Testis-specific serine/threonine kinase 2 (TSSK2) is an important target for reversible male contraception. A high-throughput screen of ≈17 000 compounds using a mobility shift assay identified two potent series of inhibitors having a pyrrolopyrimidine or pyrimidine core. The pyrrolopyrimidine 10 (IC50 22 nm; GSK2163632A) and the pyrimidine 17 (IC50 31 nm; ALK inhibitor 1) are the most potent TSSK2 inhibitors in these series, which contain the first sub-100 nanomolar inhibitors of any TSSK isoform reported, except for the broad kinase inhibitor staurosporine. The novel, potent pyrimidine TSSK2 inhibitor compound 19 (IC50 66 nm; 2-[[5-chloro-2-[2-methoxy-4-(1-methylpiperidin-4-yl)anilino]pyrimidin-4-yl]amino]-N-methylbenzenesulfonamide) lacks the potential for metabolic activation. Compound 19 had a potency rank order of TSSK1>TSSK2>TSSK3>TSSK6, indicating that potent dual inhibitors of TSSK1/2 can be identified, which may be required for a complete contraceptive effect. The future availability of a TSSK2 crystal structure will facilitate structure-based discovery of selective TSSK inhibitors from these pyrrolopyrimidine and pyrimidine scaffolds.
Bibliographical noteFunding Information:
The authors dedicate this study to Prof. John C. Herr, a devoted scientist, friend, mentor, and colleague, who passed away during the conduct of this study. The PKIS was supplied by GlaxoSmith-Kline LLC and the Structural Genomics Consortium under an open access Material Transfer and Trust Agreement: http:// www.sgc-unc.org. These studies were supported by the US National Institutes of Health (NIH 1U01HD060491, 1U01HD076542, and HHSN275201300017C) from the Contraception Research Branch of NICHD and by Schering AG, Berlin.
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- high-throughput screening
- kinase inhibitors
- male contraception
- structure–activity relationships
- testis-specific serine/threonine kinase