Evaluating Gene Therapy as a Potential Paradigm Shift in Treating Severe Hemophilia.

Hemophilia is characterized by a deficiency in coagulation factors VIII or IX. The general standard of care for severe hemophilia is frequent intravenous recombinant or plasma-derived factor replacement to prevent bleeding. While this treatment is effective in preventing bleeding, frequent infusions are burdensome for patients. Nonadherence to the therapeutic regimen leaves people with hemophilia at risk for spontaneous and traumatic bleeds into joints as well as life-threatening bleeds such as intracranial hemorrhage. The chronicity of the disorder often leads to the formation of target joints, causing long-term pain and impairing mobility. As a monogenic disorder with well-understood genetics, hemophilia is an ideal disorder for implementing innovations in gene therapies. Indeed, recent approvals of two gene therapy products have the potential to shift the hemophilia treatment paradigm. Valoctocogene roxaparvovec and etranacogene dezaparvovec-drlb are gene therapies for hemophilia A and B, respectively. These therapies, given as a single intravenous infusion, may improve patients' quality of life, decreasing treatment burden and resulting in factor expression that virtually eliminates the need for factor replacement. Since both treatments involve viral vectors targeted to the liver, short- and long-term safety and efficacy monitoring involves monitoring liver enzymes to track liver health. Long-term monitoring of efficacy, durability of gene expression, and safety are ongoing. Gene therapy presents a promising new therapeutic option for patients with hemophilia and warrants continued innovation and investigation.