Abstract: The B-cell lymphoma 2 (BCL-2) inhibitor venetoclax has an emerging role in acute myeloid leukemia (AML), with promising response rates in combination with hypomethylating agents or low-dose cytarabine in older patients. The tolerability and efficacy of venetoclax in combination with intensive chemotherapy in AML is unknown. PATIENTS AND METHODS Patients with AML who were ≥ 65 years (≥ 60 years if monosomal karyotype) and fit for intensive chemotherapy were allocated to venetoclax dose-escalation cohorts (range, 50-600 mg). Venetoclax was administered orally for 14 days each cycle. During induction, a 7-day prephase/dose ramp-up (days −6 to 0) was followed by an additional 7 days of venetoclax combined with infusional cytarabine 100 mg/m 2 on days 1-5 and idarubicin 12 mg/m 2 intravenously on days 2-3 (ie, 5 + 2). Consolidation (4 cycles) included 14 days of venetoclax (days −6 to 7) combined with cytarabine (days 1-2) and idarubicin (day 1). Maintenance venetoclax was permitted (7 cycles). The primary objective was to assess the optimal dose schedule of venetoclax with 5 + 2. RESULTS Fifty-one patients with a median age of 72 years (range, 63-80 years) were included. The maximum tolerated dose was not reached with venetoclax 600 mg/day. The main grade ≥ 3 nonhematologic toxicities during induction were febrile neutropenia (55%) and sepsis (35%). In contrast to induction, platelet recovery was notably delayed during consolidation cycles. The overall response rate (complete remission [CR]/CR with incomplete count recovery) was 72%; it was 97% in de novo AML and was 43% in secondary AML. During the venetoclax prephase, marrow blast reductions (≥ 50%) were noted in NPM1-, IDH2-, and SRSF2-mutant AML. CONCLUSION Venetoclax combined with 5 + 2 induction chemotherapy was safe and tolerable in fit older patients with AML. Although the optimal postremission therapy remains to be determined, the high remission rate in de novo AML warrants additional investigation (ANZ Clinical Trial Registry No. ACTRN12616000445471).

Abstract: Based on promising results in older adults with acute myeloid leukaemia (AML), we treated patients with NPM1 mut measurable residual disease (MRD) using off‐label venetoclax in combination with low‐dose cytarabine or azacitidine. Twelve consecutive patients were retrospectively identified, including five with molecular persistence and seven with molecular relapse/progression. All patients with molecular persistence achieved durable molecular complete remission (CR MRD‐ ) without transplantation. Six of seven patients with molecular relapse/progression achieved CR MRD‐ after 1–2 cycles of venetoclax. This paper highlights the promising efficacy of venetoclax‐based therapy to reduce the relapse risk in patients with persistent or rising NPM1 mut MRD.

