Rezpegaldesleukin Shows Promising 52-Week Hair Regrowth in Severe Alopecia

Rezpegaldesleukin (REZPEG) shows deeper, ongoing hair regrowth at 52 weeks in severe alopecia areata

Nektar Therapeutics reported 52-week topline results from a blinded 16-week extension of the Phase 2b REZOLVE‑AA study showing that continued treatment with rezpegaldesleukin (REZPEG) produced further and deeper clinical responses in people with severe to very severe alopecia areata (AA) (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Why this drug is different

Rezpegaldesleukin is a first‑in‑class agent that targets the interleukin‑2 (IL‑2) pathway to selectively expand and activate regulatory T cells (Tregs), with the goal of restoring immune tolerance rather than broadly suppressing immune signaling (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

This approach contrasts with currently approved systemic options like Janus kinase (JAK) inhibitors, which reduce immune activity across many pathways and can carry prescribing or safety limitations for long‑term use (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

How the REZOLVE‑AA study was designed

The randomized Phase 2b trial enrolled 92 adults with severe to very severe alopecia areata, defined by high baseline Severity of Alopecia Tool (SALT) scores (mean roughly 78), and tested two dose regimens of rezpegaldesleukin given subcutaneously twice monthly (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Participants completed a 36‑week induction period during which they received either low‑dose rezpegaldesleukin (18 µg/kg), high‑dose rezpegaldesleukin (24 µg/kg), or placebo, and those who had some initial hair regrowth but had not reached a SALT score ≤20 at week 36 were eligible to continue into a 16‑week blinded extension, keeping therapy through week 52 (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

What the 52‑week results showed

Thirty‑one patients entered the blinded extension period, including 27 who were on active rezpegaldesleukin treatment, and outcomes from week 36 to week 52 demonstrated ongoing improvement with continued dosing (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Among patients who continued active treatment during the extension, new responders who reached a SALT score ≤20 appeared during those extra 16 weeks: 29% in the low‑dose arm and 31% in the high‑dose arm achieved new SALT ≤20 responses, while no new responders were observed in the placebo group during the same window (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Looking at the full study duration (52 weeks), response rates improved compared with earlier time points. After one year of treatment, 25.8% of patients in the low‑dose group and 27.6% in the high‑dose group achieved SALT ≤20, versus 6.7% in the placebo arm (statistical significance p = 0.049) (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Other clinically meaningful thresholds also favored active treatment by week 52:

• SALT ≤30 responses (corresponding roughly to ≥70% scalp coverage) were seen in 30.2% of the low‑dose group and 35.0% of the high‑dose group versus 8.4% with placebo (p = 0.023) (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

• SALT50 responses (≥50% improvement from baseline) were observed in 37.7% (low dose) and 38.8% (high dose), compared with 13.6% for placebo (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

• Other response thresholds (reported as SALT30 in the topline summary) were achieved by 45.6% and 47.6% of treated patients in the low‑ and high‑dose arms, respectively, versus 24.2% for placebo (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Safety, tolerability, and treatment persistence

Most participants completed the yearlong study: study completion was high at 94%, indicating strong treatment persistence over 52 weeks (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

The safety profile remained favorable and consistent with earlier data. The majority of treatment‑emergent adverse events were mild to moderate and resolved without additional intervention (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Injection site reactions were the most commonly reported events, typically short‑lived mild reddening at the injection site. No participants discontinued treatment during the extension because of adverse events, and the company reported no new safety signals during the blinded extension (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

What clinicians quoted about the findings

Investigators emphasized that the pattern of deepening responses over time is consistent with a mechanism that increases regulatory immune activity rather than broadly suppressing inflammation. Jonathan Silverberg, MD, PhD, MPH, noted that the expanding pool of Tregs with REZPEG can translate into greater clinical benefit over time, a trend seen previously in a Phase 2 atopic dermatitis study (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

David Rosmarin, MD, highlighted the therapeutic potential of an effective biologic alternative to current systemic options, saying that the combination of a favorable safety profile and increasing numbers of patients reaching SALT ≤20 over time supports rezpegaldesleukin as a promising candidate for broader use in AA, possibly including people with moderate disease in the future (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Why the mechanism matters for alopecia areata

In autoimmune conditions such as alopecia areata, the immune system mistakenly attacks hair follicles, and insufficient regulatory control allows that attack to continue. Rezpegaldesleukin aims to rebalance the immune response by expanding Tregs, which are the cells that help keep immune reactions in check (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Because REZPEG seeks to restore immune tolerance rather than broadly shutting down immune signaling, it may offer a different long‑term safety and efficacy profile compared with treatments that work by broad immunosuppression, like JAK inhibitors (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

What’s next and what this means for patients

Rezpegaldesleukin has already received Fast Track designation from the U.S. Food and Drug Administration for both alopecia areata and atopic dermatitis, a status that can speed development and review of therapies for serious conditions with unmet need (Source: Nektar Therapeutics press release, Fast Track designation announcement).

These Phase 2b topline results support continued development but are not the final word: larger Phase 3 studies will be needed to confirm the magnitude of benefit, define long‑term safety more fully, and determine how this treatment might fit into clinical practice compared with or alongside existing options (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Bottom line

The blinded 16‑week extension of the REZOLVE‑AA study suggests that continued dosing with rezpegaldesleukin can deepen hair regrowth responses through 52 weeks in people with severe to very severe alopecia areata, with encouraging tolerability and high study completion rates (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

While these results are promising for a first‑in‑class Treg‑targeted therapy, patients and clinicians should watch for confirmatory Phase 3 data and regulatory decisions to understand how this option may be incorporated into treatment choices for alopecia areata (Source: Nektar Therapeutics press release, REZOLVE‑AA topline results).

Sources

1. Nektar Therapeutics press release. “52‑Week Topline Results from 16‑Week Blinded Treatment Extension of REZOLVE‑AA Demonstrate Deepening of Responses in Severe‑to‑Very‑Severe Alopecia Areata with Rezpegaldesleukin.” Accessed April 20, 2026. https://www.prnewswire.com/news-releases/52-week-topline-results-from-16-week-blinded-treatment-extension-of-rezolve-aa-demonstrate-deepening-of-responses-in-severe-to-very-severe-alopecia-areata-with-rezpegaldesleukin-302746837.html
2. Nektar Therapeutics press release. “Nektar Therapeutics receives Fast Track Designation for rezpegaldesleukin for the treatment of severe‑to‑very‑severe alopecia areata.” Accessed April 20, 2026. 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