Fig. 4 Epistatic asciminib resistance by V73A and Y253H

Figure 4 details the discovery and validation of a potent epistatic interaction between the ABL1 kinase domain mutation Y253H and the SH3 domain mutation V73A that confers high-level asciminib resistance. By comparing base editor screens in wild-type and Y253H-mutated K562 cells, the study identified specific guides, notably targeting V73A and Y139C, that exhibited significantly greater resistance in the double-mutant context. Functional validation using dose-response curves in both K562 and Ba/F3 cell models demonstrated that the V73A and Y253H combination potently decreases drug efficacy and potency. The experimentally observed viability for this double mutant significantly deviated from the theoretical additive effects predicted by a neutral product model, confirming a strong positive epistasis that yields resistance comparable to the clinically relevant M244V variant.