Abstract: Introduction: Molecular MRD monitoring in NPM1 mutant (mut) AML is now standard of care in many countries as prospective clinical trials have demonstrated that suboptimal reduction and/or rising levels of NPM1mut transcript are associated with disease relapse (Ivey, NEJM 2016; Balsat, JCO 2017). Higher levels of NPM1mut MRD positivity are associated with poorer outcomes after allogeneic hematopoietic stem transplantation (allo-HSCT) (Dillon, EHA 2019). Data regarding the effectiveness of pre-emptive MRD intervention is scant. A reduction in NPM1mut MRD was reported in 17/33 (52%) receiving azacitidine (Platzbecker, Lancet Oncol 2018). Among patients with NPM1mut molecular relapse in the NCRI AML17 trial, 16/27 (59%) achieved MRD negativity with 1-2 cycles of FLAG-Ida salvage chemotherapy (manuscript in preparation). As the BCL-2 inhibitor venetoclax in combination with low-dose cytarabine (LDAC) or hypomethylating agents (HMA) are known to be highly active in NPM1mut AML (Wei, JCO 2019; Strickland, EHA 2018), we hypothesized that venetoclax-based regimens could represent an effective low intensity option for patients with persistent or rising NPM1mut MRD. Methods: Consecutive patients with NPM1mut AML from 4 sites treated with venetoclax-LDAC/HMA for MRD eradication were included if previously received at least 1 cycle of intensive chemotherapy and achieved complete remission. cDNA was analyzed on bone marrow aspirate ± peripheral blood samples using a NPM1 mutant specific RT-qPCR (Ivey, NEJM 2016) according to Europe Against Cancer guidelines (Gabert, Leukemia 2003). Results are expressed as MRD level relative to the diagnostic sample (%) with both samples normalized to a control gene (ABL). Results: A total of 10 patients were treated with venetoclax (600 mg PO daily D1-14) in combination with LDAC (20 mg/m2 SC twice daily D1-10; n=8), or venetoclax (400 mg PO daily D1-14) azacitidine (75 mg/m2 SC daily D1-7; n=2) as summarized in Table 1. If concurrent posaconazole was used, the dose of venetoclax was adjusted to 100 mg PO daily. The median age of the cohort was 61.2 years (range 31-81). All patients had intermediate risk cytogenetics, including 8 with normal karyotype at diagnosis. Concurrent mutations in addition to NPM1 are shown in Table 1. The number of consolidation cycles received prior to venetoclax ranged from 0-4 and typically included high-dose cytarabine. Three patients had failed other MRD-directed therapies prior to treatment with venetoclax. Six patients (Cases #1-6) received venetoclax-LDAC/HMA for NPM1mut molecular relapse after complete molecular remission (CRMRD-), or progression after molecular persistence at low copy number (CRMRD+). Five of six (83%) achieved CRMRD- after only 1-2 cycles, with ongoing CRMRD- after a median of 134 days (range 59-447). One patient had failed to respond to FLAG-Ida but achieved CRMRD- after just 1 cycle of venetoclax-LDAC (Figure 1A). Three patients proceeded to subsequent allo-HSCT, including 2 in CRMRD- (Figures 1B and C). Follow up post-HSCT is ongoing ( 〈 60 days). Four patients (Cases #7-10) were treated for molecular persistence after completion of induction and 0-3 cycles of consolidation chemotherapy. All 4 patients responded, including 3 (75%) who achieved CRMRD-. Case #7 (Figure 1D) had received prior gemtuzumab ozogamicin and azacitidine without molecular response but then achieved CRMRD- after receiving venetoclax-azacitidine, which was sustained for 〉 23 months without an allo-HSCT. Venetoclax in combination with LDAC/HMA was well tolerated. Febrile neutropenia occurred in 2 patients (20%) and one patient had grade 4 sepsis. Grade 4 neutropenia occurred in 70% (median duration 10 days) and grade 4 thrombocytopenia in 40% (median duration 16 days). Conclusion: In the setting of molecular NPM1mut MRD relapse or persistence, venetoclax in combination with LDAC/HMA was highly effective, with MRD reductions in 100% and complete molecular remission in 80%. Future clinical exploration is warranted to validate the role of venetoclax as a pre-emptive approach to suppress persistent or rising NPM1mut MRD. Disclosures Dillon: Pfizer: Consultancy, Honoraria; TEVA: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Ivey:Novartis: Honoraria. Vassili:Amgen: Honoraria. Taussig:Celgene: Research Funding. Russell:Jazz: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau. Raj:Jazz: Honoraria, Speakers Bureau; Daiichi Sankyo: Honoraria; Pfizer: Honoraria; MSD: Honoraria; Celgene: Honoraria; Novartis: Honoraria, Speakers Bureau; Mallinckrodt: Honoraria, Speakers Bureau. Fong:Pfizer: Consultancy, Speakers Bureau; Novartis: Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau; Astellas: Consultancy. Grigg:Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; MSD: Membership on an entity's Board of Directors or advisory committees; Roche: Other: Travel. Knapper:Pfizer: 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; Daiichi Sankyo: Honoraria; Jazz: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Tolero: Membership on an entity's Board of Directors or advisory committees. 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 venetoclax as a MRD-directed therapy in AML, which is not an approved indication.

