Discovery of a Candidate Containing an (S)-3,3-Difluoro-1-(4-methylpiperazin-1-yl)-2,3-dihydro-1H-inden Scaffold as a Highly Potent Pan-Inhibitor of the BCR-ABL Kinase Including the T315I-Resistant Mutant for the Treatment of Chronic Myeloid Leukemia

BCR-ABL kinase inhibition is an effective strategy for the treatment of chronic myeloid leukemia (CML). Herein, we report compound 3a-P1, bearing a difluoro-indene scaffold, as a novel potent pan-inhibitor against BCR-ABL mutants, including the most refractory T315I mutant. As the privileged (S)-isomer compared to its (R)-isomer 3a-P2, 3a-P1 exhibited potent antiproliferative activities against K562 and Ku812 CML cells and BCR-ABL and BCR-ABLT315I BaF3 cells, with IC50 values of 0.4, 0.1, 2.1, and 4.7 nM, respectively. 3a-P1 displayed a good safety profile in a battery of assays, including single-dose toxicity, hERG K+, and genotoxicity. It also showed favorable mice pharmacokinetic properties with a good oral bioavailability (32%), a reasonable half-life (4.61 h), and a high exposure (1386 h·ng/mL). Importantly, 3a-P1 demonstrated a higher potency than ponatinib in a mice xenograft model of BaF3 harboring BCR-ABLT315I. Overall, the results indicate that 3a-P1 is a promising drug candidate for the treatment of CML to overcome the imatinib-resistant T315I BCR-ABL mutation.