Nektar's Rezpegaldesleukin Delivers Clinical Wins in Phase 2b Hair Loss Trial, Signaling Major Breakthrough in Alopecia Treatment

Nektar Therapeutics (NKTR) has unveiled impressive Phase 2b results for Rezpegaldesleukin in treating severe alopecia areata, a debilitating autoimmune condition affecting hair follicles. The REZOLVE-AA trial not only demonstrated meaningful hair regrowth across scalp, eyebrows, and eyelashes but also established the company’s first-in-class IL-2 pathway agonist as a potential game-changer in an area where existing therapies fall significantly short.

The Unmet Medical Challenge

Alopecia areata remains a difficult-to-treat autoimmune disorder where the body’s immune system mistakenly attacks hair follicles, resulting in patchy or complete baldness. While JAK inhibitors currently dominate the treatment landscape, they’re hampered by safety concerns and troubling relapse rates. This has left millions of patients seeking safer, more durable alternatives—exactly the gap Nektar appears to be filling.

Trial Results That Exceeded Expectations

The REZOLVE-AA study enrolled 92 patients who received either one of two Rezpegaldesleukin doses or placebo via subcutaneous injection twice monthly over 36 weeks. The primary efficacy measure—reduction in SALT (Severity of Alopecia Tool) scores—revealed compelling data: both active treatment groups achieved mean reductions of 28.2% and 30.3%, more than doubling the 11.2% reduction observed in the placebo arm. After excluding four patients with major protocol violations, efficacy became statistically significant, with results reaching 29.6% and 30.4% versus just 5.7% for control.

Secondary endpoints strengthened the case further. A substantially higher proportion of patients in the treatment groups achieved meaningful SALT score thresholds (≥30, ≥20, ≥10), with investigators specifically documenting visible hair regrowth not just on the scalp but also in eyebrow and eyelash regions.

Safety Profile Supports Rapid Advancement

A critical advantage for Rezpegaldesleukin lies in its tolerability. Nearly all reported adverse events remained mild to moderate and self-resolving, with a discontinuation rate of just 1.4%—substantially better than many competing therapies in the autoimmune space. This clean safety profile bolsters the company’s confidence in advancing the program.

What’s Next: 2b Hair Loss and Beyond

Nektar intends to launch Phase 3 development in 2026, supported by FDA Fast Track designation for alopecia areata. Importantly, this IL-2 pathway agonist isn’t limited to hair loss; it’s concurrently being investigated in atopic dermatitis and type-1 diabetes, positioning Rezpegaldesleukin as a multi-indication asset targeting regulatory T-cell stimulation across several autoimmune conditions.

The company will release 16-week extension data in early Q2 2026, with full results expected at a major medical conference later that year.

Market Response and Stock Movement

The market has taken notice. NKTR shares have traded between $6.45 and $66.92 over the past 12 months, reflecting the volatile but opportunity-rich biotech landscape. Following this announcement, the stock surged to $58.39 in pre-market trading, up 9.55%, as investors reassess the company’s pipeline depth and commercial potential in the growing alopecia therapeutics market.