A phase 3 trial of Priovant Therapeutics’ inflammatory disease prospect brepocitinib has hit its primary endpoint, setting the Roivant-backed biotech up to seek FDA approval for the TYK2/JAK1 inhibitor next year.
Roivant created Priovant in 2022 after striking a deal with Pfizer for brepocitinib and the TYK2 inhibitor ropsacitinib. Brepocitinib moved into phase 3 around the same time, with researchers picking the rare muscle inflammation and skin rash condition dermatomyositis as the lead indication. The drug candidate hit a setback in 2023, when it failed a midphase lupus trial, but has bounced back with a pivotal victory.
Priovant compared two doses of brepocitinib to placebo in 241 people with dermatomyositis. After 52 weeks of once-daily oral dosing, the company saw a mean Total Improvement Score (TIS) of 46.5 on the high dose compared to 31.2 for placebo, achieving the primary endpoint of the trial.
More than two-thirds of patients on the high dose had at least a moderate response to the molecule, as defined by a TIS of 40 or greater. Almost half had a TIS of 60 or greater, which Priovant classed as a major response. Cutaneous clinical remission was seen in 44% of patients on the high dose compared to 21% of people on placebo. Priovant said brepocitinib beat placebo on all nine key secondary endpoints.
Brepocitinib improved outcomes over placebo while enabling more people to come off steroids. About three-quarters of participants were receiving background steroids at the start of the trial. By Week 52, 42% of patients on the high dose had come off steroids compared to 23% of people on placebo.
Talking at a Morgan Stanley event this month, Roivant CEO Matthew Gline said all participants needed to taper steroids to “mitigate some of the placebo risk and give us a little bit more of a chance to separate.” At 31.2, the placebo TIS fell in the middle of the 20 to high 30s range that Gline said was seen in other trials.
Priovant saw a consistent dose response between the 15-mg and 30-mg arms. The safety profile of the high dose was consistent with that seen in earlier brepocitinib studies. And, with adverse events of special interest such as malignancy, cardiovascular events and thromboembolic events being no more common on the high dose than on placebo, the biotech has chosen 30 mg as the optimal dose.
Management plans to file for approval of brepocitinib in dermatomyositis in the first half of next year. The target positions Priovant to challenge Pfizer’s Octagam, an intravenous immunoglobulin that the FDA approved in dermatomyositis in 2021. Argenx is running a phase 2/3 trial of its FcRn drug Vyvgart Hytrulo in dermatomyositis and other forms of idiopathic inflammatory myopathy.
Gline said that argenx is “maybe 18 months behind us or something like that.” The lead could give Priovant a window in which to establish its drug as a go-to treatment option for the 40,000 and 70,000 people that Gline estimates have the condition in the U.S. Gline said existing and potential future drugs cost between $250,000 and $500,000 a year, providing bookends for the pricing of brepocitinib.
Dermatomyositis is the first of a set of potential indications for brepocitinib. Priovant is running a phase 3 trial in noninfectious uveitis and a midphase study in cutaneous sarcoidosis. The biotech began the phase 3 trial one year ago.