FDA Grants Fast Track Designation to Nektar's Rezpegaldesleukin in Alopecia Areata

Nektar Therapeutics announced today that the US FDA has granted Fast Track designation to its investigational biologic agent, rezpegaldesleukin, for the treatment of severe to very severe alopecia areata (AA).¹

This marks a step forward in the development of immunomodulatory treatments for chronic autoimmune hair loss conditions, particularly for patients aged 12 years and older who weigh at least 40 kilograms (88.2 pounds).

Image Credit: © Tada Images - stock.adobe.com

A Novel Approach to Immune Modulation

Rezpegaldesleukin is a biologic agent that selectively targets the interleukin-2 (IL-2) receptor complex with the aim of expanding regulatory T cells (Tregs). In autoimmune diseases such as AA, insufficient Treg activity contributes to the loss of self-tolerance and subsequent immune-mediated attack on hair follicles.² Rezpegaldesleukin is designed to address this imbalance by enhancing the proliferation and function of Tregs.

According to Nektar, the therapy has shown consistent dose-dependent increases in Treg populations across multiple clinical studies, indicating promise as a mechanistic intervention targeting the underlying immunopathogenesis of AA.

Phase 2b REZOLVE-AA Study

The Fast Track designation coincides with the ongoing phase 2b REZOLVE-AA trial (NCT06340360),³ which is evaluating rezpegaldesleukin in approximately 90 adults with severe to very severe AA.

Participants were randomized across 2 dosing regimens or placebo, with a primary endpoint focused on the mean percent change in Severity of Alopecia Tool (SALT) score after a 36-week induction period.

Key secondary outcomes include the proportion of patients achieving ≥50% reduction in SALT score at week 36, average percent improvement in SALT score at interim time points, and the proportion of patients reaching a SALT score ≤20, indicative of limited disease burden.

The study enrolled patients across approximately 30 global sites, with the majority of participants based in Poland (62%), followed by Canada (24%) and the United States (14%). Eligibility criteria required at least 50% scalp involvement by SALT scoring at both screening and randomization. Patients with diffuse alopecia, other non-AA diagnoses, or unstable disease courses in the prior 6 months were excluded from participation.

Topline results from the trial are expected by December 2025.

Regulatory Momentum

"We are pleased that rezpegaldesleukin has been granted Fast Track designation for the treatment of alopecia areata, adding to its Fast Track designation in atopic dermatitis," said Jonathan Zalevsky, PhD, senior vice president and chief research and development officer at Nektar, in a news release.¹ "Alopecia areata is a chronic, systemic, immune-mediated inflammatory disease, and there is an urgent need for novel mechanistic approaches that could treat the underlying pathogenesis of this disorder. ... We look forward to the opportunity to collaborate quickly with the agency on a potential registrational program following the completion of phase 2."

This is the second Fast Track designation for rezpegaldesleukin. Earlier this year, the FDA granted the same status for its use in moderate to severe atopic dermatitis in patients 12 and older who have not responded adequately to topical prescription therapies.⁴

Nektar is currently developing rezpegaldesleukin as a subcutaneous self-injection for various autoimmune and inflammatory conditions.

References

1. Nektar Therapeutics receives Fast Track Designation for rezpegaldesleukin for the treatment of severe-to-very severe alopecia areata. News release. Nektar Therapeutics. July 29, 2025. Accessed July 29, 2025. https://www.prnewswire.com/news-releases/nektar-therapeutics-receives-fast-track-designation-for-rezpegaldesleukin-for-the-treatment-of-severe-to-very-severe-alopecia-areata-302515436.html
2. Cohen JN, Gouirand V, Macon CE, et al. Regulatory T cells in skin mediate immune privilege of the hair follicle stem cell niche. Sci Immunol. 2024;9(91):eadh0152. doi:10.1126/sciimmunol.adh0152
3. 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. Updated April 2, 2025. Accessed July 29, 2025. https://clinicaltrials.gov/study/NCT06340360
4. Nektar Therapeutics receives fast track designation for rezpegaldesleukin for the treatment of moderate-to-severe atopic dermatitis. News release. PRNewswire. February 10, 2025. Accessed July 29, 2025. https://www.prnewswire.com/news-releases/nektar-therapeutics-receives-fast-track-designation-for-rezpegaldesleukin-for-the-treatment-of-moderate-to-severe-atopic-dermatitis-302371995.html