Long-term follow up of patients who received gene therapy for severe haemophilia A has found a beneficial effect on bleeding events and removed the need for factor VIII supplementation, British researchers have reported.
Fifteen patients took part in the trial of adeno-associated virus-mediated gene therapy, led by Professor John Pasi from Queen Mary University of London.
In 2017, a year after the therapy, 85% of the men treated with a single high-dose infusion of the viruses carrying the missing gene had “normal or near-normal” factor VIII levels.
Updated results have now been released, showing that of the 15 patients treated with the gene therapy at varying dosages, 13 are “still benefiting from a substantial fall in the rates of bleeding three years after receiving the treatment."
The findings, published in the New England Journal of Medicine, show that none of the 13 patients who have benefitted from the treatment have needed regular factor VIII to prevent bleeding during the three years.
The authors state: “Gene therapy with AAV5-hFVIII-SQ vector in participants with haemophilia A resulted in sustained, clinically relevant benefit, as measured by a substantial reduction in annualized rates of bleeding events and complete cessation of prophylactic factor VIII use in all participants.”
Professor Pasi said: “Our 2017 paper showed that gene therapy could significantly boost factor VIII levels in men with Haemophilia A.
“Our new data are critical in helping the scientific and medical communities understand this pioneering technology. This latest study confirms both safety and the long-term beneficial impact of the treatment.
“A long-term treatment that effectively ends the life-long regime of regular injections can transform care and massively improve the quality of life of hundreds of thousands of people born with this challenging genetic condition.”
The team also point out that this treatment could be particularly important where access to clotting products is difficult, such as in parts of the developing world.
Pasi KJ, Rangarajan S, Mitchell N, Lester W, Symington E, Madan B, Laffan M, Russell CB, Li M, Pierce GF, Wong WY (2020) “Multiyear Follow-up of AAV5-hFVIII-SQ Gene Therapy for Hemophilia A”, New England Journal of Medicine, doi: 10.1056/NEJMoa1908490