An inhibitor of spleen tyrosine kinase (syk), with potential anti-inflammatory, immunomodulating, and antineoplastic activities. Spleen tyrosine kinase inhibitor TAK-659 may inhibit the activity of syk, which abrogates downstream B-cell receptor (BCR) signaling and leads to an inhibition of B-cell activation, chemotaxis, adhesion and proliferation. Syk, a BCR-associated non-receptor tyrosine kinase that mediates diverse cellular responses, including proliferation, differentiation, and phagocytosis, is expressed in hematopoietic tissues and is often overexpressed in hematopoietic malignancies.