Inhibits Mer receptor tyrosine kinase (IC50 = 4.3 nM). Selective over Axl (84-fold) and Tyro3 (58-fold). UNC 2881 inhibits phosphorylation of Mer kinase in 697 B-ALL cells (IC50 = 22nM). Inhibits EGF-induced activation of a chimeric enzyme, composed of EGFR fused with Mer. Blocks collagen-mediated platelet aggregation, implying the potential of this compound for treating thrombosis.