Clascoterone
Also known as: CB-03-01, Winlevi, Breezula
Topical Androgen Receptor Inhibitor | Acne & Hair Loss
Overview
Clascoterone (cortexolone 17-alpha-propionate) is a first-in-class topical androgen receptor inhibitor developed by Cassiopea SpA. In August 2020, the FDA approved Winlevi (clascoterone cream 1%) for the treatment of acne vulgaris in patients aged 12 and older, making it the first new mechanism of action for acne treatment in nearly four decades and the first topical anti-androgen approved for acne in the United States. Clascoterone is also under development as Breezula (clascoterone solution 7.5%) for androgenetic alopecia, where it has completed Phase 3 clinical trials. The compound works by competitively inhibiting androgen receptor activation at the site of application -- the sebaceous gland for acne and the hair follicle for androgenetic alopecia -- without producing the systemic anti-androgenic effects associated with oral anti-androgens such as spironolactone or cyproterone acetate. Its steroidal structure allows it to fit precisely into the androgen receptor binding pocket, and its rapid local metabolism to cortexolone (an inactive metabolite) limits systemic exposure. This pharmacological profile makes clascoterone suitable for use in both men and women, unlike systemic anti-androgens which carry risks of feminization in male patients.
Key benefits
- First-in-class topical androgen receptor inhibitor with FDA approval for acne
- Blocks androgen action locally at the sebaceous gland and hair follicle without systemic hormonal effects
- Suitable for both men and women, unlike systemic anti-androgens
- Rapidly metabolized to inactive cortexolone, limiting systemic exposure
- No clinically meaningful effects on systemic testosterone, DHT, or gonadotropin levels
- Addresses the root androgen-driven pathology of both acne and androgenetic alopecia
Mechanism of action
Clascoterone acts as a competitive antagonist of the androgen receptor (AR). When applied topically, it penetrates the skin and binds directly to androgen receptors in target tissues -- sebaceous glands (for acne) and dermal papilla cells of hair follicles (for alopecia). By occupying the AR binding site, clascoterone prevents dihydrotestosterone (DHT) and testosterone from activating the receptor and initiating the downstream signaling cascade that drives sebum overproduction and hair follicle miniaturization. Structurally, clascoterone is a synthetic derivative of cortexolone (11-deoxycortisol), modified with a 17-alpha-propionate ester. This structural design serves two purposes: the steroidal backbone provides high binding affinity for the androgen receptor, while the ester group is rapidly cleaved by local esterases in the skin, converting clascoterone to cortexolone, which has negligible androgen receptor binding. This built-in metabolic inactivation ensures that any compound reaching systemic circulation is pharmacologically inactive, confining the anti-androgenic effect to the treatment site. In clinical studies, clascoterone showed no meaningful impact on systemic hormone levels including testosterone, DHT, luteinizing hormone, or follicle-stimulating hormone at therapeutic doses, confirming its local mechanism of action.
Molecular data
- Type
- Steroidal androgen receptor inhibitor
- Half-life
- Short topical (local action; rapidly metabolized to cortexolone)
Indications
What the research community uses this compound for, with self-reported effectiveness.
Skin
Hair Loss
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | Clascoterone 1% cream (Winlevi) | Twice daily (morning and evening) | — |
| — | Clascoterone 7.5% solution (Breezula) | Once daily | — |
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Application site irritation, redness, or dryness
- Pruritus (itching) at the application site
- Contact dermatitis in sensitive individuals
Rare side effects
- Skin peeling or scaling at the application site
- Temporary increase in acne severity during initial treatment (purging)
- Hypersensitivity reaction to clascoterone or formulation excipients
Contraindications
- Known hypersensitivity to clascoterone or any component of the formulation
- Women who are pregnant or planning to become pregnant (anti-androgens carry theoretical teratogenic risk)
- Women who are breastfeeding (safety not established)
- Active skin infections at the intended application site
References
Primary literature and clinical-trial data informing this entry.