- The effects of an experimental gene therapy for severe hemophilia appear to be holding up relatively well, according to clinical trial data released Thursday by the Dutch biotech UniQure.
- The trial enrolled patients with the less common, "B" form of the bleeding disease, and tracked 53 of them for a total of 18 months. The new results show that a year and a half after receiving UniQure's therapy, these patients had about 37% of normal levels of blood-clotting protein, equivalent to the upper range for mild hemophilia. That's just shy of the 39% of normal observed at six months post-treatment, which, to UniQure and at least some analysts, is a positive sign for the medicine's durability.
- Alongside data on clotting protein levels, UniQure reported its therapy also proved to be more effective than standard preventive treatments at reducing the number of bleeds patients experience annually, easily clearing the study's bar of showing the two to be at least equivalent.
Gene therapies have the potential to essentially fix many diseases. Yet, those currently in development are administered just once, raising questions about whether their effects can hold up over time.
To UniQure, the data disclosed Thursday bode well for its therapy. They show a small, roughly 2% difference in the levels of blood-clotting protein between when patients were evaluated at six months post-treatment and at 18 months, which, according to Stifel analyst Paul Matteis, is "within the margin of error." Protein levels were measured at 42% of normal at month 12.
Notably, the clotting protein levels in these patients were still almost as high as people without hemophilia — a significant improvement, given the trial only enrolled moderately severe to severe hemophiliacs, meaning they had 2% or less of the normal amount of blood-clotting protein and needed preventive treatments to keep their disease in check. Mild hemophiliacs, by comparison, have somewhere between 5% and 30% to 40% of the normal amount of clotting protein.
Writing to clients, Matteis noted how UniQure's latest data also align with the long-term durability seen in other hemophilia B gene therapies. An earlier version of company's therapy, for example, "has shown durable expression out past 5 years," Matteis wrote.
The durability data, combined with success on annualized bleeding rates, has given UniQure and its partner CSL Behring the confidence to forge ahead. CSL, which recently bought exclusive global rights to UniQure's therapy, plans to ask for marketing approval in the U.S. and Europe Union in the first half of 2022.
UniQure's study was halted by the Food and Drug Administration for several months this year after one patient of the 54 enrolled in the trial developed liver cancer, sparking fears the gene therapy could be a potential cause or contributing factor. An investigation by the company and an outside laboratory found no evidence treatment had triggered any genetic changes likely to have played a role in the cancer's development, and the FDA allowed the study to proceed in April.
Joseph Thome, an analyst at Cowen & Co., estimates peak worldwide sales of the therapy, should it be approved, to reach $1.2 billion.