New Hair Loss Drugs: Clascoterone & Rezpegaldesleukin

28 Years, Two Options, and a Viral Thread That Got It Half Right

A viral thread on X from longevity researcher Avi Roy (@agingroy) lit up the hair loss community in early 2026 with a simple, devastating framing: for 28 years, if you were losing your hair, you had exactly two FDA-approved options. Minoxidil — a foam that works for roughly one in three men. Finasteride — a pill that works better but carries the specter of sexual side effects. "That's it. Nothing else since 1997."¹

Then Roy announced that two new drugs had arrived, each working through completely different mechanisms than anything before. The thread went viral. Hundreds of thousands of views. Headlines followed. Hope surged in a community long accustomed to disappointment.

Here's what the thread got right: the drugs are real, the mechanisms are genuinely novel, and the clinical data is encouraging. Here's what it got wrong — or at least, what it elided: these are two drugs for two entirely different conditions, neither is FDA-approved yet for hair loss, and the "28-year drought" narrative, while emotionally resonant, isn't quite accurate. I spent three weeks digging through the Phase 3 and Phase 2b data, the press releases, the funding conflicts, and the regulatory timelines. Let me walk you through what I found.

One Drug for Thinning. One Drug for Patches. They Are Not the Same.

Before we go any further, I need to draw a bright line between two conditions that the internet constantly conflates.

Androgenetic alopecia (AGA) is the gradual, patterned thinning most people think of when they hear "hair loss." It's driven by genetics and the hormone dihydrotestosterone (DHT), which miniaturizes hair follicles over years. It affects an estimated 50 million men and 30 million women in the United States alone, with lifetime prevalence reaching 80% in men and 50% in women.² This is what minoxidil and finasteride treat.

Alopecia areata (AA) is something entirely different. It's an autoimmune disorder in which the body's own immune system attacks hair follicles, causing rapid, patchy hair loss that can progress to total scalp baldness (alopecia totalis) or complete body hair loss (alopecia universalis). It affects roughly 2% of the population over a lifetime and peaks in adults aged 25–29.³

Clascoterone targets AGA. Rezpegaldesleukin targets AA. They share a common outcome — hair on your head — but the biology underneath is as different as a broken thermostat and an arson fire. Treating them interchangeably would be like prescribing blood pressure medication for an allergic reaction because both involve the cardiovascular system.

A Topical DHT Blocker and an Immune System Reset Button

Clascoterone is a topical androgen receptor antagonist. If finasteride is a factory shutdown — it blocks the enzyme (5-alpha reductase) that converts testosterone into DHT systemically throughout your body — then clascoterone is a targeted lockout. It binds directly to the androgen receptor in scalp tissue, physically preventing DHT from docking and triggering the cascade of follicle miniaturization.⁴ Same war, different battle plan. The appeal is obvious: by acting locally rather than systemically, clascoterone could theoretically deliver the benefits of DHT blockade without the sexual side effects that have made finasteride a fraught choice for millions of men.

Clascoterone isn't entirely new to dermatology. A 1% cream formulation (brand name Winlevi) was FDA-approved in August 2020 for acne — a condition also driven by androgen activity in the skin.⁵ The hair loss application uses a higher concentration (5% solution) applied directly to the scalp, targeting the same receptor but in a different tissue context. The developer, Cosmo Pharmaceuticals (which acquired the original developer Cassiopea in 2021), has been running Phase 3 trials for AGA since 2022.

Rezpegaldesleukin operates in entirely different biological territory. It's an IL-2 mutein — a modified version of interleukin-2, a naturally occurring immune signaling molecule — engineered to selectively expand regulatory T cells (Tregs).⁶ Tregs are the immune system's peacekeepers. In alopecia areata, the immune system essentially loses the ability to recognize hair follicles as "self" and launches an inflammatory attack. Rezpegaldesleukin aims to rebuild immune tolerance by amplifying the very cells that are supposed to prevent this kind of friendly fire.

This is a fundamentally different approach from JAK inhibitors (baricitinib, ritlecitinib), which treat alopecia areata by broadly dampening the inflammatory signals. JAK inhibitors are like turning down the volume on the entire immune response. Rezpegaldesleukin is more like retraining the security team to stop attacking the wrong targets. The developer, Nektar Therapeutics, calls this "restorative immunology" — a phrase I'll note is as much marketing as science, but the underlying concept has genuine immunological grounding.

1,465 Patients, Two Phase 3 Trials, and One Phase 2b With an Asterisk

Let's start with the stronger dataset.

