TGA responses of FVIII variants. Representative thrombin profiles at 0.5 nM (A) and the dose-dependent peak thrombin responses (B) for BDD-FVIII and D519V/E665V. The estimated EC50 for BDD and D519V/E665V are 3.3 and 0.7 nM, respectively, indicating a ∼fivefold difference in potency. The specific activities of BDD-FVIII and D519V/E665V tested were 6.02 and 11.25 U/µg, respectively.