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Rezpegaldesleukin Significantly Reduces Eczema Severity Scores Versus Placebo at 16 Weeks
All three dose regimens of rezpegaldesleukin produced statistically significant and clinically meaningful reductions in eczema severity compared with placebo over 16 weeks, with the highest-frequency dose (24 μg/kg every 2 weeks) yielding a treatment difference of approximately 30 percentage points in EASI score change from baseline (95% CI −41.3 to −18.0; p<0.0001). The findings establish a consistent dose-dependent signal across all tested regimens, supporting the biological plausibility and early-phase efficacy of selective regulatory T-cell expansion as a mechanism in moderate-to-severe atopic dermatitis.
What Was Studied
The trial investigated whether rezpegaldesleukin — a subcutaneous interleukin-2 receptor agonist designed to selectively expand and enhance regulatory T cells (Tregs) — could reduce disease activity in adults with moderate-to-severe atopic dermatitis who had not previously received biological therapy. The primary outcome was the percentage change from baseline in the Eczema Area and Severity Index (EASI) score at week 16, a validated measure of disease extent and intensity.
How It Was Studied
REZOLVE-AD was an international, randomised, double-blind, placebo-controlled phase 2b trial conducted across 107 research centres and hospitals in ten countries. Adults aged 18 years or older with confirmed moderate-to-severe atopic dermatitis — defined by an EASI score of at least 16, a validated Investigator Global Assessment score of at least 3, and at least 10% affected body surface area — who were naive to biological treatments were eligible. A total of 393 patients were analysed after exclusion of two sites closed for Good Clinical Practice non-compliance, and were randomised in a 3:3:3:2 ratio to one of three subcutaneous rezpegaldesleukin regimens or placebo for a 16-week induction period. Randomisation was stratified by baseline disease severity and geographical region, and all patients, investigators, and outcome assessors were masked to treatment assignment.
What Was Observed
- Primary endpoint met for all three active arms: Rezpegaldesleukin 24 μg/kg every 2 weeks produced a mean EASI reduction of 61% from baseline versus 31% for placebo — a treatment difference of approximately 30 percentage points (95% CI −41.3 to −18.0; p<0.0001), representing a large and highly statistically significant advantage over placebo.
- Dose-dependent pattern across regimens: The 18 μg/kg every-2-weeks arm showed a treatment difference of approximately 27 percentage points versus placebo (95% CI −38.5 to −15.7; p<0.0001), and the 24 μg/kg every-4-weeks arm showed a difference of approximately 22 percentage points (95% CI −33.3 to −10.3; p=0.0002), demonstrating a consistent gradient of effect tied to dosing frequency and amount.
- Injection-site reactions were common but predominantly mild: Injection-site reactions occurred in 70% of rezpegaldesleukin-treated patients compared with 4% of placebo recipients; however, more than 99% of these reactions were mild to moderate in severity and resolved without serious consequence.
- No increase in serious adverse events or deaths: Eosinophilia was reported in 8% of the active treatment group versus 3% on placebo, and pyrexia, headache, and arthralgia each appeared in roughly 5–6% of treated patients. Crucially, no deaths occurred during the induction period, and there was no evidence of elevated risk for serious or severe adverse events across any rezpegaldesleukin arm.
Why This Matters
Rezpegaldesleukin represents a mechanistically distinct approach to treating atopic dermatitis, targeting Treg expansion rather than blocking specific inflammatory cytokines. The trial demonstrates proof-of-concept that selective IL-2 receptor agonism can produce clinically meaningful skin disease improvements, opening a potential new immunological pathway for treatment of this chronic inflammatory condition. The favourable short-term safety profile further supports the feasibility of continued development of Treg-enhancing biologics in this indication.
How to Read This Result
These are encouraging phase 2b findings from a well-designed, adequately powered international trial, but conclusions about long-term durability, maintenance dosing requirements, and comparative effectiveness against approved biologics must await data from the maintenance period and future studies.
Limitations
Two clinical sites were excluded from the efficacy and safety analyses following closure due to Good Clinical Practice non-compliance, and all missing data were handled through multiple imputation, both of which introduce some degree of analytical uncertainty. The report covers only the 16-week induction phase, leaving open questions about sustained efficacy, optimal maintenance regimens, and long-term safety. Additionally, the study population was restricted to biological-naive adults, meaning the results may not generalise to patients who have previously received or failed biologic therapies.