Key Points

  • KIN-8194 is a highly potent dual HCK and BTK inhibitor with superior anti-tumor activity over ibrutinib in MYD88 mutated B-cell lymphomas.

  • KIN-8194 overcomes ibrutinib resistance with a survival benefit in TMD-8 ABC DLBCL xenografted mice and synergizes with venetoclax.

Activating mutations in MYD88 promote malignant cell growth and survival through HCK mediated BTK activation. Ibrutinib binds to BTKCys481 and is active in B-cell malignancies driven by mutated MYD88. Mutations in BTKCys481 particularly BTKCys481Ser are common in patients with acquired ibrutinib resistance. We therefore performed an extensive medicinal chemistry campaign and identified KIN-8194 as a novel dual inhibitor of HCK and BTK. KIN-8194 showed potent and selective in vitro killing of MYD88 mutated lymphoma cells, including ibrutinib resistant BTKCys481Ser expressing cells. KIN-8194 demonstrated excellent bioavailability and pharmacokinetic parameters, with good tolerance in rodent models at pharmacologically achievable and active doses. Pharmacodynamic studies showed sustained HCK and BTK inhibition for 24 hours following single oral administration of KIN-8194 in MYD88 mutated TMD-8 ABC DLBCL xenografted mice with either wild-type BTK (BTKWT) or BTKCys481Ser expressing tumors. KIN-8194 showed superior survival benefit over ibrutinib in both BTKWT and BTKCys481Ser expressing TMD-8 DLBCL xenografted mice, including sustained complete responses >12 weeks off treatment in mice with BTKWT expressing TMD-8 tumors. The Bcl-2 inhibitor venetoclax enhanced the anti-tumor activity of KIN-8194 in BTKWT and BTKCys481Ser expressing MYD88 mutated lymphoma cells, and markedly reduced tumor growth and prolonged survival in mice with BTKCys481Ser expressing TMD-8 tumors treated with both drugs. The findings highlight the feasibility of targeting HCK, a key driver of mutated MYD88 pro-survival signaling, and provide a framework for the advancement of KIN-8194 for human studies in B-cell malignancies driven by HCK and BTK.

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