An experimental antibody therapy for chronic hepatitis D has succeeded in its second pivotal Phase 3 trial, significantly reducing viral loads and calming liver inflammation in nearly 60% of recipients, in a major step forward against what doctors regard as the most aggressive form of viral hepatitis.
US biopharmaceutical company Mirum Pharmaceuticals announced on 10 November that its drug brelovitug had cleared the AZURE-4 trial, the second late-stage study of the treatment. The findings mark a critical advance against a disease for which there are few effective treatments, and they put the drug on course for a filing with American regulators in the first half of next year.
The trial tested brelovitug against delayed treatment in 113 previously untreated patients with chronic hepatitis D virus infection. After 24 weeks of therapy with a weekly injection under the skin, 59% of patients receiving the drug met the trial's composite primary endpoint: simultaneous clearance of the virus down to negligible levels and normalisation of alanine aminotransferase, known as ALT, a blood enzyme that signals ongoing liver injury.
Hepatitis D is unusual among viruses because it cannot replicate on its own. It is a satellite virus that depends on the hepatitis B surface antigen to reproduce, which is why it only infects people who already carry hepatitis B. That dependence is also its weakness, and brelovitug is designed to exploit it: the drug is a fully human monoclonal antibody engineered to bind to the hepatitis B surface antigen and block the virus from spreading.
Doctors regard hepatitis D as the most aggressive and rapidly damaging strain of viral hepatitis known to medicine. It accelerates liver damage far faster than hepatitis B alone, driving patients towards cirrhosis and liver failure at a much younger age, and it has long been one of the hardest forms of the disease to treat. Existing options are limited, and many patients have had no effective therapy at all.
The AZURE-4 result is the second positive late-stage study for brelovitug, which is why it matters so much. A single successful trial can be a fluke; two, in different groups of patients, give regulators and doctors far more confidence that the effect is real. Mirum said it now plans to submit a Biologics License Application to the US Food and Drug Administration during the first half of 2027, with a commercial launch possible before the end of next year.
The drug already holds the FDA's Breakthrough Therapy Designation, an administrative tool that speeds up the review of treatments for life-threatening diseases. But it has not yet received marketing approval from the FDA, the European Medicines Agency or any other regulator, and the data announced so far come from corporate trial disclosures rather than a peer-reviewed medical journal. The findings must still undergo independent, rigorous peer review before their clinical standing is settled.
For patients, the most important numbers are the ones that describe how they actually felt. The trial's primary endpoint combined two measures — viral clearance and the normalisation of a key liver enzyme — because together they show that the drug is not just suppressing the virus on a laboratory test but actually calming the inflammation that destroys the liver. The fact that nearly six in ten patients met both measures at once is what makes the result striking.
The trial tested two separate dosing schedules of brelovitug against a delayed-treatment control group, a design that allows researchers to compare the drug against the natural course of the disease rather than against a placebo. The company has not yet published the full breakdown of results by dose, and the detailed data are expected to be presented at a medical conference and in a peer-reviewed publication in due course.
Hepatitis D affects millions of people worldwide, most of them in regions where hepatitis B is common, including parts of Central Asia, the Mediterranean, sub-Saharan Africa and the Amazon basin. In Pakistan, where hepatitis B and C are widespread, the disease is a significant but often under-recognised burden, and a treatment that works in a single weekly injection would be far easier to deliver than the complex regimens patients currently face.
What happens next will be decided by regulators. If the FDA accepts the application and the data hold up under peer review, brelovitug could become the first widely available targeted treatment for chronic hepatitis D, offering patients a realistic prospect of clearing the virus and halting the damage to their livers. For now, the second successful trial is the strongest signal yet that the drug works — and that a disease long regarded as untreatable may finally have a treatment.
