A once-daily pill beat placebo in two phase 3 vitiligo trials

Two phase 3 trials published in Nature Medicine report that a once-daily pill, povorcitinib, produced measurable facial repigmentation in adults with moderate-to-severe nonsegmental vitiligo, beating placebo in both studies [s1]. The result matters because there is still an unmet need for systemic repigmentation treatments for this common pigment-loss condition, and an oral option would be simpler than the creams and light therapy that dominate current care [s1]. The nuance worth holding onto from the start: the drug worked by a clear statistical margin, but the absolute response rate was modest — fewer than one in five treated patients hit the trials' main target at a year [s1].

What the trials did

STOP-V1 and STOP-V2 were parallel phase 3, randomised, double-blind, placebo-controlled trials of once-daily oral povorcitinib 30 mg, described as a highly selective JAK1 inhibitor, in adults with moderate-to-severe nonsegmental vitiligo [s1]. STOP-V1 enrolled 467 patients and STOP-V2 enrolled 449 [s1]. Both studies ran for 52 weeks, and both used the same primary endpoint: the proportion of participants achieving at least a 75% improvement in the facial Vitiligo Area Scoring Index, a measure known as F-VASI75, at week 52 [s1]. Running two identical trials in parallel is a deliberate design choice — a finding that replicates across both is far harder to dismiss than one that appears in a single study. The trials are registered as NCT06113445 and NCT06113471; the STOP-V1 registry record lists Incyte Corporation, the drug's maker, as the sponsor, with phase 3 status and an actual enrolment of 467 [s2].

What they found

In both trials, povorcitinib met the primary endpoint with a statistically significant and, in the authors' words, clinically meaningful separation from placebo [s1]. In STOP-V1, 18.9% of patients on povorcitinib reached F-VASI75 at week 52 versus 6.8% on placebo, an odds ratio of 3.1 (95% confidence interval 1.6–5.9; p=0.0003) [s1]. In STOP-V2, 18.9% on the drug reached the target versus 3.1% on placebo, an odds ratio of 7.5 (95% confidence interval 3.0–18.6; p<0.0001) [s1]. The treated response rate was essentially identical across the two studies, which is reassuring; the wider gap in STOP-V2 reflects a lower placebo response in that trial rather than a stronger drug effect.

It is worth being plain about what those numbers do and do not promise. F-VASI75 is a high bar — it asks for at least three-quarters of the facial pigment to return — and on the most favourable reading, roughly 81% of patients on povorcitinib did not clear it over a full year [s1]. Vitiligo also repigments slowly, and the face tends to respond better than the hands or feet, so a facial endpoint captures the drug at close to its best. These are real, replicated gains over placebo, but they are partial gains for a minority of those treated, not a reliable route to clear skin.

Safety

Across both trials, the share of patients with any treatment-emergent adverse event was similar between the povorcitinib and placebo groups — 68.7% and 66.7% on the drug in STOP-V1 and STOP-V2 respectively, against 63.7% and 62.7% on placebo [s1]. The most common events on povorcitinib were nasopharyngitis (11.2% and 11.3%, versus 9.8% and 11.1% on placebo), acne (10.7% and 10.8%, versus 3.0% and 2.2%) and upper respiratory tract infection (6.9% and 14.0%, versus 9.0% and 10.7%) [s1]. The acne signal stands out as clearly more frequent on the drug than on placebo [s1]. The authors report that serious events were generally single occurrences, and that the adverse effects specific to the Janus kinase inhibitor class — the blood-clot, infection and cardiovascular warnings that carry a boxed caution for oral JAK drugs — were absent or rare over the 52 weeks studied [s1].

What it means

The honest summary is narrow and specific: in two replicate year-long trials, a once-daily JAK1 inhibitor produced statistically convincing but modest facial repigmentation in adults with moderate-to-severe nonsegmental vitiligo, and was generally well tolerated over that period [s1]. That is a genuine addition for a condition with few systemic options, and the fact that the effect held across both studies strengthens the case [s1].

What these trials do not settle is just as important. Fifty-two weeks is long for a dermatology trial but short against the horizon over which someone might take a daily pill for a lifelong condition, so the durability of repigmentation, the risk of relapse if the drug is stopped, and the long-term safety profile of chronic JAK1 inhibition all remain open [s1]. The studies were sponsor-run, which is the expected first evidence for a new agent rather than an independent verdict [s2]. And because the endpoint and the body site both favour the drug, patients and clinicians should read the headline response rate as a ceiling for the face rather than a promise for the whole body. This is an early, replicated, promising data point — not yet a reason to expect dramatic results.