Abstract 5652: Olverembatinib (HQP1351) in combination with lisaftoclax (APG-2575) overcomes venetoclax resistance in preclinical models of acute myeloid leukemia (AML)

Abstract Background: Combining BCL-2 inhibitor venetoclax with hypomethylating agents is the standard of care for older patients with AML or those ineligible for intensive chemotherapy. However, resistance to venetoclax is a major clinical challenge, necessitating alternative therapeutic options. Olverembatinib targets kinases associated with leukemogenesis and venetoclax resistance, including FLT3, KIT, PDGFR, Src family kinases, PI3K, and FGFR. Here, we evaluated the effects of olverembatinib combined with investigational BCL-2 inhibitor lisaftoclax in venetoclax-resistant AML models. Methods: Primary venetoclax-resistant AML cell line OCI-AML-3 and venetoclax-induced resistant (VEN-RES) FLT3-ITD mutant AML cell lines MOLM-13 and MV-4-11 were used for in vitro experiments. Cellular proliferation was assessed using CellTiter-Glo® assays, and apoptosis was measured by flow cytometry. Western blotting was used to explore mechanisms of action. Both subcutaneous and systemic models using MOLM-13-VEN-RES models were used to evaluate antitumor effects in vivo. Results: Olverembatinib combined with lisaftoclax synergistically inhibited proliferation in all three VEN-RES AML cell lines vs. either drug alone. Flow cytometry confirmed this, revealing limited apoptotic effects with single agents but a significant increase in apoptosis when combined (p < 0.0001). In vivo, in a subcutaneous MOLM-13-VEN-RES model, lisaftoclax (100 mg/kg) administered daily for 14 days exerted no antitumor activity, with a treatment-to-control (T/C) value of 96.54%; olverembatinib (10 mg/kg) alone yielded a T/C value of 12.31%. When coadministered, the combination enhanced antitumor activity (T/C value, 5.05%), with a synergistic index of 2.36. This synergy was recapitulated in a systemic MOLM13-VEN-RES model. Mechanistically, western blot analysis showed that the combination synergistically downregulated FLT3 and its phosphorylation, along with downstream proteins such as AKT, STAT, and ERK and antiapoptotic proteins MCL-1 and BCL-xL; notably, significant upregulated phosphorylated FLT3, AKT, MCL-1, and others have been reported to be associated with mechanisms of venetoclax resistance. The combination also promoted upregulation of proapoptotic proteins BAX, BAK, BID, PUMA, and Noxa, resulting in increased cleavage of caspase-3 and PARP-1. Conclusions: In summary, olverembatinib in combination with lisaftoclax successfully overcame venetoclax resistance in preclinical AML models by downregulating key signaling pathways shown to mediate such resistance. Overall, these findings suggest a potential new therapeutic strategy for venetoclax-resistant AML. Citation Format: Yan Xiong, Zhiyan Liang, Ping Min, Bingxing Wu, Huidan Yu, Guoqin Zhai, Zhou Yu, Dajun Yang, Yifan Zhai. Olverembatinib (HQP1351) in combination with lisaftoclax (APG-2575) overcomes venetoclax resistance in preclinical models of acute myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5652.