Clascoterone
Also known as: CB-03-01, Breezula, Winlevi, Cortexolone 17α-propionate
Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
A topical androgen receptor antagonist, FDA-approved as Winlevi for acne and in late-stage development as Breezula for hair loss. It blocks androgen signalling in skin and scalp rather than providing any anabolic effect, and is metabolised to cortexolone locally. It does not move the natural ceiling. Rated 1 (basically natty).
Overview
The most clinically advanced topical antiandrogen for hair loss. Unlike RU58841 and pyrilutamide, clascoterone already has FDA approval in a related indication (acne, as Winlevi), and its hair-loss program has reported positive Phase III results from large trials run in the US and Europe rather than a single region.
Important Warnings
- •The HAIR-LOSS product (Breezula) is not approved, only the 1% acne cream (Winlevi) is
- •Using the 1% acne cream on the scalp is off-label and far below the 5% strength used in Phase III
- •Phase III efficacy figures are company topline announcements pending full publication and regulatory review
- •The two identical Phase III trials reported 539% and 168% relative improvement. Expect the lower end
- •Long-term safety data beyond the trial follow-up period does not yet exist
- •Use alongside AAS specifically has never been studied
Purpose & Use Cases
Topical Antiandrogen For Hair Loss
Blocks androgen signalling at the follicle without the systemic hormonal exposure of oral finasteride or dutasteride. This is the indication the Phase III program targeted.
Androgen-Driven Acne
Its approved use. Directly relevant on-cycle, where elevated androgens routinely drive acne, clascoterone attacks that at the receptor in the sebaceous gland rather than systemically like isotretinoin.
Receptor-Level Coverage Where 5-AR Inhibitors Do Not Apply
Theoretically applicable against DHT-derivatives and trenbolone, where finasteride has nothing to block. Untested in that population: the trials enrolled ordinary AGA patients.
Benefits
- The only topical antiandrogen in this class with an existing FDA approval (Winlevi, for acne)
- Two identically designed Phase III hair-loss trials (Scalp 1 / NCT05910450 and Scalp 2 / NCT05914805) enrolled 1,465 men across 51 sites in the US and Europe
- Scalp 1 reported a 539% relative improvement in Target-Area Hair Count versus vehicle; Scalp 2 reported 168% (both p<0.05)
- Treatment-emergent adverse events were similar to vehicle, with most not related to study drug
- Also treats the androgen-driven acne that commonly appears on-cycle
- Local inactivation to cortexolone is designed to avoid systemic antiandrogen effects
Good to Know
The two Phase III results are far apart, and both count
Scalp 1 reported a 539% relative improvement in Target-Area Hair Count versus vehicle; Scalp 2, an identically designed trial, reported 168%. Both hit statistical significance, but a three-fold spread between identical protocols is a reminder that "relative improvement versus vehicle" is a volatile metric and the honest expectation sits somewhere in that range, not at the headline number.
Winlevi and Breezula are not the same product
Winlevi is an approved 1% cream for acne. Breezula is the unapproved higher-strength solution (5% in Phase III) for hair loss. Buying Winlevi and applying it to your scalp is not running the trial protocol. It is a fraction of the strength.
It treats cycle acne at the same time
This is the only hair compound here that also addresses the other classic androgenic cosmetic complaint. Elevated androgens drive sebaceous gland activity; clascoterone blocks that at the receptor, which is its FDA-approved use.
The most credible compound in the topical antiandrogen category
RU58841 has 1990s animal data. Pyrilutamide has mixed trials concentrated in China. Clascoterone has an existing FDA approval in a related indication plus positive Phase III hair-loss data from 1,465 men across US and European sites. If this category interests you, this is the one with the strongest evidence. It is simply not purchasable for hair yet.
