Abstract: Aim Venous thromboembolism (VTE) is a major cause of morbidity and mortality and is estimated to cost approximately AUD$117 000 per person (Access Economics 2008). Despite advances in thrombosis management, recurrence rates remain high and management strategies are often heterogenous even within a single institution. While most studies have analysed specific aspects of VTE management, we aim to provide a holistic evaluation of real-world VTE management in the warfarin era including identifiying potential causal effects and complications. Method Retrospective evaluation of VTE over an 18-month period, from July 2011 to December 2012, at two major hospitals in Northeast Melbourne, Australia, including demographics, provoking factors, management, complications and mortality. Comparisons were made between cancer and non-cancer populations. Result 1003 patients, with median age of 63 (range 19-97) years, were identified including 26 recurrences (total 1029 episodes) - 577 (56%) pulmonary embolism (PE), 428 (42%) deep venous thrombosis (DVT). There was an overall male predominance (52%), particularly affecting the DVT subgroup (57% vs 48%, p=0.003) with no gender differences detected in the PE subgroup. 20% reported prior VTE and left limb DVT was more common (49% vs 43%, p=0.0008). The median follow up was 20 (range 10-32) months. NON-CANCER PATIENTS In this cohort, 63% had provoked VTE and thrombophilia screen was performed in 41%. The median duration of anticoagulation was 6 and 7 months for DVT and PE respectively. The majority (90%) was on warfarin for long-term anticoagulation. 5% required further interventions – IVC filter (n=28) and thrombolysis (n=15). 38% had end-of-treatment repeat imaging and residual clot was observed in 40%. Clot persistence was associated with increased recurrence risk, with an odds ratio of 2.64 (1.15 – 6.04, p=0.02). 8% had recurrent thrombosis with no difference between provoked versus unprovoked VTE (7.5% vs 9.0%, p=0.45). 5% reported grade III/IV bleeding, independent of duration of anticoagulation. Patients on enoxaparin had higher risk of bleeding (28% vs 10%, p 〈 0.001). The all-cause mortality rate was 11%. In the sub-analysis of below knee DVT (BKDVT), 3 patients (1.5%) were subsequently diagnosed with cancer, similar prevalence to those with major VTE (1.7%), defined as proximal DVT and/or PE. BKDVT were more likely to be provoked (72% vs 55%, p 〈 0.001) and recurrence was similar to major VTE (6.8% vs 8.7%, p=0.42) although patients with major VTE were more likely to experience grade III/IV bleeding complications (6.3% vs 1.0%, p=0.003) despite similar duration of therapy. Mortality rate in this cohort was 5.5% with no thrombosis-related deaths. CANCER PATIENTS 233 (23%) patients had active malignancy at time of VTE with 14 patients (1.4%) subsequently diagnosed. Cancer patients were older (67 vs 61 years, p 〈 0.001) and had higher clot burden with more PE (64% vs 53%, p=0.004), proximal DVT (63% vs 46%, p=0.0008) and bilateral DVT (16% vs 5%, p 〈 0.001) compared to non-cancer patients. Patients with metastatic cancer were also more likely to have unprovoked events (p=0.015). Cancer patients were more likely to require IVC filters (9% vs 3.6%, p 〈 0.001) and lifelong anticoagulation (35% vs 18%, p 〈 0.001). Recurrent thrombosis (16%, p 〈 0.001) and Grade III/IV bleeding (9%, p=0.025) were more common. However, bleeding rates in cancer patients on long-term enoxaparin were similar to warfarin. Mortality rate in the cancer patients was 63% and were related to with higher incidence of complications-related deaths (p 〈 0.001). Conclusion VTE is associated with significant mortality, even in non-cancer patients (11%). The annual recurrence rate is 6%, with malignancy and residual clot on repeat imaging being major risk factors. Cancer patients experience more Grade III/IV bleeding complications (9% vs 5%) and had higher clot burden and all-cause mortality compared to non-cancer patients. Interestingly, BKDVT, often considered a minor VTE, had comparable rates of recurrence and subsequent cancer detection to major VTE suggesting that the investigation and treatment of BKDVT should not differ from major VTE. Further evaluation of new treatment strategies as well as clinical and laboratory risk assessments are required to improve the management for VTE. This data will serve as an important baseline for future comparison in the new era of novel oral anticoagulants. Disclosures No relevant conflicts of interest to declare.

