A phase 2a clinical trial of Urovant’s vibegron in irritable bowel syndrome (IBS) patients has missed its primary endpoint. The setback dents Urovant’s prospects in one indication but still leaves it set up to win approval in overactive bladder and be acquired by Sumitovant Biopharma.
Urovant has embarked on a multifront R&D campaign since buying small molecule beta-3 agonist vibegron from Merck in 2017. The drug performed no better than a generic control in a phase 3 trial in overactive bladder patients, but Urovant forged ahead, filing for FDA approval earlier this year in a bid to establish vibegron as a rival to Astellas’ beta-3 agonist Myrbetriq.
The prospects of Urovant eventually adding IBS to the list of conditions treated by vibegron took a hit after the market closed Tuesday, when the company revealed a phase 2a trial missed its primary endpoint.
Investigators randomized 222 female IBS patients to take vibegron or placebo orally for 12 weeks. At the end of that period, 40.9% of IBS with diarrhea patients who received vibegron experienced a 30% or more improvement in average worst abdominal pain. The figure for the placebo arm was 42.9%.
Vibegron beat placebo numerically, but not statistically, against a key secondary endpoint that looked at the proportion of Global Improvement Scale (GIS) responders. The drug failed to drive a significant improvement in the GIS response rate in patients with IBS with diarrhea, mixed IBS or the combined population.
Urovant is continuing to analyze the full data set, but the efficacy results shared so far offer scant encouragement that vibegron has a future in IBS. The trial also appears free of safety and tolerability red flags, though, sparing Urovant from news that could dent its prospects in other indications.
Work on those other indications is continuing. Having completed two phase 3 trials in overactive bladder patients, Urovant is running another phase 3 trial in men with overactive bladder and benign prostatic hyperplasia (BPH). Top-line results from the BPH phase 3 are due in the second half of next year.
Sumitovant saw enough promise in the asset to pay a near-100% premium to buy Urovant for $584 million ahead of the late December PDUFA date for vibegron. With that deal in place, Urovant’s stock only slipped slightly in response to the phase 2a results.