Clascoterone is a topical androgen receptor inhibitor. As Winlevi 1% cream, the FDA approved it in August 2020 to treat acne vulgaris in patients 12 years and older. It was the first approved drug that blocks androgen signaling in the skin, rather than lowering androgen levels or blocking them throughout the body.
A stronger 5% clascoterone solution for male pattern hair loss (androgenetic alopecia) has finished two phase 3 trials. Its developer, Cosmo Pharmaceuticals, reports positive results, but those data have not been peer reviewed. As of its July 2026 report, Cosmo plans to file for approval in the US in the first quarter of 2027. No clascoterone product is approved for hair loss.
This page summarizes what the FDA and EU labels, the clinical trials and the company’s trial disclosures report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Topical androgen receptor inhibitor (steroidal antiandrogen) |
| Brand / approval | Winlevi (Sun Pharma in the US); FDA approved August 26, 2020 (NDA 213433, new molecular entity); EU authorization October 17, 2025 |
| Route | Topical cream, for use on the skin only |
| Strength | 1% (10 mg clascoterone per gram) |
| Labeled dose | A thin layer (about 1 g) to the affected area twice daily, morning and evening |
| Half-life | Not stated in the US label; plasma levels reached steady state by day 5 of twice-daily use |
| Key mechanism fact | Breaks down to cortexolone, which the developers describe as inactive, limiting effects outside the skin |
| Hair-loss product | 5% solution (referred to as Breezula); phase 3 completed, not approved, US filing planned for Q1 2027 |
| US status | Prescription only; not a controlled substance |
| WADA | Not named on the 2026 Prohibited List |
What it is
Chemically, clascoterone is cortexolone 17α-propionate, formula C₂₄H₃₄O₅, molecular weight 402.5 g/mol (FDA label). Its parent steroid, cortexolone, is also known as 11-deoxycortisol (PubChem). The drug was developed by Cosmo and its spin-out Cassiopea under the code CB-03-01 (Dhillon, Drugs 2020).
Androgens such as testosterone and dihydrotestosterone (DHT) drive sebum (skin oil) production and are central to male pattern hair loss. Clascoterone acts at the end of that pathway: it competes with DHT for the androgen receptor in the skin. This is a different approach from the drugs that act throughout the body:
| Drug | How it reduces androgen action | Route |
|---|---|---|
| Clascoterone | Blocks the androgen receptor in the skin where it is applied | Topical |
| Finasteride and dutasteride | Block 5α-reductase, lowering DHT production in the body | Oral |
| Spironolactone | Blocks androgen receptors throughout the body; conditionally recommended for acne in the AAD guideline | Oral |
| RU-58841 | Topical androgen receptor blocker; never approved | Topical |
The evidence for the mechanism comes from animal and lab work:
- In animals. In hamsters, the drug showed strong antiandrogen activity where it was applied. Injected under the skin of rats, it showed no antiandrogen activity and did not change gonadotropin (LH and FSH) output. In that model, it was about as potent locally as cyproterone acetate (Celasco et al., Arzneimittelforschung 2004).
- In human sebocytes (oil-gland cells) in culture. It bound the androgen receptor with high affinity and reduced androgen-driven lipid and inflammatory cytokine production (Rosette et al., J Drugs Dermatol 2019).
- In human scalp dermal papilla cells in culture. It inhibited androgen-driven gene activity and DHT-stimulated IL-6 production (Rosette et al., J Drugs Dermatol 2019).
The FDA label itself is more cautious. It states that clascoterone is an androgen receptor inhibitor, but “the mechanism of action … for the topical treatment of acne vulgaris is unknown.”
Pharmacokinetics
Clascoterone is designed to act in the skin and break down quickly once it is absorbed. Skin and plasma esterases hydrolyze it to cortexolone, which is then metabolized to tetrahydrocortexolone. Glucuronide conjugates are excreted in urine (Di Stefano et al., Clin Pharmacol Drug Dev 2025). In those phase 1 studies, 1% or less of the applied dose was excreted in urine as conjugates.
The label’s maximum-use study had 20 adults with moderate to severe acne apply a mean of about 6 g of cream twice daily for 2 weeks (FDA label):
| Parameter (day 14, adults) | Value |
|---|---|
| Time to steady state | By day 5 |
| Peak plasma concentration (Cmax) | 4.5 ± 2.9 ng/mL |
| Average plasma concentration | 3.1 ± 1.9 ng/mL |
| Exposure over the dosing interval (AUC) | 37.1 ± 22.3 h·ng/mL |
| Plasma protein binding (in vitro) | 84–89% |
| Cortexolone in plasma | Generally below or near the 0.5 ng/mL limit of quantitation |
| Exposure in adolescents aged 12–17 | Similar to adults |
The label gives no elimination half-life, and excretion “has not been fully characterized in humans.” At about twice the exposure seen with the maximum dose, the cream did not prolong the QT interval to a clinically relevant extent.
