Alkynylnicotinamide‐Based Compounds as ABL1 Inhibitors with Potent Activities against Drug‐Resistant CML Harboring ABL1(T315I) Mutant Kinase

The introduction of imatinib into the clinical scene revolutionized the treatment of chronic myelogenous leukemia (CML). The overall eight‐year survival rate for CML has increased from about 6 % in the 1970s to over 90 % in the imatinib era. However, about 20 % of CML patients harbor primary or acquired resistance to tyrosine kinase inhibitors. ABL1 point mutations in the BCR‐ABL1 fusion protein, such as ABL1(T315I), typically emerge after prolonged kinase inhibitor treatment. Ponatinib (AP24534) is currently the only approved CML drug that is active against the ABL1(T315I) mutation. However, ponatinib has severe cardiovascular toxicities; hence, there have been efforts to find safer CML drugs that work against ABL1 secondary mutations. We reveal that isoquinoline‐ or naphthyridine‐based compounds, such as HSN431, HSN576, HSN459, and HSN608 potently inhibit the enzymatic activities of ABL1, ABL1(T315I), and ABL1(E255K). These compounds inhibit the proliferation of ABL1‐driven CML cell lines, K652 and KCL22 as well as the drug‐resistant cell line, KCL22‐IR, which harbors the secondary mutated ABL1(T315I) kinase. Ponatinib gets serious competitors: Ponatinib (AP24534) is currently the only approved drug for treating CML that is active against the ABL1(T315I) mutation. However, its severe cardiovascular toxicities have led to efforts to find safer CML drugs that work against ABL1 secondary mutations. Alkynyl aminoisoquinolines and alkynylaminonaphthyridines from this study potently inhibit ABL1(T315I). As a result, these compounds inhibit the imatinib‐resistant CML cell line, KCL22‐IR.