An orally available inhibitor of spleen tyrosine kinase (Syk), with potential antineoplastic activity. Upon oral administration of entospletinib, this agent may inhibit the activity of Syk, which inhibits B-cell receptor (BCR) signaling and leads to an inhibition of tumor cell activation, migration, adhesion and proliferation. Syk, a non-receptor cytoplasmic, BCR-associated tyrosine kinase, is expressed in hematopoietic tissues and is often overexpressed in hematopoeitic malignancies.