646, Cancer 2014;120:3660). Testing typically focuses on conventional cytospin (CC) of CSF, but CC is limited by interobserver variability and insensitivity (Blood 2014;124:3799). Alternatively, MFC is more sensitive (ASH 2018, #658). A previous study in children with ALL found leukemia detection in the CNS by CC or MFC at diagnosis to be associated with an increased risk of both isolated bone marrow and any CNS relapse (ASH 2018, #657). To our knowledge, this use of MFC has not specifically been studied in hyperCVAD, a commonly used chemotherapy regimen for the initial treatment of adult ALL. We hypothesized that baseline lymphoblast detection in the CSF by MFC is predictive of CNS relapse. METHODS: We included data collected from 11/6/07 to 6/22/20. Patients (pts) ≥18 years old who received ≥4 cycles (equivalent of cycle 2B) of hyperCVAD as first-line therapy were eligible. Pts must have had MFC done on CSF at baseline. Pts with mixed phenotype or insufficient follow-up data were excluded. CNS ppx with hyperCVAD historically uses intra-CSF (ie, intrathecal or intraventricular) methotrexate 12 mg on day 2 and cytarabine 100 mg on day 8 of each cycle for 6-12 doses without cranial radiation, though all patients were treated per physician discretion. CC and MFC results were taken from clinical reports and verified by an independent hematopathologist (Dr. Cherian). Baseline CSF positivity (CSF+) and negativity (CSF-) were defined by MFC, with any percentage of lymphoblasts considered CSF+. COG definitions of CNS status by CC were also used (J Clin Oncol 2016;34:2380). Univariate Cox models evaluated associations to CNS relapse. Kaplan-Meier curves were used to estimate the probabilities of overall survival (OS) and cumulative incidence of CNS relapse. RESULTS: We identified 92 eligible pts. Disease and treatment characteristics are summarized in Table 1, and results of initial CSF testing are shown in Table 2. Twenty-one pts were CSF+ by MFC at baseline: by CC, 6 of these were positive, 6 were negative, 7 were equivocal (ie, morphologic review was unable to rule out blasts), and 2 did not have baseline CC. None were positive by CC but negative by MFC. Eight of 29 (38%) with circulating blasts had a traumatic (>10 RBC/uL of CSF) first lumbar puncture (LP). Of these 8, 4 (50%) were CSF+. Five (5%) pts had an Ommaya reservoir placed during treatment. Pts received a median of 8 doses of intra-CSF chemo (range, 5-52). All but 7 pts (8%) received a combination of methotrexate and cytarabine like above. Twenty CSF+ pts (95%) achieved CSF- after a median of 1 dose of intra-CSF chemo (range, 1-5). Out of the 71 CSF- pts, none became CSF+ during initial treatment despite being tested a median of 5 times (range, 2-10). Eight pts (9%) had CNS relapse (3 isolated, 5 concurrent medullary relapse). Comparisons between baseline CSF testing, intra-CSF treatment, and CNS relapse are shown in Table 2. CSF+ pts received significantly greater doses of intra-CSF chemo. Of the 21 CSF+ pts, 5 (24%) had CNS relapse (2 isolated, 3 concurrent), and out of the 71 CSF- pts, 3 (4%) had CNS relapse (1 isolated, 2 concurrent; p=0.014). Among univariate models of CSF+ vs -, traumatic LP vs not, B vs T lineage, LDH, and WBC, only CSF+ was significantly associated with CNS relapse (hazard ratio 4.8, 95% confidence interval [CI] 1.2-20, p=0.031). Estimated 3-year cumulative incidence of CNS relapse for CSF+ was 15% vs 3.3% for CSF- (Figure 1). Median OS for the whole cohort was not reached, with estimated 3-year OS of 74% (95% CI, 65%-84%). CONCLUSIONS: MFC of CSF is more predictive of CNS relapse risk than CC in the context of front-line hyperCVAD, questioning the use of CC if MFC is performed. Further, CNS relapses were significantly more frequent when CSF+ despite administration of significantly more intra-CSF chemo. Traumatic LP per se did not increase risk of CNS relapse if CSF- by MFC. Surveillance during treatment by MFC in CSF- pts identified no cases of occult CNS relapse, arguing against this routine practice. Future studies should consider incorporating MFC of CSF into risk-adapted CNS-directed treatment strategies. Disclosures Shustov: Seattle Genetics: Research Funding. Becker:Accordant Health Services/Caremark: Membership on an entity's Board of Directors or advisory committees; Cardiff Oncology: Research Funding; SecuraBio: Research Funding; Novartis: Research Funding; Pfizer: Research Funding; JW Pharmaceutical: Research Funding; Glycomimetics: Research Funding; Abbvie: Research Funding; Bristol Myers Squibb: Research Funding; Invivoscribe: Research Funding. Oehler:Takeda: Consultancy; BMS: Consultancy; Pfizer, Inc: Research Funding. Halpern:Bayer: Other; Novartis: Other; Jazz Pharmaceuticals: Other; Imago BioSciences: Other; Tolero Pharmaceuticals: Research Funding. Walter:Amgen: Consultancy, Research Funding; Arog: Research Funding; Argenx: Consultancy; Aptevo: Consultancy, Research Funding; Amphivena: Current equity holder in publicly-traded company; Agios: Consultancy, Research Funding; StemLine: Research Funding; Selvita: Research Funding; Seattle Genetics: Research Funding; Race Oncology: Consultancy; Pfizer: Consultancy, Research Funding; New Link Genetics: Consultancy; Macrogenics: Research Funding; Kite: Consultancy; Jazz: Consultancy, Research Funding; ImmunoGen: Research Funding; Genentech: Consultancy; Daiichi: Consultancy; Celgene: Consultancy, Research Funding; Boston Biomedical: Consultancy; BiVictriX: Consultancy; BioLineRx: Consultancy, Research Funding; Astellas: Consultancy. Godwin:Pfizer Inc.: Research Funding; Immunogen Inc.: Research Funding. Cassaday:Kite/Gilead: Consultancy, Research Funding; Merck: Research Funding; Seattle Genetics: Current Employment, Current equity holder in publicly-traded company; Amgen: Consultancy, Research Funding; Vanda Pharmaceuticals: Research Funding; Pfizer: Honoraria, Research Funding.

