Abstract: Background In a recent phase-III trial CPX-351 (Jazz Pharmaceuticals, Palo Alto, CA), a liposomal encapsulation of cytarabine and daunorubicin, has shown higher remission rates and longer overall survival (OS) in patients aged 60 to 75 years with AML with myelodysplasia-related changes (AML-MRC) or therapy-related AML (t-AML) in comparison to conventional 7+3 regimen. Based on this CPX-351 has been approved in the USA 2017 and in Europe 2018 for adult patients with newly-diagnosed AML-MRC or t-AML. Still, several issues such as age ( & lt;60 years), measurable residual disease (MRD), molecular subgroups and outcome after allo-HCT were not addressed in the phase-III trial. Aiming to investigate these open aspects and to provide more clinical experience with CPX-351, we performed a real-world analysis of patients with AML treated with CPX-351 as first-line therapy. Design/Methods: For this retrospective analysis, we collected data on baseline characteristics, treatment details including allo-HCT and outcome from patients with newly-diagnosed AML-MRC or t-AML, who were treated with CPX-351 according to the EMA label between 2018 and 2020 in 25 German centers participating in the Study Alliance Leukemia (SAL), German Cooperative Transplant Study Group and the AML Study Group (AMLSG). Results: A total of 188 patients (median age 65 years, range 26 to 80) with t-AML (29%) or AML-MRC (70%) including 46 patients (24%) & lt;60 years could be analyzed. Eigthy-six percent received one, 14% two induction cycles and 10% received consolidation with CPX-351. Following induction, CR/CRi rate was 47% including 64% of patients with available information achieving measurable residual disease (MRD) negativity ( & lt;10-3) as measured by flow cytometry at local laboratories. Additionally, 35 patients were categorized as MLFS at first remission control, which achieved CRi (n=16) or CR (n=10) in the further course without additional therapy. After median follow-up of 9.3 months, median overall survival (OS) was 21 months and 1-year OS rate was 64%. In multivariate analysis, complex karyotype predicted lower response (p=.0001), and pretreatment with hypomethylating agents (p=.02) and adverse European LeukemiaNet 2017 genetic risk (p & lt;.0001) were associated with lower OS. Allo-HCT was performed in 116 patients (62%) including 101 of these patients with CR prior transplant and resulted in 1-year OS of 73% (median survival not reached), especially in MRD negative patients (p=.048). With 69% of patients developing grade III/IV non-hematologic toxicity following induction and a day 30-mortality of 8% the safety profile was consistent with previous findings. Conclusion: The results from this real-world analysis confirm CPX-351 as an efficient treatment for these high-risk AML patients bridging to facilitating allo-HCT in many patients with encouraging outcome after transplantation. Disclosures Röllig: AbbVie: Honoraria, Research Funding; Amgen: Honoraria; Bristol-Meyer-Squibb: Honoraria, Research Funding; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Gaidzik: Janssen: Speakers Bureau; Pfizer: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Unglaub: Novartis: Consultancy, Other: travel costs/ conference fee; JazzPharma: Consultancy, Other: travel costs/ conference fee. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Haenel: Celgene: Consultancy, Honoraria; Amgen: Consultancy; Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Bayer Vital: Honoraria; Jazz: Consultancy, Honoraria; GSK: Consultancy. Vucinic: Novartis: Honoraria; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Fransecky: Novartis: Honoraria; Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Kobbe: Celgene: Research Funding. Holderried: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Speakers Bureau; Gilead Sciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi: 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; MSD: Speakers Bureau; Daiichi Sankyo: Other: travel support; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Therakos: Other: Travel support; Janssen: Other: Travel support; Abbvie: Other: Travel support; Eurocept Pharmaceuticals: Other: Travel support; Medac: Other: Travel support. Heuser: Astellas: Research Funding; Bayer AG: Honoraria, Research Funding; BMS/Celgene: Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; BergenBio: Research Funding; Daichi