Venetoclax Plus Intensive Chemotherapy in AML and Advanced MDS: Assessment of Leukemia Stem Cell Eradication By High-Resolution MRD Assay

Background: For the past five decades the standard of care for fit patients with acute myeloid leukemia (AML) has been induction with the "7+3" regimen, using a combination of cytarabine (AraC) and anthracycline (daunorubicin, idarubicin) followed by consolidation high-dose AraC (HiDAC). With this approach, approximately 70% of younger (≤60 years of age) and 60% of older (>60 yrs) fit patients achieve a complete remission, with 30-50% of those patients attaining measurable residual disease (MRD) negative state by multiparameter flow cytometry (MFC). However, even patients with MRD-negative remissions relapse due to remaining chemotherapy-resistant pre-leukemic and leukemic stem cells (LSCs). Eradication of residual disease at the LSC level is therefore the ultimate goal to achieve durable remissions and cure.

The combination of Venetoclax (Ven) with chemotherapy can have a synergistic effect; by reducing the apoptotic threshold, Ven can facilitate increased apoptosis induced by genotoxic agents, while at the same time chemotherapy can downregulate MCL-1 that drives Ven resistance. Ven in combination with hypomethylating agents has shown to not only eradicate AML blasts but also target and eliminate LSCs. Early phase trials combining Ven with intensive chemotherapy (IC) have shown encouraging safety and efficacy signals. However, the optimal dose and schedule of Ven that can best synergize with IC to eradicate LSCs remain unknown. Here we present a phase 1b study evaluating the safety and tolerability of Ven in combination with daunorubicin (dauno)/AraC) induction followed by HiDAC consolidation in patients with newly diagnosed AML or high-risk myelodysplastic syndrome (MDS).

Objective: The primary objectives of this study are to evaluate the safety, tolerability, and to determine the maximum tolerated dose (MTD) of the combination of Ven plus dauno & AraC, as well as HiDAC IC. Secondary objectives are response per 2017 ELN and revised IWG criteria, survival, event-free survival and duration of response. A key exploratory objective is to comprehensively analyze LSC and assess rates of LSC eradication by means of MFC and single cell sequencing ("high-resolution MRD assay").

Design: This is a Phase 1b, open-label, dose-escalation study, evaluating Ven in combination with IC in previously untreated, adult patients with AML and high-risk MDS (NCT05342584). In Part 1, we are utilizing a 3+3 design to evaluate the safety and tolerability of different Ven doses in combination with IC. In Part 2, we will evaluate the safety and clinical activity in additional 12 patients at the dose determined in Part 1. To evaluate for LSC MRD, bone marrow aspirates obtained at the time of each disease evaluation will be analyzed by high-resolution MRD assays. Specifically, we will perform multicolor flow cytometry assays optimized for primary samples and able to distinguish, quantify, and sort pre-LSCs and LSCs. Furthermore, we will combine this assay with ultra-deep sequencing (1Million x) to detect very low levels of mutant cells, importantly within the LSC compartment.

Eligible patients must have a new diagnosis of AML or high-risk MDS (blasts>10% AND R-IPSS>3.5%), be 18-75 yrs of age and deemed fit for intensive chemotherapy. During induction, escalating Ven doses (400 mg x8 -> 11 -> 14 days) will be combined with AraC 100mg/m2 and 2 doses of dauno (60 and 90mg/m2) in patients aged 60yrs or younger, whereas dauno 60 will be used for all patients older than 60yrs. During consolidation, the Ven dose will be escalated (200 -> 400mg) in a similar 3+3 design at a fixed 7-day duration in combination with age-adjusted high dose AraC regimen (1.5g/m2 in ≤60yrs and 1g/m2 in >60yrs, every 12hrs on days 1,3,5).

Conclusion: This study will evaluate the optimal dosing of Venetoclax and daunorubicin as part of the Ven plus "7+3" induction regimen. It will also evaluate the optimal dose of Venetoclax in combination with HiDAC consolidation chemotherapy. This trial will utilize a novel highly-sensitive LSC MRD assay to test the efficacy of Venetoclax in eliminating LSCs when combined with conventional chemotherapy.

Mantzaris:Kite Pharma: Honoraria. Shastri:Janssen: Consultancy; Rigel Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; NACE: Honoraria; Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding. Feldman:Ichnos Sciences: Current Employment.