Approved medical use
United States. Winlevi is indicated for the topical treatment of acne vulgaris in patients 12 years and older (FDA label). Labeled use:
- cleanse the area gently and let it dry;
- apply a thin, even layer (about 1 g) twice daily, morning and evening;
- keep it away from the eyes, mouth and mucous membranes;
- do not apply it to cuts, abrasions, eczema or sunburned skin.
The label lists no contraindications. Drugs@FDA lists the original approval as a type 1 new molecular entity on August 26, 2020 (Drugs@FDA).
European Union. The EMA’s committee (CHMP) gave a positive opinion on August 25, 2025, and the EU authorized Winlevi on October 17, 2025 (EMA EPAR). The EU label differs from the US label:
- Indication: acne vulgaris in adults, but only facial acne in adolescents aged 12 to under 18.
- Pregnancy: it must not be used during pregnancy. Patients get a card advising them to rule out pregnancy before starting, and to use contraception during treatment and for at least 10 days after stopping.
- Monitoring: it is under additional monitoring, and treatment should be started and supervised by an experienced doctor.
Guidelines. The 2024 American Academy of Dermatology acne guideline makes a conditional recommendation for topical clascoterone. Its strong recommendations go to benzoyl peroxide, topical retinoids, topical antibiotics and oral doxycycline. It strongly recommends oral isotretinoin (Accutane) for acne that is severe, scarring, causes psychosocial burden, or fails standard therapy (Reynolds et al., JAAD 2024). Clascoterone was not tested against isotretinoin in its approval trials.
What the research shows
Acne: the two phase 3 trials
Approval rested on two identical, multicenter, randomized, double-blind, vehicle-controlled trials (CB-03-01/25 and /26; NCT02608450 and NCT02608476). They randomized 1,440 patients aged 9 and older with moderate or severe facial acne (Hebert et al., JAMA Dermatol 2020). Patients had 30–75 inflammatory lesions and 30–100 non-inflammatory lesions (comedones) and applied about 1 g of cream or vehicle to the whole face twice daily for 12 weeks. The vehicle was the same cream without the drug.
The FDA label reports week-12 results for the 1,421 patients aged 12 and older. About 62% were female and about 83% had moderate acne at baseline:
| Week-12 outcome | Trial 1: clascoterone (n = 342) | Trial 1: vehicle (n = 350) | Trial 2: clascoterone (n = 367) | Trial 2: vehicle (n = 362) |
|---|---|---|---|---|
| IGA success | 18.8% | 8.7% | 20.9% | 6.6% |
| Difference vs vehicle (95% CI) | 10.1% (4.1–16.0) | — | 14.3% (8.9–19.7) | — |
| Non-inflammatory lesions, mean % reduction | 32.6% | 21.8% | 29.6% | 15.7% |
| Inflammatory lesions, mean % reduction | 44.6% | 36.3% | 47.1% | 29.7% |
| Inflammatory lesions, mean absolute reduction | 19.3 | 15.4 | 20.1 | 12.6 |
IGA success means an Investigator’s Global Assessment of clear (0) or almost clear (1), with at least a 2-grade improvement from baseline. Put simply, about 1 in 5 patients reached clear or almost clear skin in 12 weeks, compared with fewer than 1 in 10 on vehicle. The EMA described the effect as “modest” but statistically significant and clinically relevant.
Earlier trials
- Pilot trial, 2011. 77 men with facial acne applied placebo, clascoterone 1% or tretinoin 0.05% cream once daily for 8 weeks. Clascoterone was significantly better than placebo on total lesion count, inflammatory lesion count and acne severity index (Trifu et al., Br J Dermatol 2011).
- Phase 2b dose-finding trial. 363 patients were randomized to 0.1%, 0.5% or 1% cream, or vehicle, for 12 weeks. Treatment success was 8.6% with 1% twice daily and 2.7% with vehicle. The 1% twice-daily dose was chosen for phase 3 (Mazzetti et al., J Drugs Dermatol 2019).
Long-term use
An open-label extension enrolled 609 patients from the phase 3 trials and treated them with clascoterone for up to 9 more months, on the face, trunk or both (Eichenfield et al., JAAD 2020). Results:
- 347 completed the study.
- 18.1% had at least one treatment-emergent adverse event; the most common was nasopharyngitis (a cold).