Aberrant activation of mTOR signaling in acute myeloid leukemia (AML) results in a survival advantage that promotes the malignant phenotype. To improve our understanding of factors that contribute to mammalian target of rapamycin (mTOR) signaling activation and identify novel therapeutic targets, we searched for unique interactors of mTOR complexes through proteomics analyses. We identify cyclin dependent kinase 9 (CDK9) as a novel binding partner of the mTOR complex scaffold protein, mLST8. Our studies demonstrate that CDK9 is present in distinct mTOR-like (CTOR) complexes in the cytoplasm and nucleus. In the nucleus, CDK9 binds to RAPTOR and mLST8, forming CTORC1, to promote transcription of genes important for leukemogenesis. In the cytoplasm, CDK9 binds to RICTOR, SIN1, and mLST8, forming CTORC2, and controls messenger RNA (mRNA) translation through phosphorylation of LARP1 and rpS6. Pharmacological targeting of CTORC complexes results in suppression of growth of primitive human AML progenitors in vitro and elicits strong antileukemic responses in AML xenografts in vivo.

Patients with acute myeloid leukemia (AML) and a FLT3 internal tandem duplication (ITD) have poor outcomes to current treatment. A phase 2 hypothesis-generating trial was conducted to determine whether the addition of the multitargeted kinase inhibitor midostaurin to intensive chemotherapy followed by allogeneic hematopoietic cell transplantation (alloHCT) and single-agent maintenance therapy of 12 months is feasible and favorably influences event-free survival (EFS) compared with historical controls. Patients 18 to 70 years of age with newly diagnosed AML and centrally confirmed FLT3-ITD were eligible: 284 patients were treated, including 198 younger (18-60 years) and 86 older (61-70 years) patients. Complete remission (CR) rate, including CR with incomplete hematological recovery (CRi) after induction therapy, was 76.4% (younger, 75.8%; older, 77.9%). The majority of patients in CR/CRi proceeded to alloHCT (72.4%). Maintenance therapy was started in 97 patients (34%): 75 after alloHCT and 22 after consolidation with high-dose cytarabine (HiDAC). Median time receiving maintenance therapy was 9 months after alloHCT and 10.5 months after HiDAC; premature termination was mainly a result of nonrelapse causes (gastrointestinal toxicity and infections). EFS and overall survival at 2 years were 39% (95% confidence interval [CI], 33%-47%) and 34% (95% CI, 24%-47%) and 53% (95% CI, 46%-61%) and 46% (95% CI, 35%-59%) in younger and older patients, respectively. EFS was evaluated in comparison with 415 historical controls treated within 5 prospective trials. Propensity score-weighted analysis revealed a significant improvement of EFS by midostaurin (hazard ratio [HR], 0.58; 95% CI, 0.48-0.70; P < .001) overall and in older patients (HR, 0.42; 95% CI, 0.29-0.61). The study was registered at www.clinicaltrials.gov as #NCT01477606.

Impairment of normal hematopoiesis and leukemia progression are 2 well-linked processes during leukemia development and are controlled by the bone marrow (BM) niche. Extracellular matrix proteins, including laminin, are important BM niche components. However, their role in hematopoiesis regeneration and leukemia is unknown. Laminin α4 (Lama4), a major receptor-binding chain of several laminins, is altered in BM niches in mice with acute myeloid leukemia (AML). So far, the impact of Lama4 on leukemia progression remains unknown. We here report that Lama4 deletion in mice resulted in impaired hematopoiesis regeneration following irradiation-induced stress, which is accompanied by altered BM niche composition and inflammation. Importantly, in a transplantation-induced MLL-AF9 AML mouse model, we demonstrate accelerated AML progression and relapse in Lama4-/- mice. Upon AML exposure, Lama4-/- mesenchymal stem cells (MSCs) exhibited dramatic molecular alterations, including upregulation of inflammatory cytokines that favor AML growth. Lama4-/- MSCs displayed increased antioxidant activities and promoted AML stem cell proliferation and chemoresistance to cytarabine, which was accompanied by increased mitochondrial transfer from the MSCs to AML cells and reduced reactive oxygen species in AML cells in vitro. Similarly, we detected lower levels of reactive oxygen species in AML cells from Lama4-/- mice post-cytarabine treatment. Notably, LAMA4 inhibition or knockdown in human MSCs promoted human AML cell proliferation and chemoprotection. Together, our study for the first time demonstrates the critical role of Lama4 in impeding AML progression and chemoresistance. Targeting Lama4 signaling pathways may offer potential new therapeutic options for AML.

Uproleselan (GMI-1271) is a novel E-selectin antagonist that disrupts cell survival pathways, enhances chemotherapy response, improves survival in mouse xenograft and syngeneic models, and decreases chemotherapy toxicity in vivo. A phase 1/2 study evaluated the safety, tolerability, and antileukemic activity of uproleselan (5-20 mg/kg) with MEC (mitoxantrone, etoposide, and cytarabine) among patients with relapsed/refractory (R/R) acute myeloid leukemia (AML). Among the first 19 patients, no dose-limiting toxicities were observed. The recommended phase 2 dose (RP2D) was 10 mg/kg twice daily. An additional 47 patients with R/R AML were treated with uproleselan at the RP2D plus MEC. At the RP2D, the remission rate (complete response [CR]/CR with incomplete count recovery [CRi]) was 41% (CR, 35%), and the median overall survival (OS) was 8.8 months. In a separate cohort, 25 newly diagnosed patients age ≥60 years received uproleselan at the RP2D plus cytarabine and idarubicin (7 + 3). In these frontline patients, the CR/CRi rate was 72% (CR, 52%), and the median OS was 12.6 months. The addition of uproleselan was associated with low rates of oral mucositis. E-selectin ligand expression on leukemic blasts was higher in patients with relapsed vs primary refractory AML and in newly diagnosed older patients with high-risk cytogenetics and secondary AML. In the R/R cohort, E-selectin expression >10% was associated with a higher response rate and improved survival. The addition of uproleselan to chemotherapy was well tolerated, with high remission rates, low induction mortality, and low rates of mucositis, providing a strong rationale for phase 3 randomized confirmatory studies. This trial was registered at www.clinicaltrials.gov as #NCT02306291.

