Venetoclax in combination with ponatinib for the treatment of asciminib-resistant chronic myeloid leukemia

Asciminib, an allosteric inhibitor specifically targeting the myristoyl pocket of BCR::ABL1, has expanded therapeutic options for heavily pretreated patients with chronic myeloid leukemia (CML), and for those with the BCR::ABL1 T315I mutation [1-3].Several clinical studies evaluating asciminib in frontline CML therapy are currently ongoing (e.g., ASCI4FIRST, ASCI4START, ASCEND), with promising preliminary results indicating superior efficacy, improved tolerability, and a lower rate of treatment discontinuation due to toxicity compared to ATP-competitive inhibitors [4-6].However, clinical trials of asciminib in both advanced-line and first-line CML treatment also report the emergence of resistance, often due to acquired or persisting mutations in BCR::ABL1 [2,4].The full spectrum of these mutations remains unidentified, underscoring the need for further investigation and the exploration of backup therapeutic strategies, including combination therapies.This EUTOS 2022 (European Treatment and Outcome Study) work sought to investigate BCR::ABL1 mutations and other genetic alterations associated with asciminib resistance in CML myeloblastic clones and to assess the sensitivity of asciminib-resistant CML cells to treatment in vitro and on a preclinical mouse model.Established asciminib-resistant (ASCI-R) clones of KCL-22 cell line (n = 8; Supplementary Methods) were analyzed using Next Generation Sequencing (NGS) to identify somatic mutations in SH3, SH2, and kinase (KD) domains of BCR::ABL1 and in 62 selected leukemia-associated genes [7].7/8 ASCI-R clones harbored mutations in the KD BCR::ABL1 and 5/8 ASCI-R clones exhibited clone-specific mutations in other leukemia-associated genes including ASXL1, EZH1, GATA2, NOTCH1, SF3B1, TET2, TP53, and ZRSR2 (Fig. 1A; Supplementary Table S1A), alongside with other mutations intrinsic to KCL-22 cells (Supplementary Table S1B).Mutations conferring resistance to asciminib were found at various regions of KD BCR::ABL1 including the myristoyl pocket (A337T -Clone D62; A337V -Clone B73; E509G -