Inhibitors of the RET tyrosine kinase based on a 2-(alkylsulfanyl)-4-(3-thienyl)nicotinonitrile scaffold

In an approach to optimize 2-(4-fluorobenzylsulfanyl)-4-(2-thienyl)-5,6,7,8-tetrahydroquinoline-3-carbonitrile (1a), a weak inhibitor of the cancer-related tyrosine kinase RET originating from a screening campaign, analogues with 3-thienyl substitution were prepared. Among the novel derivatives, 2-amino-6-{[2-(4-chlorophenyl)-2-oxoethyl]sulfanyl}-4-(3-thienyl)pyridine-3,5-dicarbonitrile (13g) was identified as a submicromolar RET inhibitor, displaying 3- and 100-fold selectivity versus ALK and ABL kinases, respectively. The novel inhibitor exhibited antiproliferative activity in the micromolar concentration range against both RET-dependent and RET-independent cancer cell lines. Docking experiments suggest a binding mode of the new inhibitors in the ATP binding pocket of the target kinase, explaining the observed structure–activity relationships.

Graphical abstractThe title compounds were developed as inhibitors of the cancer-related tyrosine kinase RET and tested for antiproliferative activity against cancer cell lines.Figure optionsDownload full-size imageDownload as PowerPoint slide