Abstract: BACKGROUND: Midostaurin is a first-generation, type I multi-targeted kinase inhibitor with inhibitory activity against FLT3-ITD and -TKD mutations. Midostaurin is approved by FDA and EMA in combination with intensive induction and consolidation chemotherapy for adult patients with AML exhibiting an activating FLT3 mutation; the EMA label also includes single-agent maintenance therapy following consolidation chemotherapy. We conducted a phase-II trial (AMLSG 16-10) to evaluate midostaurin with induction chemotherapy followed by allogeneic hematopoietic-cell transplantation (HCT) and a one-year midostaurin maintenance therapy in younger and older patients with acute myeloid leukemia (AML) and FLT3 internal tandem duplication (ITD). METHODS: Patients 18 to 70 years of age with newly diagnosed FLT3-ITD-positive AML were eligible. Primary and key secondary endpoints were event-free (EFS) and overall survival (OS); results were compared to those of a historical control cohort of 415 patients with FLT3-ITD AML. Statistical analysis was performed using a double-robust adjustment with propensity score weighting and covariate adjustment. Major differences in trial design compared to the pivotal CALGB 10603/RATIFY trial were: i) only AML with FLT3-ITD were eligible; ii) AML with FLT3 tyrosine kinase domain mutations (only) and core-binding factor AML were not eligible; iii) older patients 60-70 years of age were eligible; iv) all patients were assigned to allogeneic HCT; v) a one-year maintenance treatment with midostaurin was included also after allogeneic HCT; vi) a continuous dosing schedule of midostaurin was applied with the aim to achieve a better target inhibition. Results: The trial accrued 440 patients, including 312 younger (18-60 yrs) and 128 older (61-70 yrs) patients. Complete remission (CR)/CR with incomplete hematologic recovery rate, median EFS and OS of the 440 patients were 74.9%, 13.6 and 36.2 months, respectively. Multivariate analysis of EFS showed a highly significant hazard reduction for an event for patients treated within AMLSG 16-10 trial compared to the historical controls (HR 0.55; 95%-confidence interval [CI], 0.47, 0.65; P & lt;0.001); this effect was significant in the younger (HR 0.59; 95%-CI, 0.49, 0.71; P & lt;0.001) and the older patient cohort (HR 0.42; 95%-CI, 0.30, 0.60; P & lt;0.001). Multivariate analysis also showed a highly significant beneficial effect on OS (HR 0.57; 95%-CI, 0.47, 0.68; P & lt;0.001), again for both age subgroups. Allogeneic HCT in first CR/CRi was performed according to protocol in 199 of 440 (45%) patients (48% and 38% in younger and older patients, respectively), and an additional 60 patients received allogeneic HCT in firstline therapy (n=33 pts. in CR/CRi after salvage therapy and 27 pts. with active disease); the treatment effect of midostaurin remained significant in sensitivity analysis including allogeneic HCT (n=259) as a time-dependent covariate. Addition of midostaurin to chemotherapy was safe in younger and older patients. Conclusions: In comparison to a historical control cohort, the addition of midostaurin to intensive therapy led to a significant improvement in EFS and OS in both younger and older adult patients with AML and FLT3-ITD. Figure: Survival distribution for the primary endpoint event-free survival (EFS) and key secondary endpoint overall survival (OS) according to study population and age group. A EFS by cohort and age group (≤60 versus & gt;60 years) B OS by cohort and age group (≤60 versus & gt;60 years) Figure 1 Figure 1. Disclosures Döhner: Astellas: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Astex: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; GEMoaB: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding; Berlin-Chemie: Consultancy, Honoraria; Helsinn: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Jazz: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Oxford Biomedicals: Consultancy, Honoraria; Pfizer: Research