Vir's Hepatitis Delta Treatment Clears Pivotal Phase 3 Trial as 79% of Patients Reach Undetectable Virus

SAN FRANCISCO — Vir Biotechnology announced on Sunday, 8 November 2026, that its pivotal Phase 3 ECLIPSE 1 trial of the investigational combination elebsiran and tobevibart met its primary endpoint in adults with chronic hepatitis delta, a severe liver disease with few treatment options. According to the company, 44 percent of treated patients achieved both undetectable virus and normal liver enzyme levels at Week 48, compared with none in the delayed-treatment group, and 79 percent reached undetectable virus. The results were presented at AASLD The Liver Meeting 2026 in Denver, Colorado, and the company said it plans to submit the treatment to the United States Food and Drug Administration (FDA) in mid-2027.

Illustration: A laboratory scientist examines a stylised image of the liver and virus particles, representing hepatitis delta research.

What Happened

ECLIPSE 1 enrolled 124 patients, randomised 2:1 to monthly subcutaneous elebsiran and tobevibart or delayed treatment, with the delayed group starting therapy at Week 12. Its primary endpoint was undetectable virus — hepatitis delta virus RNA target not detected (HDV RNA TND) — together with normalisation of alanine aminotransferase (ALT), a liver enzyme that rises with liver inflammation or damage.

The headline result was a 44 percent response rate on that combined endpoint at Week 48, against 0 percent in the delayed-treatment group at Week 12 (p<0.0001). The key secondary endpoint was also met: 79 percent of treated patients had undetectable virus at Week 48, versus 0 percent in the delayed group. A virologic response was recorded in 100 percent of treated patients, against 0 percent in the delayed group.

The benefit held with and without cirrhosis, the scarring that marks advanced liver disease: undetectable virus was achieved in 85 percent of patients with cirrhosis (46 patients) and 73 percent of those without it (37 patients). On safety, the company said the regimen was well tolerated: one Grade 3 treatment-related adverse event — a fall in neutrophil count that resolved in 15 days — and no treatment interruptions or discontinuations. Most events were mild to moderate and transient; the most common was flu-like symptoms, mainly after the first dose and mostly resolving within 24 to 48 hours.

Nancy Reau of Rush University Medical Center said the results showed the combination "could offer a meaningful new treatment option for people living with this serious, progressive disease." Vir Biotechnology also announced expanded Phase 2 SOLSTICE data: all 28 patients who completed 96 weeks reached undetectable virus, and 89 percent with paired liver stiffness measurements (24 of 27) had improved or stable liver stiffness at Week 96.

SOLSTICE also included a small, exploratory analysis of stopping treatment. Ten patients, seven with cirrhosis, chose to stop after at least 96 weeks of undetectable virus and were followed for 12 to 48 weeks. All 10 had a sustained viral response 12 weeks after their last dose, with no viral rebound or ALT flares. But the company stressed that these preliminary, interim findings from the first 10 eligible patients "should not be interpreted as a complete assessment of the safety or efficacy of the investigational regimen or as establishing a sustained treatment-free response or cure." A cure, or safe stopping, therefore remains unproven.

Illustration: Researchers review clinical trial data and an investigational medicine vial in a modern pharmaceutical laboratory.

Background

Chronic hepatitis delta is a liver infection caused by the hepatitis delta virus (HDV) — a different virus from hepatitis B, although the two are closely linked. HDV is a satellite virus that cannot replicate without the hepatitis B virus (HBV). According to the World Health Organization (WHO), chronic hepatitis delta occurs only in people living with hepatitis B, and it affects nearly 5 percent of people with chronic hepatitis B worldwide — an estimated 12 million people. Hepatitis B vaccination is therefore the most effective way to prevent hepatitis delta.

That dependence does not make hepatitis delta milder. The WHO calls it the most severe form of chronic viral hepatitis, because it progresses more rapidly towards liver-related death and liver cancer than hepatitis B alone. Recently classified as carcinogenic by the International Agency for Research on Cancer, it progresses rapidly to cirrhosis, liver failure and liver-related death. People with detectable virus face a higher risk of liver-related events — including cirrhosis, liver cancer, transplantation and death — than patients whose virus is undetectable, which is why the trial focused on driving the virus to undetectable levels rather than merely reducing it.

