LOXO-305, A Next Generation, Highly Selective, Non-Covalent BTK Inhibitor in Previously Treated Mantle Cell Lymphoma, Waldenström’s Macroglobulinemia, and Other Non-Hodgkin Lymphomas: Results from the Phase 1/2 BRUIN Study

Background:Covalent BTK inhibitors (BTKi) have transformed the management of MCL, WM, and MZL. Despite the marked efficacy of covalent BTKi, treatment failure can occur through the development of resistance and discontinuation for adverse events. Covalent BTKi also share pharmacologic liabilities (e.g. low oral bioavailability, short half-life) that may lead to suboptimal BTK target coverage, for example in rapidly proliferating tumors with high BTK protein turnover, ultimately manifesting as acquired resistance in some patients (pts). To address these limitations, LOXO-305, a highly selective, non-covalent BTKi that inhibits both wild type (WT) and C481-mutated BTK with equal low nM potency was developed. The aim of the BRUIN trial was to define the safety and early efficacy of LOXO-305 in pts with B-cell malignancies. Here we report these data in pts with previously treated MCL, WM, and other NHLs.