Sankyo: Honoraria, Research Funding; Karyopharm: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Research Funding; Tolremo: Honoraria; AbbVie: Honoraria; Janssen: Honoraria. Sauer: Pfizer: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Takeda: Consultancy, Other: DSMB/SAB Member. Goetze: Abbvie: Other: Advisory Board; BMS/Celgene: Other: Advisory Board, Research Funding. Döhner: Jazz Roche: Consultancy, Honoraria; Agios and Astex: Research Funding; Astellas: Research Funding; Abbvie: Consultancy, Honoraria; Janssen: Honoraria, Other: Advisory Board; Daiichi Sankyo: Honoraria, Other: Advisory Board; Novartis: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding. Döhner: Jazz Pharmaceuticals: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria; Helsinn: Honoraria; GEMoaB: Honoraria; Amgen: Honoraria, Research Funding; Astellas: Honoraria, Research Funding; Astex Pharmaceuticals: Honoraria; AstraZeneca: Honoraria; Berlin-Chemie: Honoraria; Oxford Biomedica: Honoraria; Roche: Honoraria. 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. Schetelig: Roche: Honoraria, Other: lecture fees; Novartis: Honoraria, Other: lecture fees; BMS: Honoraria, Other: lecture fees; Abbvie: Honoraria, Other: lecture fees; AstraZeneca: Honoraria, Other: lecture fees; Gilead: Honoraria, Other: lecture fees; Janssen: Honoraria, Other: lecture fees . Germing: Novartis: Honoraria, Research Funding; Janssen: Honoraria; Bristol-Myers Squibb: Honoraria, Other: advisory activity, Research Funding; Celgene: Honoraria; Jazz Pharmaceuticals: Honoraria. Schroeder: JAZZ: Honoraria, Research Funding.

Abstract: Background Venetoclax (VEN)-based combination therapy with hypomethylating agents (HMA) has been approved for first-line treatment in patients ineligible for intensive treatment based on two randomized trials. There is some evidence for efficacy also in the in relapsed/ refractory setting (R/R), but comparative controlled data is lacking. Here, we report our experience of VEN-Azacitidine (AZA) in R/R AML salvage treatment and bridge to allogeneic cell transplantation (allo-HCT) in fit patients compared to historical data from the Study Alliance Leukemia (SAL) registry (ClinicalTrials.gov Identifier: NCT03188874). Design/Methods We analyzed all patients with R/R AML after initial intensive therapy, who started VEN-AZA salvage treatment at the University Hospital Heidelberg, between October 2018 and October 2020. Patients, who were bridged to allo-HCT were compared in a multivariable analysis to data of R/R AML patients from the SAL registry receiving an allo-HCT. Results: A total of 26 patients (median age 60 years, range 23 to 79) were included. All patients initially received intensive therapy, 16 patients (62%) had been refractory to intensive induction therapy with DA (daunorubicin, cytarabine) (11 patients)/ CPX-351 (2 patients) or to an intensive salvage therapy regime with HAM (2 patients)/ Cytarabin-Bortezomib (1 patient). Ten patients (38%) had morphologic (7 patients) or molecular relapse (3 patients) after intensive first line therapy. The distribution of AML according to WHO-2016 classification was n=10 recurrent genetic abnormalities (n= 7, mutated NPM1; n=1, biallelic CEBPA mutations; n=1, mutated RUNX1; n=1, CBFB-MYH11), n=10 AML with MRC, n=6 AML NOS. According to the 2017 ELN classification, 9 patients (34,5%) had low risk, 8 (31%) intermediate risk and 9 (34,5%) adverse risk disease. All patients received AZA 75mg/m² for 7 days combined with VEN 400mg/day after initial ramp up or a reduced dose of 100mg/day in case of co-medication with azoles in 28 days cycles. Best response was CR/CRi in 58% (n=15), PR in 23% (n=6) patients. Day 30-mortality was 0%, day 60-mortality was 4% (n=1). Allo-HCT was performed in 20 patients (77%). Pre-Allo-HCT remission status was CR/CRi in 11 (55%), PR in 4 (20%) patients and MLFS in 1 patient and 4 patients had active disease (n=3, relapse after achieving CR/CRi on VEN-AZA, n=1 refractory to VEN-AZA.). At the time of analysis 15 (75%) of the 20 bridged patients were alive and 11 (55%) are still in CR resulting in a median relapse-free survival in bridged patients of 406 days, whereas all patients not proceeding to allo-HCT died after a median of 139 days. In total, 63 patients with R/R AML were identified in the SAL-registry proceeding to allo-HCT with non VEN-based salvage attempt. Pre-Allo-HCT remission