Funding; Roche: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Ulm University Hospital: Current Employment. Fiedler: Servier: Consultancy, Other: Meeting attendance, Preparation of information material; Stemline: Consultancy; Daiichi Sanyko: Consultancy, Other: Meeting attendance, Preparation of information material; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Honoraria; MorphoSys: Consultancy, Honoraria; Jazz: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material; Celgene: Consultancy, Honoraria; Ariad/Incyte: Honoraria; Amgen: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material, Patents & Royalties, Research Funding; Abbvie: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material. Wulf: Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Clinigen: Consultancy, Honoraria. Salih: BMS: Honoraria; Celgene: Honoraria; Pfizer: Honoraria; Synimmune GmbH: Honoraria; Novartis: Honoraria. Lübbert: Imago BioSciences: Honoraria; Janssen: Honoraria, Research Funding; Pfizer: Honoraria; Syros: Honoraria; Aristopharm: Research Funding; Cheplapharm: Research Funding; Janssen: Research Funding; Teva: Research Funding; Hexal: Honoraria; Astex: Honoraria; Abbvie: Honoraria. Kühn: Abbvie: Honoraria; Kura Oncology: Honoraria, Research Funding; Pfizer: Honoraria. Schroeder: Abbvie: Honoraria; Astellas: Honoraria; Celgene: Honoraria; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Pfizer: Honoraria. Salwender: Oncopeptides: Honoraria; GlaxoSmithKline: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Takeda: Honoraria; Amgen: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Chugai: Honoraria; AbbVie: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Janssen-Cilag: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Bristol-Myers Squibb/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Pfizer: Honoraria. Götze: Abbvie: Honoraria; Celgene/BMS: Honoraria, Research Funding. Westermann: Amgen: Consultancy, Honoraria; BMS: Honoraria; Novartis: Consultancy, Honoraria; Stem Cell Line: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Astellas: Honoraria. Fransecky: Abbvie: Honoraria, Research Funding; Takeda: Honoraria; Amgen: Honoraria; Novartis: Honoraria; Medac: Honoraria. Mayer: Novartis: Other: Travel support; Celgene: Other: Travel support; Roche: Other: Travel support; Amgen: Other: Travel support; BMS: Other: Travel support; Pfizer: Other: Travel support; Jazz: Other: Travel support; Astellas: Other: Travel support. Hertenstein: Sanofi: Honoraria; Novartis: Honoraria; Celgene: Honoraria; BMS: Honoraria. Tischler: AstraZeneca: Other: Travel support; Novartis: Other: Travel support; Janssen: Honoraria; GSK: Other: Travel support; Sanofi-Aventis: Other: Travel support; Abbvie: Other: Travel support. Paschka: Abbvie: Honoraria, Other: Travel support; Agios: Honoraria, Speakers Bureau; Astellas: Honoraria, Speakers Bureau; Astex: Honoraria; Celgene: Honoraria, Other: Travel support; Jazz: Honoraria; Novartis: Honoraria, Other: Travel support; Otsuka: Honoraria; Pfizer: Honoraria; Sunesis: Honoraria; BMS: Other, Speakers Bureau; Celgene: Honoraria; Janssen: Other; Takeda: Other. Gaidzik: Janssen: Speakers Bureau; Pfizer: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Heuser: Tolremo: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer Pharma AG: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Research Funding; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; BergenBio: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding. Schlenk: Astellas: Honoraria, Research Funding, Speakers Bureau; Celgene: Honoraria; Daiichi Sankyo: Honoraria, Research Funding; Hexal: Honoraria; Neovio Biotech: Honoraria; Novartis: Honoraria; Pfizer: Honoraria, Research Funding, Speakers Bureau; Roche: Honoraria, Research Funding; AstraZeneca: Research Funding; Boehringer Ingelheim: Research Funding; Abbvie: Honoraria; Agios: Honoraria. Bullinger: Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Astellas: