Gene Therapy for Hemophilia.

Concept Gene therapy with adeno-associated virus (AAV) vectors treats hemophilia A or B by delivering a functional F8 or F9 gene to hepatocytes. This single infusion enables endogenous production of FVIII or FIX protein, reducing bleeding in patients. Evolution Long-term clinical studies have provided insight into the efficacy, safety, and durability of AAV-mediated gene therapies for hemophilia A and B. Gene therapies have now been approved for hemophilia A (valoctocogene roxaparvovec) and hemophilia B (etranacogene dezaparvovec; fidanacogene elaparvovec) in select regions. Application The approved gene therapies are associated with a strong reduction in bleeding tendency and increased FVIII or FIX activity levels, without the need for additional FVIII or FIX replacement therapies, in the vast majority of patients. Future Steps Improvements in AAV technology, protein expression, and immunogenicity may render AAV-mediated gene therapies more efficient, longer lasting and safer for people with hemophilia A or B.