European Commission Approves CSL’s Gene Therapy for Hemophilia B

Rare Daily Staff

The European Commission granted conditional marketing authorization to CLS for its Hemgenix hemophilia B gene therapy, the first gene therapy approved for the rare bleeding disorder.

Hemgenix is approved for treatment of severe and moderately severe hemophilia B (congenital factor IX deficiency) in adults without a history of factor IX inhibitors. The multi-year clinical development of Hemgenix was led by UniQure and sponsorship of the clinical trials transitioned to CSL after it licensed global rights to commercialize the treatment.

Hemophilia B is a genetic bleeding disorder resulting from missing or insufficient levels of blood clotting Factor IX, a protein needed to produce blood clots to stop bleeding. Symptoms can include prolonged or heavy bleeding after an injury, surgery, or dental procedure; in severe cases, bleeding episodes can occur spontaneously without a clear cause. Prolonged bleeding episodes can lead to serious complications, such as bleeding into joints, muscles or internal organs, including the brain.

Most individuals who have Hemophilia B and experience symptoms are men. The prevalence of Hemophilia B in the population is about one in 40,000. Hemophilia B represents about 15 percent of patients with hemophilia. Many women carriers of the disease have no symptoms. However, an estimated 10 to 25 percent of women carriers have mild symptoms. In rare cases, women may have moderate or severe symptoms.

Treatment typically involves replacing the missing or deficient clotting factor to improve the body’s ability to stop bleeding and promote healing. Patients with severe Hemophilia B typically require a routine treatment regimen of intravenous infusions of factor IX replacement products to maintain sufficient levels of clotting factor to prevent bleeding episodes.

Hemgenix is a one-time gene therapy product given as a single dose by IV infusion. Hemgenix consists of a viral vector carrying a gene for clotting Factor IX. The gene is expressed in the liver to produce factor IX protein, to increase blood levels of factor IX and thereby limit bleeding episodes. It received Priority Review, Orphan, and Breakthrough Therapy designations.

In the United Kingdom, The Medicines and Healthcare products Regulatory Agency is currently reviewing CSL’s submission for Hemgenix. Hemgenix was approved by the U.S. Food and Drug Administration in November 2022.

In the ongoing clinical trial, Hemgenix reduced the rate of annual bleeds with a single infusion by delivering a functional gene that acts as a blueprint for coagulation Factor IX, a protein important for blood clotting.

The European Commission’s decision follows the CHMP’s positive opinion in December 2022, based on findings from the pivotal HOPE-B trial, the largest gene therapy trial in hemophilia B to date. These findings showed that hemophilia B patients treated with Hemgenix demonstrated stable and durable increases in mean factor IX activity levels (with a mean factor IX activity of 36.9 percent) which led to an adjusted annualized bleed rate (ABR) reduction of 64 percent. Following infusion of Hemgenix, 96 percent of patients discontinued routine factor IX prophylaxis and mean factor IX consumption was reduced by 97 percent at 18 months post-treatment, compared to the lead-in period.

The HOPE-B study 24-month analysis continued to show a sustained and durable effect of Hemgenix. In a clinical setting, the treatment is generally well-tolerated with no serious treatment-related adverse events.

“The approval of Hemgenix in Europe is a result of that focus and a milestone for the hemophilia B community, and we now need to work to ensure that as many eligible patients across Europe can access this innovative treatment as possible.,” said Lutz Bonacker, senior vice president and general manager of Commercial Operations Europe, CSL Behring. “We are fully committed to working together with payers and other stakeholders to achieve this.”

Photo: Lutz Bonacker, senior vice president and general manager of Commercial Operations Europe, CSL Behring