Abstract: Introduction Rising molecular measurable residual disease (MRD) is an arbiter of clinical relapse in acute myeloid leukemia (AML). Venetoclax (VEN) is active against IDH and NPM1 mutant (mt) AML as monotherapy (Konopleva et al, 2016 and Chua et al, 2020) and can yield MRD negative remission when combined with low dose ara-C (LDAC) in patients unfit for intensive chemotherapy (DiNardo and Tiong et al, 2020). In a retrospective study, we showed that VEN in combination with hypomethylating agents or LDAC could erase rising NPM1mt MRD in 6/7 cases (Tiong et al, 2020). We now present a prospective phase 2 study of VEN and LDAC in patients with molecular MRD failure or oligoblastic AML relapse. Methods This multicenter phase 2 study stratified patients into oligoblastic relapse (marrow blasts 5-15%; Group A), or molecular MRD failure (Group B) as defined by the European LeukemiaNet (ELN) recommendations (failure confirmed by 2 interval samples) (Schuurhuis et al, 2018). Patients received VEN 600 mg (days 1-28) and LDAC 20 mg/m 2 (days 1-10). Primary objectives were morphologic or MRD response (≥1 log reduction) in groups A and B, respectively. Key secondary objectives were allogeneic hematopoietic cell transplantation (allo-HCT) realization and relapse-free (RFS) and overall survival (OS). The study had Alfred Health ethics approval (196/19). NPM1mt and other fusion transcript levels (per 10 5 ABL) from bone marrow were analyzed by RT-qPCR, IDH1 and IDH2 by Bio-Rad TM droplet digital PCR. Results The study enrolled 32 patients, with 29 evaluable (cut-off date 15/7/21). The median age of the study population was 62 years; 79% had intermediate cytogenetic risk, 66% NPM1mt, 11% FLT3-ITD and 37% IDH1/IDH2 mt. Most received prior intensive chemotherapy (93%) and 2 (7%) allo-HCT in first remission. Median interval from AML diagnosis to study entry was 12.6 months (Table 1). After a median follow-up of 7.9 months, patients had received a median of 3 cycles (range 1-14) of VEN-LDAC, with 13 patients ongoing. The main reasons for treatment cessation were allo-HCT (n=10; 34%) or donor lymphocyte infusion (n=2; 7%), treatment failure (n=3) or an adverse event (n=1). Hematologic complete/incomplete response (CR/CRi) among 11 patients with oligoblastic relapse (group A) was 73% and included: CR (n=5, 45%) or CRi (n=3, 27%), with an additional patient with morphologic leukemia-free state and 2 patients with stable disease. Overall, across both groups, median RFS and OS were not reached, estimated at 78% and 91% at 1 year, respectively. Among 18 patients with molecular MRD failure (group B) treated with VEN+LDAC, molecular response (≥1 log reduction) was achieved in 72%, and the RFS and OS were estimated at 83% and 87% at 1 year, respectively. Analysis of a sub-group of patients with NPM1mt (n=18); 6 and 12 from Groups A and B, respectively revealed the median NPM1mt transcript level at study entry to be 8985 copies (IQR 826, 94,431). A molecular response was achieved in 14 (78%) patients, including 9 (50%) with complete molecular remission (CR MRD-), with most responses achieved within 2 cycles of therapy (Figure B). Treatment with VEN-LDAC was generally well tolerated, with 15 serious adverse events reported within the first 2 cycles, including infection (n=6; 19%) and febrile neutropenia (n=3; 9%). Only one subject discontinued treatment due to stroke. Conclusions In this prospective study, in patients with first oligoblastic relapse or MRD failure, VEN in combination with LDAC induced a high rate of molecular MRD remission that was rapidly achieved, resulting in a high rate of survival at 12-months ( & gt;90%) and with low toxicity. Follow-up is ongoing to determine the durability of response. Treatment of patients with MRD or early clinical failure may represent an attractive clinical