This autoimmune disease causes hair loss in both women and men, affecting 160 million people worldwide
Nektar Therapeutics has announced top-line results from its trial of rezpegaldesleukin to treat severe to very severe alopecia areata (AA).
The phase 2b REZOLVE-AA trial includes 92 patients, randomised to receive either one of two rezpegaldesleukin doses or a placebo.
In both rezpegaldesleukin dose subgroups, the majority of patients experienced hair growth at week 16 of the study or later.
The safety and tolerability profiles of rezpegaldesleukin were found to be favourable, with almost all adverse events being mild to moderate and self-resolving.
Rezpegaldesleukin targets the interleukin-2 receptor complex, stimulating proliferation of powerful inhibitory immune cells known as regulatory T cells, which may result in bringing the immune system back into balance.
David Rosmarin, Chair of the Department of Dermatology and Associate Professor of Dermatology at the Indiana University School of Medicine, said: "These study results demonstrate that treatment with rezpegaldesleukin can lead to meaningful hair regrowth in patients with alopecia areata, including eyebrow and eyelash growth.
"Importantly, this occurs without the burdens of intensive testing and monitoring for dermatologists and without serious safety concerns."
AA is an autoimmune disease where the immune system attacks the body's hair follicles, causing hair loss. Lifetime incidence of the condition in both men and women is 2%: nearly 6.7 million people in the US and 160 million people worldwide will develop AA in their lifetime.
Jonathan Silverberg, professor of dermatology at The George Washington University School of Medicine and Health Sciences, said: "As physicians, we have long been in search of an effective biologic for alopecia areata.
"Importantly, this is the first biologic to show a truly meaningful level of clinical effect in patients, which could expand the number of patients we can treat with this immune disorder."
As well as being associated with other autoimmune conditions, AA can cause self-consciousness, depression and anxiety, greatly impacting quality of life. There is an urgent unmet need for new AA treatments, as current treatments have high relapse rates.
Howard Robin, president and CEO of Nektar Therapeutics, said: "In 2026, we plan to advance rezpegaldesleukin into a phase 3 programme for the treatment of alopecia areata and leverage rezpegaldesleukin's existing Fast Track designation with the goal of making this important potential treatment available to patients worldwide as soon as possible."
The US FDA granted Fast Track designation for rezpegaldesleukin twice in 2025: in July for severe AA in adults and adolescents who weigh at least 40kg and in February for inadequately controlled atopic dermatitis in adults and adolescents.
Rezpegaldesleukin is being developed as a self-administered injection for various autoimmune and inflammatory diseases.