Abstract: Background: Adaptive resistance mechanisms leading to treatment failure have been identified in older patients receiving venetoclax (VEN) in combination with either azacitidine or low dose cytarabine (LDAC) as frontline therapy for acute myeloid leukemia (AML). These include the expansion or secondary emergence of kinase activating mutations, including FLT3-ITD in patients with non-adverse karyotype (NON-ADV), as well as TP53 mutations among patients with adverse karyotype (ADV)(DiNardo & Tiong et al, Blood 2020). INTERVENE is a phase 2 study evaluating the safety and efficacy of the "risk-stratified" addition of a novel third agent to VEN-LDAC, delivered in tandem to LDAC to minimize the risk of myelotoxicity (Figure 1A). To mitigate VEN resistance associated with activated kinases in NON-ADV risk AML, midostaurin (MIDO), a FLT3/multi-kinase inhibitor, was incorporated in combination with VEN. To address VEN resistance associated with TP53 defects in ADV risk AML, a HDAC inhibitor pracinostat (PRAN) was incorporated in accordance with pre-clinical studies suggesting synergistic induction of TP53 independent cell death with VEN plus HDAC inhibition (Salmon et al, ASH 2018). We hereby report the results of the dose-finding safety run-in phase of the study. Methods: Eligibility: Patients with treatment naïve AML (excluding APL), aged ≥60 years and unfit for intensive chemotherapy were included. Prior hypomethylating agents for antecedent myeloid neoplasms were permitted with a 14-day washout. Patients were stratified according to cytogenetic risk, as per Medical Research Council 2010 criteria. Treatment: VEN D1-28 (with dose ramp-up in cycle 1) was combined with LDAC (20mg/m 2 SC D1-10), with the third agent starting after/on the last day of LDAC (Fig 1A). Each cycle was 28 days. In the NON-ADV stratum (VEN-LDAC-MIDO), 2 dose levels were explored: (L1) VEN 400mg + LDAC + MIDO 50mg BD D11-28; (L2) VEN 600mg + LDAC + MIDO 50mg. In the ADV stratum (VEN-LDAC-PRAN), 3 dose levels were tested: (L1) VEN 400mg + LDAC + PRAN 45mg starting D10 and given 3x/week orally for a total of 9 doses; (L2) VEN 600mg + LDAC + PRAN 45mg; (L3) VEN 600mg + LDAC + PRAN 60mg. Azole antifungals were prohibited in cycle 1 but allowed from cycle 2 with VEN dose modification. Endpoints (safety run-in): Primary: occurrence of dose-limiting toxicities (DLT) during cycle 1 and determination of recommended phase 2 doses (RP2D) using a Bayesian Logistic Regression Model. Secondary: Preliminary response rates. Molecular studies: Next generation sequencing using a custom 48-gene Roche KAPA HyperCapture myeloid panel and FLT3-ITD targeted amplicon sequencing were performed on baseline bone marrow samples. First patient enrolled: 7SEP2020. Data cut-off: 29JUN2021. Results: 32 patients were enrolled: 18 in NON-ADV and 14 in ADV strata, respectively. Two patients in the NON-ADV stratum withdrew within the first 7 days due to non-therapy related reasons (1=personal, 1=incidental lung lesion) and were not DLT/response evaluable. Median age was 77 years (68-87; 69% ≥75 years). 43.8% (14/32) had secondary/therapy related AML. Although gastrointestinal adverse events (AE) during cycle 1 were more common in VEN-LDAC-PRAN arm with nausea (57 vs 17%), vomiting (36% vs 6%) and diarrhea (50% vs 22%), grade 3+ toxicities were uncommon (0-7%)(Table 2). Occurrence of febrile neutropenia was similar between the two arms. 30-day mortality was 0% and 14% (2/14: 1=infection, 1=disease progression) for NON-ADV and ADV strata, respectively. No DLTs were observed in either stratum across all dose levels, thus the RP2D was the highest dose level explored for both triplet combinations. The intention-to-treat overall response rate CR+CRi+CRh was 72.2% (13/18) in the NON-ADV arm and 57.1% (8/14) in ADV arm. The expanded response rate including PR and MLFS was 77.8% (14/18) and 71.4% (10/14) in the NON-ADV and ADV strata, respectively. Median time to best response was 1 cycle (range 