Survivors of Hodgkin lymphoma (HL) have an increased risk of subsequent malignant neoplasms (SMNs). Response-adapted treatment may decrease this risk by reducing exposure to therapy associated with SMN risk. The Children’s Oncology Group study AHOD0031 evaluated response-adapted therapy for children and adolescents with intermediate-risk HL. We report the SMNs among 1711 patients enrolled in AHOD0031. Patients were treated with 4 cycles of doxorubicin, bleomycin, vincristine, etoposide, prednisone, and cyclophosphamide with or without involved-field radiation therapy (RT). Patients with a slow early response to initial chemotherapy were randomized to 2 additional cycles of dexamethasone, etoposide, cisplatin and cytarabine or no additional chemotherapy, and all received RT. At a median follow-up of 7.3 years, an analysis of SMNs was performed. The 10-year cumulative incidence of SMN was 1.3% (95% confidence interval [CI], 0.6-2.0). SMNs included 3 patients with acute myeloid leukemia (AML), 11 with solid tumors, and 3 with non-Hodgkin lymphoma. Sixteen of 17 patients with an SMN had received combined modality therapy. The standardized incidence ratio for SMN was 9.5 (95% CI, 4.5-15.2) with an excess absolute risk of 1.2 per 1000 person-years. The cumulative incidence of SMNs was higher among patients who received RT (P = .037). In multivariate analysis, RT, B symptoms, and race were associated with SMN risk. Given the latency from exposure, we have likely captured all cases of secondary leukemia and myelodysplastic syndrome (MDS). Longer follow-up is needed to determine the risk of solid tumors. Avoidance of RT without sacrificing disease control should remain a goal for future therapeutic approaches. This trial was registered at www.clinicaltrials.gov as #NCT00025259.

First-line therapy for younger patients with peripheral T-cell non-Hodgkin lymphoma (T-NHL) consists of 6 courses of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) with or without etoposide (CHOEP), consolidated by high-dose therapy and autologous stem cell transplantation (auto-SCT). We hypothesized that allogeneic stem cell transplantation (allo-SCT) could improve outcomes. 104 patients with peripheral T-cell non-Hodgkin lymphoma, except ALK+ anaplastic large cell lymphoma, 18 to 60 years, all stages, and all age adjusted International Prognostic Index scores, except 0 and stage I, were randomized to 4 cycles of CHOEP and 1 cycle of dexamethasone, cytosine-arabinoside, and platinum (DHAP) followed by high-dose therapy and auto-SCT or myeloablative conditioning and allo-SCT. The primary end point was event-free survival (EFS) at 3 years. After a median follow-up of 42 months, the 3-year EFS after allo-SCT was 43%, as compared with 38% after auto-SCT. Overall survival at 3 years was 57% vs 70% after allo- or auto-SCT, without significant differences between treatment arms. None of the 21 responding patients proceeding to allo-SCT relapsed, as opposed to 13 of 36 patients (36%) proceeding to auto-SCT. Eight of 26 patients (31%) and none of 41 patients died of transplant-related toxicity after allo- and auto-SCT, respectively. The strong graft-versus-lymphoma effect after allo-SCT was counterbalanced by transplant-related mortality. This trial is registered at www.clinicaltrials.gov as #NCT00984412.

Background: Anthracycline and cytarabine ("3+7") have been the standard induction therapy for acute myeloid leukemia (AML) for almost 4 decades. Only 60%-70% patients can achieve complete remission (CR) with "3+7" induction treatment in de nove AML. The novel induction regimens with higher CR rate are urgent needed. Venetoclax, a b-cell lymphoma 2 (BCL-2) inhibitor combining with hypomethylation agents (HMA) or low dose cytarabine has showed a high response rate and safe in elder AML patients [Dinardo CD, N Engl J Med. 2020; Dinardo CD, Lancet Oncol 2018; Wei AH, J Clin Oncol 2019]. Recently, venetoclax combined with FLAG-IDA induction achieved 90% CR rate in newly diagnosed adult AML (Dinardo CD, J Clin Oncol. 2021). Whether venetoclax combined with standard 3+7 regimen (daunorubicin + cytarabine) as induction therapy can further improve the CR rate in adult AML patients need to be investigated in a well-designed trial. Objective: To evaluate the efficacy and safety of "3+7" (daunorubicin and cytarabine) combined with venetoclax induction regimen (DAV regimen) in young adult patients with de novo AML. Design, setting and participants: Single-arm, prospective clinical trial conducted in the First Affiliated Hospital, Zhejiang University College of Medicine, China. Eligible patients (18-60 years old) with de novo AML (exclude acute promyelocytic leukemia) were enrolled since December 25, 2020, with final follow-up in July 31,2021. Interventions: Patients were treated with daunorubicin 60mg/m 2 on days 1-3 (d1-3) and cytarabine 100 mg/m 2/d by continuous intravenous infusion daily on d1-7, combined with venetoclax (100mg d4, 200mg d5, 400mg d6-11). Main outcomes and measures: The primary endpoint was the percentage of patients who achieved CR/CR with incomplete count recovery (CRi) after once cycle of DAV regimen. Secondary endpoints included minimal residual disease (MRD), overall survival (OS), event-free survival (EFS) and adverse events. Results: Thirty-two patients were enrolled. Median age was 40 years old (range, 19-59), with poor-risk in 25% (8/32) of patients (European LeukemiaNet 2017 risk). Other characteristics of patients were listed in Table 