Discovery of O-(3-carbamimidoylphenyl)-l-serine amides as matriptase inhibitors using a fragment-linking approach.

Matriptase is a cell-surface trypsin-like serine protease of epithelial origin, which cleaves and activates proteins including hepatocyte growth factor/scatter factor and proteases such as uPA, which are involved in the progression of various cancers. Here we report a fragment-linking approach, which led to the discovery of O-(3-carbamimidoylphenyl)-l-serine amides as potent matriptase inhibitors. The co-crystal structure of one of the potent inhibitors, 6 in complex with matriptase catalytic domain validated the working hypothesis guiding the development of this congeneric series and revealed the structural basis for matriptase inhibition. Replacement of a naphthyl group in 6 with 2,4,6-tri-isopropyl phenyl resulted in 10 with improved matriptase inhibition, which exhibited significant primary tumor growth inhibition in a mouse model of prostate cancer. Compounds such as 10, identified using a fragment-linking approach, can be explored further to understand the role of matriptase as a drug target in cancer and inflammation.