An alopecia shot's hair gains held for months in a small follow-up

In Short. In a small early trial of a shot for an immune-driven kind of hair loss, most of the few people who had regrown hair by the end of treatment still had it months after stopping. The group was tiny and the trial's main test narrowly came up short, so only a larger trial can show whether the gain lasts.

ALOPECIA AREATA is an autoimmune disease, one in which the immune system attacks hair follicles. Doctors score the damage with the Severity of Alopecia Tool, or SALT, a number for the share of the scalp without hair. A score of 20 or less means at least 80% of the scalp has hair. One treatment idea is to enlist regulatory T cells, immune cells that calm other immune cells. A natural signal called interleukin-2, or IL-2, makes them multiply, and a drug can deliver it.

Researchers test such a drug against a placebo, a dummy injection. Patients are randomized, meaning assigned by chance, and double-blind, meaning neither they nor their doctors know who got which. A trial built this way is placebo-controlled. A phase 2b trial is a middle-stage test of dose and signal before large final trials. Nektar Therapeutics, the sponsor, ran one called REZOLVE-AA (NCT06340360) of its drug rezpegaldesleukin in people whose SALT score started at 50 or more. Nektar's tables count 92 people, 35 on the high dose, 37 on the low and 20 on placebo. The U.S. trial registry, ClinicalTrials.gov, lists 94 enrolled. No source found explains the gap.

The primary endpoint, the main result a trial is designed to test, was the average percent drop in SALT score at week 36. Nektar reported in December 2025 drops of 28.2% on the high dose, 30.3% on the low and 11.2% on placebo (arms of 35, 37 and 20). It said this narrowly missed statistical significance, the usual test of whether a gap is more than chance. Without four people it said should not have been enrolled (an exclusion its slides call post hoc, meaning chosen after the data were in), the figures were 29.6%, 30.4% and 5.7% (33, 36 and 19 people), which Nektar said met the test.

People still above a SALT of 20 at week 36 who showed some regrowth could continue, still blinded, for 16 weeks. That is an extension, extra treatment after the main phase. Nektar said 31 entered, 14 on the low dose, 13 on the high and 4 on placebo. In it, 29% of the 14 and 31% of the 13 newly reached a SALT of 20 or less, eight of 27 in all, against none of the four on placebo.

Nektar presented the follow-up on Oct. 1 at a dermatology congress in Vienna. People were followed for 24 weeks after treatment ended. That look is an exploratory analysis, a check on a question the trial was not built to answer. It is not the primary endpoint. The headline figures rest on eight people, the extension patients who reached a SALT of 20 or less by week 52, four per dose. Nektar said 6 of 8 (75%) still scored 20 or less four months after the last dose, and 5 of 8 (63%) at six months. Its slides, but not its release, add six people treated for 36 weeks only. Four of the six kept that score at four months and one at six months. A SALT of 10 or less, near-complete regrowth, rose from 7% at week 52 to 19% six months off, among the 27 who entered the extension on the drug. The slides give no head counts for these, and 4 of the 27 left the study before the six-month visit.

Baricitinib, a JAK inhibitor (a pill that blocks an inflammation signal inside cells), was studied in a different trial, BRAVE-AA1. Forty people with a SALT of 20 or less at week 52 were switched to placebo. By week 152, 80% of patients taken off had lost their benefit, defined as a worsening of more than 20 SALT points, against 7% of those who kept taking it. Some authors work for Eli Lilly, which makes baricitinib. Nektar's slides also compare its result with older low-dose JAK inhibitor data and call its own superior. Those are different trials, with different follow-up lengths (about two years there) and definitions of loss, so the numbers cannot be compared directly.

Nektar said its phase 3 trial, ZENITH AA, will enroll 850 people, use a SALT of 20 or less at week 52 as its primary endpoint, and start in early 2027.

This follow-up is a small-sample signal that gains can last after stopping in people who had already responded, and with eight people behind the headline figures it is not proof of what phase 3 will show.