The FDA has approved a Genentech drug meant to prevent or reduce bleeding in hemophilia A patients who have developed an immune response to currently available treatments for the condition.
But Thursday’s approval of emicizumab-kxwh (Hemlibra) comes with a warning about severe blood clots. In clinical trials testing the drug from Genentech, the South San Francisco, CA, subsidiary of Swiss pharma giant Roche, blood clotting complications were observed in some patients who were also given a rescue treatment for their bleeds.
Jefferies analyst Jeffrey Holford said in a research note that the boxed warning on emicizumab’s label is not a surprise given the discussion about the safety concerns during the clinical trials. But he added that since discontinuing the use of the rescue agent, no further problems were observed in patients.
“Beyond its superior efficacy, Hemlibra’s simple weekly subcutaneous injection will help transform the lives of patients that would otherwise require multiple infusions per week,” Holford wrote.
Hemophilia A patients have a deficiency of the blood clotting protein factor VIII. This deficiency puts patients at risk for dangerous bleeds from cuts and scrapes, but also internal bleeds that seep into tissues and joints and lead to long-term damage. The National Hemophilia Foundation estimates that 20,000 people in the U.S. have some form of hemophilia, which affects mostly males. Hemophilia A is the most common form of the disorder.
Standard hemophilia treatment includes replacing the missing blood clotting proteins by infusion as frequently as three times per week. But in some patients, this treatment causes the body to produce antibodies, called inhibitors, that diminish the effectiveness of the infused proteins. The FDA approval covers adults and children who have these inhibitors.
Emicizumab is once-a-week, self-injected drug meant to prevent bleeding or reduce the frequency of bleeds. In its Phase 3 studies, Genentech reported that its drug reduced the rate of bleeds by 87 percent. But those results followed disclosures of one patient death, and five patients who experienced blood clotting complications during the trial.
In February, Roche issued a statement to the European Haemophelia Consortium that said an investigator concluded the patient death was caused by a rectal hemorrhage unrelated to emicizumab. The company added that the blood-clotting complications were associated with high doses of a treatment that bypasses the inhibitor blocked by the immune system. After discontinuing these bypassing agents, measures of blood vessel damage indicators improved. The FDA says that common side effects of the Genentech drug include reactions at the injection site, headache, and joint pain.
Genentech’s hemophilia drug will cost $482,000 in the first year, dropping to $448,000 in subsequent years. Holford said that the price is a roughly 50 percent discount to the cost of existing treatments, which should help the drug penetrate the market for hemophilia therapies. Jefferies projects the drug could reach $5 billion in annual sales.
Genentech said emicizumab will become available to patients “shortly after approval.” The drug is still under regulatory review in Europe. The company is also conducting additional studies that could expand use of the drug to more patients. A Phase 3 study testing the drug in those who don’t have inhibitors to factor VIII—a much larger group of hemophilia A patients—is expected to report data by the end of this year.
Photo by Genentech.