Nektar Therapeutics has received FDA Fast Track designation for its investigational therapy rezpegaldesleukin, targeting severe-to-very severe alopecia areata in adults and adolescents

The immune-modulating biologic, designed to stimulate regulatory T cells, is currently being evaluated in a global Phase 2b trial, with topline results expected in December 2025.

Nektar Therapeutics has announced that the US Food and Drug Administration (FDA) has granted Fast Track designation to rezpegaldesleukin for the treatment of severe-to-very severe alopecia areata (AA) in adults and adolescents aged 12 and older, weighing at least 40 kilograms.

Rezpegaldesleukin is an investigational biologic designed to stimulate the proliferation of regulatory T cells (Tregs) by targeting the interleukin-2 receptor complex. These immune cells help moderate the body’s immune response, which can become imbalanced in autoimmune and inflammatory conditions. Data from earlier clinical trials have shown that the drug can safely and dose-dependently increase Tregs.

“Alopecia areata is a chronic, systemic, immune-mediated disease, and there is an urgent need for new approaches that target its underlying biology,” said Jonathan Zalevsky, senior vice president and chief research and development officer at Nektar.

“We remain on track to report topline results from our Phase 2b REZOLVE-AA trial in December and look forward to working closely with the agency on a potential registrational path.”

The FDA’s Fast Track designation is intended to accelerate the review of drug candidates that target serious conditions and address unmet medical need. It allows for more frequent communication with the agency and may also qualify the candidate for priority or rolling review.

The REZOLVE-AA trial is a randomized, placebo-controlled study evaluating two dose regimens of rezpegaldesleukin in approximately 90 patients with severe-to-very severe alopecia areata who have not been treated with JAK inhibitors or other biologics. The trial’s primary endpoint is the mean percentage change in Severity of Alopecia Tool (SALT) score at week 36. Secondary endpoints include ≥50% SALT reduction, absolute SALT scores ≤20, and other timepoint assessments.

Patients were enrolled across 30 global sites, with 62% from Poland, 24% from Canada, and 14% from the US. The trial began in March 2024.

Nektar also received Fast Track designation for rezpegaldesleukin in February 2025 for moderate-to-severe atopic dermatitis in patients whose condition is inadequately controlled with topical therapies. The therapy is being developed as a self-administered injection and is wholly owned by the company.

Alopecia areata affects nearly 700,000 people in the US, with 6.7 million likely to experience it at some point in their lives. The autoimmune condition is associated with psychological distress, and available treatments often lack durability and have high relapse rates.