Pirtobrutinib (LOXO-305)

Pirtobrutinib (LOXO-305) (CAS No.: 2101700-15-4) is a synthetic small molecule research compound classified as a next generation, highly selective, non covalent Brutons tyrosine kinase inhibitor within the B cell receptor signaling research space, and it is broadly used in oncology focused mechanism studies of BTK dependent hematologic malignancy biology and resistance evolution. Mechanistically, it binds BTK through a reversible interaction and retains inhibitory activity against multiple C481 substitution variants that can reduce sensitivity to covalent BTK inhibitors, thereby supporting its utility for investigating kinase target engagement, downstream signaling suppression, and adaptive pathway remodeling in preclinical systems. Across reported profiling datasets, its biochemical and cellular potency is in the nanomolar range, including low nanomolar activity in engineered cellular contexts, with strong kinase selectivity characterized by greater than 300 fold preference for BTK relative to large kinase panels and minimal detectable inhibition of surveyed non kinase off targets at micromolar test concentrations. In biomedical research workflows, Pirtobrutinib is commonly applied in BTK pathway interrogation, comparative inhibitor benchmarking, mutation informed resistance modeling, and translational pharmacology studies using BTK dependent cell lines and mouse xenograft models where regression of BTK driven lymphoma phenotypes has been observed under experimental conditions; the concentrations or doses used in experiments typically depend on specific experimental designs and research objectives, including assay format, exposure duration, and model specific pharmacodynamic endpoints.