Src Inhibitor 1 (Src Kinase Inhibitor 1) is a potent and selective dual site Src tyrosine kinase inhibitor.

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].

Assays (25.5 μL volume) are carried out robotically at room temperature (21°C) and are linear with respect to time and enzyme concentration under the conditions used. Assays are performed for 30 min using Multidrop Micro reagent dispensers in a 96-well format. The concentration of magnesium acetate in the assays is 10 mM and [γ-33P]ATP (800 c.p.m./pmol) is used at 5, 20 or 50 μM as indicated, in order to be at or below the Kmfor ATP for each enzyme.The assays are initiated with MgATP, stopped by the addition of 5 μL of 0.5 M orthophosphoric acid and spotted on to P81 filter plates using a unifilter harvester. The IC50 values of inhibitors are determined after carrying out assays at ten different concentrations of each compound[2].