Nektar Therapeutics (NASDAQ:NKTR) presented new clinical and biomarker findings for rezpegaldesleukin, or REZPEG, at the EADV 2026 Congress, highlighting six-month off-treatment results in severe to very severe alopecia areata and molecular findings from its Phase IIb atopic dermatitis program.
REZPEG is an IL-2 pathway agonist designed to selectively expand regulatory T cells, or T-regs. The company is developing the therapy for atopic dermatitis, alopecia areata and Type 1 diabetes.
Alopecia Areata Durability Data
The company selected the 24 micrograms per kilogram every-two-week regimen for its planned Phase III study. In the Phase IIb trial, patients showing hair growth at week 36 but who had not yet achieved a Severity of Alopecia Tool, or SALT, score of 20 or below could enter a blinded 16-week extension, resulting in up to 52 weeks of treatment.
A SALT score of 20 or below corresponds to at least 80% scalp hair coverage. Among patients receiving 52 weeks of REZPEG treatment, newly reported response rates were 29% for the 18 micrograms per kilogram group and 31% for the 24 micrograms per kilogram group. No new SALT 20-or-below responses were observed among four placebo patients in the extension cohort.
Nektar said responses continued to increase through week 52 rather than plateauing. The company also reported similar week-52 SALT 20-or-below response rates among patients with current alopecia areata episodes shorter than four years and those with episodes lasting four years or longer, at 29% and 30%, respectively. Approximately 37% of REZPEG-treated patients had a current continuous episode lasting at least four years.
Among patients who had achieved SALT 20 or below after 52 weeks of REZPEG treatment, 75% maintained that response four months after stopping treatment and 63% maintained it at six months. Nektar compared those figures with historical low-dose baricitinib data, which it said showed 30% and 20% of patients, respectively, maintaining the same threshold at four and six months after discontinuation.
In a separate analysis of 21 patients who completed 52 weeks of treatment and had observed data at the end of follow-up, nearly half maintained or further increased hair growth six months after treatment ended. Nektar also reported that 41% of patients in the 52-week cohort achieved a deeper best response during the off-treatment period, while 22% maintained their prior best response.
The proportion of extension patients reaching a SALT score of 10 or below rose from 7% at week 52 to 19% six months after treatment stopped, according to the company. Nektar said the 52-week safety data remained consistent with prior REZPEG studies and that no new safety signals or adverse events requiring routine laboratory monitoring were observed.
Phase III Plans
Nektar plans to begin its Phase III ZENITH-AA trial in early 2027. The study is expected to enroll approximately 850 patients and compare REZPEG at 24 micrograms per kilogram every two weeks with placebo over a 52-week induction period.
Tagliaferri said the study is expected to include JAK inhibitor-naive patients, patients previously treated with JAK inhibitors and adolescents. Patients who do not reach SALT 20 or below after one year may continue every-two-week dosing in the planned long-term extension, while the company intends to evaluate monthly and quarterly maintenance regimens among responders.
Atopic Dermatitis Biomarker Findings
Chief Research and Development Officer Jonathan Zalevsky also reviewed a biomarker substudy from the Phase IIb REZOLVE-AD trial in moderate to severe atopic dermatitis. The parent trial enrolled 393 biologic-naive patients, while the substudy examined blood and skin tape-strip samples from 100 patients, including 59 receiving REZPEG at 24 micrograms per kilogram every two weeks and 41 receiving placebo.
Nektar reported that REZPEG produced T-reg-associated molecular changes in skin by week two, including increased expression of FOXP3 and IL-2 receptor alpha genes. The company also reported modulation of Th1, Th2, Th17, Th22 and JAK-STAT signaling pathways in skin and blood samples.
Early changes in serum biomarkers, including increases in IL-10 and TGF-beta1 and reductions in CCL17, also known as TARC, were associated with week-16 improvement in the Eczema Area and Severity Index, or EASI, among REZPEG-treated patients, according to Nektar.
The company said it expects to report 52-week off-treatment data from its Phase IIb atopic dermatitis study in the first quarter of 2027.
About Nektar Therapeutics (NASDAQ:NKTR)
Nektar Therapeutics is a biopharmaceutical company focused on discovering and developing medicines that use the body’s immune system to treat cancer and autoimmune diseases. The company’s research programs are based on proprietary drug-design and immunology technologies intended to improve the activity, targeting, or dosing of therapeutic agents.
Nektar’s pipeline has included NKTR-255, an investigational interleukin-15 receptor agonist designed to activate natural killer cells and support antitumor immune responses.
