P077 | EFFICACY OF VENETOCLAX ALONE AND IN COMBINATION WITH PONATINIB ACROSS MOLECULAR SUBTYPES OF ACUTE LYMPHOBLASTIC LEUKEMIA

Background In adult patients (pts) with acute lymphoblastic leukemia (ALL), despite initial responses to chemotherapy or immunotherapies like inotuzumab or blinatumomab, relapse rates are high, the prognosis remains poor. Venetoclax (Ven), a selective BCL2 inhibitor, is approved for acute myeloide leukemia (AML) in combination with azacitidine. Ven has shown promising activity in both B-ALL and T-ALL. Studies also indicate that combining Ven with ponatinib (Pona) may be effective in Ph+ B-ALL, offering potential for high-risk pts (PMDI: 33780038; 39546748). Aims To evaluate the efficacy of Ven and the potential synergy of the Ven–Pona combination across a broad panel of ALL cell lines and primary ALL samples representing diverse molecular subtypes, including Ph-like, ZNF384/KMT2A-rearranged (-r) ones. Methods We treated 17 cell lines (4 AML, 2 T-ALL, 11 B-ALL) and 26 primary samples from adult ALL pts (21 B-ALL, 2 T-ALL, 3 MPAL) with increasing concentrations of Ven for 24/48/72h. Cell proliferation was assessed using the RealTime-Glo assay. We performed RNA-seq in all treated pts to identify molecular features and gene expression. Results Among AML lines, KMT2A-r MV4-11, MOLM13, and MONO-MAC6 were more sensitive than OCI-AML3 (non-KMT2A-r). In the T-ALL setting, the two cell lines exhibited markedly different sensitivities to the treatment: MOLT4 had an IC50 of 0.84 µM, while JURKAT had 8.37 µM IC50. B-ALL cell lines showed variable responses: JIH-5 (EP300-ZNF384) and REH (ETV6-RUNX1) were most sensitive (IC50: 0.001–0.002 µM), followed by SUPB15 (Ph+), HAL01 (TCF3-HLF), 697 (TCF3-PBX1), MHH-CALL4 (Ph-like), NALM6 (DUX4-r), RS4;11 (KMT2A-r), MUTZ5 (Ph-like), KOPN8 (KMT2A-r), and NALM19 (Ph-/-/-)(Fig. 1A). The Ven–Pona combo was synergistic in SUPB15 and additive in other B-ALL lines, including the most resistant NALM19. Primary samples showed heterogeneous responses (IC50 range 0.01-99.8 µM); notably, very high-risk samples harboring BCL2-r or BCL2L1-NRIP1 were among the most sensitive (IC50 0.01; 0.17 µM). Strong synergy was observed in three dose points in BCL2L1-NRIP1 primary cells (Fig.1B). Response is not associated to BCL2/BCL2L1 expression. Conclusions Ven shows potent preclinical activity in different ALL cell lines/primary samples. The Ven–Pona combination is effective even in resistant models, warranting further clinical investigation in high-risk or relapsed ALL pts. Thanks to: Ricerca Corrente by the Italian MoH L3P1946 and TrevisoAIL.