An orally available formulation containing an inhibitor of Bruton agammaglobulinemia tyrosine kinase (BTK), with potential antineoplastic activity. Upon administration, tirabrutinib covalently binds to BTK within B cells, thereby preventing B cell receptor signaling and impeding B cell development. As a result, this agent may inhibit the proliferation of B cell malignancies. BTK, a cytoplasmic tyrosine kinase and member of the Tec family of kinases, plays an important role in B lymphocyte development, activation, signaling, proliferation and survival.