Vir Biotechnology Hepatitis Delta Treatment Meets Phase III Goals, With 79% Virus-Free at Week 48

Key Points

• Vir’s combination treatment met the Phase III trial’s primary and key secondary endpoints: at week 48, 44% of treated patients had both undetectable hepatitis delta virus and normalized ALT, while 79% had undetectable virus. The delayed-treatment comparison group had 0% on these measures at week 12, a different assessment time.
• All treated patients completed 48 weeks without discontinuations or dose interruptions; the company reported no serious adverse events and one treatment-related grade 3 event. In a small exploratory group that stopped treatment after prolonged viral suppression, no rebounds or ALT flares were seen, but Vir cautioned that longer follow-up is needed.
• Vir expects results from the ECLIPSE 2 and 3 trials in Q1 2027 and plans to use data from all three ECLIPSE studies to support a global regulatory package, including a planned U.S. FDA submission in mid-2027.

Vir Biotechnology NASDAQ: VIR said its combination treatment for chronic hepatitis delta met the primary and key secondary endpoints in the pivotal Phase III ECLIPSE 1 trial, with 79% of treated patients achieving undetectable virus at 48 weeks.

The company also presented longer-term Phase II data and an exploratory analysis suggesting that some patients maintained a viral response after stopping the regimen. President and CEO Marianne De Backer cautioned that the discontinuation findings involve a small group and require longer follow-up.

Phase III Results

ECLIPSE 1 enrolled 124 patients randomized 2-to-1 to receive elebsiran and tobevibart or delayed treatment. The delayed-treatment group remained untreated for 12 weeks before crossing over to the combination.

The primary endpoint required both undetectable hepatitis delta virus RNA and normalization of ALT, a measure associated with liver injury. At week 48, 44% of patients receiving the combination met that endpoint, compared with 0% of the delayed-treatment group at week 12. The comparison therefore used different assessment times for the two groups.

For the key secondary endpoint, 79% of treated patients had undetectable virus at week 48, compared with 0% of the delayed-treatment group at week 12. De Backer said every treated patient achieved a virologic response, defined as undetectable virus or at least a two-log reduction in viral RNA.

Approximately 55% of trial participants had compensated cirrhosis at enrollment. At week 48, about 85% of patients with compensated cirrhosis had undetectable virus, compared with 73% of those without cirrhosis. De Backer said the difference was not necessarily statistically significant.

All treated patients completed 48 weeks of therapy without discontinuations or dose interruptions, according to De Backer. She said there were no serious adverse events and one treatment-related grade three event: a decrease in neutrophil count that resolved within 15 days without interrupting treatment. Flu-like symptoms were among the more common adverse events, predominantly after the first dose.

Longer-Term and Off-Treatment Data

In the Phase II SOLSTICE trial, all 28 patients who remained on combination treatment through week 96 had undetectable virus, De Backer said. ALT normalization was reported in 53% of all patients at that point.

An exploratory analysis examined the first 10 patients who stopped the combination after maintaining undetectable virus for at least 96 weeks. All remained on background hepatitis B therapy and had sustained virologic responses for at least 12 weeks after stopping the combination. Seven had reached 24 weeks of follow-up, and one had reached 48 weeks. Vir reported no viral rebounds or ALT flares in the group.

“These finite treatment data represent an initial exploratory analysis in a small number of patients with varying durations of follow-up,” De Backer said. She added that more patients and longer follow-up are needed to assess the durability of response and the regimen’s potential as a finite or curative treatment.

Regulatory Plans

Vir expects top-line results from its fully enrolled ECLIPSE 2 and ECLIPSE 3 trials in the first quarter of 2027. ECLIPSE 2 is studying patients switching from bulevirtide, while ECLIPSE 3 is comparing the combination head-to-head with bulevirtide.

De Backer said data from all three ECLIPSE studies are expected to support a global regulatory package, including a planned U.S. Food and Drug Administration submission in mid-2027. The company is also planning to collect additional treatment-discontinuation data from SOLSTICE and the ECLIPSE program.

About Vir Biotechnology (NASDAQ:VIR)

Vir Biotechnology is a clinical-stage biopharmaceutical company focused on developing treatments for infectious diseases and cancer. Its research draws on immunology and includes approaches such as monoclonal antibodies, small-interfering RNA therapies and T-cell-based treatments.

The company's pipeline has included programs targeting chronic hepatitis B and influenza, as well as investigational cancer therapies. Vir has also pursued research and development collaborations to advance its programs.

Historically, Vir partnered with GlaxoSmithKline to develop sotrovimab, an antibody treatment for COVID-19.

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