This Src SH2 binding disruptor (FW = 577.68 g/mol; CAS 268741-42-0) targets the cysteine residue in the phosphotyrosine-binding pocket of the Src SH2 domain in Src family tyrosine kinases (e.g., Src, Fyn, Yes, Yrk, Lyn, Hck, Fgr, Blk, Lck, Frk/Rak and Iyk/Bsk). A fluorescence- polarization-based competitive binding assay was utilized to determine the IC50 of AP-22161 binding to the Src SH2 domain, the Yes SH2 domain and the tandem ZAP SH2 domains. Src has been implicated in the regulation of osteoclast functional activity, and AP 22161 inhibits resorption of dentine. AP22161 demonstrates no sign of toxicity at tested concentrations, as monitored by the presence of tartrate-resistant acid phosphatase (TRAP)-positive cells and surrounding fibroblasts. See also UCS15A; pYEEI; and z–ITAM peptide. Target(s): Src SH2 (IC50 = 0.24 μM); YES SH2 (IC50 = 29.4 μM); ZAP SH2 (IC50 = 422 μM); dentine resorption by rabbit osteoclasts (IC50 = 43 μM).