Breezula for Hair Loss: What the Phase 3 Results Really Show
Published by AmpleLab Research
The two main pharmacological approaches to androgenetic hair loss work in very different ways: minoxidil affects the growth cycle without directly targeting androgens, while finasteride and dutasteride lower DHT throughout the body by blocking the enzyme that produces it. Clascoterone, developed under Cosmo Pharmaceuticals as the topical solution Breezula, is neither. It's a competitive androgen receptor antagonist applied directly to the scalp: DHT is still produced at normal levels throughout the body, but clascoterone competes with it for the receptor at the follicle, reducing DHT's ability to act there locally. The mechanism itself isn't new, a Roussel-Uclaf compound called RU58841 worked the same way and was studied for AGA back in the 1990s, but it never progressed through the clinical development needed for approval. What would be new is a topical androgen receptor antagonist reaching regulatory approval specifically for AGA, something no drug in this category has achieved so far.
In December 2025, Cosmo announced topline results from its two pivotal Phase 3 trials, and the headline number that circulated everywhere was a 539% relative improvement over placebo. That number is real, and it's also only half the story: the second, identically designed trial reported 168%, a genuinely large gap between two trials meant to replicate each other. This article covers the mechanism, what the Phase 3 data actually shows once that gap is accounted for, and where the drug currently stands on the path to approval.
The Mechanism, and Why It's Genuinely Different
Clascoterone (cortexolone 17α-propionate) is a synthetic steroid, structurally derived from progesterone and 11-deoxycortisol, but it isn't a corticosteroid and doesn't act like one. At the follicle, it competes with DHT for the androgen receptor on dermal papilla cells, the cluster of cells at the base of the follicle that drives miniaturisation when DHT signalling is too high, reducing the ability of DHT to activate androgen signalling locally. Our article on DHT and the androgen pathway covers this receptor biology in more depth, and our finasteride vs dutasteride comparison covers the systemic route this drug is designed to reduce reliance on.
The design intent is predominantly local action: clascoterone is metabolised rapidly once absorbed into an inactive form, limiting how much reaches general circulation, though systemic exposure isn't reduced to zero. That's meaningfully different from finasteride or dutasteride, which work precisely by lowering DHT throughout the body. Systemic side effects like libido or mood changes are a direct consequence of that systemic action, not an off-target accident. A receptor-level, predominantly local anti-androgen is designed to reduce that systemic trade-off, at least in principle; how completely it does so is still being established through the ongoing 12-month safety data discussed below.
Worth being precise about naming, since it causes real confusion: clascoterone at 1% concentration, in a cream, is already FDA-approved as Winlevi for acne (since August 2020, with EU marketing authorisation following on 17 October 2025). Breezula is the same active molecule at five times the concentration, 5%, formulated as a leave-on scalp solution rather than a face cream, and studied specifically for AGA. Same molecule, different strength, different format, different indication, and as of writing, only one of the two is actually approved anywhere.
The Laboratory Evidence Behind the Mechanism
Beyond receptor-binding theory, there's direct tissue-level evidence for how clascoterone behaves in balding follicles specifically.
Researchers took scalp biopsies from 5 men with confirmed male pattern hair loss (Hamilton-Norwood III-VI) and cultured them ex vivo, meaning the tissue was kept alive outside the body rather than treated in a living patient. Clascoterone and minoxidil 5% were each applied directly to separate samples. Both restored dermal papilla inductivity and increased hair matrix keratinocyte proliferation to a broadly similar extent in this model. Clascoterone additionally reduced secretion of IL-6, a cytokine linked to suppressed hair growth, more than minoxidil did in this model. Worth being clear about the limits here: this is a 5-patient ex vivo study, not a clinical trial, and some of the researchers are affiliated with Cosmo. It's genuine mechanistic evidence for how the drug behaves in real balding tissue, not proof of a clinical effect, and the conflict of interest is worth knowing about even though it doesn't invalidate the finding.
The Phase 3 Data, and the 539% vs 168% Problem
On December 3, 2025, Cosmo announced topline results from SCALP 1 and SCALP 2 (NCT05910450 and NCT05914805), two identically designed Phase 3 trials that together randomised 1,465 men across 51 sites in the US and Europe, the largest Phase 3 programme ever run for a topical AGA treatment.
Both trials met their primary endpoint, statistically significant improvement in Target-Area Hair Count (TAHC) versus vehicle (p<0.05). SCALP 1 reported a 539% (5.39x) relative improvement; SCALP 2 reported 168% (1.68x). Treatment-emergent adverse events were reported as similar across both studies and similar to vehicle, with most not considered related to the study drug. This is company-reported topline data, not yet a peer-reviewed publication with full absolute numbers, so treat it as a first, favourable look rather than the final word.
The gap between 539% and 168%, in two trials designed to replicate each other, is worth actually understanding rather than picking whichever number sounds better. Because the headline figures are relative improvements versus vehicle, they can be influenced by differences between the two trial populations and their underlying hair counts, rather than by a difference in how well the drug itself performed. Cosmo's CEO has attributed the difference to baseline hair counts.
Cosmo CEO Giovanni Di Napoli told the outlet the difference between the two trials was driven entirely by baseline hair counts, not by a difference in drug performance, explaining that when two groups see a similar absolute increase in hair count but start from different baselines, the trial with the lower starting point will show a larger relative percentage. That's a plausible and internally consistent explanation, but it's still a company statement rather than something that can be independently verified until the full absolute data are published, so the underlying reason for the discrepancy can't yet be checked directly.
