Discovery of a novel BTK inhibitor S-016 and identification of a new strategy for the treatment of lymphomas including BTK inhibitor-resistant lymphomas

Bruton's tyrosine kinase (Btk) has emerged as a therapeutic target for B-cell malignancies, which is substantiated by the efficacy of various irreversible or reversible Btk inhibitors. However, on-target Btk mutations facilitating evasion from Btk inhibition lead to resistance that limits the therapeutic efficacy of Btk inhibitors. In this study we employed structure-based drug design strategies based on established Btk inhibitors and yielded a series of Btk targeting compounds. Among them, compound S-016 bearing a unique tricyclic structure exhibited potent Btk kinase inhibitory activity with an IC₅₀ value of 0.5 nM, comparable to a commercially available Btk inhibitor ibrutinib (IC₅₀ = 0.4 nM). S-016, as a novel irreversible Btk inhibitor, displayed superior kinase selectivity compared to ibrutinib and significant therapeutic effects against B-cell lymphoma both in vitro and in vivo. Furthermore, we generated Btk inhibitor-resistant lymphoma cells harboring Btk C481F or A428D to explore strategies for overcoming resistance. Co-culture of these DLBCL cells with M0 Macrophages led to the polarization of M0 Macrophages toward the M2 phenotype, a process known to support tumor progression. Intriguingly, we demonstrated that SYHA1813, a compound targeting both VEGFR and CSF1R, effectively reshaped the tumor microenvironment (TME) and significantly overcame the acquired resistance to Btk inhibitors in both BTK-mutated and wild-type Btk DLBCL models by inhibiting angiogenesis and modulating macrophage polarization. Overall, this study not only promotes the development of new Btk inhibitors but also offers innovative treatment strategies for B-cell lymphomas, including those with Btk mutations.