- 19 adverse events in 14 patients were judged related to the cream, and 9 patients stopped because of them.
- No serious adverse event was judged treatment related.
Long-term efficacy was not a primary endpoint.
Androgenetic alopecia (the 5% solution)
The hair-loss product is a different formulation: a 5% solution, five times the concentration of the acne cream. Cosmo’s news page for the phase 3 results uses the name Breezula, but the product has no approved brand name. Its status from primary sources:
| Stage | Trial / document | Status and results |
|---|---|---|
| Phase 2 | NCT02279823: 5% solution vs minoxidil 5% vs vehicle, twice daily for 26 weeks, 95 men | Completed in 2016; no results posted on ClinicalTrials.gov and no peer-reviewed report found |
| Phase 3 | SCALP 1 (NCT05910450): 703 men aged 18 and older, sites in the US and the country of Georgia | Completed January 2026; no results posted on ClinicalTrials.gov |
| Phase 3 | SCALP 2 (NCT05914805): 762 men aged 18 and older, US, Poland and Germany sites | Completed July 2025; no results posted on ClinicalTrials.gov |
| Topline results | Cosmo press release, December 3, 2025 | Both trials met the hair-count endpoint vs vehicle (p under 0.05) |
| 12-month results | Cosmo press release, April 15, 2026 | Continued hair gains to month 12 on treatment; safety comparable to vehicle |
| Regulatory filing | Cosmo half-year report, July 23, 2026 | Not yet filed; US submission planned for Q1 2027 and EU for Q2 2027 |
Both phase 3 trials share the same design (NCT05910450; NCT05914805):
- Part 1: 6 months of double-blind treatment with the 5% solution or vehicle, applied twice daily.
- Part 2: 6 more months in which responders were re-randomized to stay on the drug or switch to vehicle (or the reverse).
- Co-primary endpoints at month 6: the change in non-vellus (thick, pigmented) hairs in a target scalp area, called the target area hair count (TAHC), and patients’ own rating of hair coverage.
Cosmo’s December 2025 release reports the following results for the 1,465 randomized men (Cosmo, December 2025):
- Hair count: one trial showed a 539% and the other a 168% “relative improvement” in TAHC compared with vehicle. The release does not say which trial was which, and gives no absolute hair counts or confidence intervals.
- Patient-reported outcome: significant in one trial, a positive trend in the other, and significant when the two were combined.
- Safety: treatment-emergent adverse events were similar to vehicle.
The April 2026 release reports that men treated for 12 months had a 2.39-fold greater TAHC improvement than men switched to vehicle after month 6, and that men kept gaining hair from month 3 to month 12 on continued treatment. It gives no p-values or absolute counts (Cosmo, April 2026).
The July 2026 half-year report confirms that the program is complete and that submissions have not yet been made. It also says scientific publications from the program “are expected to follow” (Cosmo, July 2026).
Reading the hair-loss numbers. A “539% relative improvement” compares the drug’s hair-count change with a small vehicle change, so it can sound much larger than the absolute difference in hairs. Until the absolute counts are published or reviewed by a regulator, the size of the benefit is unknown. The trials included only men, and there are no head-to-head results against minoxidil or finasteride.
Using the acne cream on the scalp is off-label. The approved cream is 1%, and the hair-loss trials used a separately formulated 5% solution.
People taking testosterone or other androgens
No published trial has tested clascoterone in people taking testosterone or other anabolic steroids. A Stanford trial of the 1% cream for acne in transgender men on masculinizing hormone therapy (18 participants) was active but no longer recruiting, with no results posted (NCT05891795). In rats, injected clascoterone showed no antiandrogen activity, and plasma levels in people are low. Whether it affects androgen action outside the skin in people on high androgen doses has not been studied.
Side effects and risks
Local skin reactions
In the phase 3 trials, local skin reactions were about as common with clascoterone as with vehicle (FDA label):
| New or worsening reaction | Clascoterone (n = 674) | Vehicle (n = 656) |
|---|---|---|
| Erythema (redness) | 12.2% | 15.4% |
| Scaling/dryness | 10.5% | 10.4% |
| Pruritus (itching) | 7.7% | 8.2% |
| Stinging/burning | 4.2% | 4.3% |
| Edema (swelling) | 3.6% | 3.5% |
| Striae rubrae (red stretch marks) | 2.5% | 1.5% |
| Skin atrophy (thinning) | 1.6% | 2.6% |
| Telangiectasia (visible small vessels) | 1.2% | 1.8% |
The label advises reducing how often the cream is applied, or stopping it, if irritation occurs. It also advises limiting other drying or irritating skin products. In a 2-year study in rats, 1% and 5% clascoterone cream increased skin and subcutaneous atrophy at the application site, but did not cause cancer.