status was CR/CRi in 18 (28%), PR in 15 (24%), unknown in 13 patients (21%) and 17 (27%) patients had active disease (n=9 relapsed, n=8 refractory). Patients of the SAL registry were younger (median, 55 years; range, 22-75 years) and more patients were ELN-int (low risk, 32%, n=20; int, 52%, n=33, adv, 16%, n=10). Median follow-up in the VEN-AZA and the SAL cohorts were 1.4 years and 4.6 years, respectively. Cox-regression modeling of survival measured from the date of being refractory/relapsed revealed a non-significant effect of the cohorts favoring the VEN-AZA salvage therapy (HR, 0.87, p=0.73). However, stratified univariable survival analysis revealed in trend better survival (p=0.10) in the VEN-AZA compared to the SAL cohort with 77% (95%-CI, 62-95%) and 74% (95%-CI, 57-97%) as well as 84% (95%-CI, 76-94%) and 52% (95-CI, 41-68%) 1- and 2-years survival, respectively. Conclusion: Our data confirms the efficacy of VEN-AZA in patients with R/R AML and underlines its potential as an effective strategy for bridging to successful allo-HCT. Disclosures Unglaub: JazzPharma: Consultancy, Other: travel costs/ conference fee; Novartis: Consultancy, Other: travel costs/ conference fee. Schlenk: Boehringer Ingelheim: Research Funding; AstraZeneca: Research Funding; Roche: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria; Neovio Biotech: Honoraria; Hexal: Honoraria; Daiichi Sankyo: Honoraria, Research Funding; Celgene: Honoraria; Astellas: Honoraria, Research Funding, Speakers Bureau; Abbvie: Honoraria; Agios: Honoraria. Middeke: Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Gilead: Consultancy; Abbvie: Consultancy, Honoraria; Jazz: Consultancy; Pfizer: Consultancy, Honoraria; Sanofi: Honoraria, Research Funding; Astellas: Consultancy, Honoraria; Novartis: Consultancy; Glycostem: Consultancy; UCB: Honoraria. 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: GSK: Consultancy; Jazz: Consultancy, Honoraria; Bayer Vital: Honoraria; Takeda: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Crysandt: Pfizer: Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria. Fransecky: Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Seggewiss-Bernhardt: Astra-Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; ipsen: 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; Abbvie: 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; EusaPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees. Platzbecker: AbbVie: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Geron: Honoraria; Takeda: Honoraria. Baldus: Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria; Novartis: Honoraria. Dreger: Bluebird Bio: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; BMS: Consultancy; AbbVie: Consultancy, Speakers Bureau; Janssen: Consultancy; Gilead Sciences: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Müller-Tidow: Pfizer: Research Funding; Janssen: Consultancy, Research Funding; Bioline: Research Funding. Sauer: Takeda: Consultancy, Other: DSMB/SAB Member; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Abbvie: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau. OffLabel Disclosure: off-label use of Venetoclax-based combination therapy in relapsed or refractory AML

Abstract: The BCL2 inhibitor venetoclax (VEN) in combination with azacitidine (5-AZA) is currently transforming acute myeloid leukemia (AML) therapy. However, there is a lack of clinically relevant biomarkers that predict response to 5-AZA/VEN. Here, we integrated transcriptomic, proteomic, functional, and clinical data to identify predictors of 5-AZA/VEN response. Although cultured monocytic AML cells displayed upfront resistance, monocytic differentiation was not clinically predictive in our patient cohort. We identified leukemic stem cells (LSC) as primary targets of 5-AZA/VEN whose elimination determined the therapy outcome. LSCs of 5-AZA/VEN-refractory patients displayed perturbed apoptotic dependencies. We developed and validated a flow cytometry-based “Mediators of apoptosis combinatorial score” (MAC-Score) linking the ratio of protein expression of BCL2, BCL-xL, and MCL1 in LSCs. MAC scoring predicts initial response with a positive predictive value of more than 97% associated with increased event-free survival. In summary, combinatorial levels of BCL2 family members in AML-LSCs are a key denominator of response, and MAC scoring reliably predicts patient response to 5-AZA/VEN. Significance: Venetoclax/azacitidine treatment has become an alternative to standard chemotherapy for patients with AML. However, prediction of response to treatment is hampered by the lack of clinically useful biomarkers. Here, we present easy-to-implement MAC scoring in LSCs as a novel strategy to predict treatment response and facilitate clinical decision-making. This article is highlighted in the In This Issue feature, p. 1275

