Should gene therapy be used for newborns with hemophilia?

Hemophilia results from a deficiency of blood coagulation factors and leads to spontaneous bleeding. The disease is an attractive model for gene therapy because small amounts of the deficient protein can reduce the risk of bleeding. Therapeutic levels of coagulation Factor VIII (deficient in hemophilia A) and Factor IX (hemophilia B) have been achieved in mice and dogs, and five gene therapy trials have been initiated in adult patients [1–4]. These human trials include intramuscular or hepatic artery injection of an adeno-associated virus (AAV) vector for hemophilia B, intravenous injection of retroviral or adenoviral vectors for hemophilia A, and implantation of genetically-modified fibroblasts for hemophilia A.