Clascoterone: SCALP-1 and SCALP-2

In December 2025, Cosmo Pharmaceuticals released topline results from two identically designed Phase 3 trials — SCALP-1 and SCALP-2 — enrolling a combined 1,465 men with mild-to-moderate androgenetic alopecia across 51 sites in the US and Europe. Both were six-month, double-blind, vehicle-controlled studies with 2:1 randomization to clascoterone 5% solution or vehicle, applied twice daily.⁷

Those numbers deserve context. A "539% relative improvement" sounds extraordinary, but relative improvements can be misleading when the baseline vehicle response is small. If vehicle-treated patients gained 2 hairs per cm² and clascoterone patients gained 12.8, that's a 539% relative improvement — technically accurate, genuinely meaningful, but not the kind of dramatic transformation the percentage suggests. Cosmo has not released absolute hair count data in their press communications, which is a pattern I note without attributing motive.⁸

The safety data, however, is genuinely encouraging. Adverse event rates in the clascoterone groups matched placebo. No systemic hormonal effects were detected. For a community that has spent decades debating whether finasteride's sexual side effects are real, reversible, or catastrophized, a topical mechanism with a clean safety profile at six months is significant — even if we need the 12-month data to be confident.

Rezpegaldesleukin: REZOLVE-AA

The rezpegaldesleukin story is more complicated. In December 2025, Nektar Therapeutics released results from REZOLVE-AA, a Phase 2b study enrolling 92 patients with severe-to-very-severe alopecia areata. Patients received subcutaneous injections of rezpegaldesleukin (24 µg/kg or 18 µg/kg) or placebo twice monthly for 36 weeks.⁹

I want to be fair to Nektar here. Excluding patients who violated enrollment criteria is standard practice in clinical trials — it's literally what the per-protocol analysis is designed to do. One excluded patient had less than six months of disease duration, which is a genuine confounder in AA trials because spontaneous remission rates are higher in early disease. The per-protocol analysis is legitimate.¹⁰

But I also want to be honest: when your Phase 2b trial enrolls 92 patients, misses significance in the ITT analysis, achieves it only after post-hoc exclusions, and the company has been in litigation with its former partner Eli Lilly (who walked away from the drug in 2023 over efficacy concerns), the word "proof-of-concept" — which Nektar used prominently in their press release — carries more weight than the data comfortably supports.¹¹

Press Releases, Funding Conflicts, and the Data You Haven't Seen

Here's what bothers me most about both drugs: as of March 2026, neither set of Phase 3/2b results has been published in a peer-reviewed journal. Everything we know comes from company press releases and investor presentations. This is not unusual for recently completed trials — peer review takes time — but it means the clinical community hasn't independently verified the methodology, the statistical analyses, or the adverse event data.

For clascoterone, the funding conflict is straightforward: Cosmo Pharmaceuticals sponsored the trials, owns the drug, and stands to profit enormously from approval in a market projected to exceed $28 billion by 2030. Their topline results look clean and the trial design is solid (large sample, dual studies, vehicle-controlled, blinded), but until independent statisticians review the raw data, the relative improvement numbers remain company-curated talking points.^7,8

For rezpegaldesleukin, the conflict runs deeper. Nektar regained full rights to the drug in April 2023 after Eli Lilly terminated its license agreement — reportedly because Lilly saw insufficient efficacy signal across multiple indications. Nektar subsequently restructured its entire pipeline around rezpegaldesleukin. The company's stock price, investor confidence, and corporate survival are tied to this drug working. That context doesn't invalidate the data, but it's the kind of thing a peer reviewer would note prominently.^11,12

The "28-Year Drought" Isn't Quite What You've Been Told

The viral framing — nothing new since finasteride in 1997 — is emotionally effective but factually incomplete. It's accurate if you're talking exclusively about FDA-approved systemic or topical treatments specifically indicated for androgenetic alopecia. But the hair loss treatment landscape has evolved more than that narrative suggests.

For AGA, dermatologists have been prescribing dutasteride off-label for years. It's a dual 5-alpha reductase inhibitor that reduces serum DHT by approximately 98%, compared to finasteride's 71%. Multiple systematic reviews show it outperforms finasteride for hair count and thickness, though it was never submitted for FDA approval for this indication because the manufacturer (GSK) determined the market economics didn't justify a second approval trial.¹³ Topical finasteride formulations have also emerged through compounding pharmacies, though the FDA issued safety warnings about compounded topical finasteride products in 2024.¹⁴

For alopecia areata, the landscape has transformed dramatically in the past four years. Three JAK inhibitors have received FDA approval: baricitinib (2022), ritlecitinib (2023), and deuruxolitinib (2024). These oral medications broadly suppress the JAK-STAT signaling pathway that drives the autoimmune attack on hair follicles, and they've shown SALT score improvements comparable to — and in some studies exceeding — what rezpegaldesleukin demonstrated in its Phase 2b trial.¹⁵

This matters because it reframes the rezpegaldesleukin story. Nektar isn't offering the first treatment for a neglected disease; they're entering a market where three oral drugs already exist. Their theoretical advantage — more targeted immune modulation with less broad immunosuppression — is plausible but unproven. And their drug requires biweekly subcutaneous injections, whereas the competition is pills. That's a high bar for a Phase 2b dataset with an asterisk.

Two Genuinely Novel Drugs. One Strong Dataset. One Shaky One.

Let me separate these two drugs in my final assessment, because they deserve different levels of confidence.