Hympavzi may be available as prophylaxis in US before year’s end
Therapy OK'd for hemophilia A or B adults, children without inhibitors
Hympavzi (marstacimab-hncq) may be available by prescription in the U.S. before the end of the year. The therapy was approved this month as a routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and children, ages 12 and older, with hemophilia A or B who haven’t developed inhibitors.
Developer Pfizer has tagged Hympavzi with a wholesale acquisition cost of $795,600 per year, which compares to the “pricing for prophylactic treatments for hemophilia A or B now on the market,” Younos Abdulsattar, Pfizer’s U.S. rare disease medical lead, said in a Q&A with Hemophilia News Today.
Patients’ actual out-of-pocket costs will vary based on their insurance coverage and many may not have to pay the full price. To help eligible patients reduce their cost for Hympavzi, the company will offer a copay assistance program. Information about it is available by calling 1-888-733-2030.
Hympavzi is under regulatory review in the European Union, where it garnered a positive opinion from an advisory committee of the European Medicines Agency (EMA), and in other countries.
“Pfizer is continuing to work with regulatory authorities across the world,” Abdulsattar said.
Hemophilia is a genetic disease caused by a missing or faulty clotting protein — factor VIII (FVIII) in hemophilia A and factor IX (FIX) in hemophilia B — that results in excessive bleeding, which can occur spontaneously or after injury or surgery. Treatment often involves frequent infusions into a vein of FVIII or FIX, either as on-demand to treat active bleeds or a prophylaxis to prevent them.
“Patients taking these frequent infusions experience issues with regularly accessing a vein and, in some cases, the requirement of storage, preparation, and mixing of a treatment that can be disruptive to daily routines,” Abdulsattar said, adding, for many patients, “the time-consuming nature of prophylaxis” is the number one reason they miss a routine infusion.
What makes Hympavzi unlike factor replacement treatment?
Hympavzi became the first treatment for hemophilia A or B to come in a single-dose, prefilled syringe or pen that’s ready to be injected under the skin by patients or caregivers.
“Hympavzi will offer a straightforward, once-weekly subcutaneous administration via an autoinjector pen with minimal preparation required,” Abdulsattar said.
Unlike factor replacement treatment, which provides a version of the missing or faulty clotting protein, Hympavzi reduces the activity of a protein that normally prevents blood clots from forming. Reducing the protein’s activity should help blood to clot, thereby preventing or reducing the frequency of bleeding episodes.
“The approval of Hympavzi is a meaningful advancement in that it offers not only bleed protection and a generally manageable safety profile, but also once-weekly subcutaneous administration,” Abdulsattar said.
Hympavzi is the first nonfactor, once-weekly subcutaneous treatment for people with hemophilia B.
The BASIS of Hympavzi’s approval
Hympavzi’s approval drew on data from BASIS (NCT03938792), an ongoing Phase 3 clinical study where men and boys with hemophilia A or B, ages 12-74, who did or didn’t have inhibitors received standard-of-care treatment for six months and then switched to Hympavzi once weekly for 12 months. Inhibitors are neutralizing antibodies that prevent factor replacement treatment from working effectively.
Among the patients without inhibitors who were receiving on-demand factor replacement treatment, switching to Hympavzi reduced the annualized bleeding rate for treated bleeds by 92%. Hympavzi also outperformed routine prophylaxis with factor replacement treatment, with patients seeing a 35% reduction in the annualized rate of treated bleeds.
Data from the patients who’d developed inhibitors, “many of whom face similar challenges to those living without inhibitors in terms of convenience or if they are experiencing bleeding while on previous treatments,” are expected next year. Earlier studies suggest these patients may also benefit from Hympavzi, according to Abdulsattar.
“We are committed to developing treatments that can meet the unique treatment needs of a wide range of patients, which is why we look forward to the possibility of expanding this treatment option to more patients with hemophilia A or B pending next year’s results and subsequent filings for regulatory approvals,” Abdulsattar said.
Patients with or without inhibitors who complete BASIS can enroll in an open-label extension study (NCT05145127), which will let them continue receiving Hympavzi for up to seven years. The goal is to see if the medication maintains its safety and effectiveness in the long term.
An interim analysis of 107 patients without inhibitors who rolled over from BASIS showed an estimated mean annualized bleeding rate of 3.06 over up to 23 months, or nearly two years. Those who initially received on-demand factor replacement treatment saw their treated bleed rates drop from 38 to 3.7. Treated bleed rates fell from 7.85 to 2.79 for those on routine prophylaxis.
BASIS KIDS (NCT05611801), another ongoing Phase 3 clinical trial, is testing Hympavzi in up to 100 teens and children as young as 12 months with hemophilia A or B,with or without inhibitors. The goal is to assess the therapy’s safety and changes in the number of bleeding episodes over a year of treatment. The results are expected in 2028.
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