Vir Biotechnology’s phase 3 trial in chronic hepatitis delta (CHD) has hit its primary endpoint, giving the biopharma the first piece of the package it needs to file for FDA approval next year.
San Francisco-based Vir ran the pivotal Eclipse 1 trial to evaluate monthly subcutaneous administration of elebsiran and tobevibart in adults with CHD. Gilead won FDA approval for Hepcludex in CHD in May, while Mirum Pharmaceuticals reported a phase 3 win for its CHD contender brelovitug in September, setting the stage for a three-way fight for the nascent market.
The Eclipse 1 readout suggests Vir has a competitive drug candidate. Investigators enrolled 124 patients, two-thirds of whom started receiving the drug combination immediately and one-third of whom began treatment at Week 12.
At Week 48, 44% of patients who started treatment immediately had undetectable levels of hepatitis delta virus (HDV) RNA and normal levels of ALT, a liver enzyme, hitting the trial's primary endpoint. No patients in the delayed-treatment arm met the primary endpoint at Week 12.
Vir dug into the success in secondary endpoints. At Week 48, 79% of people in the immediate-treatment arm had undetectable virus levels and 53% had normal ALT levels. Everyone in the immediate-treatment group had either undetectable virus or at least a 2-log10 reduction in levels. The only response in the delayed-treatment group at Week 12 was a 5% rate of ALT normalization.
Cross-trial comparisons are complicated by differences between the studies—Leerink analysts have said Mirum’s enrollment of patients with severe disease is “a key point of differentiation”—but the available data suggest Vir’s asset is competitive. After 48 weeks on Hepcludex, 20% of patients had undetectable HDV RNA and 56% had (PDF) normal ALT levels.
In the wake of the readout, Vir shares rose 17% to $14.25 in premarket trading Monday from a Friday closing price of $21.21.
Vir shared the data alongside phase 2 results showing that all 28 patients who completed 96 weeks of combination therapy had undetectable virus. In an exploratory analysis, 10 patients who stopped treatment continued to have undetectable virus levels after 12 to 48 weeks of follow-up. The analysis “suggests curative potential,” Vir said.
The biotech continues to test the combination in two other pivotal trials, with data expected in the first quarter of next year. Vir plans to use data from all three pivotal trials to seek approval in the U.S. in mid-2027. One of the phase 3 trials is comparing Vir’s combination to Gilead’s Hepcludex.