Src Inhibitor 1 is a potent and selective dual site Src tyrosine kinase inhibitor with IC₅₀ values of 44 nM for Src and 88nM for Lck. IC50 & Target: IC50: 44 nM (Src), 88 nM (Lck)^[1] In Vitro: Src-I1 is competitive with both ATP and peptide binding sites of the kinase. The IC₅₀ values are 44 and 88 nM for Src and Lck, respectively^[1]. Src-I1, is found to be a potent inhibitor of Src (IC₅₀=0.18 μM), but also inhibited other Src family members, such as Lck, Csk and Yes with similar potency to Src, and RIP2 (IC₅₀=0.026 μM) with even greater potency. In addition, it inhibited CHK2 with similar potency to Src, and Aurora B with slightly lower potency^[2].