Venetoclax Combined with “7+3” Induction Chemotherapy Induces High Rates of MRD-Negative Remission in Newly Diagnosed AML Patients Fit for Intensive Chemotherapy Irrespective of Age

Introduction:

Approximately 70% of patients (pts) with acute myeloid leukemia (AML) treated with the “7+3” regimen achieve complete remission (CR), with 30-50% of those attaining measurable residual disease (MRD) negative state by multiparameter flow cytometry (MFC). However, despite initial responses, the majority of pts eventually relapse. Venetoclax (Ven) added to intensive chemotherapy (IC) facilitates apoptosis of leukemic stem cells (LSC), and may result in deeper, more durable remissions. Moreover, IC induces MCL-1 downregulation and may overcome Ven resistance. We present safety and efficacy results from a phase 1b study of escalating cumulative Ven doses combined with daunorubicin (Dauno)+cytarabine (AraC) followed by high-dose cytarabine (HiDAC) chemotherapy in pts with newly diagnosed AML (NCT05342584).

Objectives:

The primary objective of this study is to determine the optimal dose of Ven in combination with Dauno & AraC and HiDAC chemotherapy. Secondary objectives are response per 2022 ELN, survival (OS), event-free survival (EFS) and duration of response (DoR). A key exploratory objective is to assess rates of LSC eradication by means of MFC and single cell DNA (Tapestri, Mission Bio) and RNA sequencing (“high-resolution MRD assay”).

Methods:

Eligible pts must have a new diagnosis of AML, be 18-75 yrs of age and deemed fit for intensive chemotherapy. In a 3+3 design, Ven in escalating duration (400 mg D1-8 or -11 or -14, including 2-day ramp-up) is combined with AraC 100mg/m2 (D2-8) and Dauno 60mg/m2 (D2-4) in 2 separate age groups (<60 and ≥60yrs); Dauno 90mg/m2 was initially studied in pts < 60yrs, but since 04/2023 the dose is no longer explored. During consolidation, fixed dose Ven (200 mg x7days) is used in combination with age-adjusted HiDAC (1.5g/m2 in <60yrs and 1g/m2 in ≥60yrs, every 12hrs on days 1,3,5). In the expansion phase, additional pts in each age group will undergo 1:1 randomization between the starting and highest tolerated dose determined during dose escalation, for a total of 20 pts per dose cohort in both phases.

Results:

Twenty-seven AML pts enrolled and 25 completed the induction phase to date, 2 are actively treated. Median age was 59yrs, 44% were females and 67% ethnic or racial minorities. Fourteen (52%) pts had poor-risk genotypes by ELN 2022. Fourteen pts were treated with Ven x 8d, 11 in Dauno60 and 3 in Dauno90 cohorts, 7 pts with Ven x11d and 6 pts with Ven x14d. No DLTs were observed, and the toxicity profile was similar to historical experience with the “7+3” regimen. There were no induction mortality deaths. Twenty pts (20/25, 80%) achieved a composite complete remission (CRc) with single induction (19 CRs and 1 CRi), 10/13 in <60 and 10/12 in ≥60yr groups. Median time to ANC≥0.5K/uL and PLT≥50K/uL was 26 days and time to CR was 32 days. Of those in CRc, all except three pts < 60yrs were MFC-MRD negative (17/20, 85%). Among 8 patients with available MRD PCR testing, 6 achieved molecular MRD-negative and 2 low-level molecular MRD CRs. With a median 5.6-month follow-up time, median EFS or OS have not been reached, 25/27 (93%) patients are alive (10/12 ≥60yrs), 12 pts have completed the protocol, 5 continue on therapy and 5 underwent allogeneic transplantation. From those in CRc, 7 younger and 8 older pts (75%) remain in remission without evidence of hematologic or molecular relapse. Of 5 pts with complex karyotype plus TP53 mutated AML, 3 did not respond and 2 had an early treatment failure. Table 1 summarizes patient characteristics, toxicity and outcomes.

Conclusions:

Ven 400mg in combination with “7+3” induction chemotherapy is safe and highly effective in achieving MRD negative remissions in the vast majority of patients. Responses were low in TP53 mutated pts, suggesting no benefit of the addition of venetoclax to intensive chemotherapy, similar to what has been observed when venetoclax is added to standard dose hypomethylating agents in those pts, for whom non-cytotoxic approaches are being explored. The study is completing enrollment in the Dauno60 + Ven x14d cohorts and is entering the expansion phase in order to better explore the optimal Ven dose to combine with the “7+3” regimen. Updated results, as well as rates of LSC elimination post-induction will be presented at the meeting.