Mirum's hepatitis delta drug cuts viral levels in late-stage trial

Mirum Pharmaceuticals (MIRM) said that its experimental treatment for hepatitis delta reduced levels of the virus in patients, meeting the primary goal of a late-stage study.

The drug, brelovitug, is a monoclonal antibody that binds to the hepatitis B surface antigen, a protein found on the surface of the virus. Mirum was testing it in chronic hepatitis delta, a liver infection that affects people already infected with hepatitis B. The company estimates the disease affects about 230,000 people in the US and Europe. It can cause severe symptoms, leading to liver damage and, in some cases, death.

At 24 weeks, 56 per cent of patients given a 300mg dose of brelovitug and 45 per cent of those given 900mg showed reduced hepatitis D virus levels and normal liver enzyme levels. No patient in the delayed-treatment group did so, the company said. Mirum said the drug was well tolerated across dose groups, with a safety profile consistent with previously reported data.

The only treatment currently approved by the US Food and Drug Administration for the condition is Hepcludex, sold by Gilead Sciences (GILD). Lisa Walter, an analyst at RBC Capital Markets, said brelovitug "has a better benefit/risk profile" and that the results position it as the best-in-class option. Mirum expects the drug to generate peak sales of at least $1bn.

Full results will be presented at an upcoming medical congress. The company expects to submit a marketing application to the FDA in the first half of 2027.