KIN-8194

Here, we show that KIN-8194, a dual inhibitor of BTK and HCK with in vivo activity against Myd88-L265P-driven diffuse large B-cell lymphoma and Waldenström Macroglobulinemia, has a potent growth inhibitory effect in MCL cell lines and primary MCL cells, irrespective of their sensitivity to BTKi (ibrutinib and acalabrutinib). Taken together, our data demonstrate that KIN-8194 inhibits growth and integrin-mediated adhesion of BTKi-sensitive MCL cells, as well as MCL cells with primary or acquired BTKi resistance. This renders KIN-8194 a promising novel treatment for MCL patients.

These structural insights provided a baseline for the understanding of the dual inhibitory activity of KIN-8194. Establishing the cruciality of the interactions between the KIN-8194 and Arg and Lys residues could guide the structure-based design of novel dual BTK/HCK inhibitors with improved therapeutic activities.

Consistent with these observations, treatment of primary MYD88 mutated WM LPCs cells with either A419259 or KIN-8194 also showed marked reduction in both p-HCK and p-SYK expression by PhosFlow analysis. Taken together, our findings show that SYK is activated by HCK in MYD88 Mut B-cell lymphomas cells; broaden the pro-survival signaling generated by aberrant HCK expression in response to MYD88 Mut ; and help further establish HCK as an important therapeutic target in MYD88 Mut B-cell lymphomas.

Activating mutations in MYD88 promote malignant cell growth and survival through HCK mediated BTK activation. 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.