Enhanced factor VIII activation accelerates thrombin generation and hemostatic potency in mice.

Enhanced factor VIII activation by cleaving only at Arg372 improves thrombin generation and hemostatic efficacy in mice, with faster activation and lower doses needed.

• Why it matters: Understanding how specific cleavage events influence FVIII activation can lead to more effective therapies for bleeding disorders like hemophilia A, especially when vWF binding is impaired.
• What they did: Engineered a FVIII variant (FVIII-2RKR) requiring only Arg372 cleavage, tested in plasma assays and mouse models, revealing increased activity, faster activation, and improved hemostatic function at lower doses.
• The result: FVIII-2RKR showed superior early hemostasis despite reduced vWF binding, indicating that targeted activation enhances therapeutic potential and that vWF is not essential for local FVIII activity at injury sites.