Orally bioavailable and highly selective inhibitor of Bruton's tyrosine kinase (BTK) with potential antineoplastic activity; inhibiting BTK activity, B-cell-mediated signaling and the growth of malignant B cells that overexpress BTK; an experimental drug candidate for chronic lymphocytic leukemia (CLL), mantle cell lymphoma, diffuse large B-cell lymphoma, and multiple myeloma etcBTK, a member of the BTK/Tec family of non-recetor cytoplasmic tyrosine kinases, is required for B cell receptor (BCR) signaling, plays a key role in B-cell maturation, and is overexpressed in a number of B-cell malignancies