1. The CR rate were 90.6% (29/32) (Table 1). Seven out eight (87.5%) patients with poor-risk achieved CR. Measurable residual disease-negative composite CR was attained in 65.5% (19 out 29) of total patients achieved CR, and 71.4% (5 out 7) of poor-risk patients achieved CR (Table 1). Common adverse events (>30%) included fatigue, nausea, bleeding, febrile neutropenia, infection, neutropenia, anemia and thrombocytopenia. The main grade ≥ 3 hematologic toxicities during induction were neutropenia (100%), anemia (100%) and thrombocytopenia (100%). The main grade ≥ 3 nonhematologic toxicities during induction were infection (81.3%), bleeding (28.1%) and mucositis (3.1%) (Table 1). No tumor lysis syndrome was observed. After a median follow-up of 118.5 days, no patient relapsed or died, and 24.1% (7/29) received allogeneic hematopoietic stem-cell transplantation in CR1. Conclusions: The novel combination of "3+7" (daunorubicin and cytarabine) with venetoclax (DAV regimen) was effective and well tolerated in young adult patients with de novo AML, with high CR rate and deep remission. Trial registration: The trial was registered in the Chinese Clinical Trial Register, number ChiCTR2000041509. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Background: Chidamide, as a novel subtype-selective histone deacetylase inhibitors (HDACi), can directly inhibit tumor cell cycle progression and induce tumor cell apoptosis, inhibit phenotypic transformation of tumor cells and pro-drug resistance/pro-metastasis activity of the microenvironment, induce differentiation of tumor stem cells, and reverse epithelial-mesenchymal transformation of tumor cells, thereby restoring the sensitivity of drug-resistant tumor cells to drugs and enhancing the effect of chemotherapy agents through loosening chromatin and exposing DNA. The efficacy and safety of chidamide-BEAC (carmustine, etoposide, cytarabine, and cyclophosphamide, Chi-BEAC) conditioning regimen combined with autologous stem cell transplantation (ASCT) were evaluated in a current phase II clinical trial for the treatment of high-risk and relapsed/refractory aggressive lymphoma. Methods: A total of 70 patients with high-risk diffuse large B-cell lymphoma (DLBCL), peripheral T-cell lymphoma (PTCL), or mantle cell lymphoma (MCL) who had achieved complete remission (CR) or partial remission (PR) after first-line therapy or second-/third-line therapy were recruited from January 2018 to June 2021. Three of the patients were not evaluated after ASCT and two patients withdrew from the study; 65 patients were then evaluated for the effectiveness of Chi-BEAC treatment. Results: DLBCL and MCL are referred as B-cell non-Hodgkin lymphoma (B-NHL) and PTCL is referred as T and NK-cell non-Hodgkin lymphoma (T&NK-NHL) in the study. The median neutrophil engraftment time was 10 d (7-13 d) and median platelet engraftment time was 11 d (8-13 d). The CR rate at 3-6 months after transplantation was 75.4% in the 65 evaluable patients. The median progression free survival (PFS) and overall survival (OS) had not reached at the end of the follow-up period (median 18.1 month; range 1.8-42.0 months). The estimated PFS and OS at 24 months was 78.5% and 84.2%, respectively. Stratified analyses showed that in patients with B-NHL who previously received first-line treatment, the CR rate at 3-6 months after transplantation was 77.8%, and 2-year PFS was 74.8%. The survival rate might be better than previously reported for SWOG9704 (Stiff et al., 2013; PMID 24171516)-a 2-year PFS of 69%-and for DLCL04 (Chiappella et al., 2017; PMID 28668386)-a 2-year failure-free survival of 71%. In our patients with B-NHL who previously received second-/third-line treatments, the CR rate at 3-6 months after transplantation was 71.4%, and 2-year PFS was 77.1%. The survival rate might also be higher than previously reported for the CORAL trial (Gisselbrecht et al., 2010; PMID: 20660832), which showed a 2-year PFS of approximately 65%. In our patients with T&NK-NHL the CR rate at 3-6 months after transplantation was 73.3%, and 2-year PFS was 93.3%, The survival rate might be higher than previously reported for the NLG-T-01 trial (Francesco d'Amore et al., 2012; PMID: 22851556), which showed a 2-year PFS of approximately 55%. PFS stratification analysis showed that previous treatment outcomes affected the PFS: patients who had achieved CR before transplantation demonstrated better PFS than patients who had achieved PR (P = 0.199), while there was no significant difference between patients with different pathological subtypes (B or T&NK-NHL) or different risk groups. Most non-hematological adverse events (AEs) were of grade 1/2. Grade 4 AE only occurred in one patient, i.e., γ-glutamyl transpeptidase (GGT) elevation. Grade 3 AEs that occurred in ≥ 5% of the patients included febrile agranulocytosis (37.7%), hypokalemia (24.7%), hyponatremia (23.4%), GGT elevation (9.1%), and diarrhea (5.2%), which were well tolerated. Conclusions: This study showed that inclusion of the HDACi chidamide in conditioning regimen for ASCT greatly increased the PFS and OS, especially in patients with T&NK-NHL, and revealed an acceptable safety profile for refractory and relapsed lymphoma patients. Therefore, chidamide-containing conditioning regimen may be a great choice for patients with refractory and relapsed lymphoma, and awaits further confirmation by additional large-scale multi-center investigations. Disclosures No relevant conflicts of interest to declare.

