An experimental injected drug for alopecia areata, an autoimmune condition that makes hair fall out, kept working for many people months after they stopped taking it, its maker Nektar Therapeutics reported on October 1, 20261. The drug is called rezpegaldesleukin, or REZPEG for short2. The new numbers come from a small group: of 8 people who had regrown most of their scalp hair after a year of treatment, 5 still had that coverage six months after their last dose1.
The results were presented in Vienna at the European Academy of Dermatology and Venereology (EADV) Congress, a large skin-medicine meeting, by David Rosmarin, chair of dermatology at Indiana University School of Medicine3. They have not yet appeared in a peer-reviewed journal.
What happened
Alopecia areata has a frustrating pattern: hair falls out, sometimes grows back, then falls out again4. Today’s approved pills, called JAK inhibitors, generally have to be taken continuously to keep hair regrowth, Rosmarin said3.
Nektar’s drug works differently. It is a modified form of interleukin-2, a natural immune signal5, designed to boost regulatory T cells, which Rosmarin described as “the brakes in the immune system”3. In alopecia areata, the hair follicle loses its usual protection from the immune system, letting inflammatory cells attack it; Rosmarin suggested that boosting these brake cells might help restore that protection3.
The headline figures Nektar reported:
- Among people treated for 52 weeks who reached a SALT score of 20 or lower (a hair-loss scale where 20 or lower means at least 80% of the scalp is covered), 75% (6 of 8) kept that level four months after stopping and 63% (5 of 8) kept it at six months1.
- Some kept improving off the drug. The share with a SALT score of 10 or lower, meaning about 90% coverage, rose from 7% at week 52 to 19% six months after treatment ended1.
- In a separate analysis of 21 people with data at the end of follow-up, nearly half kept or increased their hair growth six months after stopping6.
“The fact that there is a deepening of response—that we have people improving even 6 months after stopping treatment—is really remarkable and very different from the JAK inhibitor class of medicines that we have now,” Rosmarin said.
That quote comes from his interview with Dermatology Times3.
How the trial was run
The study, called REZOLVE-AA, is a Phase 2b trial, a mid-stage test meant to check whether a drug helps and at what dose. It enrolled 92 adults with severe or very severe alopecia areata who had never taken a JAK inhibitor or another biologic drug7. The public trial registry lists 94 people actually enrolled5. Participants were randomly assigned to one of two doses or to a placebo (a dummy shot), given as injections under the skin twice a month for 36 weeks7. People started with heavy hair loss: average SALT scores near 78, and a typical illness length of about 6 to 7 years8.
The trial’s main goal was the average percentage drop in SALT score at week 367. People who still had a SALT score above 20 at week 36 but showed some regrowth could keep their dose for 16 more weeks3. Thirty-one people did: 14 on the lower dose, 13 on the higher dose and 4 on placebo8. During those extra weeks, 29% on the lower dose and 31% on the higher dose newly reached a SALT score of 20 or lower, compared with none on placebo1.
Those week-52 results were first announced in April 2026. Across the whole study, 25.8% and 27.6% of people on the two doses had a SALT score of 20 or lower at week 52, versus 6.7% on placebo8. The October update added the six months off treatment.
Nektar also reported that responses looked similar whether people’s current bout of hair loss had lasted less than four years (29%) or four years or more (30%)1. On safety, the company said results through 52 weeks were consistent with earlier studies, with no new safety signals and no side effects requiring routine lab monitoring6.
What it does not show yet
The off-treatment finding rests on 8 people1, so one or two people more or less would change the percentages a lot. The sources do not give how many people the 7% and 19% figures were based on. There is no placebo group in the off-treatment comparison, so it is unclear how much of the lasting regrowth comes from the drug and how much from the natural ups and downs of the condition.
Nektar compared its numbers with older data for baricitinib (Olumiant), a JAK inhibitor pill, saying 30% and 20% of people on a low dose of that drug kept the same level of coverage four and six months after stopping6. That is a comparison between different trials with different patients, chosen by the company, not a head-to-head test.
The trial only included people who had never taken a JAK inhibitor or biologic7, so the results say nothing yet about people who already tried those drugs. The full results have not been posted to the public trial registry5. A trade publication noted that a 92-person mid-stage study is mainly useful for choosing doses and seeing an early signal, not for approval2.
Who is behind it
Nektar Therapeutics, a San Francisco company, sponsors the trial5 and issued the press release with the new numbers1. The drug has also been known by the codes NKTR-358 and LY34718512. Nektar hosted an investor call on the day of the presentation, joined by Benjamin Ungar, director of the Alopecia Center of Excellence at Mount Sinai7. The sources do not describe whether Rosmarin or Ungar have financial ties to Nektar.
In April, another dermatologist, Jonathan Silverberg of George Washington University, said in a company statement that the data pointed to the potential for the drug to be “the first safe and effective biologic in alopecia areata”8. These are hopes for the drug, not measured results.
How it fits the field
Baricitinib was approved by the FDA for severe alopecia areata in June 2022, with roughly one in three patients reaching meaningful hair coverage in its main trials2. It gained approval for teenagers 12 and up on September 27, 20269, as Biohack reported. Another JAK inhibitor, deuruxolitinib (Leqselvi), is approved for adults9.
Nektar is not the only company chasing lasting regrowth after treatment stops. At the same meeting, Q32 Bio reported that all 12 people who had regrowth on its experimental antibody, bempikibart, kept it during 16 weeks off treatment9. The National Alopecia Areata Foundation, a patient group, noted that both drugs are still experimental and not FDA-approved for the condition9. Pfizer has also run a larger trial of its own JAK3-blocking pill in the condition, designed for roughly 660 patients2.
What to watch next
Nektar plans to start a larger trial, called ZENITH AA, in early 2027 with about 850 people with severe or very severe alopecia areata. Its main goal will be the share of people reaching a SALT score of 20 or lower at week 521. The FDA gave the drug Fast Track status, which can speed up review, in July 20252. The company also said the data support testing monthly or every-three-months dosing after the first year for people who respond1. Key questions are whether lasting regrowth off the drug holds up in hundreds of people with a placebo comparison, and whether the full data appear in a peer-reviewed journal.