Honoraria; Bristol-Myers Squibb / Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Hexal: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Menarini: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Döhner: Amgen: Honoraria; BMS/Celgene: Honoraria, Research Funding; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria, Research Funding; Roche: Honoraria; Daiichi Sankyo: Honoraria; Agios: Research Funding; Astex: Research Funding; Astellas: Research Funding. Ganser: Novartis: Honoraria; Jazz Pharmaceuticals: Honoraria; Celgene: Honoraria. OffLabel Disclosure: Midostaurin as single-agent maintenance therapy following allogeneic hematopoietic cell transplantation

Abstract: BACKGROUND: Current guidelines for AML ascribe disease-risk partly based on NPM1 and FLT3 mutational status. NPM1 mutations (mut) occur in 25%-30% of patients (pts) with AML and are associated with favorable prognosis in the absence of co-occurring FLT3-ITD. FLT3-ITD alterations are observed in ~15-30% of AML pts and confer poor prognosis, whereas the prognostic implication of FLT3-TKD point mutations (~7% of pts) is less clear. Post-IC, absence of MRD is associated with favorable relapse-free and overall survival (RFS/OS). In the randomized, phase 3 QUAZAR AML-001 trial, Oral-AZA (CC-486) significantly prolonged OS and RFS vs placebo (PBO) in older pts with AML in first remission after IC (Wei, NEJM 2020). It is of high interest to understand the effects of Oral-AZA in pts with NPM1 and/or FLT3 mutations, and whether their outcomes are influenced by post-IC MRD status. OBJECTIVE: Evaluate survival outcomes with Oral-AZA vs PBO in pts with NPM1mut ± FLT3mut at AML diagnosis (Dx), and OS by baseline (BL) MRD status (+/-) in pts with NPM1/FLT3 mutations. METHODS: In QUAZAR AML-001, pts aged ≥55 years with AML and NCCN intermediate or poor-risk cytogenetics at Dx were randomized 1:1 to receive Oral-AZA 300 mg or PBO QD within 4 mo after attaining first CR/CRi with IC (induction ± consolidation). NPM1 and FLT3 statuses (mut or wild-type [wt]) at AML Dx (before IC) were collected from pt diagnostic case report forms. MRD analyses were conducted by MFC (≥0.1% MRD+ cutoff) in bone marrow aspirate samples collected at screening (post-IC; ie, BL). OS and RFS were estimated from the time of randomization using Kaplan-Meier methods. Multivariate (MV) Cox regression analyses of the prognostic effects on OS/RFS were performed, with NPM1 and FLT3 mutational status and cytogenetic risk at Dx; post-IC MRD status (+/-) at BL, and randomized Tx (Oral AZA vs PBO) as variables. RESULTS: Of 472 pts enrolled , 469 (99.4%) had mutational data available at Dx, and the MRD-evaluable cohort comprised 463 pts (98.1%). In all, 137 pts (29%; Oral-AZA n = 66, PBO n = 71) had NPM1mut at AML Dx, and NPM1mut was significantly correlated with MRD- status at BL (post-IC)(P = 0.0178). Among pts with NPM1mut, OS was significantly improved in pts receiving Oral-AZA vs PBO, whether pts were MRD- (median 48.6 vs 26.2 mo, respectively) or MRD+ (median 39.4 vs 10.3 mo) at BL (both P & lt; 0.0001) (Figure). While median OS for NPM1mut pts in the Oral-AZA arm was nominally improved for MRD- pts vs. those MRD+ (48.6 vs. 39.4 mo, respectively), median OS for NPM1mut pts in the PBO arm was substantially influenced by post-IC MRD status (26.2 vs 10.3 mo for MRD- and MRD+ pts, respectively) (Figure). Similarly, median RFS for pts with NPM1mut/MRD- in the Oral-AZA and PBO arms was 24.9 vs 9.9 mo, respectively, and for pts with NPM1mut/MRD+ was 19.4 vs 4.6 mo. In all, 66 pts (14.1%) had FLT3-ITD (n = 46) and/or FLT3-TKD mut (n = 24) at AML Dx; NPM1 and FLT3-ITD status was NPM1mut + FLT3-ITD - in 107 pts, NPM1mut + FLT3-ITD + in 30 pts, and NPM1wt + FLT3-ITD + in 16 pts. In the Oral-AZA arm, median OS in pts with FLT3mut was not meaningfully different from that in pts with FLT3wt (28.2 and 24.7 mo, respectively), but FLT3mut conferred a negative prognosis in the PBO arm (median OS 9.7 mo, vs 15.2 mo for FLT3wt