Rezpegaldesleukin (REZPEG)
Rezpegaldesleukin (REZPEG) is in Phase 2 for alopecia areata, developed by Nektar Therapeutics.
A PEGylated interleukin-2 that grows regulatory T cells, with placebo-controlled data to 52 weeks in severe alopecia areata and a Phase 3 planned.
- Developed by
- Nektar Therapeutics
- Current phase
- Phase 2
- Mechanism
- Immunomodulator
- Indications
- Alopecia areata
- Also known as
- REZPEG, NKTR-358, NKTR358, LY3471851
- Last public activity
- September 2026
- Copy last reviewed
- September 2026
- Record confidence
- High
Tests whether it works, at what dose, in a few hundred people.
Retunes the immune system more broadly than a single pathway.
A research record, not medical advice: being listed here says nothing about whether a treatment works or whether it is right for you. Talk to a dermatologist about your own case.
How it is meant to work
An engineered IL-2 given subcutaneously twice a month, built to expand regulatory T cells, the cells that restrain an immune attack. The JAK inhibitors block signalling in the attacking cells; this works the opposite lever. The registry still carries Lilly's former code for it, LY3471851; the alopecia areata programme is Nektar's own.
Why it matters
REZOLVE-AA enrolled 92 adults with severe to very severe disease, by Nektar's count. At week 36 the mean SALT reduction was 28.2% on the higher dose and 30.3% on the lower, against 11.2% on placebo; neither difference reached statistical significance until the company excluded four patients for eligibility violations. Thirty-one patients, four of them on placebo, then continued blinded treatment for a further 16 weeks; at week 52 Nektar reports 25.8% and 27.6% of the two dose arms at a SALT score of 20 or below against 6.7% on placebo, and 94% of that extension group completed the year. Injection-site reactions were the main adverse event, mostly mild. The FDA granted Fast Track in 2025 and the company says the data support late-stage development. The numbers are Nektar's topline releases, not yet a paper.
Development history
- Phase 2
First Phase 2 trial on record: NCT06340360 — A Phase 2b Study to Evaluate Rezpegaldesleukin (Rezpeg) in the Treatment of Severe to Very Severe Alopecia Areata in Adult Patients (Rezolve AA)
ClinicalTrials.gov ↗
Registered trials
Pulled automatically from ClinicalTrials.gov. Matching is by name and development code, so occasional gaps are possible — tell us if you spot one.
A Phase 2b Study to Evaluate Rezpegaldesleukin (Rezpeg) in the Treatment of Severe to Very Severe Alopecia Areata in Adult Patients (Rezolve AA)
Nektar Therapeutics · n=94 · April 2024
Listing a trial is not a recommendation to join one. Eligibility, risks and costs vary enormously — discuss any trial with your own doctor first.
Sources
- A Phase 2b Study to Evaluate Rezpegaldesleukin (Rezpeg) in the Treatment of Severe to Very Severe Alopecia Areata in Adults (REZOLVE-AA) — ClinicalTrials.gov
- 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 — Company release, April 2026
- REZOLVE-AA Phase 2b study of rezpegaldesleukin establishes proof-of-concept in patients with severe-to-very-severe alopecia areata — Company release, December 2025
Related programmes
Other programmes in the register with the same mechanism: Immunomodulator.
Cite this page
Hair Pipeline, "Rezpegaldesleukin (REZPEG) — development record", hairpipeline.com/pipeline/rezpegaldesleukin