A novel strategy to circumvent venetoclax resistance in relapsed/refractory Acute Myeloid Leukemia

Abstract Background: Venetoclax (VEN), a selective B-cell lymphoma-2 (BCL-2) inhibitor, significantly improves outcomes in acute myeloid leukemia (AML). However, with the expanding clinical use of venetoclax (VEN) in AML management, effective treatment options for VEN-resistant disease remain critically limited. Previous studies have indicated that mitochondrial calcium critically regulates VEN sensitivity in leukemia stem cells (LSCs). This suggested mitoxantrone, a mitochondrial calcium uniporter (MCU) inhibitor, may effectively target VEN-resistant AML. Mitoxantrone hydrochloride liposome (Lipo-MIT), a novel anthracycline nano-drug, has demonstrated improved pharmacokinetics and anti-leukemic activity. We developed the MAV regimen that includes Lipo-MIT, cytarabine and VEN for relapsed/refractory (R/R) AML (NCT06621212). Methods This prospective study enrolled patients (≥18 years) with R/R AML and Eastern Cooperative Oncology Group (ECOG) performance status 0-2. Patients were treated with Lipo-MIT (30 mg/m2, day 1, intraveous infusion), cytarabine (100 mg/m2, day 1-7, intraveous infusion), and venetoclax (100 mg day 2, 200 mg day 3, 400 mg day 4-8, orally) as induction therapy every 4 weeks up to 2 cycles. Upon achieving composite complete remission (CRc), patients were recommended for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Transplant-ineligible patients received consolidation therapy consisting of cytarabine and venetoclax for fit patients, or low-intensity therapy for unfit patients. Primary endpoint was the CRc rate. Secondary endpoints were measurable residual disease (MRD) negative rate by flow cytometry, overall response rate (ORR), survival and safety. Results Between July 2024 and May 2025, 20 patients (median age 56 years; range 24-77) were enrolled. Four (20%) had primary refractory AML, while 16 (80%) had relapsed disease, including two with secondary AML evolving from antecedent myelodysplastic syndrome or chronic myelomonocytic leukemia. According to the European LeukemiaNet (ELN) 2022 criteria, the genetic risk stratification revealed favorable risk in 3 patients (15%), intermediate risk in 3 patients (15%), and adverse risk in 14 patients (70%). Patients had received a median of 3 prior induction cycles (rang 1-6), with 1 patient having prior allo-HSCT and 14 patients (70%) having prior VEN exposure. Efficacy was evaluable in all 20 patients. Following one induction cycle, CRc rates were 65% (13/20) in all patients, 72.2% (13/18) in de novo AML and 70.6% (12/17) in patients with ≤ 4 prior induction cycles. The ORR was 70% (14/20). In patients achieving CRc, MRD-negative rate was 84.6% (11/13). In patients with prior VEN exposure, the CRc rate was 64.3% (9/14), with 75% (6/8) in VEN-relapsed cases and 50% (3/6) in primary VEN-refractory cases. The CRc rates by ELN 2022 risk were: favorable 100% (3/3), intermediate 66.7% (2/3), adverse 57.1% (8/14). Whereas the results showed initial efficacy in several MDS-related molecular alterations, showing CRc rates of 100% (2/2), 83.3% (5/6), 75% (3/4) and 50% (2/4) in STAG2, ASXL1, RUNX1 and SRSF2, respectively. With a median follow-up of 3.0 months (range 0.8-10.2), median relapse-free survival and overall survival were not reached. The treatment-related adverse events (TRAEs) were predominantly hematological toxicity. In patients achieving CRc, the median duration of neutrophil counts＜0.5×109/L was 24 days (range 10-41) and platelet counts＜25×109/L was 21.5 days (range 4-46). The common grade 3/4 non-hematological TRAEs included febrile neutropenia (30%), pulmonary infection (15%), and sepsis (10%). Conclusion The MAV regimen demonstrates preliminary efficacy and manageable toxicity in R/R AML, showing particular potential to overcome VEN resistance in relapsed patients with prior venetoclax exposure. This clinical trial remains ongoing.