pts). Risk of death was reduced 46% with Oral-AZA vs PBO in pts with FLT3mut (HR 0.54 [95%CI 0.25, 1.14]). When considering MRD status, median OS in FLT3mut/MRD- pts was 28.2 vs. 15.9 mo in the Oral-AZA (n = 14) and PBO (n = 17) arms, respectively, and was 24.0 vs 8.0 mo in FLT3mut/MRD+ pts (Oral-AZA, n = 16; PBO, n = 18). In MV analyses, Oral-AZA significantly improved OS vs PBO when adjusted for other variables (P = 0.035); NPM1 status (P = 0.001), FLT3status (P = 0.035), and cytogenetic risk at Dx (P & lt; 0.001) were each also significantly predictive of OS, as was post-IC MRD status (P & lt; 0.001). All except FLT3 status (P = 0.737) were significantly predictive of RFS. CONCLUSIONS: Oral-AZA prolonged OS and RFS vs PBO in pts with NPM1mut, with improvements beyond the prognostic benefit conferred by MRD-, suggesting that pts with NPM1mut and MRD- can attain substantial OS benefit with Oral-AZA maintenance. An OS benefit was also observed with Oral-AZA vs PBO in pts in FLT3mut at Dx, but outcomes may be confounded by co-occurring NPM1mut, so further investigation is needed. MV analyses confirmed the independent prognostic influence of Oral-AZA, NPM1 and FLT3 mutations at Dx, cytogenetic risk at Dx, and post-IC MRD status on OS. Figure 1 Figure 1. Disclosures Döhner: Janssen: Honoraria; Helsinn: Honoraria; Gilead: Honoraria; GEMoaB: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Berlin-Chemie: Honoraria; AstraZeneca: Honoraria; Astex Pharmaceuticals: Honoraria; Astellas: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Oxford Biomedica: Honoraria; Pfizer: Research Funding; Roche: Honoraria. Wei: Astellas: Honoraria; Novartis, Celgene, AbbVie, Servier, AstraZeneca, and Amgen: Research Funding; Novartis, Janssen, Amgen, Roche, Pfizer, Abbvie, Servier, BMS, Macrogenics, Agios, Gilead: Membership on an entity's Board of Directors or advisory committees. Roboz: Glaxo SmithKline: Consultancy; Helsinn: Consultancy; AbbVie: Consultancy; Jasper Therapeutics: Consultancy; Bayer: Consultancy; Novartis: Consultancy; Actinium: Consultancy; Agios: Consultancy; Blueprint Medicines: Consultancy; Astellas: Consultancy; AstraZeneca: Consultancy; Jazz: Consultancy; Daiichi Sankyo: Consultancy; Astex: Consultancy; Mesoblast: Consultancy; Amgen: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Bristol Myers Squibb: Consultancy; Janssen: Consultancy; Otsuka: Consultancy; Celgene: Consultancy; Janssen: Research Funding; Pfizer: Consultancy; Roche/Genentech: Consultancy. Montesinos: Agios: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Tolero Pharmaceutical: Consultancy; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Forma Therapeutics: Consultancy; Glycomimetics: Consultancy; Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau; Stemline/Menarini: Consultancy. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Ravandi: AstraZeneca: Honoraria; AbbVie: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Xencor: Honoraria, Research Funding; Syros Pharmaceuticals: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Research Funding; Novartis: Honoraria; Astex: Honoraria, Research Funding; Prelude: Research Funding; Taiho: Honoraria, Research Funding. Dombret: Amgen: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding; Servier: Research Funding; Abbvie: Honoraria; BMS-Celgene: Honoraria; Daiichi Sankyo: Honoraria. Sandhu: Celgene: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Amgen: Consultancy; Bioverativ: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy; Gilead: Consultancy. Skikne: Bristol Myers Squibb: Current Employment. See: Bristol Myers Squibb: Current Employment. Ugidos: Bristol Myers Squibb: Current Employment. Risueño: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Chan: Bristol Myers Squibb: Current Employment. Thakurta: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Beach: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Lopes de Menezes: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties.

