The first FDA-approved treatment for hepatitis D is an entry inhibitor that helps stop the virus from infecting new liver cells in people already living with hepatitis B.
Hepatitis D, also called hepatitis delta virus (HDV), is the most severe form of viral hepatitis, but it is not widely understood.
HDV can only infect people who already have hepatitis B. This means patients are managing two liver viruses at the same time. The co-infection can speed up liver damage and increase the risk of liver scarring, liver failure and death.
Globally, the WHO estimates that HDV affects nearly 5% of people with chronic hepatitis B. The WHO’s cancer agency also recently classified HDV as carcinogenic to humans.
The FDA has granted accelerated approval to Hepcludex (bulevirtide-gmod), marking the first FDA-approved treatment for adults with chronic HDV in the US.
This once-daily injection is an entry inhibitor, which works by blocking the virus from entering and infecting new liver cells. It is specifically indicated for patients without cirrhosis or those with compensated cirrhosis, a stage where the liver is scarred but still functioning.
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The FDA’s decision was based on two treatment markers: a significant reduction in viral levels, known as HDV RNA, in the blood and the return of alanine aminotransferase (ALT), a liver enzyme, to normal ranges.
Because elevated ALT typically indicates that the liver is inflamed or injured, achieving normal levels can be an important sign that liver inflammation is improving.
These results were primarily established in MYR301, a Phase III study that compared patients who began daily bulevirtide treatment immediately with a control group that waited about one year to start the medication.
After one year, 48% of patients in the bulevirtide group achieved a combined response, meeting both the viral reduction and ALT normalization targets, compared with 2% of those in the group waiting for treatment.
The study also monitored how many patients achieved undetectable viral levels, meaning HDV could no longer be detected by the study’s blood test. This figure increased steadily with continued use, starting at 20% after one year, rising to 36% after two years and reaching 50% by Week 144.
The Hepcludex label includes a boxed warning that stopping treatment may lead to severe acute worsening of hepatitis D and hepatitis B.
As the accelerated approval was based on viral reduction and liver enzyme normalization markers, Gilead must verify long-term clinical benefit in an ongoing confirmatory study. Continued FDA approval may depend on these data.
While bulevirtide is already available in Europe and other global markets, US patients now have access to the treatment. Gilead also offers resources through its Support Path program to help patients and healthcare providers understand coverage and financial options.
Related: Bepirovirsen Shows Promise in Phase III for Chronic Hepatitis B
Beyond this recent approval, clinical development continues for several other investigational HDV treatments.
Vir Biotechnology is testing a combination of tobevibart, an investigational antibody, and elebsiran, a gene-silencing therapy known as a small interfering RNA, in its Phase III ECLIPSE program. Following positive Phase II results that showed sustained viral suppression, the company expects initial Phase III data in late 2026, with more results expected in early 2027.
Meanwhile, Mirum Pharmaceuticals is developing brelovitug, an investigational monoclonal antibody, designed to target a viral protein involved in both hepatitis B and hepatitis D infection. In May 2026, Phase IIb data showed that brelovitug met study goals for both viral reduction and liver enzyme normalization within 24 weeks. Mirum expects key Phase III data in the second half of 2026, with a potential US regulatory submission in 2027.
FAQs
Why does hepatitis D only affect people with hepatitis B?
Hepatitis D only affects people who have hepatitis B because the hepatitis D virus depends on hepatitis B to complete its lifecycle. HDV uses the hepatitis B surface antigen, a protein produced during HBV infection, to form infectious virus particles. Without HBV infection, HDV cannot propagate or establish an ongoing infection in the body.
What does FDA accelerated approval mean?
Accelerated approval allows the FDA to approve certain drugs for serious conditions based on early markers that are reasonably likely to predict clinical benefit.
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