FDA Approves First Gene Therapy for Hemophilia A
The US Food and Drug Administration approved the gene therapy valoctocogene roxaparvovec (Roctavian, BioMarin) for adults with severe hemophilia A.
Valoctocogene roxaparvovec, a one-time, single-dose IV infusion, is the first gene therapy approved in the United States for severe hemophilia A and will cost around $2.9 million. BioMarin has said the price tag reflects “the possibility of freedom from years” of infusions, which come to about $800,000 each year.
However, last December, ICER set the upper bounds for the gene therapy at about $1.96 million. The extent to which the gene therapy will provide freedom from infusions, for how long, and in which patients are not completely understood.
Hemophilia A is caused by a mutation in the gene that produces a protein called coagulation factor VIII, which is essential for blood clotting. Valoctocogene roxaparvovec delivers a functional gene to liver cells via an adeno-associated virus serotype 5; the gene instructs the cells to make the missing clotting factor.
“Adults with severe hemophilia A face a lifelong burden, with frequent infusions and a high risk of health complications, including uncontrolled bleeding and irreversible joint damage,” Steven Pipe, MD, professor of pediatrics and pathology at the University of Michigan and an investigator for the Phase 3 study that led to the approval, said in a statement. The approval of valoctocogene roxaparvovec “has the potential to transform the way we treat adults based on years of bleed control following a single, one-time infusion.”
About 6500 US adults live with severe hemophilia A, and BioMarin said it anticipates approximately 2500 will be eligible to receive the gene therapy following the approval. The US indication is limited to patients without a history of factor VIII inhibitors and without detectable antibodies to the adeno-associated virus serotype 5.
Last August, the European Medicines Agency authorized the gene therapy for use in Europe, but according to Forbes and PharmaPhorum, uptake in Europe has been delayed due to reimbursement issues, given the cost of treatment and clinical uncertainties.
Data to date, however, are promising for most patients. Approval was based on BioMarin’s open-label, single-arm GENEr8-1 study in 134 men with severe congenital hemophilia A. Patients received a single infusion of 6 x 1013 vector genomes per kilogram.
Among the 132 patients available for 2-year evaluation, median factor VIII activity was in the range for mild hemophilia (6% to 39% of normal) with an 84.5% reduction in bleeding events from baseline.
More than 80% of participants had no bleeding events requiring treatment, and there was a 98% reduction from baseline in mean use of exogenous factor VIII.
Overall, at 2 years, only 4.5% of patients had factor VIII activity consistent with severe hemophilia A; 9.1% had activity consistent with moderate disease; 59.8% had activity consistent with mild disease, and 26.5% had activity in the normal range above 40 IU/dL.
Trial investigators estimated that the typical half-life of the transgene-derived factor VIII production system is 123 weeks.
Among the six men who resumed prophylaxis, most had fewer bleeding events than when they were on prophylaxis before the infusion. All patients developed antibodies to the virus delivery vector, precluding retreatment.
Elevated alanine aminotransferase levels were the most common adverse event, occurring in 88.8% of patients, which were treated with immunosuppressants for a median of 33 weeks. Elevations persisted at 2 years in 29% of patients.
The other most common adverse events were headache (38.1%), nausea (37.3%), and increases in aspartate aminotransferase (35.1%).
M. Alexander Otto is a physician assistant with a master’s degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape and is also an MIT Knight Science Journalism fellow. Email: [email protected]
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