Abstract: TP53 mutations (TP53MT) have been associated with poor outcomes in various hematologic malignancies, but no data exist on its role in patients with myelofibrosis undergoing hematopoietic stem cell transplantation (HSCT). Here, we took advantage of a large international multicenter cohort to evaluate the role of TP53MTin this setting. Among 349 included patients, 49 (13%) had detectable TP53MT, of whom 30 showed a multi-hit configuration. Median variant allele frequency was 20.3%. Cytogenetic risk was favorable (71%), unfavorable (23%), and very high (6%), with complex karyotype present in 36 patients (10%). Median survival of TP53MT patients was 1.5 years vs 13.5 years for the TP53WT group (P & lt;0.001). Outcome was driven by multi-hit TP53MT constellation (P & lt;0.001), showing 6-year survival of 56% for single-hit vs 25% for multi-hit TP53MT carriers vs 64% for TP53WT. Outcome was independent of current transplant-specific risk factors and conditioning intensity. Similarly, cumulative incidence of relapse was 17% for single-hit vs 52% for multi-hit vs 21% for TP53WT. Ten patients with TP53MT (20%) presented as leukemic transformation vs only 7 (2%) in the TP53WT group (P & lt;0.001). Out of the 10 patients with TP53MT, 8 showed multi-hit constellation. Median time to leukemic transformation was shorter for multi-and single-hit TP53MT (0.7 and 0.5 years, respectively) vs 2.5 years for TP53WT. In summary, multi-hit TP53MT represents a very high-risk group in myelofibrosis patients undergoing HSCT, whereas single-hit TP53MTalone showed similar outcome to non-mutated patients, informing prognostication for survival and relapse together with current transplant-specific tools.

Abstract: Growth Factor Independence 1 (GFI1) is a DNA-binding transcription factor and a key regulator of haematopoiesis. GFI1-36N is a germline variant causing a change of serine (S) to asparagine (N) at position 36. We previously reported that the GFI1-36N allele has a prevalence of 10-15% among patients with acute myeloid leukemia (AML) and 5-7% among healthy Caucasians and promotes the development of this disease. Using a multi-omics approach, we show here that GFI1-36N expression is associated with increased frequencies of chromosomal aberrations, mutational burden and mutational signatures in both murine and human AML and impedes homologous recombination-directed (HR) DNA repair in leukemic cells. GFI1-36N exhibits impaired binding to N-Myc downstream-regulated gene 1 (Ndrg1) regulatory elements, causing decreased NDRG1 levels, which leads to a reduction of O6-methylguanine-DNA-methyltransferase (MGMT) expression levels illustrated by both transcriptome and proteome analyses. Targeting MGMT via temozolomide, a DNA alkylating drug, and HR via olaparib, a PARP1 inhibitor, caused synthetic lethality in human and murine AML samples expressing GFI1-36N, whereas the effects were insignificant in non-malignant GFI1-36S or GFI1-36N cells. In addition, mice transplanted with GFI1-36N leukemic cells treated with a combination of temozolomide and olaparib had significantly longer AML-free survival than mice transplanted with GFI1-36S leukemic cells. This suggests that reduced MGMT expression leaves GFI1-36N leukemic cells particularly vulnerable to DNA damage initiating chemotherapeutics. Our data provide critical insights into novel options to treat AML patients carrying the GFI1-36N variant.