Dosage Guidelines
| Experience Level | Dosage Range |
|---|---|
| Beginner | 1 – 1 applications/day |
| Intermediate | 2 – 2 applications/day |
Concentration is the meaningful variable, not application count. The Phase III hair-loss program used a 5% topical solution; earlier Phase II work in male AGA reported increases in target hair count and hair width with a 7.5% solution twice daily, and concentrations of 2.5%, 5% and 7.5% have been studied. The approved acne product (Winlevi) is a 1% cream, a much lower strength than the hair-loss formulation, so using the acne cream for scalp coverage is not equivalent to the trial protocol. The hair-loss product is not yet on the market; Cosmo planned FDA and EMA submissions after completing 12-month safety follow-up in spring 2026.
Clascoterone is designed to be hydrolysed in the skin to cortexolone, which is inactive at the androgen receptor. The mechanism by which the drug is intended to act locally without producing systemic antiandrogen effects. This local-inactivation design is the same idea behind RU58841, but here it is attached to a molecule that has cleared FDA review for a topical indication.
Side Effects
Application site reactions
uncommonLocal irritation, erythema, dryness or scaling. In the Phase III hair-loss trials, treatment-emergent adverse events were reported as similar to vehicle, with most not related to study drug.
Reduce frequency or volume if irritation appears.
Local HPA-axis effects (with the acne cream, at scale)
rareClascoterone is structurally a corticosteroid derivative. The Winlevi labelling addresses the theoretical potential for hypothalamic-pituitary-adrenal suppression with extensive application, which is why large-surface-area use is treated with more care than a small scalp application.
Do not apply over large body surface areas. Follow labelled use for the approved product.
Unknown effects beyond trial duration
uncommonThe hair-loss formulation is not yet marketed and long-term safety follow-up was still completing as of 2026. Multi-year real-world data does not exist.
None beyond recognising the limitation.
General Mitigation Strategies
Tolerability in the Phase III hair-loss program was reported as comparable to vehicle, which is a meaningfully stronger safety position than the research-chemical alternatives in this category. The realistic issues are local irritation and the corticosteroid-derived caution about extensive application. Anyone using the approved 1% acne cream off-label on the scalp should understand they are applying a fraction of the strength studied for hair.
Post Cycle Therapy (PCT)
No HPT axis interaction from topical use. No PCT implications.
How It Works
Clascoterone competes with DHT for binding at androgen receptors in the target tissue (sebaceous glands in acne, hair follicles in androgenetic alopecia) blocking downstream androgen-driven signalling. It is then hydrolysed locally to cortexolone, which does not activate the androgen receptor. Acting at the receptor rather than on 5-alpha-reductase means the mechanism is theoretically indifferent to which androgen is driving the effect.
Hormonal & Androgenic Profile
N/A: an androgen receptor antagonist.
Not an aromatase or estrogen tool.
None: it competes at the androgen receptor rather than inhibiting 5-alpha-reductase. Theoretically that covers the compounds finasteride cannot help with (DHT-derivatives, 19-nors, trenbolone), though this has not been studied in AAS users.
No documented cardiovascular effect from topical use.
Fundamentals
Reference on the practices relevant to Clascoterone: how they are done and where they go wrong. Not a recommendation to use it.
Common Stacks
- Clascoterone + Minoxidil: independent mechanisms
- Clascoterone for someone dealing with both cycle acne and hair loss
- Note the hair-loss formulation is not yet marketed. The approved product is a 1% acne cream
Legal Status
The 1% cream is FDA-approved as Winlevi for acne vulgaris. The hair-loss product (Breezula, a higher-strength solution) is NOT yet approved, Cosmo Pharmaceuticals reported positive Phase III topline results in December 2025 and planned parallel FDA and EMA submissions after 12-month safety follow-up. Using the approved acne cream for hair loss is off-label.
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
Clascoterone is an androgen receptor antagonist, not an anabolic agent, and it holds current FDA approval for human therapeutic use (Winlevi), so it is not caught by the S0 non-approved substances clause that applies to RU58841 and pyrilutamide. It is not listed on the WADA Prohibited List and has no performance-enhancing action.