The Food and Drug Administration (FDA) has approved Hemgenix® (etranacogene dezaparvovec-drlb) as the first gene therapy for appropriate adults with hemophilia B (congenital factor IX deficiency).

Hemgenix is an adeno-associated virus vector-based gene therapy indicated for adults with hemophilia B who currently use factor IX prophylaxis therapy, or have current or historical life-threatening hemorrhage, or have repeated, serious spontaneous bleeding episodes. It is designed to deliver a copy of a gene encoding the Padua variant of human coagulation factor IX. The single dose treatment generates factor IX proteins that are 5 to 8 times more active than normal.

The approval was based on data from the HOPE-B trial (ClinicalTrials.gov Identifier: NCT03569891), a phase 3, open-label, single arm study that included 54 male participants with severe or moderately severe hemophilia B. Patients were initially enrolled in a 6-month observational period during which they continued to receive current standard of care. After the lead-in period, patients received a single intravenous dose of etranacogene dezaparvovec and entered a follow-up period of 5 years.

The primary endpoint was a noninferiority test of annualized bleeding rate (ABR) during months 7 to 18 after etranacogene dezaparvovec treatment compared with the 6-month lead-in period. 

Results showed that during months 7 to 18 post-infusion, the estimated mean ABR was 1.9 bleeds/year (95% CI, 1.0-3.4) compared with an estimated mean ABR of 4.1 bleeds/year (95% CI, 3.2-5.4) during the lead-in period. The ABR ratio was reported to be 0.46 (95% CI, 0.26-0.81), demonstrating noninferiority of ABR during months 7 to 18 vs the lead-in period. 

Additionally, 94% (n=51/54) of participants treated with etranacogene dezaparvovec discontinued use of prophylaxis and remained free of previous continuous routine prophylaxis therapy.

The most common adverse reactions reported with treatment included elevated ALT/AST, headache, blood creatinine kinase elevations, flu-like symptoms, infusion-related reactions, fatigue, and malaise.

Hemgenix is supplied as a customized kit to meet dosing requirements for each patient, with each kit containing 10 to 48 single-use vials. The total number of vials in each kit corresponds to the dosing requirement for each patient based on body weight.

CSL Behring plans to make Hemgenix available as soon as possible.

References

  1. US Food and Drug Administration approves CSL’s Hemgenix® (etranacogene dezaparvovec-drlb), the first gene therapy for hemophilia B. News release. Company. Accessed November 22, 2022. https://www.prnewswire.com/news-releases/us-food-and-drug-administration-approves-csls-hemgenix-etranacogene-dezaparvovec-drlb-the-first-gene-therapy-for-hemophilia-b-301685654.html.
  2. Hemgenix. Package insert. CSL Behring; 2022. Accessed November 22, 2022. https://labeling.cslbehring.com/PI/US/Hemgenix/EN/Hemgenix-Prescribing-Information.pdf.