Until recently, treatment options were extremely limited. The established option, bulevirtide (Hepcludex), is an entry inhibitor that blocks both viruses from entering liver cells. Authorised in Europe in 2020 (conditional) and 2023 (full), it received FDA accelerated approval on 22 May 2026 — the first FDA-approved drug specifically for chronic hepatitis delta, for adults without cirrhosis or with compensated cirrhosis. Before that, the only United States treatment was pegylated interferon alfa, an older therapy poorly tolerated by many patients. Bulevirtide is a daily injection, approved on virus reduction and ALT normalisation.

The new combination attacks the virus's life cycle at two points at once. Elebsiran is an investigational small interfering RNA (siRNA) that targets hepatitis B; it is designed to degrade hepatitis B virus RNA and limit production of hepatitis B surface antigen, the protein hepatitis delta needs to replicate. Tobevibart is an investigational broadly neutralising monoclonal antibody against that antigen, designed to block both viruses from entering liver cells. The two drugs are given as separate, sequential subcutaneous injections once a month, at home or by a healthcare provider, according to the company. ECLIPSE 1 is one of three ECLIPSE trials: ECLIPSE 2 tests switching to the combination after bulevirtide failure, and ECLIPSE 3 is head-to-head against bulevirtide. Regulators have granted expedited designations (FDA Breakthrough Therapy and Fast Track; EMA PRIME and orphan drug status), which speed review but are not approvals.

Why It Matters

The results matter first because of the size of the gap they address. Chronic hepatitis delta is rare compared with hepatitis B, but it is the most aggressive form of chronic viral hepatitis, and the people who have it have had very few options. A once-monthly treatment that drove the virus to undetectable levels in nearly four out of five patients in a randomised Phase 3 trial — including most patients who already had cirrhosis — would, if the findings hold up, substantially change what patients and doctors can expect. Benefit with and without cirrhosis matters because advanced disease is common by the time hepatitis delta is diagnosed.

The results also matter because of how the treatment is given. Bulevirtide requires a daily injection; a monthly regimen given at home or by a healthcare provider could be easier to stay on long term, and staying on treatment matters, because stopping can allow the virus to return. But the comparison with bulevirtide is untested: the head-to-head ECLIPSE 3 trial is still under way, with results expected in the first quarter of 2027. Until then, the combination can only be said to have performed strongly against delayed treatment.

There are also reasons for caution. The results are company topline figures from a press release and a conference presentation — not yet peer-reviewed, and independent experts have not yet seen the full data. The 124-patient trial was small, and the delayed-treatment group went untreated for only 12 weeks. The most eye-catching secondary finding — the exploratory SOLSTICE suggestion that some patients might one day stop treatment — comes from just 10 patients, and the company has warned against reading it as evidence of a cure. The treatment is investigational and unapproved anywhere; the planned mid-2027 FDA submission only starts a review that could take many more months and could still end in rejection or a request for more data. The field is moving fast: bulevirtide only became the first FDA-approved hepatitis delta treatment in May 2026, and Mirum Pharmaceuticals' brelovitug reported positive Phase 3 results in September 2026.

Illustration: A doctor talks with a smiling patient in a bright, sunlit clinic room, representing hope for people living with chronic hepatitis delta.

What Happens Next

The immediate next step is the remaining ECLIPSE data. Vir Biotechnology said data from the ECLIPSE 2 and ECLIPSE 3 pivotal trials are expected in the first quarter of 2027. ECLIPSE 2 will show whether patients who did not achieve viral suppression on bulevirtide can benefit from switching to the new combination, while ECLIPSE 3 will provide the first direct comparison with bulevirtide — the result doctors will most want to see before deciding where the new regimen fits. Data from all three trials will support a global filing package, with a United States FDA submission planned for mid-2027.

The company was scheduled to discuss the results on a conference call at 8:30 a.m. Eastern Time on Monday, 9 November 2026, with a live webcast on its investor relations website, archived for 30 days. Listeners will want more detail than a topline release provides — how long suppression lasted, how results varied across subgroups, and what the company will tell regulators about the SOLSTICE finite-treatment data. SOLSTICE follow-up continues.

