MCL1 and acute lymphoblastic leukemia: Importantly, the synergistic anti-T-ALL effects of S63845 plus venetoclax were documented in vivo at several different dosage levels by isobologram analysis (Fig. 2c), indicating that MCL1 and BCL-2 inhibitors are synergistic at multiple dosage levels leading to T-ALL cell apoptosis in vivo with acceptable tolerance by normal cells.