In Vitro: Src Inhibitor 1 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. Src Inhibitor 1 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.