For patients and their families, the message for now is one of cautious optimism. No new treatment is available as a result of this announcement, and elebsiran and tobevibart cannot be prescribed outside of a clinical trial. People living with chronic hepatitis delta should speak with their own liver specialist about what the results mean, the current approved options and whether any ongoing trial might be relevant. The next milestones are the ECLIPSE 2 and ECLIPSE 3 readouts in early 2027 and the planned FDA filing in mid-2027.

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FAQ

What is hepatitis delta, and how is it different from hepatitis B?

Hepatitis delta is a liver infection caused by the hepatitis delta virus (HDV), a different virus from the one that causes hepatitis B. HDV is a satellite virus that can only replicate in people who already have hepatitis B — the WHO says chronic hepatitis delta occurs only in people living with hepatitis B. Hepatitis delta sits on top of hepatitis B, making the disease more severe and faster-moving. Earlier blog stories about a hepatitis B treatment approval and a hepatitis B vaccine trial concerned that different virus, not hepatitis delta.

What did the ECLIPSE 1 trial actually show?

According to Vir Biotechnology's topline results, announced on 8 November 2026, 44 percent of treated patients achieved both undetectable virus and normal ALT levels at Week 48, compared with 0 percent in the delayed-treatment group at Week 12. The key secondary result was that 79 percent of treated patients reached undetectable virus at Week 48, versus 0 percent in the delayed-treatment group, and a virologic response was recorded in 100 percent of treated patients. These are company-reported topline results that have not yet been peer-reviewed.

Is elebsiran and tobevibart approved, and when could it become available?

No. Elebsiran and tobevibart are investigational drugs that are not approved anywhere yet. Vir Biotechnology expects ECLIPSE 2 and ECLIPSE 3 data in the first quarter of 2027 and plans an FDA submission in mid-2027. Review typically takes many months and approval is not guaranteed, so availability before 2028 is unlikely — and only if regulators are satisfied by the full data.

How safe was the treatment in the trial?

According to the company, the regimen was well tolerated in ECLIPSE 1. There was one Grade 3 treatment-related adverse event — a decrease in neutrophil count that resolved in 15 days — and no treatment interruptions or discontinuations. Most events were mild to moderate and transient; the most common was flu-like symptoms, mainly after the first dose and mostly resolving within 24 to 48 hours. In the longer-running SOLSTICE Phase 2 trial, adverse events were mild to moderate, with no drug-related discontinuations or serious adverse events. Full safety data are not yet published.

Could patients one day stop taking the treatment?

That is an open question, and the evidence so far is very limited. In an exploratory SOLSTICE analysis, 10 patients who had maintained undetectable virus for at least 96 weeks stopped treatment, and all 10 still had a sustained viral response 12 weeks later, with no viral rebound or ALT flares during 12 to 48 weeks of follow-up. But Vir Biotechnology stressed that these are preliminary, interim findings from a small, self-selected group with incomplete follow-up, and that they should not be read as establishing a cure or a sustained treatment-free response. Longer follow-up in more patients is needed before doctors can say whether finite treatment is possible.

Sources

• Vir Biotechnology, "Vir Biotechnology Announces Primary Endpoint Met in Pivotal Phase 3 ECLIPSE 1 Trial for Elebsiran and Tobevibart in Chronic Hepatitis Delta," Business Wire, 8 November 2026.
• Vir Biotechnology, "Vir Biotechnology Announces Expanded Phase 2 SOLSTICE Data for Elebsiran and Tobevibart in Chronic Hepatitis Delta, Showing Deep and Sustained Viral Suppression, and Exploratory Finite Treatment Data," Business Wire, 8 November 2026.
• World Health Organization, "Hepatitis D" fact sheet, who.int (accessed 9 November 2026).
• The Lancet Microbe, "Bulevirtide approved by FDA for chronic hepatitis D," 2026.
• Morningstar, "Vir Biotechnology Announces Primary Endpoint Met in Pivotal Phase 3 ECLIPSE 1 Trial for Elebsiran and Tobevibart in Chronic Hepatitis Delta" (Business Wire syndication), 8 November 2026.
• Gastroenterology & Hepatology, "Update on Treatment for Hepatitis Delta," September 2026.

Disclaimer: This article is for general information only and is not medical advice. It summarises company-reported trial results and public health information, and it is not a substitute for advice from a qualified healthcare professional. If you have questions about hepatitis delta or its treatment, please speak with your doctor or liver specialist.