<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>An orally available inhibitor of spleen tyrosine kinase (Syk), with potential antineoplastic activity. Upon oral administration of spleen tyrosine kinase inhibitor GS-9973, 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.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>