The orally available Btk inhibitor ibrutinib (PCI-32765) protects against osteoclast-mediated bone loss

Ibrutinib is a first-in-class, orally available Btk (Bruton’s tyrosine kinase) inhibitor which has been shown to be effective in the treatment against certain types of leukemia and autoimmune disorders. Btk regulates the expression of genes involved in the differentiation and function of osteoclasts, and therefore inhibiting Btk suppresses osteoclastic bone resorption. Results from in vitro testing showed the suppressive effects on osteoclasts and murine models of RA showed ibrutinib treatment protected bone destruction in joints by targeting B lymphocytes, macrophages and mast cells, all of which are part of RA pathology. In this study, Shinohara et al. showed ibrutinib protected against bone loss in osteoporosis, suggesting that ibrutinib is a potential therapeutic agent for certain osteoclast-related diseases such as osteoporosis and RA.