ATC code: B01AX06 On July 1st, FDA approved Rivaroxaban (trade name: Xarelto , Research code: BA-59-7939, NDA 022406), an anti-coagulant to prevent deep vein thrombosis (DVT) in patients with knee or hip replacement surgery. Rivaroxaban is the first orally applied direct inhibitor of Factor Xa (FXa), a key regulatory of the coagulation cascade . In DVT, a blood clot is formed which can dislodge and travel to the lungs, causing pulmonary embolism which can be potentially fatal. Factor Xa (EC number 3.4.21.6 , UniProt ID P00742 , OMIM 613872 ) is a serine endopeptidase , cleaving prothrombin into its active form, thrombin , which then activates further downstream factors which ultimately lead to platelet activation and fibrin formation, clotting the damaged blood vessels. The sequence of Factor X is >Factor X MGRPLHLVLLSASLAGLLLLGESLFIRREQANNILARVTRANSFLEEMKKGHLERECMEE TCSYEEAREVFEDSDKTNEFWNKYKDGDQCETSPCQNQGKCKDGLGEYTCTCLEGFEGKN CELFTRKLCSLDNGDCDQFCH