Four years on, BioMarin’s hemophilia gene therapy is still going strong—it staved off bleeding episodes in patients with hemophilia A and reduced their reliance on infusions of a blood-clotting factor that they lack.
Seven patients who received the highest dose of the treatment, valoctocogene roxaparvovec, or valrox, saw their bleeding episodes plummet 95% over four years, according to updated phase 1/2 data presented virtually at the annual meeting of the World Federation of Hemophilia. Before gene therapy, those patients needed more than 130 infusions of factor VIII to manage their disease each year; after treatment, that number dropped to an average of five infusions per year.
Six of the seven patients (86%) were bleed-free in the fourth year and all seven remain off prophylactic doses of factor VIII. The FDA is expected to make a decision on valrox, to be marketed under the name Roctavian, by Aug. 21.
“It is exciting to observe that all study participants remain off Factor VIII prophylaxis therapy, while also experiencing a greater than 90 percent reduction in bleeding episodes from a single administration of valoctocogene roxaparvovec,” said Dr. John Pasi, the study’s chief investigator, in a statement. “These data demonstrate the very real potential of a paradigm shift in the treatment of hemophilia A and that ongoing research into gene therapies could represent an entirely new way to approach meeting the high unmet need in patients with severe hemophilia A.”
Frequent infusions are the norm for people with hemophilia A, who make a faulty version of factor VIII, or too little of it. A one-and-done treatment that restores their ability to make the clotting factor would free them from lifelong treatment—that is, if the gene therapy’s effects last.
So far, analysts are impressed. J.P. Morgan analyst Cory Kasimov called the data “Roc solid,” while SVB Leerink’s Joseph Schwartz called the treatment’s durability “respectable.”
Schwartz did note that the treatment’s effects on factor VIII activity levels waned over time, with the four-year figures for patients who got the highest dose showing a “noticeable decrease” from those recorded at the three-year follow-up. And the three-year data had already shown a drop in factor VIII levels, raising the possibility that patients might need to be re-dosed to keep up protection against bleeds.
“However, [management] stated that [patients] with the highest levels decreased the most,” he added.
Kasimov echoed the sentiment: “[The] magnitude of FVIII activity decline was a focus point for investors but demonstrated relative stability/ potential plateau over the four-year time frame… Dr. Pasi not surprisingly conveyed optimism on the data and highlighted that the decline in FVIII activity is “shallow” and longer-term duration remains “watch-and-wait.”