Background: Liposomal daunorubicin/cytarabine (CPX-351) and hypomethylating agent+venetoclax (HMA+V) have shown survival advantage as frontline therapies for older and biologically adverse AML. Although HMA+V is approved for chemotherapy ineligible pts, there is increased use of the combination in older fit pts. with biologically adverse AML. However, clinical outcomes between the two treatments have not been compared and will have a major clinical impact. Our aim was to compare CPX-351 vs HMA+V as upfront treatment for newly diagnosed AML using a multi-center retrospective study. Methods: This is a multicenter retrospective study drawing from 4 large U.S. academic medical centers (Weill Cornell, Northwestern, Moffitt, Memorial Sloan Kettering). Eligibility included pts who received either CPX-351 or HMA+V as frontline therapy for AML. Response was determined using ELN 2017 guidelines. To evaluate the association between treatment type and categorical factors of interest, and the primary outcome variable of treatment response, the chi-square test or Fisher's exact test was used. For the outcome variable of bone marrow response status, multivariable logistic regression analysis was performed. For the relapse free survival (RFS) and overall survival (OS) outcomes, Kaplan-Meier survival analysis was performed, and the log-rank test was employed to compare between categories of treatment-type and prognostic factors of interest. Multivariable cox proportional hazards regression analysis was performed to assess the independent effect of treatment and demographic/prognostic factors of interest on outcomes of RFS/OS. Results: Our study included 211 CPX-351 and 226 HMA+V treated pts. 11 pts were excluded due to missing age or ELN risk. Pt. characteristics and univariate analyses are summarized in Table 1 and 2. Overall CR+CRi rates, median RFS and OS for CPX-351 vs. HMA+V were 57.8% vs. 56.6%, 32.5 vs. 14.1 months (p=0.11) and 17.3 vs. 11.1 months (p=0.007). In multivariable analysis, after adjusting for age, ELN risk, prior myeloid malignancy, and prior HMA therapy, there was no difference between CPX-351 vs. HMA+V in CR+CRi (HR 1.32, p=0.23, 95% CI 0.8-2.1) and RFS (HR 0.92, p=0.75, CI 0.59-1.46). There was a significant difference favoring CPX-351 for OS (HR 0.74, p=0.04, CI 0.55-0.99). When analyses were restricted to pts aged 60-75 years (n= 152 CPX-351, n= 100 HMA+V), rates of CR+CRi were 59.2% vs. 54.0% (p=0.41), and median RFS and OS for CPX-351 vs. HMA+V treated pts was 32.5 vs. 13.3 months (p= 0.80) and OS 17.1 vs. 10.3 months (p=0.12). Multivariable analysis after adjusting for above variables showed no difference in CR+CRi, RFS and OS between CPX-351 vs. HMA+V (CR+CRi: HR 1.28, p=0.55, 95% CI 0.77-2.27, RFS: HR 0.70, p=0.17, CI 0.42-1.17 and OS: HR 0.80, p=0.20, CI 0.57-1.12). Multivariable subgroup analyses demonstrated significant advantage favoring CPX-351 for RFS in TP53 mutated pts (HR 0.37, 95% C.I. 0.14-0.96, p=0.04). Subgroup analyses for OS are summarized in Figure 2. Among patients where minimal residual disease (MRD) data was available (n=93 CPX-351, n=133 HMA+V), MRD negativity by flow was 34.4% (n=32) and 39.1%(n=52) for CPX-351 and HMA+V pts, respectively (p=0.47). Among pts aged 60-75 years, 47.7% and 19% of patients underwent HSCT in CPX-351 and HMA+V groups (p Conclusion: Our analysis demonstrated significant difference in OS favoring CPX-351 in the overall cohort and in several clinical subgroups, while no difference in CR+CRi and RFS was seen. The survival advantage in the CPX-351 group may be due to higher HSCT rates in CPX-351 treated pts. Among pts that did not proceed to HSCT, there was no difference in CR+CRi, RFS and OS between the treatment groups. We suspect that greater HSCT rates in the CPX-351 cohort were due to fewer comorbidities among CPX-351-treated pts or other biases, and comorbidity analyses are pending and will be reported. Figure 1 Figure 1. Disclosures Ritchie: Bristol Myers Squibb: Consultancy, Research Funding; Abbvie: Consultancy, Honoraria; NS Pharma: Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria; Protaganist: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Incyte: Consultancy, Honoraria, Speakers Bureau; ARIAD Pharmaceuticals: Ended employment in the past 24 months, Speakers Bureau; Jazz: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Celgene/BMS: Consultancy, Other: travel support, Speakers Bureau. Lee: Pin Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Innate: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees. Goldberg: Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Arog: Research Funding; Aprea: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Research Funding; Prelude Therapeutics: Research Funding; Aptose: Consultancy, Research Funding; DAVA Oncology: Honoraria; Celularity: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Dinner: Pfizer: Consultancy, Honoraria; Kite/Gilead: Consultancy, Honoraria. Sweet: AROG: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees. Roboz: Novartis: Consultancy; Bristol Myers Squibb: Consultancy; Glaxo SmithKline: Consultancy; Jazz: Consultancy; Astex: Consultancy; Blueprint Medicines: Consultancy; Mesoblast: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Pfizer: Consultancy; Bayer: Consultancy; Otsuka: Consultancy; Celgene: Consultancy; Daiichi Sankyo: Consultancy; Janssen: Consultancy; Jasper Therapeutics: Consultancy; Roche/Genentech: Consultancy; Helsinn: Consultancy; Amgen: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Agios: Consultancy; Actinium: Consultancy; AbbVie: Consultancy; Janssen: Research Funding. Desai: Agios: Consultancy; Kura Oncology: Consultancy; Takeda: Consultancy; Astex: Research Funding; Bristol Myers Squibb: Consultancy; Janssen R&D: Research Funding.

