New clinical data from Nektar Therapeutics for rezpegaldesleukin (Rezpeg), an investigational therapy for atopic dermatitis (AD), suggests it may also improve asthma symptoms in patients who suffer from both conditions.

The findings, presented at the American College of Allergy Asthma and Immunology (ACAAI) 2025 Annual Scientific Meeting, which took place from 6-10 November 2025. The data comes from the ongoing Phase IIb REZOLVE-AD study (NCT06136741), which is evaluating REZPEG in patients with moderate-to-severe AD.

Significant Improvement in Asthma Control

A key focus of the new analysis was on the 99 patients in the trial who also had a history of asthma. Researchers used the Asthma Control Questionnaire (ACQ-5) to measure symptoms. At the 16-week mark, all three doses of Rezpeg showed an overall reduction in mean ACQ-5 scores. The two higher dose arms (24 µg/kg administered every two or four weeks) achieved statistical significance compared to placebo, which saw a worsening of scores.

The improvement was particularly pronounced in patients with more severe asthma. Among the 25 patients with uncontrolled asthma at the study’s start, all active REZPEG doses demonstrated a meaningful improvement. The placebo-adjusted reductions in ACQ-5 scores in this group were substantial, ranging from 1.0 to 1.4 points.

“For the 24 µg/kg q2w treatment arm, 75% of patients with uncontrolled asthma at baseline had a clinically significant improvement in ACQ-5 at Week 16,” the data reported.

Mechanism of Action

Rezpeg is a first-in-class IL-2 pathway agonist designed to stimulate regulatory T-cells (Tregs). These cells play a crucial role in maintaining immune system balance and preventing overreaction to harmless triggers.

“These observations of improvement in asthma control in REZOLVE-AD support the broad potential of rezpegaldesleukin’s Treg mechanism across multiple T-cell mediated inflammatory diseases,” said Dr. Jonathan Zalevsky, Chief Research and Development Officer at Nektar Therapeutics, the company developing the drug.

This mechanism is seen as fundamentally different from other recently approved or advanced biologics for AD, which have not demonstrated this cross-over benefit for lower airway symptoms.

“The results with rezpegaldesleukin in patients with atopic dermatitis and comorbid asthma demonstrate that promotion of Treg activity may also have benefits to the lower airways, an observation which warrants further investigation,” said lead study author Dr. Jonathan Corren of UCLA.

Path Forward and Additional Data

Based on the strength of the data, Nektar plans to advance the 24 µg/kg q2w dose with a 24-week induction period into Phase III studies. The company also expects to report top-line Phase IIb (NCT06340360) data for Rezpeg in alopecia areata in December 2025, with long-term 52-week maintenance data from the REZOLVE-AD study expected in Q1 2026.

REZPEG has received Fast Track designation from the US Food and Drug Administration (FDA) for both moderate-to-severe AD and severe alopecia areata, potentially accelerating its development path.