Vir Biotechnology is targeting a mid-2027 regulatory submission for its monthly chronic hepatitis delta regimen, with head-to-head data against Gilead’s Hepcludex expected next quarter.
Vir’s hepatitis delta combo tamps down virus as Gilead showdown looms
Vir Biotechnology is touting the potential curative value of its experimental chronic hepatitis delta combination after the regimen scored in a late-stage study, with close to half of patients achieving undetectable rates of the virus and normalized liver enzyme levels.
The biotech’s stock climbed 15% Monday morning following the announcement, rising from $12.21 at Friday close to $13.99 per share at time of publication.
The Phase 3 trial, dubbed Eclipse 1, enrolled 124 patients with chronic hepatitis delta (CHD)—a severe and progressive viral liver infection. The open-label study randomized patients to receive monthly subcutaneous injections of the experimental siRNA therapy elebsiran and investigational monoclonal antibody tobevibart either immediately or delayed by three months, with the delayed group acting as a control.
Eclipse 1 hit its main goal, with 44% of patients who received elebsiran and tobevibart right away achieving undetectable rates of hepatitis delta virus (HDV) RNA and normal levels of the liver enzyme ALT at week 48. That’s compared to a 0% response rate in the delayed treatment group at week 12, according to Vir’s late-breaker presented yesterday at the American Association for the Study of Liver Diseases in Denver.
Safety was the study’s other primary endpoint, with Vir finding the regimen to be “well-tolerated with a favorable safety profile,” according to the company. One grade 3 treatment-related adverse event (TRAE) occurred when a patient experienced neutropenia, or low numbers of neutrophils in the blood; this safety event resolved in 15 days. No treatment discontinuations were recorded, and the most common TRAE was flu-like symptoms.
Breaking the data down, undetectable HDV RNA occurred across patients regardless of the status of cirrhosis, or severe liver scarring, with an 85% response rate for 46 cirrhotic patients and 73% for 37 non-cirrhotic patients—meeting the study’s secondary endpoint.
Now, Vir is focusing on two other pivotal trials of elebsiran and tobevibart in CHD—ECLIPSE 2 and ECLIPSE 3—with data from all three studies expected to support a mid-2027 FDA regulatory submission. Vir has out-licensed potential commercialization rights for the combo in Europe, Australia and New Zealand to Norgine Pharma. The deal, struck in December 2025, earned Vir €55 million ($61.6 million) upfront and up to €495 million ($554.5 million) in milestones.
H.C. Wainwright analysts viewed the ECLIPSE 1 data as “meaningful clinical de-risking” ahead of the two upcoming topline readouts , which are expected in the first quarter of next year. The ECLIPSE 2 trial is evaluating patients switching from Gilead’s antiviral Hepcludex (bulevirtide)—the first and only targeted antiviral to ever receive approval in CHD. ECLIPSE 3 is pitting Vir’s investigational duo against Hepcludex, which secured accelerated approval in May earlier this year.
In addition to facing off with Gilead, Vir is also revving up to compete with Mirum Pharmaceuticals, which in September reported a Phase 3 win for its investigational monoclonal antibody brelovitug in CHD and expects to file an approval application with the FDA in the first half of next year.
“To our knowledge, no other late-stage chronic hepatitis delta program is expected to include comparable bulevirtide switch and head-to-head data as part of its regulatory package,” Vir CEO Marianne De Backer said on a Monday investor call tied to the data release.
At the same time, Vir also posted expanded mid-phase data from the SOLSTICE trial evaluating monthly subcutaneous administration of elebsiran and tobevibart for CHD. All of the 28 patients who received 96 weeks of treatment achieved undetectable virus levels.
In an exploratory analysis of the first 10 patients who discontinued treatment after prolonged viral suppression, Vir said patients sustained viral response for 12 to 48 weeks, as of the data cutoff.
“Our message today is simple. We believe these data support the potential for elebsiran and tobevibart to deliver a best-in-disease profile and importantly, open the door to something that has not been possible for the majority of patients with hepatitis data today—the potential for curative treatment,” De Backer said.
“If sustained off-treatment viral control can ultimately be confirmed, we believe it has the potential to fundamentally change the paradigm from managing a lifelong chronic infection to a disease that could potentially be cured,” the CEO added.