1-6). Updated response and survival outcomes will be presented at the meeting. Conclusion: The addition of MIDO or PRAN to VEN-LDAC was tolerable in older/unfit patients with treatment naïve AML. Preliminary efficacy with this risk-stratified approach compared favorably to prior studies with VEN-LDAC alone (Wei et al Blood 2020: CR+CRi 56% in NON-ADV, 28% in ADV). The randomized phase 2 part of this tandem triplet strategy with the goal of preventing adaptive resistance is underway. Figure 1 Figure 1. Disclosures Chua: Abbvie: Other: Conference travel and accommodation . Reynolds: Alcon: Current equity holder in publicly-traded company; Abbvie: Research Funding; Novartis AG: Current equity holder in publicly-traded company. Enjeti: Astra Zeneca: Honoraria; Sanofi: Honoraria; AbbVie: Honoraria; Roche: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hiwase: AbbVie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Marlton: Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; F. Hoffmann-La Roche Ltd: 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; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees; Queensland Health: Current Employment; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bajel: Abbvie, Amgen, Novartis, Pfizer: Honoraria; Amgen: Speakers Bureau. Grove: Astellas: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Cooney: Amgen: Other: Travel, accommodation, expenses ; Roche: Other: Travel, accommodation, expenses ; Novartis: Other: Online conference registration . Beligaswatte: Astellas: Membership on an entity's Board of Directors or advisory committees. Anstee: Walter and Eliza Hall Institute: Patents & Royalties: Dr Anstee was a former employee of the Walter and Eliza Hall Institute and is eligible for a fraction of the royalty stream related to Venetoclax. Perera: Abbvie: Speakers Bureau; BMS: Speakers Bureau. Ritchie: Takeda: Research Funding; BMS: Research Funding; Novartis: Honoraria; CRISPR Therapeutics: Research Funding; Amgen Inc: Honoraria, Research Funding; CSL: Honoraria. Wei: Genentech: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees; Macrogenics: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: 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; Amgen: 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, Research Funding, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. OffLabel Disclosure: This presentation will focus on the ALLG INTERVENE clinical trial combining venetoclax+LDAC+midostaurin or venetoclax+LDAC+pracinostat. Although venetoclax and midostaurin are individually FDA-approved in some indications, the combinations examined in this clinical trial have not been approved by FDA.

Abstract: Randomized trials in acute myeloid leukemia (AML) have demonstrated improved survival by the BCL-2 inhibitor venetoclax combined with azacitidine in older patients, and clinical trials are actively exploring the role of venetoclax in combination with intensive chemotherapy in fitter patients with AML. As most patients still develop recurrent disease, improved understanding of relapse mechanisms is needed. We find that 17% of patients relapsing after venetoclax-based therapy for AML have acquired inactivating missense or frameshift/nonsense mutations in the apoptosis effector gene BAX. In contrast, such variants were rare after genotoxic chemotherapy. BAX variants arose within either leukemic or preleukemic compartments, with multiple mutations observed in some patients. In vitro, AML cells with mutated BAX were competitively selected during prolonged exposure to BCL-2 antagonists. In model systems, AML cells rendered deficient for BAX, but not its close relative BAK, displayed resistance to BCL-2 targeting, whereas sensitivity to conventional chemotherapy was variable. Acquired mutations in BAX during venetoclax-based therapy represent a novel mechanism of resistance to BH3-mimetics and a potential barrier to the long-term efficacy of drugs targeting BCL-2 in AML.

