What Is Hemgenix? Uses, Dosage, and What You Need to Know in 2026

Hemgenix (etranacogene dezaparvovec-drlb) is a one-time gene therapy for adults with hemophilia B — a rare, lifelong bleeding disorder caused by a deficiency of blood clotting Factor IX. Approved by the FDA on November 22, 2022, Hemgenix was the first-ever gene therapy approved for hemophilia B and remains the only one available as of 2026.

What Is Hemgenix Used For?

Hemgenix is indicated for the treatment of adults with hemophilia B (congenital Factor IX deficiency) who meet one or more of the following criteria:

Currently use Factor IX prophylaxis therapy (preventive infusions to avoid bleeding episodes)

Have a current or historical life-threatening hemorrhage

Have repeated, serious spontaneous bleeding episodes

Hemgenix is not approved for children and is not intended for administration in women. It is for adult males (18+) with hemophilia B. The drug is also not appropriate for patients with active Factor IX inhibitors.

What Is Hemophilia B and Why Does It Need Gene Therapy?

Hemophilia B is an X-linked genetic bleeding disorder caused by a mutation in the F9 gene, resulting in absent or insufficient production of Factor IX — a protein essential for blood clotting. The condition affects approximately 1 in 40,000 people and accounts for about 15% of all hemophilia cases. It almost exclusively affects males.

Before Hemgenix, the standard treatment was regular IV infusions of recombinant or plasma-derived Factor IX concentrate — typically 2–3 times per week for prophylaxis, at a cost of $550,000–$750,000 annually. Despite this, many patients still experienced spontaneous bleeds, joint damage, and reduced quality of life. Gene therapy represented the long-sought solution: fix the underlying genetic defect rather than continuously replacing the missing protein.

What Is the Hemgenix Dosage?

Hemgenix dosing is weight-based:

Recommended dose: 2 × 10¹³ genome copies (gc) per kilogram of body weight, administered as 2 mL/kg

Route: Single intravenous (IV) infusion only

Frequency: One time only — Hemgenix cannot be re-administered

For a 126–130 kg patient: The dose volume is approximately 252–260 mL. The weight-specific kit contains 10–48 vials depending on the weight tier.

Maximum infusion rate: Not to exceed 500 mL/hour; diluted in 0.9% normal saline prior to administration

How Effective Is Hemgenix?

In the pivotal Phase 3 HOPE-B trial — the largest gene therapy trial for hemophilia B to date — 54 adults with moderately severe to severe hemophilia B received a single dose of Hemgenix. Results showed:

54% reduction in annualized bleed rate (months 7–18 post-infusion) compared to baseline on prophylaxis

94% of patients were able to discontinue routine Factor IX prophylaxis

Mean Factor IX activity of 39.0 IU/dL at 6 months and 36.9 IU/dL at 18 months post-infusion (normal range is approximately 50–150 IU/dL)

No serious adverse reactions were reported across 57 patients studied

Who Makes Hemgenix?

Hemgenix was originally developed by uniQure, a Dutch gene therapy biotech company. In 2021, uniQure entered a commercialization agreement with CSL Behring (a subsidiary of Australian biotechnology company CSL Limited), which holds global marketing rights. CSL Behring is the manufacturer and commercial distributor. The two companies received the 2023 Prix Galien USA Award for Best Product for Rare/Orphan Disease for Hemgenix.

What Is the Current Availability of Hemgenix in 2026?

In March 2026, CSL Behring announced a temporary global stockout of Hemgenix related to manufacturing complexity and quality control requirements — not safety or efficacy concerns. Patients and providers should contact HEMGENIX Connect (1-833-436-0021) or use medfinder to check availability at certified hemophilia treatment centers near them.

For full details on the 2026 shortage, see Hemgenix Shortage Update: What Patients Need to Know in 2026. And use medfinder.com to search for available Hemgenix near you.