Background: Acute myeloid leukemia (AML) is characterized by a high relapse rate, indicating insufficient clearance of leukemia-initiating cells. Depending on genetic risk stratification, consolidating chemotherapy proves to significantly reduce the risk of relapse. In particular, in younger AML patients higher dosage of cytarabine appears to improve long-term outcome, while there is no apparent benefit of multiagent combination, compared to cytarabine monotherapy. However, to this end the optimal dosage of single agent cytarabine in consolidation therapy after 7+3 remission induction remains elusive. Methods: Here, we retrospectively assessed the impact of different dosages of cytarabine consolidation on outcome in a large real-world data set from the German Study Alliance Leukemia-Acute Myeloid Leukemia (SAL-AML) registry. Patients below 65 years of age, registered between April 2005 and September 2020 with non-acute promyelocytic leukemia, who attained complete remission after intensive induction and received at least one consolidation cycle with intermediate (IDAC) or high dose cytarabine (HiDAC) were selected. To account for differences in patient and disease characteristics between both groups, the average treatment effect was estimated by propensity score weighting. Results: 642 patients received HiDAC consolidation with a median dosage of 5794.88 (IQR, 4745.48-5971.56) mg/m 2/d with a median number of 3 cycles (IQR, 2-3), whereas 178 patients received IDAC consolidation with 1946.16 (IQR, 1869.51-2469.15) mg/m 2/d with a median of 2 cycles (IQR, 1-3). IDAC-treated patients showed in average a higher age (median (IQR) 58.5 (49-62) years vs. 50 (41-56) years) and more comorbidities with 43.8% having an HCT-CI score of 2-4, compared to 22.3% among HiDAC-treated patients. Alongside, significantly more secondary (5.1% vs. 3.1%) and therapy-related (12.4% vs. 4.1%) AML as well as more adverse (14.5% vs. 6.5%) and less favorable (40.6% vs. 56%) genetic risk features according to ELN 2017 risk classification were found among IDAC-treated patients. After propensity score weighting for differences in patient and disease characteristics, overall survival after 5 years was comparable between HiDAC-treated (71.1 %) and IDAC-treated (67.7%) patients. Moreover, no significant differences in relapse-free survival were observed after 5 years (47.4 vs. 45.2%). Notably, more patients treated with IDAC received allogeneic stem cell transplantation in first remission (37.6 vs. 19.8%) while significantly more HiDAC-treated patients underwent allogeneic stem cell transplantation in relapse (30.8 vs. 20.2%). Censoring for allogeneic stem cell transplantation in first remission revealed no significant survival difference with regard to cytarabine dosage. Considering only ELN favorable risk AML patients, there was no difference in 5-years overall (80.5% vs. 83.9%) nor relapse-free (57.7% vs. 56.8%) survival. Of note, significantly more patients treated with HiDAC suffered from ≥3 CTCAE infectious complications (56.7 vs. 44.1%), which was more striking in patients above 50 years of age. The rate of other ≥3 CTCAE non-hematological toxicities and secondary malignancies was comparable in both treatment groups. Conclusion: This retrospective analysis suggests no significant benefit of high dose cytarabine compared to intermediate dosages in consolidation for AML patients under 65 years of age, independent of ELN risk group. Disclosures Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Haenel: Jazz: Consultancy, Honoraria; GSK: Consultancy; Bayer Vital: Honoraria; Takeda: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Brummendorf: Takepart Media: Honoraria; Repeat Diagnostics: Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Patents & Royalties, Research Funding; Janssen: Honoraria; Bristol Myers: Research Funding. Fransecky: Abbvie: Honoraria, Research Funding; Medac: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Takeda: Honoraria. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Held: MSD: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Roche: Research Funding; Acortech Biopharma: Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Platzbecker: Janssen: Honoraria; Celgene/BMS: Honoraria; AbbVie: Honoraria; Geron: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Baldus: Amgen: Honoraria; Celgene/BMS: Honoraria; Novartis: Honoraria; Jazz: Honoraria. Mueller-Tidow: Janssen Cilag: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Bioline: Consultancy, Research Funding.

Abstract Purpose: Treatment of patients with myelodysplastic syndromes with excess blasts (MDS-EB) remains a great challenge. In this study, we evaluated the tolerance and efficacy of the combination of low-dose decitabine, cytarabine, all-trans retinoic acid and granulocyte colony-stimulating factor (DLAAG) for MDS-EB patients. Methods: A total of 18 patients with MDS-EB were enrolled in this study and 1 patient who did not follow-up the bone marrow evaluation was excluded from analysis. This study is registered at ClinicalTrials.gov, NCT03356080.The DLAAG regimen consisted of subcutaneous injection of decitabine (0.1-0.2mg/kg, d1-3/w, lasted for 1-3 weeks), cytarabine (6-15mg/m 2,q12h,d1-10), oral all-trans retinoic acid (45mg/m 2/d, d4-6; 15mg/m 2/d, d7-20) and G-CSF (300ug, from d0 until neutrophil count recovery to 20×10 9 cells/L). Results: Patient characteristics A total of 18 patients (11 males, 7 females) with a median age of 61 years (range 45 to 88 years) were enrolled in our study. The clinical characteristics of the patients were shown in Table 1. Response and survival The clinical outcome and overall survival (OS) of patients were summarized in Table2 including 1 could not evaluable after the first protocol. As shown in Table3, after one course of DLAAG, the CR and OR rate was 55.56% and 77.78% respectively. In addition, 3 patients suffered the disease progression (PD) (n=3,16.67%). We found that those who achieved the bone marrow remission after DLAAG had significantly pro-longed OS than others (p=0.0001, Fig.1). The Kaplan-Meier analysis revealed the median overall survival for all patients enrolled was 15 months (Fig.2A), and the relapse-free survival (RFS) for patients achieving CR or CRm was 11 months (Fig.2B). Genetic mutations and response to DLAAG Paired samples (pre- and post-treatment) of the objects were tested for gene mutations which were recurrently mutated in myeloid malignancies, except 1 patient who was failure to perform bone marrow review. 