Abstract: Co-senior authors Andrew Brunner and Andrew H. Wei contributed equally to this work Background: MBG453 is a high-affinity humanized anti-TIM-3 (T-cell immunoglobulin domain and mucin domain-3) IgG4 antibody in development for the treatment of MDS, AML, and other malignancies. TIM-3 is an immune checkpoint with a complex regulatory role in both adaptive and innate immune responses and is also preferentially expressed on leukemic stem and progenitor cells, making it a potential target in MDS and AML. MBG453 has been shown to enhance immune cell-mediated killing of AML cells in vitro. Hypomethylating agents (HMAs) have been shown to increase immune checkpoint expression in MDS and AML, providing rationale to study the combination of HMAs with MBG453. Methods: Patients with Revised International Prognostic Scoring System (IPSS-R) high or very high-risk (HR) MDS and newly diagnosed, or relapsed/refractory (R/R), AML following ≥ 1 prior therapy who were not candidates for standard chemotherapy and who were HMA naive were enrolled in this multi-center, open label phase Ib dose-escalation study (NCT03066648). Escalating doses of MBG453 were administered i.v. every 2 weeks (Q2W; days 8, 22) or every four weeks (Q4W; day 8) in combination with decitabine (20 mg/m2; i.v. days 1-5). The primary objectives were to characterize the safety and tolerability of MBG453 in combination with decitabine and to identify recommended doses for future studies. Secondary objectives included assessing preliminary efficacy and pharmacokinetics of the combination. Dose escalation followed a Bayesian logistic regression model based on dose-limiting toxicities (DLTs). Adverse events (AEs) were graded using NCI-CTCAE v4.03. The International Working Group criteria for MDS (Cheson et al, 2006) or AML (Cheson et al, 2003) were used to assess efficacy. Results: As of March 25, 2019, 17 HR-MDS, 4 chronic myelomonocytic leukemia (CMML), and 38 AML patients have received decitabine and MBG453 at 240 mg Q2W (n=22), 400 mg Q2W (n=21), or 800 mg Q4W (n=16). MTD has not been reached. Median age was 70 years (range 23-87 years). 24 patients are ongoing (duration of exposure 1.1 to 18.6 months) with 35 patients discontinued (disease progression [n=19, 32%], AE [n=1, 2%] , patient/physician decision [n=13, 22%], death [n=2, 3%] ). There was one DLT consisting of a grade 3 ALT elevation that was corticosteroid responsive. The most common treatment emergent grade 3/4 AEs were febrile neutropenia (39%), neutropenia (34%), thrombocytopenia (31%), and anemia (29%). A total of 8 patients (14%) developed ≥ grade 2 suspected immune related AEs (irAEs) considered to be MBG453 related; 4 of whom (7%) presented with grade 3/4 events: ALT elevation (n=2), arthritis (n=1), and GGT increase (n=1). No study treatment-related deaths were observed. 16 HR-MDS and 31 AML patients have had post-baseline disease response assessments. Median duration of decitabine and MBG453 is 3.9 months (range 0.7-18.6 months). Evidence of activity with MBG453 in combination with decitabine has been seen at doses ranging from 240 mg Q2W to 800 mg Q4W. 8 of 16 (50%) HR-MDS patients achieved mCR or CR. None of the responding HR-MDS patients has had disease recurrence with exposure durations currently ranging from 3.4 to 18.6 months; two patients in mCR underwent allogeneic stem cell transplant. 4 of 14 (29%) newly diagnosed AML patients have achieved a response of PR or better (2 PR, 2 CR), with 3 additional patients exhibiting ≥ 50% bone marrow blast reduction, and 10 of 14 (71%) continuing on study. 5 of 17 (29%) R/R AML patients have achieved a response of CRi, with 5 additional patients exhibiting ≥ 50% bone marrow blast reduction. Exposure durations for all AML responders currently range from 2.1 to 17.9 months. Median onset of response among all patients was 2.0 months. TIM-3 expression was detected on leukemic cells, with modulation of TIM-3 expression following treatment with decitabine. Conclusions: In this ongoing study in patients with HR-MDS and AML, the combination of MBG453 and decitabine was safe and well tolerated, and exhibited evidence of anti-leukemic activity with encouraging preliminary response rates occurring at a median of 2 cycles, with durability in both HR-MDS and AML. These findings validate TIM-3 as a promising therapeutic target in MDS and AML and support further clinical development of MBG453 in combination with HMAs in patients with MDS and AML. Disclosures Borate: AbbVie: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Esteve:Novartis: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy; Daiichi Sankyo: Consultancy; Celgene: Consultancy, Speakers Bureau; Jazz Pharmaceuticals: Consultancy; Roche: Consultancy; Astellas: Consultancy, Speakers Bureau; Pfizer: