An orally available formulation containing an inhibitor of Bruton agammaglobulinemia tyrosine kinase (BTK), with potential antineoplastic activity. Upon administration, ONO-4059 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.