Gene Therapy Could Possibly Cure Hemophilia A!

Gene therapy may be the answer to preventing bleeding episodes in hemophilia A patients. A small study with significant results was published in the New England Journal of Medicine. In the study, scientists injected AAV5-hFVIII-SQ, a genetically modified variant of the adeno-associated virus (AAV) as a slow intravenous infusion over around an hour in nine men with severe hemophilia A. The virus was previously modified to promote the production of factor VIII by the cells of the body, which is deficient in these patients. One patient was previously taking on-demand factor VIII injections for hemophilia A, while the others were on preventive injections. A low and an intermediate dose of the modified virus were administered in one patient each, while seven patients received high-dose treatment.

The scientists found that:

• The factor VIII activity level improved in all the participants who received high-dose therapy. The increase in factor VIII levels was noted between 2 and 9 weeks following the injection, and stabilized between 20 to 24 weeks. In fact, six out of seven patients achieved factor VIII levels within the normal range. Patients with low and intermediate doses had lower than normal levels of factor VIII (3IU or less), which indicates the dose-related benefit of the treatment.
• The level of factor VIII was sustained even one year after receiving the injection.
• The frequency of bleeding episodes decreased significantly, as a result of which most patients who received the high-dose treatment did not require factor VIII injections. The need for repeated factor VIII injections or pain medications reduced, thereby improving the quality of life in the patients. Neutralizing antibodies against factor VIII were not produced in any individual.
• A mild elevation in the liver enzyme alanine aminotransferase was noted. An increase in aspartate aminotransferase levels was noted in four patients. Other evidences of possible liver damage were not noted.
• One patient developed progression of previous chronic joint disease. Other mild adverse effects noted included joint disease, back pain, fatigue and productive cough, which may or may not have been associated with the treatment.
• Though four participants showed high levels of factor VIII intermittently, there were no adverse episodes of excessive clotting like stroke or heart attack These patients had normal levels of platelet count, prothrombin time, and activated partial-thromboplastin time, which are indicative of normal bleeding and clotting.

The study thus stresses on the potential of gene therapy to improve the life of patients with hemophilia A and eliminate the need for regular injections. Further studies in larger number of patients are required to establish the efficacy and detect any adverse effects of this novel approach of treating hemophilia A.

About Hemophilia A

Hemophilia A is a genetic disorder where the patient lacks a protein in the blood called factor VIII. A deficiency of the protein makes the patient bleed easily on exposure to trauma, or even spontaneously in severe cases. Bleeding into the joints can result in painful joint swelling and arthritis. Uncontrolled bleeds in the brain and other parts of the body can be fatal. The condition predominantly affects males while females tend to be carriers.

Hemophilia A patients are treated with replacement of factor VIII either on an as-and-when needed basis to heal a bleeding episode or as a preventive treatment on a regular basis. Preventive treatment with factor VIII has some disadvantages-it needs to be injected up to 3 times weekly, and the patient can still suffer from bleeding episodes at times when the factor VIII level is low.

Reference:

1. Rangarajan S et al. AAV5-Factor VIII Gene Transfer in Severe Hemophilia A. New England Journal of Medicine (2017); DOI: 10.1056/NEJMoa1708483

Source-Medindia