Fig. 2.

Conceptual diagrammatic structures of the four FDA-approved direct oral factor Xa inhibitors binding to the active site. Structures for rivaroxaban and apixaban are derived from known structures, while betrixaban and edoxaban are extrapolated based on these structures. Not drawn to scale. S1 and S4 represent binding regions for the factor Xa active site; Ox oxazolidinone moiety, Cl chloride, H hydrogen participating in bonding, CH ₃ methyl group, H ₂ O water, Tyr tyrosine, Gly glycine, Gln glutamine, FDA (Food and Drug Administration). From Steinberg B and Becker RC. J Thromb Thrombolysis 2014; 37: 234–241. With permission