Roivant and Priovant's drug for rare skin, muscle disease shows promise in trial

By Kamal Choudhury

Sept 17 (Reuters) - Roivant ROIV.O and partner Priovant Therapeutics said on Wednesday that their experimental drug for a rare disease affecting skin and muscles has shown promising results in a late-stage clinical trial.

Shares of Roivant were up over 13% at $16.05, set for an all-time closing high if gains hold.

The drug, brepocitinib, was being tested for dermatomyositis, a condition that causes painful skin rashes and progressive muscle weakness. Left untreated, the disease can severely reduce a patient's quality of life.

The companies said the drug showed improvement in both skin and muscle symptoms, reducing or stopping the need for steroids that are commonly used, but can cause long-term side effects.

In the trial, patients receiving a daily 30 mg oral dose of brepocitinib achieved a mean total improvement score of 46.5 after 52 weeks, compared with 31.2 for placebo. The difference was statistically significant, with benefits seen as early as week four, companies said.

Drug development scene for dermatomyositis has been a "bit of a graveyard," said Ben Zimmer, chief executive of Priovant. Roivant CEO Matt Gline added that the brepocitinib trial marked the "first successful registrational trial for a targeted therapy" in the disease.

J.P.Morgan analyst Brian Cheng said the depth and speed of response could position brepocitinib as the "new gold standard" in treating dermatomyositis.

Cheng estimates non–risk-adjusted peak sales of $1.6 billion from dermatomyositis alone by 2037.

Pfizer PFE.N in 2021 licensed brepocitinib to Priovant Therapeutics, a joint company created with Roivant.

The companies plan to file for U.S. approval in the first half of 2026.

According to the National Institutes of Health, dermatomyositis affects fewer than 5,000 people in the U.S.

Octapharma's Octagam 10% is the only FDA-approved treatment for the condition.