Abstract: Treatment with Hypomethylating agents (HMA) such as 5-Azazytidine (AZA) in combination with the BCL-2 inhibitor Venetoclax (VEN) has recently become the standard of care for AML patients unsuitable for intensive induction chemotherapy and shows results superior to treatment with AZA alone (DiNardo et al., 2020, NEJM). However upfront resistance and relapse following initial response remain major obstacles. It has recently been proposed that monocytic differentiation predicts resistance to AZA/VEN treatment in AML (Pei et al., 2020 Cancer Discovery). This appears to be due to increased expression of other anti-apoptotic proteins such as MCL-1 in monocytic AMLs, which conveys resistance to AZA/VEN therapy, as survival of leukemic cells in these patients is no longer dependent on BCL-2. However, an independent study found no impaired outcome in patients with monocytic AMLs treated with HMA/VEN (Maiti et al., 2020, Blood, ASH abstract). Here, we show that monocytic AML cell lines and bulk cells of monocytic primary AML cells are indeed intrinsically resistant to AZA/VEN treatment. However, in a collective of 30 patients treated with HMA/VEN at Heidelberg University Medical Center between 2018 and 2020, monocytic differentiation assessed by flow cytometry was not an independent risk factor for refractory disease. We hypothesized that the conflicting data may be caused by intra-patient heterogeneity of AZA/VEN sensivitity and assessed killing efficiency in various immunophenotypic subpopulations of 12 primary AML patient samples in vitro. The CD64 +CD11b +, differentiated blast population made up & gt;50% of leukemic cells in monocytic and & lt;20% in primitive samples and showed high levels of resistance to AZA/VEN therapy in both primitive and monocytic leukemias but did not engraft when transplanted into NSG mice, arguing they do not contain leukemic stem cells (LSC). In contrast, we found immature CD64 -CD11b - GPR56 + LSC to be sensitive to AZA/VEN treatment irrespective whether they were derived from monocytic or primitive types of primary AMLs. As expected, LSCs from either monocytic or primitive AMLs initiated disease in NSG mice, highlighting that targeting LSCs is essential for the effect of AML therapy. Next, we investigated expression of BCL-2, MCL-1 and BCL-xL in the same primary patient samples and observed high MCL-1 expression in monocytic AML samples. However, MCL-1 expression was restricted to the CD64 +CD11b + population whereas in the LSC sub-populations robust expression of BCL-2 but low levels of MCL-1 and BCL-xL were detected, independent of whether monocytic or primitive AMLs were analyzed. To further validate the sensitivity of LSCs of monocytic AML to BCL-2-I, we established a platform combining BH-3 profiling with multi-color flow cytometry, allowing for single cell assessment of cellular dependencies on independent apoptotic pathways. We found that LSCs of both AML types show high VEN/BAD but low MS-1 induced apoptosis, functionally confirming the expression patterns of BCL-2 and MCL-1. As LSCs are rare in monocytic samples, investigation of samples in bulk are dominated by MCL-1 expressing and resistant non-LSCs, explaining the overall higher MCL-1 expression/survival of monocytic compared to immature AML cells. However, our data uncovers sensitivity of LSCs to AZA/VEN independent of overall monocytic or primitive sample classification and provide a mechanistic explanation for the clinical data of Maiti et al. and our Heidelberg AML collective, which found no increased resistance of monocytic AMLs to AZA/VEN treatment. Disclosures Unglaub: JazzPharma: Consultancy, Other: travel costs/ conference fee; Novartis: Consultancy, Other: travel costs/ conference fee. Schlenk: Abbvie: Honoraria; Agios: Honoraria; 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. Müller-Tidow: Janssen: Consultancy, Research Funding; Bioline: Research Funding; Pfizer: Research Funding.