Consultancy. Porkka:Daiichi Sankyo: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Knapper:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Tolero: Consultancy; Daiichi Sankyo: Honoraria; Pfizer: Consultancy. Vey:Janssen: Honoraria; Novartis: Consultancy, Honoraria. Scholl:Novartis: Other: Project funding; Pfizer: Other: Advisory boards; Gilead: Other: Project funding; AbbVie: Other: Advisory boards; Daiichi Sankyo: Other: Advisory boards. Garcia-Manero:Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Wermke:Novartis: Honoraria, Research Funding. Janssen:Amsterdam University Medical Center, location VUmc, Amsterdam, The Netherlands: Employment; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Other: Founder of the HematologyApp which is supported by BMS, among others, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Founder of the HematologyApp which is supported by Pfizer, among others; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Founder of the HematologyApp which is supported by Incyte, among others; AbbVie: Membership on an entity's Board of Directors or advisory committees; Janssen: Other: Founder of the HematologyApp which is supported by Janssen, among others; MSD: Other: Founder of the HematologyApp which is supported by MSD, among others; Daiichi-Sankyo: Other: Founder of the HematologyApp which is supported by Daiichi-Sankyo, among others; Roche: Other: Founder of the HematologyApp which is supported by Roche, among others; Takeda: Other: Founder of the HematologyApp which is supported by Takeda, among others. Traer:AbbVie: Consultancy; Notable Labs: Equity Ownership; Agios: Consultancy; Astellas: Consultancy; Daiichi Sankyo: Consultancy. Chua:Alfred Hospital, Melbourne, Australia: Employment. Narayan:Takeda: Other: Employment (spouse); Merck: Other: Equity ownership (spouse); Genentech: Other: Equity ownership (spouse). Tovar:Hospital Clinic Barcelona: Employment. Kontro:Amgen: Consultancy; Astellas: Consultancy; AbbVie: Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees. Ottmann:Roche: Honoraria; Pfizer: Honoraria; Fusion Pharma: Honoraria; Takeda: Honoraria; Novartis: Honoraria; Celgene: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Amgen: Honoraria, Research Funding. Sun:Novartis Institutes for BioMedical Research: Employment; Novartis: Other: Novartis stock owner (stock share as long-term employee incentive). Longmire:Novartis Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Szpakowski:Novartis Institutes for Biomedical Research: Employment, Other: Novartis Stock. Liao:Novartis: Employment. Patel:Novartis Pharmaceuticals: Employment. Rinne:Novartis: Employment; N-Of-One, Inc: Consultancy. Brunner:Astra Zeneca: Research Funding; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Celgene: 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. Wei:Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Research Funding; Janssen: Honoraria; Servier: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Macrogenics: 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, Research Funding; Amgen: 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, Patents & Royalties: AHW is a former employee of the Walter and Eliza Hall Institute and receives a fraction of its royalty stream related to venetoclax, Research Funding, Speakers Bureau; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: MBG453 is an investigational anti-TIM-3 antibody that is being evaluated in hematological malignancies and solid tumors

Abstract: The clinical benefit of adding venetoclax (VEN) to hypomethylating agents or low-dose cytarabine in older and/or unfit patients with newly diagnosed acute myeloid leukemia (AML) has been confirmed in phase 3 studies. With the increased uptake of VEN-based therapies for patients with AML, a pertinent question is whether treatment can be safely ceased among patients who have achieved sustained remission. We hypothesized that a proportion of patients opting to cease therapy may benefit from a treatment-free remission (TFR) period without indefinite treatment. We report the retrospective outcomes of 29 patients in remission for a minimum of 12 months on VEN-based therapy, with 55% continuing therapy until disease progression and 45% electively ceasing treatment (STOP). With follow-up exceeding 5 years, we observed a median TFR lasting 45.8 months among the STOP cohort, with & gt;50% of patients still in sustained remission at the data cutoff. The risk of relapse and duration of relapse-free and overall survival were similar between the 2 cohorts. Factors favoring sustained TFR within the cohort included NPM1 and/or IDH2 mutation at diagnosis, complete remission without measurable residual disease, and at least 12 months of VEN-based combination therapy prior to treatment cessation.

