REZOLVE-AA Data Show Durable Hair Regrowth With Rezpegaldesleukin

New long-term data from the phase 2b REZOLVE-AA trial suggest that rezpegaldesleukin (rezpeg), an investigational regulatory T-cell (Treg)-stimulating biologic, may provide durable hair regrowth in patients with severe-to-very-severe alopecia areata (AA), including sustained and deepening responses after treatment discontinuation.

The findings were presented at the 2026 European Academy of Dermatology and Venereology (EADV) Congress in Vienna, Austria, by David Rosmarin, MD, chair of the Department of Dermatology and associate professor of dermatology at Indiana University School of Medicine.

In an interview with Dermatology Times, Rosmarin highlighted continued improvement with extended treatment as one of the most notable findings from the study.

“The first important point is that with continued treatment, there are more patients achieving better results with hair regrowth from week 36 through week 52,” Rosmarin said. “Even when we look as subjects approach week 52, they still haven't hit the plateau yet.”

Responses Continue Through Week 52

REZOLVE-AA (NCT06340360) is a global phase 2b study evaluating rezpegaldesleukin in patients with severe-to-very-severe AA who had not previously received a Janus kinase (JAK) inhibitor or other biologic therapy.

During the initial 36-week induction period, 92 patients were randomized to receive 1 of 2 twice-monthly doses of rezpegaldesleukin or placebo. Patients with a Severity of Alopecia Tool (SALT) score greater than 20 at week 36 who demonstrated hair growth could continue their assigned rezpegaldesleukin dose for an additional 16 weeks.

Among patients continuing into the treatment extension, 29% receiving the 18-µg/kg dose and 31% receiving the 24-µg/kg dose achieved new SALT scores of 20 or lower between weeks 36 and 52. A SALT score of 20 or lower corresponds to at least 80% scalp hair coverage.

A subgroup analysis also suggested responses were similar regardless of the duration of the current AA episode. SALT scores of 20 or lower were achieved by 29% of patients whose current episode had lasted less than 4 years and 30% of those whose episode had lasted 4 years or longer.

Hair Regrowth Persists—and Deepens—Off Treatment

The off-treatment findings particularly distinguished the results, according to Rosmarin.

Among patients who completed 52 weeks of treatment and achieved a SALT score of 20 or lower, 75% (6 of 8) maintained that response after 4 months without treatment. At 6 months off treatment, 63% (5 of 8) continued to maintain the response.

Some patients experienced additional hair regrowth despite no longer receiving therapy. SALT scores of 10 or lower increased from 7% at week 52 to 19% after 6 months off treatment.

“One of the really neat aspects about this novel mechanism for stimulating T regulatory cells, or the brakes in the immune system, is that patients can not only maintain their response, but even have a deepening of response,” Rosmarin said.

He noted that durability could have practical implications beyond efficacy alone, potentially allowing for less frequent maintenance dosing or providing greater flexibility when treatment is temporarily interrupted.

“There are a lot of reasons why there might be interruptions in treatment,” Rosmarin explained, pointing to insurance disruptions, travel, and pregnancy as potential examples. “Being able to maintain the response is a real value add.”

That durability may be particularly meaningful in AA because regrowing hair can take considerably longer than regaining disease control in some other inflammatory conditions.

“For someone who may take 3 years to regrow their hair, for them to start losing it again is very devastating, and it takes a really long time to recover,” Rosmarin said.

A Different Approach to Immune Regulation

Rezpegaldesleukin targets the interleukin-2 receptor complex to stimulate regulatory T cells, which play an important role in controlling immune responses and maintaining immune tolerance.

Rosmarin said this mechanism may help explain the persistence of response observed after treatment withdrawal.

“What’s novel about the stimulation of the Tregs, or the brakes in the immune system, is that it can have a more lasting effect,” he said. “The Tregs can remain in the area.”

Loss of immune privilege at the hair follicle is an important component of AA pathogenesis, allowing inflammatory immune cells to target the follicle. Rosmarin suggested that stimulating Tregs could potentially help restore this immune privilege.

“With the stimulation of Tregs, we have the opportunity to try to restore immune privilege and give, again, a much more long-lasting response,” he said.

Rosmarin also contrasted the off-treatment findings with the experience seen with currently available JAK inhibitors, for which continued treatment is generally necessary to maintain hair regrowth.

“The fact that there is a deepening of response—that we have people improving even 6 months after stopping treatment—is really remarkable and very different from the JAK inhibitor class of medicines that we have now,” he said. “I think it really speaks to the value add for stimulating Tregs and a truly novel mechanism.”

Moving Into Phase 3

Across the REZOLVE-AA and REZOLVE-AD programs, the safety profile of rezpegaldesleukin through 52 weeks was reported as favorable and consistent with previously reported findings.

The REZOLVE-AA findings are now supporting advancement into phase 3. The planned ZENITH-AA trial is expected to enroll approximately 850 patients with severe-to-very-severe AA, with the proportion of patients achieving a SALT score of 20 or lower at week 52 serving as the primary end point. The study is expected to begin in early 2027.

Rosmarin said the continued improvement through week 52, together with sustained responses following treatment withdrawal, supports further evaluation of the Treg-targeting approach.

“I’m really optimistic as we uncover more about this really unique mechanism,” he said.

References

1. Rosmarin D, et al. Rezpegaldesleukin, a novel regulatory T cell-inducing biologic, demonstrates efficacy and safety in severe-to-very-severe alopecia areata: 52-week results from the phase 2b REZOLVE-AA study. Presented at: European Academy of Dermatology and Venereology (EADV) Congress; September 30-October 3, 2026; Vienna, Austria. Pasted markdown
2. Nektar Therapeutics. New rezpegaldesleukin data supporting long-term durability and disease improvement in patients with alopecia areata and atopic dermatitis at EADV Congress 2026. Published October 1, 2026. Pasted markdown
3. Nektar Therapeutics. 52-week topline results from 16-week blinded treatment extension of REZOLVE-AA demonstrate deepening of responses in severe-to-very-severe alopecia areata with rezpegaldesleukin. Published April 27, 2026. Nektar Therapeutics
4. Nektar Therapeutics. Data from phase 2b REZOLVE-AD and REZOLVE-AA studies of rezpegaldesleukin presented at 2026 American Academy of Dermatology Annual Meeting. Published March 2026. Nektar Therapeutics
5. Nektar Therapeutics. Nektar Therapeutics receives Fast Track designation for rezpegaldesleukin for the treatment of severe-to-very severe alopecia areata. Published July 29, 2025. PR Newswire