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JAK1 Pill Regrew Facial Pigment in Only 1 in 5 Adults With Vitiligo

Two year-long trials found a daily pill helped some adults with vitiligo regain facial pigment, but most saw no major change.

By Dr. Josh Axe · November 5, 2026 · 1 source · Understand

Photo: Pexels

A once-daily pill called povorcitinib helped facial skin regrow lost pigment in about 1 in 5 adults with vitiligo, an autoimmune skin condition, according to two phase 3 trials published November 2, 2026, in Nature Medicine.

18.9% vs 6.8%repigmented

18.9% vs 3.1%repigmented

916adults, 52 weeks

Two parallel phase 3 trials, STOP-V1 and STOP-V2, enrolled 467 and 449 adults with moderate-to-severe nonsegmental vitiligo and followed them for 52 weeks on a once-daily 30 mg dose of povorcitinib, an oral pill that selectively blocks JAK1, a protein immune cells use to send attack signals, compared with a placebo pill. The trials measured facial repigmentation using a standard scoring tool for vitiligo's visible skin patches, with success defined as regaining at least 75% of lost facial pigment. In STOP-V1, 18.9% of patients on the drug reached that mark versus 6.8% on placebo. In STOP-V2, 18.9% reached it versus 3.1% on placebo.

Side effects were similar in both groups: any treatment-emergent adverse event (any side effect reported during treatment) occurred in 68.7% of drug-treated patients versus 63.7% on placebo in STOP-V1, and 66.7% versus 62.7% in STOP-V2. The most common side effects with the drug were nasopharyngitis (cold-like symptoms, 11.2-11.3% versus 9.8-11.1% on placebo), acne (10.7-10.8% versus 2.2-3.0% on placebo) and upper respiratory infections (6.9-14.0% versus 9.0-10.7% on placebo). Serious side effects were rare and mostly isolated events, and the authors reported that side effects specific to JAK inhibitors as a drug class were absent or rare.

Vitiligo develops when the immune system attacks melanocytes, the cells that produce skin pigment, leaving patches of depigmented skin. JAK1 is one of the signaling proteins immune cells use to coordinate that attack, and blocking it is thought to quiet the immune assault enough for some pigment-producing cells to recover and repopulate the skin.

Facial Repigmentation at 52 Weeks: Drug vs Placebo

Nature Medicine, 2026, Ezzedine et al.

Most patients, including a majority on the active drug, did not reach the 75% facial repigmentation threshold within the year studied, and the trials did not report what happens to regained pigment after people stop taking the pill.

Dr. Axe’s Take

One in five regrowing most of their facial pigment in a year is a real result, but four in five did not get there, and acne, a side effect, hit roughly 1 in 10 on the drug versus 1 in 30 to 45 on placebo. This pill quiets the immune attack on pigment cells; it doesn't address what started that attack. In my view, that's the deeper question, and I'd look at it through gut health and overall immune balance. Watch for new acne, and ask what happens to the color after stopping. If you're on povorcitinib, don't change it on your own; any change happens with your prescriber.

— Dr. Axe

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Study summary

Who: 916 adults with moderate-to-severe nonsegmental vitiligo (STOP-V1: 467; STOP-V2: 449).
Design: Two phase 3, randomized, placebo-controlled trials, 52 weeks.
Dose: Povorcitinib 30 mg once daily, oral, versus placebo.
Primary result: 75% facial repigmentation: 18.9% vs 6.8% (STOP-V1) and 18.9% vs 3.1% (STOP-V2) on drug vs placebo.
Secondary: Any adverse event: 68.7% on povorcitinib vs 63.7% on placebo (STOP-V1), 66.7% vs 62.7% on placebo (STOP-V2); acne 10.7-10.8% on povorcitinib vs 2.2-3.0% on placebo.
Funding / conflicts: Funder listed in the journal record: Incyte Corporation. Competing interests: Authors consult for AbbVie, Pfizer, Sanofi, Bristol Myers Squibb, Johnson & Johnson and Boehringer Ingelheim; authors own shares; authors serve on advisory boards for AbbVie.
Date: Nov 2, 2026