Cosmo hasn't yet published the full absolute hair-count figures for both trials publicly, which is what would let this be evaluated properly rather than through the more dramatic relative number.
What can be said honestly right now: both trials hit statistical significance on the same primary endpoint, which is a real and meaningful result. What can't be said honestly yet is that the drug produces a "539% improvement," full stop, since that specific figure is one trial's result, not the programme's, and the other trial's own result was more modest. The more defensible summary is that clascoterone showed a statistically significant benefit over placebo in both trials, with the actual clinical magnitude still to be clarified once absolute numbers and full peer-reviewed data are available.
The 12-Month Data and What It Adds
The Phase 3 trials had a six-month vehicle-controlled period, after which the vehicle group was switched onto active clascoterone, and the full cohort continued to be followed for 12 months. Cosmo has reported that men who remained on clascoterone the whole time continued to gain hair count through month 12, while those switched from vehicle to active treatment at month six showed a smaller cumulative gain by that point, a statistically significant 239% (2.39x) difference favouring the group treated for the full year. That's an early signal that hair-count benefit can continue accumulating with ongoing treatment rather than plateauing by six months, though again, this is company-reported topline data rather than a peer-reviewed publication, and durability beyond the 12-month mark hasn't been studied yet.
On safety, Cosmo already has a real-world safety base to draw on beyond these trials: Winlevi (clascoterone 1% cream) has been in routine acne use since 2020, giving years of pharmacovigilance data on the underlying molecule. Winlevi provides real-world safety experience with the molecule, but it cannot substitute for safety data on chronic exposure to the 5% scalp formulation, which is five times the concentration and applied to a different, much larger area of skin. The topline safety and tolerability profile from the Phase 3 programme itself has been described as comparable to vehicle, which is encouraging but, again, not yet independently verified through full published data.
The Actual Timeline, and How It's Already Shifted
At the December 2025 topline announcement, Cosmo described regulatory submission preparations as "underway," pending completion of the required 12-month safety follow-up, which the company expected to finish in spring 2026.
Cosmo's most recent guidance, from its half-year 2026 results, confirms the Phase 3 programme is complete with positive 12-month efficacy and safety data supporting chronic use, and states the company "remains on track to submit regulatory applications in the United States in the first quarter of 2027 and in Europe in the second quarter of 2027." That's a more specific and somewhat later target than the loose "pending spring 2026 data" framing from the original December announcement, an example of how these timelines tend to move, even for a well-funded company with a genuinely strong dataset.
Filing isn't approval. A regulatory submission is typically followed by a standard review period before any decision, and delays or requests for additional data are common at this stage of drug development, so approval, if granted, would follow sometime after these filing dates rather than alongside them. As of writing, Breezula is not approved anywhere and is not available for purchase through any legitimate channel.
What About Using Winlevi for Hair Right Now?
Because Winlevi (clascoterone 1% cream) is already available on prescription for acne, some people have looked into using it off-label on the scalp while Breezula remains unapproved. Worth being direct about why that's a weaker proposition than it sounds: Winlevi is formulated at one-fifth the concentration studied in the AGA trials, in a cream base designed for facial skin rather than a solution designed for scalp penetration, and there's no published trial data on its effectiveness for hair loss at that concentration or in that format. We're not covering dosing or off-label use here, in line with our usual approach to unapproved or off-label treatments, but the concentration and formulation mismatch alone is a good reason for scepticism about whether it would replicate anything close to the Phase 3 results.
Frequently Asked Questions
Is the 539% figure accurate?
It's an accurate figure from one of the two Phase 3 trials, but it's not the whole programme's result. The second identically designed trial reported 168% relative improvement for the same endpoint. Both hit statistical significance, but the size of the effect looks quite different depending on which trial's number gets quoted, and the full absolute hair-count data needed to properly compare them hasn't been published yet.
How is clascoterone different from finasteride?
Finasteride lowers DHT production throughout the body by inhibiting the enzyme 5-alpha reductase. Clascoterone leaves DHT production untouched and instead blocks the receptor at the follicle so DHT can't act there locally. The intended trade-off is that clascoterone avoids the systemic hormonal exposure responsible for finasteride's more commonly discussed side effects, though independent, long-term human safety data for the scalp-specific 5% formulation is still being established.
When will Breezula be available?
Cosmo currently targets a US regulatory filing in Q1 2027 and an EU filing in Q2 2027, with any approval decision coming later if the applications are accepted and the reviews proceed without major delays. This timeline has already moved once since the Phase 3 data was announced, so treat any specific date, including this one, as subject to further change.
Is Breezula the same as Winlevi?
Same active molecule (clascoterone), different product. Winlevi is a 1% cream, FDA-approved for acne since 2020. Breezula is a 5% scalp solution studied specifically for androgenetic alopecia and not yet approved anywhere. The concentration, formulation, and application site are all different enough that Winlevi's acne approval doesn't tell you much about how the 5% scalp solution will ultimately perform or be reviewed for hair loss.
Selected Research
This article is provided for educational purposes and does not constitute medical advice. Breezula (clascoterone 5% solution) is an investigational drug not approved by any regulator and not available for purchase through any legitimate channel. Winlevi (clascoterone 1% cream) is approved for acne only; using it off-label for hair loss has not been studied and is not something we're covering here. AmpleLab products are cosmetic formulations, unrelated to clascoterone, and are not intended to diagnose, treat, cure, or prevent any condition.
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