Abstract: Background:The small molecule BCL-2 inhibitor Venetoclax (VEN) has emerged as a promising frontline therapy in combination with low dose cytarabine (LDAC) or hypomethylating agents in older patients with acute myeloid leukemia (AML)(DiNardo et al, Lancet Oncol 2018, Blood 2019; Wei et al,JCO 2019). The anti-leukemic activity of single agent VEN as monotherapy in newly diagnosed AML is unknown. This information would be useful for studies considering VEN as a maintenance therapy. We have previously presented preliminary outcomes from a phase 1b/2 study: Chemotherapy and Venetoclax in Elderly AML Trial (CAVEAT), which incorporated a 7-day single agent VEN run-in phase prior to combination with chemotherapy (Wei et al, ASH 2018). The study procedures incorporated a bone marrow assessment performed at study screening and on day 8, prior to commencement of chemotherapy (Figure 1A). This allowed us to explore the single agent activity of venetoclax on bone marrow blasts in treatment naïve patients with AML and to assess molecular dynamics of response. Methods:The CAVEAT trial included 51 de novo or secondary patients with AML aged ≥65 years and considered fit for intensive chemotherapy. The study enrolled patients to 5 VEN dose cohorts (50-100-200-400-600mg). VEN was administered on days 1-14 during induction. Chemotherapy commenced on day 8, with a 7-day VEN monotherapy pre-phase. Molecular studies:a 54-gene myeloid NGS panel (Illumina TruSight) and MassARRAY MALDI-TOF mass spectrometry was performed on DNA extracted from bone marrow aspirates. FLT3-ITD testing was by fragment analysis, PCR and capillary electrophoresis. Minimal residual disease (MRD) testing was performed by digital droplet PCR for IDH mutations (assay sensitivity: 10-4-10-5). Results: A total of 46 patients had paired BM assessments at screening and on day 8 for comparison. A ≥50% relative reduction in BM blasts was recorded in 13/46 (28%) patients. Figure 1B shows the relative BM blast reduction stratified by molecular subgroups. Patients with NPM1(n=9) or IDH2 (n=8) mutation achieved greater BM blast reductions (median of 56% and 55%, respectively) than IDH1 (n=6), TP53 (n=10) or FLT3-ITD (n=5) mutant cases (median of 37%, 17% and 7%, respectively). Three NPM1 mutant cases with & lt;25% blast reduction had contemporaneous kinase activating mutations (FLT3-ITD, FLT3-TKD and c-KIT). Molecular studies were performed on serial screening and day 8 bone marrow samples in 21 patients (Figure 1C). Variant allele frequency (VAF) reductions were observed in 6/8 (75%) NPM1 and 6/11 (55%) IDH 1/2 mutant cases. 1/8 (13%) NPM1 mutant and 4/11 (36%) IDH 1/2 mutant cases had reduction in molecular burden to below the limit of detection (5%) by day 8. Minimal reduction in VAF was seen in DNMT3A, SRSF2, NRAS/KRAS and FLT3-ITD mutations. 4 out of 5 (80%) FLT3-ITD mutant cases had an increase in VAF at day 8. Clinically, complete remission (CR) and CR with incomplete count recovery (CRi) rates after chemotherapy were seen for the following mutations: NPM1(80%), IDH2 (100%), IDH1 (62%) and TP53 (36%) (Figure 1D). Despite all four response-evaluable patients with FLT3-ITD achieving CR/CRi, 3/4 relapsed with detectable FLT3-ITD (at 0.8, 1.5 and 12.3 months respectively). Median survival for each genomic sub-group were NPM1 (12.5m), IDH2 (not reached), IDH1 (6.1m),TP53 (3.8m), FLT3-ITD (5.5m). CyTOF analyses for changes in BCL-2 family expression are underway and results will be presented at the meeting. Conclusion: Treatment naïve NPM1 and IDH2 mutant AML blasts are highly sensitive to VEN