Vir's hepatitis delta combination hits Phase 3 goal as 79% reach undetectable virus

Vir Biotechnology said its monthly two-drug combination for chronic hepatitis delta met every endpoint in its pivotal Phase 3 trial, with 44% of treated patients reaching undetectable virus and normal liver enzyme levels after 48 weeks, against none in a delayed-treatment group. The company announced the topline ECLIPSE 1 results on November 8 after presenting them at the liver specialists' annual meeting in Denver.

The trial enrolled 124 adults with chronic hepatitis delta, randomised two-to-one to immediate treatment with elebsiran 200 mg and tobevibart 300 mg every four weeks, or to treatment delayed by 12 weeks. Seventy-nine percent of treated patients had no detectable hepatitis delta virus at week 48, the trial's key secondary measure, and every treated patient had a virologic response by week 24. Undetectable virus was seen in 85% of patients with cirrhosis and 73% of those without. The regimen was generally well tolerated; one patient had a severe treatment-related fall in neutrophil count that resolved in 15 days, and nobody stopped treatment because of side effects.

Chronic hepatitis delta is the most severe form of chronic viral hepatitis, affecting an estimated 12 million people worldwide, and it strikes only people already infected with hepatitis B. Until May 2026 there was no approved treatment in the United States specifically for it, when the Food and Drug Administration gave accelerated approval to bulevirtide, a daily injection; in its pivotal trial 20% of patients reached undetectable virus at week 48. Vir's combination works differently: elebsiran is an RNA therapy that cuts production of the hepatitis B surface protein the delta virus needs, while tobevibart is an antibody that blocks the virus entering liver cells. The FDA has granted the combination breakthrough therapy and fast track status.

The figures come from Vir's own release and the conference presentation, and the specialist publication HCPLive, working from the same release and abstract, reports the same numbers: 44% on the primary endpoint, 79% undetectable at week 48, and 124 patients enrolled. The longer-term Phase 2 numbers also match the company's second release: all 28 patients who completed 96 weeks of combination treatment had undetectable virus, and all 10 who then stopped treatment stayed virus-free for at least 12 weeks, seven of them for 24 weeks and one for 48. Those are small, early numbers from an exploratory analysis, and the Phase 3 comparison was open-label, pitting 48 weeks of treatment against 12 weeks without it rather than against an existing drug.

The results set up a United States filing in mid-2027, once data from two further Phase 3 trials arrive in the first quarter of 2027: ECLIPSE 2, in patients who did not respond to bulevirtide, and ECLIPSE 3, a head-to-head test against it. Vir has already licensed European, Australian and New Zealand rights to Norgine. If regulators accept the data, patients would get a once-monthly pair of injections they can take at home, rather than a daily one.

The finite-treatment hint is the part that could matter most, and it is also the least proven: ten patients stopping treatment without the virus returning raises the possibility of a course of therapy with an end, rather than treatment for life, but the company itself calls the analysis exploratory. Vir will discuss both sets of results on a call on Monday at 8:30 a.m. ET.