Discovery of a Factor Xa Inhibitor (3R,4R)-1-(2,2-Difluoro-Ethyl)-Pyrrolidine-3,4-Dicarboxylic Acid 3-[(5-Chloro-Pyridin-2-Yl)-Amide] 4-{[2-Fluoro-4-(2-Oxo-2H-Pyridin-1-Yl)-Phenyl]-Amide} as a Clinical Candidate.