2 patients (11.1%) had no genetic or cytogenetic abnormalities either at baseline or during therapy (they were tested at baseline and d28). Most patients (15 out of 18) had at least one somatic mutation. In this latter group, only 1 patient acquired specific mutation of IDH2 during the therapy (it was tested on d28, data was not shown), while all the other genes were mutated in patients at baseline. Collectively, the most frequently mutated genes at diagnosis were RUNX1 (n=5, 29.4%), ASXL1 (n=4, 23.5%), as well as the overexpression of WT1 (n=4, 23.5%), and the others with an incidence of more than 10% were TET2(n=3,17.6%),TP53 (n=2, 11.8%), EZH2 (n=2, 11.8%), STAG2 (n=2, 11.8%), SF3B1 (n=2, 11.8%) and U2AF1 (n=2, 11.8%).Genes less frequently mutated such as CEBPA,CUX1 et al. were not shown. Remarkably, the proportion of patients with the above gene mutations showing no significant increasing during therapy as compared to baseline, the clones of WT1/TET2/TP53/EZH2/STAG2 can decrease or even disappear(Fig.3A).Moreover, we noted the complete response in patients with ASXL1, TP53 mutations or WT1 overexpression despite the concomitant presence of complex cytogenetic at diagnosis, whereas patients with the EZH2 mutation were less likely to respond (Fig.3B). Subgroup analysis A subgroup analysis based on the 2016 WHO classification revealed an association of EB-I patients with longer OS(P=0.002) (Fig. 4A). On the other hand, based on the IPSS score our study revealed that the lower-risk group patients have better OS (p= 0.0054) (Fig. 4B).In addition to this, we also compared the OS in different groups of age and karyotype, but there were no statistical difference (Fig. 4C-D). Safety and Tolerability All patients who received the therapy were eligible for toxicity evaluation. Given the patient-population enrolled and treatment regimen, myelosuppression occurred in all patients (Table 4). The grade 3 to 4 hematological toxicities including neutropenia and thrombocytopenia were common after treatment. Febrile neutropenia occurred in 77.8% of the patients. Conclusion: This study suggested the novel combination of LD-DAC, Ara-C, ATRA and G-CSF might be an optimal introduction therapy for patients with MDS-EB, and this combination warrants further investigation in larger trials. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Introduction Approximately 25-30% of adult acute myeloid leukemias (AMLs) have FLT3 mutation. Among the two main types, internal tandem duplication (ITD) and tyrosine kinase domain (TKD) point mutations, FLT3-ITD is associated with poorer clinical outcomes. Recently, midostaurin was found to improve survival when combined with 7+3 induction for FLT3-ITD or FLT3-TKD AML. Additionally, increased CD33 expression in AML patient samples has been linked to FLT3-ITD+ blasts. This suggests the combined targeting of CD33 and FLT3 in AML patients as a novel treatment approach. Hence, we introduce a combination therapy of gemtuzumab ozogamicin (GO) - a humanized CD33 antibody conjugated to a calicheamicin derivative - and midostaurin with 7+3 (cytarabine + daunorubicin) for newly diagnosed FLT3-mutated AML. Methods This Phase I open-label, dose-finding study was designed to determine the maximum tolerated dose schedule of GO administered with midostaurin and 7+3 induction and to assess the safety and preliminary efficacy of this combination. Patients needed to be >18 years old, have newly diagnosed AML, be fit for 7+3 induction, and harbor a FLT3-ITD or -TKD mutation per next-generation sequencing or PCR testing. In cohorts of 3, patients were assigned to 1 of 4 dose levels according to the "keyboard" Bayesian toxicity probability interval design (Table 1) applied to a target dose-limiting toxicity (DLT) rate of 20%. Non-hematologic DLTs were defined as study drug-related grade ≥3 toxicities, with exceptions for infections, elevated liver enzymes (that resolve in ≤5 days), GI symptoms (≤3 days), and electrolyte abnormalities (≤1 day). Hematologic DLTs were grade 4 neutropenia or grade ≥3 thrombocytopenia at 6 weeks after the start of the induction cycle and in the absence of AML. The DLT evaluation period covered the induction and, if applicable, re-induction cycles. Clinical responses were determined by 2017 ELN criteria. CD33 expression on AML blasts was quantified before and after treatment. Upon completion of 1 or 2 induction cycles, patients with a CR or CRi could receive up to 2 cycles of consolidation therapy, consisting of cytarabine (HiDAC or MiDAC depending on age Results Eight patients have been enrolled out of the planned accrual of 24. The median age was 59 (range: 35-72) years, and every patient identified as White and Non-Hispanic. At screening, all patients had FLT3-ITD mutations. The median bone marrow blast percentage was 64% (range 17%-91%), with the majority of blasts expressing CD33 (median 96%, range 80-100%, 2 patients missing data due to recent enrollment). The current numbers of patients treated by dose level (DL) were: 3 on DL1 (IV GO 3 mg/m 2 Day 1), 3 on DL2 (IV GO 3 mg/m 2 Day 1 and 4), and 2 on DL3 (IV GO 3 mg/m 2 Day 1, 4, and 7). No DLTs were observed among the six patients in DL1 or DL2. Likewise, no DLTs were observed in the two patients in DL3. The most common treatment-emergent adverse events included grade 3 febrile neutropenia (75% of patients), grade 3/4 mucositis (25%), grade 3 sepsis (25%), and grade 3 esophagitis (12.5%). One patient had a serious adverse event: a GO-related Grade 4 sinusoidal obstruction syndrome occurring ~4 months into treatment and lasting 23 days. The median duration of study therapy was 62 days (range 20-95 days); reasons for discontinuation were disease progression (n=2), non-compliance (n=1), and allogeneic HCT (n=5). The overall response rate and composite complete remission rate were both 75% (95% CI: 34.9% - 96.8%). There were no treatment-related deaths in the first 30 days. Due to the early nature of this study, survival outcomes have not been calculated and post-induction CD33 expression data are not available. Conclusions In newly diagnosed FLT3-mutated AML patients, induction chemo/immunotherapy with GO, midostaurin, and 7+3 has yielded promising responses and has been well tolerated with no DLTs thus far. Additional patients and correlative analyses of CD33 expression will provide further insight into the safety and efficacy of this regimen for a patient population with historically poor prognosis. Figure 1 Figure 1. Disclosures Borate: Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Blueprint Medicine: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rampal: Membership on an entity's Board of Directors or advisory committees; Galecto, Inc.: Consultancy; Promedior: Consultancy. Saultz: IKENA: Research Funding. Traer: ImmunoGen: Membership on an entity's Board of Directors or advisory committees; Servier/Agios: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Schrodinger: Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees. Walter: Amgen: Research Funding; Aptevo: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Immunogen: Research Funding; Macrogenics: Consultancy, Research Funding; Jazz: Research Funding; Pfizer: Consultancy, Research Funding; Selvita: Research Funding; Amphivena: Consultancy, Other: ownership interests; Agios: Consultancy; Astellas: Consultancy; BMS: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Kite: Consultancy.