HPA axis suppression
The label warns of HPA axis suppression. The HPA (hypothalamic-pituitary-adrenal) axis is the system that controls the body’s own cortisol output. Under maximum-use conditions over 2 weeks:
| Group | Abnormal cosyntropin test at day 14 |
|---|---|
| Adults | 1/20 (5%) |
| Adolescents aged 12–17 | 2/22 (9%) |
| Children aged 9–11 (not an approved age) | 2/27 |
The cosyntropin stimulation test measures how well the adrenal glands respond to stimulation; a post-stimulation cortisol of 18 mcg/dL or less was counted as abnormal. All patients had normal results about 4 weeks after stopping, and none had clinical signs of adrenal suppression. The abnormal results were not related to plasma drug levels or the amount applied (Bhatia et al., J Drugs Dermatol 2024; Mazzetti et al., J Drugs Dermatol 2019).
The label lists conditions that increase absorption: large treated areas, prolonged use and occlusive dressings. It adds that children may be more susceptible to systemic toxicity.
Potassium and hormonal effects
- Potassium. Shifts from normal to high potassium occurred in 5% of patients on clascoterone and 4% on vehicle. None were reported as adverse events or led to stopping, and they were not related to drug levels. The rate was highest in children under 12 (Del Rosso et al., J Clin Aesthet Dermatol 2023). The label does not require potassium monitoring.
- Reproductive. The label lists polycystic ovaries and amenorrhea (absent periods) among adverse reactions identified in clinical trials and long-term safety studies. It gives no rates.
Pregnancy and breastfeeding
There are no human pregnancy data. In rats given clascoterone by injection under the skin, malformations occurred at all doses tested, starting at about 8 times the maximum human exposure. In rabbits, post-implantation loss rose at 39 times the human exposure. The US label does not contraindicate use in pregnancy, but the EU label does and asks for contraception (EMA EPAR). There are no data on breastfeeding.
Interactions
No clinical drug interaction studies have been done. In lab tests, clascoterone did not meaningfully inhibit or induce the major CYP liver enzymes. The label concludes it is not expected to change levels of drugs metabolized by them.
Legal status and use outside medicine
- US: a prescription drug; it is not named in the DEA’s anabolic steroid schedule (21 CFR 1308.13).
- EU: prescription only, under additional monitoring.
- Sport: clascoterone is not named on the WADA 2026 Prohibited List (WADA 2026 Prohibited List).
- Hair loss: the 5% solution is investigational. Any product sold as a clascoterone hair-loss solution is not an approved medicine.
Key takeaways
- A skin-targeted antiandrogen. Clascoterone blocks androgen receptors where it is applied and breaks down to cortexolone, keeping systemic exposure low (average plasma level about 3 ng/mL at maximum use).
- Approved for acne only. Winlevi 1% cream is FDA approved (2020) and EU authorized (2025) for acne in patients 12 and older; the EU limits adolescents to facial acne.
- Modest acne benefit. In two phase 3 trials, 19–21% reached clear or almost clear skin at 12 weeks, compared with 7–9% on vehicle.
- Mostly local side effects, with a real HPA caveat. Redness, dryness and itching occurred at rates similar to vehicle. Reversible lab-test HPA axis suppression appeared in 5–9% of patients under maximum use.
- Hair-loss solution not yet approved. Two phase 3 trials of a 5% solution were positive by the company’s account. Absolute results are unpublished, and Cosmo plans a US filing in Q1 2027.
- Different from finasteride and dutasteride. Those lower DHT throughout the body. Clascoterone acts on the receptor in the skin, and there are no head-to-head trials between them.
Sources
- Sun Pharmaceutical Industries. Winlevi (clascoterone) cream 1% prescribing information. Revised January 2025. DailyMed.
- Food and Drug Administration. Drugs@FDA: Winlevi, NDA 213433 (original approval August 26, 2020). FDA.
- European Medicines Agency. Winlevi (clascoterone): EPAR, EMEA/H/C/006138. EMA.
- Hebert A, Thiboutot D, Stein Gold L, et al. Efficacy and safety of topical clascoterone cream, 1%, for treatment in patients with facial acne: two phase 3 randomized clinical trials. JAMA Dermatol. 2020;156(6):621–630. PubMed.
- Eichenfield L, Hebert A, Gold LS, et al. Open-label, long-term extension study to evaluate the safety of clascoterone (CB-03-01) cream, 1% twice daily, in patients with acne vulgaris. J Am Acad Dermatol. 2020;83(2):477–485. PubMed.