alone and combination with cytarabine and anthracycline chemotherapy results in a high clinical response rate. TP53 and FLT3-ITD mutant cases were more resistant and outcomes were poor despite VEN combined with chemotherapy. Figure 1 Disclosures Reynolds: Alfred Health: Employment, Other: Biostatistician for trials funded by the Australian government and Abbvie, Amgen, Celgene, GSK, Janssen-Cilag, Merck, Novartis, Takeda, but sponsored by Alfred Health.; AUSTRALASIAN LEUKAEMIA & LYMPHOMA GROUP (ALLG): Consultancy; Novartis AG: Equity Ownership; Novartis Australia: Honoraria. Fong:Pfizer: Consultancy, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau; Astellas: Consultancy; Novartis: Speakers Bureau. Ting:NHMRC: Research Funding. Fleming:Amgen: Honoraria, 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; BMS: Honoraria; Pfizer: Honoraria; Ariad: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. Moujalled:Walter and Eliza Hall Institute of Medical Research: Patents & Royalties: Share in venetoclax royalties . Ivey:Novartis: Honoraria. Roberts:AbbVie: Research Funding; Janssen: Research Funding; Walter and Eliza Hall Institute: Employment, Patents & Royalties: receives a fraction of its royalty stream related to venetoclax. Wei:AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: AHW is a former employee of the Walter and Eliza Hall Institute and receives a fraction of its royalty stream related to venetoclax, Research Funding, Speakers Bureau; Astellas: 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, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Macrogenics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy, 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, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Honoraria, Research Funding; Janssen: Honoraria. OffLabel Disclosure: Venetoclax is a BCL-2 inhibitor that is FDA-approved in some indications. This presentation will focus on correlative study results in the CAVEAT trial which combines venetoclax with modified intensive chemotherapy in AML, which is not an approved indication.

Abstract: Venetoclax is an effective treatment for certain blood cancers, such as chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). However, most patients relapse while on venetoclax and further treatment options are limited. Combining venetoclax with immunotherapies is an attractive approach; however, a detailed understanding of how venetoclax treatment impacts normal immune cells in patients is lacking. In this study, we performed deep profiling of peripheral blood (PB) cells from patients with CLL and AML before and after short-term treatment with venetoclax using mass cytometry (cytometry by time of flight) and found no impact on the concentrations of key T-cell subsets or their expression of checkpoint molecules. We also analyzed PB from patients with breast cancer receiving venetoclax long-term using a single-cell multiomics approach (cellular indexing of transcriptomes and epitopes by sequencing) and functional assays. We found significant depletion of B-cell populations with low expression of MCL-1 relative to other immune cells, attended by extensive transcriptomic changes. By contrast, there was less impact on circulating T cells and natural killer (NK) cells, with no changes in their subset composition, transcriptome, or function following venetoclax treatment. Our data indicate that venetoclax has minimal impact on circulating T or NK cells, supporting the rationale of combining this BH3 mimetic drug with cancer immunotherapies for more durable antitumor responses.