Discovery of Potent and Selective SH2 Inhibitors of the Tyrosine Kinase ZAP-70

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Abstract
A series of 1,2,4-oxadiazole analogues has been shown to be potent and selective SH2 inhibitors of the tyrosine kinase ZAP-70, a potential therapeutic target for immune suppression. These compounds typically are 200−400-fold more potent than the native, monophosphorylated tetrapeptide sequences. When compared with the high-affinity ζ-1-ITAM peptide (Ac-NQL-pYNELNLGRREE-pYDVLD-NH2, wherein pY refers to phosphotyrosine) some of the best 1,2,4-oxadiazole analogues are approximately 1 order of magnitude less active. This series of compounds displays an unprecedented level of selectivity over the closely related tyrosine kinase Syk, as well as other SH2-containing proteins such as Src and Grb2. Gel shift studies using a protein construct consisting only of C-terminal ZAP-70 SH2 demonstrate that these compounds can effectively engage this particular SH2 domain.