Discovery of a Novel, Selective, and Orally Bioavailable Class of Thrombin Inhibitors Incorporating Aminopyridyl Moieties at the P1 Position

A novel class of thrombin inhibitors incorporating aminopyridyl moieties at the P1 position has been discovered. Four of these thrombin inhibitors (13b,c,e and 14d) showed nanomolar potency (Ki 0.8−12 nM), 300−1500-fold selectivity for thrombin compared with trypsin, and good oral bioavailability (F = 40−76%) in rats or dogs. The neutral P1 was expected to increase metabolic stability and oral absorption. Identification of this novel aminopyridyl group at P1 was a key step in our search for a clinical candidate.