- Mazzetti A, Moro L, Gerloni M, Cartwright M. A phase 2b, randomized, double-blind vehicle controlled, dose escalation study evaluating clascoterone 0.1%, 0.5%, and 1% topical cream in subjects with facial acne. J Drugs Dermatol. 2019;18(6):570–575. PubMed.
- Mazzetti A, Moro L, Gerloni M, Cartwright M. Pharmacokinetic profile, safety, and tolerability of clascoterone (cortexolone 17-alpha propionate, CB-03-01) topical cream, 1% in subjects with acne vulgaris: an open-label phase 2a study. J Drugs Dermatol. 2019;18(6):563–568. PubMed.
- Trifu V, Tiplica GS, Naumescu E, et al. Cortexolone 17α-propionate 1% cream, a new potent antiandrogen for topical treatment of acne vulgaris. A pilot randomized, double-blind comparative study vs. placebo and tretinoin 0·05% cream. Br J Dermatol. 2011;165(1):177–183. PubMed.
- Celasco G, Moro L, Bozzella R, et al. Biological profile of cortexolone 17alpha-propionate (CB-03-01), a new topical and peripherally selective androgen antagonist. Arzneimittelforschung. 2004;54(12):881–886. PubMed.
- Rosette C, Agan FJ, Mazzetti A, et al. Cortexolone 17α-propionate (clascoterone) is a novel androgen receptor antagonist that inhibits production of lipids and inflammatory cytokines from sebocytes in vitro. J Drugs Dermatol. 2019;18(5):412–418. PubMed.
- Rosette C, Rosette N, Mazzetti A, et al. Cortexolone 17α-propionate (clascoterone) is an androgen receptor antagonist in dermal papilla cells in vitro. J Drugs Dermatol. 2019;18(2):197–201. PubMed.
- Di Stefano AFD, Radicioni MM, Garhöfer G, et al. Pharmacokinetics, safety, and skin irritation and sensitization potential of clascoterone cream in early-phase clinical study participants. Clin Pharmacol Drug Dev. 2025;14(10):742–753. PubMed.
- Bhatia N, Eichenfield LF, Mazzetti A, et al. Hypothalamic-pituitary-adrenal axis response in patients with acne vulgaris treated with clascoterone. J Drugs Dermatol. 2024;23(6):433–437. PubMed.
- Del Rosso J, Stein Gold L, Squittieri N, Thiboutot D. Is there a clinically relevant risk of hyperkalemia with topical clascoterone treatment? J Clin Aesthet Dermatol. 2023;16(6):20–24. PubMed.
- Reynolds RV, Yeung H, Cheng CE, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2024;90(5):1006.e1–1006.e30. PubMed.
- Dhillon S. Clascoterone: first approval. Drugs. 2020;80(16):1745–1750. PubMed.
- Cassiopea SpA. A study to evaluate the efficacy and safety of clascoterone solution in treatment of male pattern hair loss (SCALP 1). ClinicalTrials.gov NCT05910450. ClinicalTrials.gov.
- Cassiopea SpA. A study to evaluate the efficacy and safety of clascoterone solution in treatment of male pattern hair loss (SCALP2). ClinicalTrials.gov NCT05914805. ClinicalTrials.gov.
- Intrepid Therapeutics. A phase 2 study to evaluate the safety and efficacy of CB-03-01 solution, a comparator solution and vehicle solution in males with androgenetic alopecia. ClinicalTrials.gov NCT02279823. ClinicalTrials.gov.
- Stanford University. Clascoterone for steroid-related acne vulgaris in transgender male patients receiving masculinizing hormone therapy. ClinicalTrials.gov NCT05891795. ClinicalTrials.gov.
- Cosmo Pharmaceuticals. Cosmo announces breakthrough phase III topline results from Scalp 1 and Scalp 2 for clascoterone 5% solution in male hair loss. Press release, December 3, 2025. Cosmo.
- Cosmo Pharmaceuticals. Phase III 12-month data for clascoterone 5% topical solution confirm positive safety for chronic use and continued hair growth. Press release, April 15, 2026. Cosmo.
- Cosmo Pharmaceuticals. Cosmo reports double-digit recurring revenue growth in H1 2026, advances clascoterone 5% topical solution toward regulatory submission, and confirms full-year guidance. Press release, July 23, 2026. Newsfile.
- National Center for Biotechnology Information. PubChem compound summary: cortodoxone (11-deoxycortisol), CID 440707. PubChem.
- World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.
- Code of Federal Regulations. 21 CFR 1308.13, Schedule III. 21 CFR 1308.13.