Abstract: Background: Venetoclax (ven) combined with azacitidine (aza/ven), decitabine (dec/ven), and low-dose cytarabine (LDAC/ven) is approved as frontline therapy for older or otherwise unfit AML patients (pts) and also frequently used for pts with relapsed/refractory (RR)-AML. However, clinical outcomes of AML pts who receive an allogeneic stem cell transplant (alloSCT) after ven combination (ven combo) therapy are unclear. Methods: All AML pts who received treatment with aza/ven, dec/ven or LDAC/ven as either initial induction or for RR disease at Memorial Sloan Kettering Cancer Center from 08/2016 to 02/2020 and underwent a subsequent allo-SCT were included. The response to ven therapy prior to alloSCT was determined using the 2017 European LeukemiaNet response criteria. The overall response rate was defined as the combination of the complete response (CR) + complete response with incomplete count recovery (CRi) + morphologic leukemia free state (MLFS) rate. Measurable residual disease (MRD) was assessed by multiparameter flow cytometric analysis of bone marrow aspirate samples. Any level of residual disease was considered MRD+. Overall survival (OS) after alloSCT was calculated from the day of graft infusion until death or time of last follow-up. Results: A total of 130 pts were treated with ven combo therapy with 18 pts (13.8% of all pts) receiving a subsequent alloSCT. Median age was 65 years (A). While 3 pts received a ven combo as the first treatment for AML, 15 pts had RR-AML. Aza/ven was most commonly used (72%) and the majority of pts (83%) received 1-2 cycles of ven therapy prior to alloSCT. For 7, 6, 4 and 1 pts the donor was a matched related, a matched unrelated, a mismatched unrelated, or haploidentical; only one pt had received a prior alloSCT for AML (B). Unmodified peripheral blood stem cells (66%) and reduced intensity conditioning regimens (77%) were most commonly used. In pts who proceeded to an alloSCT, 12/18 pts achieved a response after ven combination therapy: 4/18 MRD-CR/CRi, 4/18 MRD+CR/CRi, 4/18 MLFS; 6/18 pts had persistent disease (C and D). It is important to note that these response rates were specific to patients who received an alloSCT after ven combination therapy. While pts with DNMT3A, NPM1, IDH1/2 and FLT3 mutations had a high response rate to ven therapy prior to alloSCT, none of the pts with TP53 or NRAS mutations achieved a response prior to alloSCT (E). Only DNMT3A mutations were statistically significantly associated with a high response rate prior to alloSCT (ORR 100%, CR/CRi 63%, p=0.01). AlloSCT was able to convert pts with MRD+ or persistent disease into an MRD- state in 50% of cases (F). With a median follow up of 10 months, the median OS was not reached; 56% of pts relapsed after alloSCT. Median time to relapse for all pts was 18 months (95% CI 4 months-not reached [NR]). Disease status prior to alloSCT was a powerful predictor of post-transplant outcomes. Pts who achieved CR, CRi, or MLFS with ven therapy prior to alloSCT had significantly prolonged OS (median OS not reached) compared with pts who had persistent disease prior to alloSCT (median OS 7 months, 95% CI 2.14 months-NR; p=0.029; G). The poor OS for pts with persistent disease prior to alloSCT was mainly driven by a high incidence of relapse for these pts compared to pts who achieved a response to ven combos (H). The median time to relapse after alloSCT was 17.9 months (95% CI 6.1 months-NR) for pts who achieved CR, CRi, or MLFS prior to alloSCT, and only 3.3 months (95% CI 1.9 months-NR, p=0.052) for pts with persistent disease prior to alloSCT. While 67% of pts experienced grade I-II acute graft versus host disease (aGVHD), only 1 pt was found to have grade III aGVHD and no pt experienced grade IV aGVHD. Median time to aGVHD after alloSCT was 1.4 months (95% CI 0.89 months-NR). Conclusion: Venetoclax combination therapy can bridge some AML pts to subsequent alloSCT. Most pts who underwent alloSCT received reduced-intensity conditioning given their advanced age and comorbidities. Pts who achieved CR, CRi, or MLFS with ven-based therapy prior to alloSCT had more favorable outcomes after alloSCT. With more widespread use of venetoclax, we anticipate that alloSCT following good responses to venetoclax combination therapy will become more common in pts with AML. Longer-term studies are needed to determine durability of post-alloSCT responses following pre-alloSCT venetoclax combination therapy. Figure Disclosures Ponce: Kadmon: Membership on an entity's Board of Directors or advisory committees; Generon: Membership on an entity's Board of Directors or advisory committees; Ceramedix: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding. Young:Amgen: Other: Common stock; Merck: Other: Common stock; Pfizer: Other: Common stock. Gyurkocza:Actinium: Research Funding. Chan:AbbVie: Current equity holder in publicly-traded company; Bristol-Myers Squibb: Current equity holder in publicly-traded company. Xiao:Stemline Therapeutics: Research Funding. Glass:Gerson Lehman Group: Consultancy. King:Abbvie: Other: advisory board. Cai:Imago Biosciences, Inc.: Consultancy, Current equity holder in private company; DAVA Oncology: Honoraria. Stein:Celgene Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; Abbvie: Consultancy; Seattle Genetics: Consultancy; Syndax: Consultancy, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Biotheryx: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees; Astellas Pharmaceuticals: 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. Giralt:GSK: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Actinuum: Other: Advisory board, Research Funding; Amgen: Other: Advisory Board, Research Funding; OMEROS: Research Funding; Jensenn: Membership on an entity's Board of Directors or advisory committees, Research Funding; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; TAKEDA: Membership on an entity's Board of Directors or advisory committees, Research Funding; JAZZ Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; MILTENYI: Research Funding; PFIZER: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; SPECTRUM Pharma: Membership on an entity's Board of Directors or advisory committees; KITE: Membership on an entity's Board of Directors or advisory committees. Perales:Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Medigene: Membership on an entity's Board of Directors or advisory committees, Other; NexImmune: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Other; Cidara Therapeutics: Other; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; MolMed: Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Miltenyi Biotec: Research Funding; Kite/Gilead: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees. Tallman:Novartis: Membership on an entity's Board of Directors or advisory committees; Cellerant: Research Funding; Orsenix: Research Funding; ADC Therapeutics: Research Funding; UpToDate: Patents & Royalties; Abbvie: Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees; Glycomimetics: Research Funding; Rafael: Research Funding; Amgen: Research Funding; Bioline rx: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Delta Fly Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; BioSight: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees. Goldberg:Genentech: 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; Celgene: Consultancy; Aptose: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics: Research Funding; Aprea: Research Funding; AROG: Research Funding; Celularity: Research Funding; Pfizer: Research Funding; Dava Oncology: Honoraria.