Background: The optimal treatment strategy for managing Acute Myeloid Leukemia (AML) and the use of reliable and predictive biomarkers to guide selection of cytotoxic chemotherapy regimens among patients with diverse genomic profiles remain unmet needs in the clinic. The combination of MEC [mitoxantrone (MIT), etoposide (VP16), and cytarabine (ARA-C)] is a commonly used regimen for relapsed or refractory AML patients. Unfortunately, many patients do not respond to MEC, and which of the three drug agents matters most for each individual patient is not known. Predictors of response are needed urgently. Methods: The Computational Omics Biology Model (CBM) is a computational multi-omic biology software model created using artificial intelligence heuristics and literature sourced from PubMed to generate a patient-specific protein network map. The aberration and copy number variations from individual cases served as input into the CBM. Disease-biomarkers unique to each patient were identified within patient-specific protein network maps. Biosimulations were conducted on the Cellworks Biosimulation Platform by measuring the effect of chemotherapy on a cell growth score comprised of a composite of cell proliferation, viability, apoptosis, metastasis, and other cancer hallmarks. Biosimulation of drugs was conducted by mapping the interaction of various drug combinations with the patient's genomic and pathway alterations based on signaling pathway mechanisms and their phenotypic consequences. The Cellworks Biosimulation Platform identified unique chromosomal signatures that permit a stratification of patients that are most likely to respond to MIT, VP16, or ARA-C as well as their combinations. 65 AML patients were selected for this study largely based on genomic data published in TCGA and PubMed: ARA-C [N=12, 7 responders (R) & 5 non-responders (NR)]ARA-C + MIT [N=30, 29 R & 1 NR]ARA-C + MIT + VP16 [N=23, 12 R & 11 NR] Results: Of the12 patients treated with ARA-C alone, 5 were predicted to be NR and 7 were predicted to be R. Of the 5 NR, 4 had 5q del which resulted in loss of APC, CSNK1A1 and SLC22A4 (nucleoside carrier) forming the non-response biomarkers for ARA-C. Notably, the biosimulation predicted lenalidomide to be beneficial for these patients. Out of 7 R, 4 patients also had 5q del, but were predicted to be R because of co-occurring aberrations involving CLSPN del, DHODH del, MSH2 del, EP300 del, CREBBP del, MSH6 Del, and RRM2 del. These genes were exclusively present in ARA-C responders. Of 53 patients who received ARA-C + VP16 + MIT or ARA-C + MIT, 41 patients were predicted to be R and 12 patients were predicted to be NR. The genomic aberrations predicted by biosimulation to be associated with response to this regimen include: NPM1-mut, TET2-mut, IDH1-mut, IDH2-mut, RAD17-del, NRAS-mut (Table 1). Notably, CBM predicted 19 of the 41 R had no genomic biomarkers of response to VP16 or MIT, suggesting these patients might have benefited equally from ARA-C alone with less toxicity and cost. Finally, 11/65 patients were predicted NR to MEC treatment. In the biosimulation, treatment failure was associated with high aberration frequencies of KMT2C-mut/del, FLT3 mut, TWIST1 del, LIMK1 del, SNAI2 amp, FNTA amp, and KAT6A amp. Of note, these genomic markers suggested a likelihood of benefit from other therapies, including vincristine, JQ1 and rigosertib. Conclusions: The Cellworks Biosimulation Platform identified novel polygenic biomarkers of response that can be employed to determine the optimal therapy for relapsed AML patients. Biosimulation permits avoidance of cytotoxic drugs with little chance of efficacy and reveals vulnerabilities in each patient's cancer that can be exploited to improve disease control. In AML, biosimulation promises to improve intensive therapy regimens by tailoring chemotherapy to optimize disease control and minimize toxicity. Figure 1 Figure 1. Disclosures Marcucci: Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings; Abbvie: Other: Speaker and advisory scientific board meetings. Kumar: Cellworks Group Inc.: Current Employment. Castro: Cellworks Group Inc.: Current Employment; Omicure Inc: Consultancy; Caris Life Sciences Inc.: Consultancy; Exact sciences Inc.: Consultancy; Bugworks: Consultancy; Guardant Health Inc.: Speakers Bureau. Grover: Cellworks Group Inc.: Current Employment. Patil: Cellworks Group Inc.: Current Employment. Alam: Cellworks Group Inc.: Current Employment. Azam: Cellworks Group Inc.: Current Employment. Mohapatra: Cellworks Group Inc.: Current Employment. Tyagi: Cellworks Group Inc.: Current Employment. Kumari: Cellworks Group Inc.: Current Employment. Prasad: Cellworks Group Inc.: Current Employment. Nair: Cellworks Group Inc.: Current Employment. Lunkad: Cellworks Group Inc.: Current Employment. Joseph: Cellworks Group Inc.: Current Employment. G: Cellworks Group Inc.: Current Employment. Chauhan: Cellworks Group Inc.: Current Employment. Basu: Cellworks Group Inc.: Current Employment. Behura: Cellworks Group Inc.: Current Employment. Ghosh: Cellworks Group Inc.: Current Employment. Husain: Cellworks Group Inc.: Current Employment. Mandal: Cellworks Group Inc.: Current Employment. Raman: Cellworks Group Inc.: Current Employment. Patel: Cellworks Group Inc.: Current Employment. Mundkur: Cellworks Group Inc: Current Employment. Christie: Cellworks Group Inc.: Current Employment. Macpherson: Cellworks Group Inc.: Current Employment. Howard: Servier: Consultancy; Cellworks Group Inc.: Consultancy; Sanofi: Consultancy, Other: Speaker fees.