trial setting for investigation of novel, non-intensive AML therapies. This approach will be investigated in a future multi-arm, precision-based platform trial called INTERCEPT (Investigating Novel Therapy to Target Early Relapse and Clonal Evolution as Pre-emptive Therapy in AML). Figure 1 Figure 1. Disclosures Tiong: Servier: Consultancy, Speakers Bureau; Amgen: Speakers Bureau; Pfizer: Consultancy. Hiwase: Novartis: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Fleming: Amgen Inc: Research Funding. Bajel: Amgen: Speakers Bureau; Abbvie, Amgen, Novartis, Pfizer: Honoraria. Fong: Amgen, BMS: Speakers Bureau; Amgen: Research Funding; AbbVie, Amgen, Novartis, Pfizer, Astellas: Honoraria. Wei: Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Agios: 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, Speakers Bureau; Genentech: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; 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; Amgen: 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; Pfizer: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Macrogenics: 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. OffLabel Disclosure: This presentation will discuss the use of venetoclax in targeting measurable residual disease and early relapse of acute myeloid leukemia.

Abstract: Assessment of measurable residual disease (MRD) by RT-qPCR is strongly prognostic in patients with NPM1-mutated AML treated with intensive chemotherapy, however there are no data regarding its utility in venetoclax-based non-intensive therapy, despite high efficacy in this genotype. We analysed the prognostic impact of NPM1 MRD in an international real-world cohort of 76 previously untreated patients with NPM1-mutated AML who achieved CR/CRi following treatment with venetoclax and hypomethylating agents (HMA) or low dose cytarabine (LDAC). 44 patients (58%) achieved bone marrow (BM) MRD negativity and a further 14 (18%) a reduction of ≥4 log10 from baseline as their best response, with no difference between HMA and LDAC. The cumulative rate of BM MRD negativity by the end of cycles 2, 4 and 6 was 25%, 47% and 50%. Patients achieving BM MRD negativity by the end of cycle 4 had 2-year overall (OS) of 84% compared to 46% if MRD positive. On multivariable analyses MRD negativity was the strongest prognostic factor. 22 patients electively stopped therapy in BM MRD negative remission after a median of 8 cycles with 2-year treatment-free remission of 88%. In patients with NPM1-mutated AML attaining remission with venetoclax combination therapies, NPM1 MRD provides valuable prognostic information.

Abstract: Background: Venetoclax (VEN) is a potent small molecule BH3-mimetic drug that selectively targets the prosurvival protein BCL-2 and has an emerging role for treatment in Acute Myeloid Leukaemia (AML). This ongoing Phase 1b study aims to evaluate the optimal dose, safety and efficacy of VEN in combination with modified intensive chemotherapy in fit, elderly patients with AML who have not received prior induction chemotherapy. Here we present updated data including molecular correlates of response and treatment outcomes. Methods: Eligibility: Patients were enrolled with AML (excluding APL), age ≥65 years (≥60 years if monosomal karyotype), ECOG 0-1 and adequate organ function. Prior HMA/LDAC was permitted after a 14-day washout. Treatment: 1) Dose escalation cohorts comprised VEN 50mg (Cohort A), 100mg (B), 200mg (C), 400mg (D) or 600mg (E); 2) a 7-day VEN pre-phase incorporating dose ramp-up to minimise tumour lysis risk followed by a 7-day overlap with chemotherapy (day -6 to +7); 3) attenuated induction chemotherapy with cytarabine 100mg/m2/day IVI d1-5 staggered with idarubicin 12mg/m2 IV d2-3. For patients in remission, 4 cycles of consolidation were administered, comprising 14 days of VEN (day -7 to +7) with bolus cytarabine (100mg/m2/day IV d+1-2) and idarubicin (12mg/m2 IV d+1) followed by 7 cycles of VEN monotherapy maintenance; planned to commence q28d. Antifungal azoles were avoided during VEN exposure. The first patient was enrolled 17JUL2016. Molecular studies- Next generation sequencing using a 54-gene TruSight myeloid panel was performed on baseline bone marrow samples. FLT3-ITD testing was performed by capillary electrophoresis. RT-qPCR was used to detect minimal residual disease (MRD) in NPM1-mutated cases (assay sensitivity: 10-5-10-6). Results: The data cut-off date was 13JUL2018. 44 patients were enrolled with 3 patients still in the induction cycle. Median age was 72 years (range 63-80 years; 23% ≥75 years), 66% of patients were male, 41% had secondary AML and 38% prior hypomethylating agent (HMA) exposure. Main grade ≥3 non-haematological adverse events during induction were febrile neutropenia (56%), sepsis (32%), rapid atrial fibrillation (15%), diarrhoea (12%), nausea (10%) and localised infection (10%). No clinical TLS was observed. One hematologic dose-limiting toxicity was reported in cohort E (VEN 600mg), but a maximum tolerated dose has not been reached. We observed progressive delay in platelet count recovery as patients proceeded with each cycle of therapy (median time to platelets ≥50x109/L was 25d in induction, 37d in consolidation 1 and 57d in consolidation 4). Treatment-related mortality was 7% in induction. 18/38 (47%) had ≥30% relative reduction in bone marrow (BM) blasts after 7 days of pre-phase VEN monotherapy, with no correlation between VEN dosage and the degree of BM blast reduction. Overall CR/CRi rate was 71%. CR/CRi was achieved in 95% of patients with de novo AML (vs 42% in secondary/therapy-related AML). Response rates were 88% in intermediate vs 46% in adverse cytogenetic risk AML. Responses in patients with prior HMA therapy were 43% and 84% for previously untreated patients. Molecular data were available for 41 patients. 98% had ≥1 mutation detected. (Figure 1) Responses in response-evaluable patients were most common in NPM1 mutant AML (100%; n=7), followed by RUNX1 (90%; n=11), RAS (90%; n=10) and IDH (89%; n=9). Lowest responses were observed in TP53 mutant AML (33%; n=9). NPM1 MRD assessment was performed on 6 patients, of which 5 (83%) achieved NPM1 MRD negativity. (Figure 2) Updated response, response duration and survival data will be presented, along with molecular characteristics of relapse. Conclusion: To date, VEN up to 600mg in combination with 5+2 induction chemotherapy is tolerable in fit elderly patients with AML. Initial response rates 〉 80% were observed in de novo AML, as well as NPM1, RUNX1, RAS and IDH mutant AML, whereas responses were lower in patients with prior HMA exposure, adverse karyotype, secondary and TP53 mutant AML. Molecular determinants of relapse require further study. Disclosures Wei: Servier: Consultancy, Honoraria, Other: Advisory committee, Research Funding; Amgen: Honoraria, Other: Advisory committee, Research Funding; Novartis: Honoraria, Other: Advisory committee, Research Funding, Speakers Bureau; Pfizer: Honoraria, Other: Advisory committee; Celgene: Honoraria, Other: Advisory committee, Research Funding; Abbvie: Honoraria, Other: Advisory board, Research Funding, Speakers Bureau. Fong:Celgene: Other: Advisory board; Novartis: Other: Advisory board; Amgen: Research Funding; Pfizer: Other: Speaker fees. Reynolds:Novartis: Equity Ownership, Other: former employee of Novartis AG and holds stock in the company. . Roberts:Janssen: Research Funding; AbbVie: Research Funding; Genentech: Research Funding; Walter and Eliza Hall: Employment, Patents & Royalties: Employee of Walter and Eliza Hall Institute of Medical Research which receives milestone and royalty payments related to venetoclax.