Clascoterone for hair loss: what the trials actually show

Clascoterone for hair loss comes up fair often as the "next big thing" in hair loss treatment and the headline "539% more hair" does make it sound like a massive breakthrough, but the full results haven’t been published. A UK pharmacist goes through what the numbers can and can’t tell you, the safety questions, and when it could reach the UK.

You've read the headlines, you've seen the posts in hair loss communities and you're wondering should I bother with finasteride and minoxidil when I can just wait for this instead? The short answer is no, do not wait. As with every hair loss breakthrough the license is still years away and the evidence isn't even known yet. The early results are encouraging. In two large trials involving 1,465 men, it did better than a dummy lotion on hair counts.^[1] But those results come from Cosmo, the company developing it, which also paid for the trials.^[2] They also haven’t published the actual hair counts, and nothing from these trials has been peer reviewed yet.^[3]

Clascoterone works by blocking androgen receptors, the parts of your cells that hormones such as testosterone and dihydrotestosterone (DHT) attach to. It’s currently licensed for acne as Winlevi 10mg/g cream, in the US since 2020 and in the UK since January 2025, for people aged 12 and over.^[4] [5]

The hair loss version you see people talking about is different and is a 5% solution, five times the strength of the acne cream, applied to the scalp twice a day. You may also see it called Breezula, a name the company has used for it, or by its development code, CB-03-01. It currently isn’t licensed for hair loss in the UK or US or anywhere else.^[6] [7]

DHT, a hormone your body makes from testosterone, is part of what drives male pattern hair loss. In men who are genetically prone to it, DHT attaches to androgen receptors in the hair follicles and switches on genes that contribute to hair loss.^[8]

Finasteride and clascoterone step in at different points. Finasteride blocks the enzyme that turns testosterone into DHT, so it lowers DHT in your blood and your scalp.^[9] Clascoterone doesn’t stop DHT being made. It blocks the receptor DHT attaches to, and the idea is that it does this where you put it rather than around your whole body. This is the big appeal for clascoterone as it isn't altering your hormone levels in the blood it instead just stops the hromone acting on the scalp and in theory it will help avoid some of the side effects that put men off trying finasteride or dutasteride. If you want more information on DHT blockers you can check our dutasteride vs finasteride guide for more detail.

But this is a theory and what they hope to find and has not yet been proven to be clinically correct. No trial has tested whether clascoterone avoids those effects. Cosmo says the hair loss trials found no significant hormonal side effects, but it hasn’t published the data.^[11]

Minoxidil is different to all three of these and is thought to work by improving blood flow to the follicles and keeping hairs in their growth phase for longer, though exactly how isn’t fully understood.^[12] This is why it’s so often combined with a DHT blocker such as finasteride.

Nobody knows yet whether clascoterone adds any extra hair gains to other medications either. The trials excluded men who had used minoxidil in the previous 12 weeks, or finasteride or dutasteride in the previous 6 months, so there’s no data on combining them.^[2]

Clascoterone 5% has been through two matching phase 3 trials, SCALP 1 and SCALP 2, the ran between 2023 and 2026. Together they involved 1,465 adult men with mild to moderate hair loss, at 51 sites in the US, Georgia, Germany and Poland. It is important to note that they were sponsored and paid for by Cassiopea, Cosmo’s Italian subsidiary, which doesn't immediately write off the results but needs to be taken into account when reading data about the results of the trial.^[2] [13]

For the first 6 months, two in three men were given clascoterone and one in three a dummy lotion with no drug in it, applied twice a day to the crown and temples. It was a double-blind study and neither the men nor the study doctors knew who had which.

The trials had two main measures at 6 months. One was the change in the number of thicker hairs, rather than fine fuzz, in a marked patch of scalp. The other was how the men rated their own hair coverage on a questionnaire.

Cosmo announced the results in December 2025. On hair counts, clascoterone did better than the dummy lotion in both trials, and the difference was statistically significant. On the men’s own ratings, it was significantly better in one trial and showed a positive trend in the other, and the two trials together were significantly better. Cosmo hasn’t said which trial was which.

This tells us that it does beat the placebo, but we don’t know by how much by. Apart from two ratios, 539% and 168%, which we look at next, Cosmo hasn’t released any hair counts, and nothing has been published in a journal or peer reviewed. In July 2026 it said scientific papers are expected to follow.

Two more things worth knowing. Cosmo says side effects were similar to the dummy lotion and the dermatologist quoted in its announcements was one of the trial investigators, so those quotes aren’t independent.^[11]

The 539% comes from Cosmo’s announcement, not a published paper, and it isn’t a hair count. Cosmo describes it as a 5.39 times relative improvement over the dummy lotion. That reads as the change on clascoterone divided by the change on the dummy lotion, although Cosmo hasn’t said exactly how it was calculated.^[1]

Without the actual numbers we can't actually use this to gauge how well it works, as say the men on the dummy lotion gained 1 hair in the marked patch, and the men on clascoterone gained 5.4. That’s 5.4 times as much, but. If the dummy group gained 10 and the clascoterone group 54, the ratio would be the same, but the difference would be 44 hairs.

So the ratio on its own can’t tell you how much hair anyone grew. It also depends heavily on the dummy group. If one trial’s dummy group gained 1 hair and the other’s gained 6.5, the same 4.4 extra hairs on clascoterone would work out at roughly 539% in the first trial and 168% in the second.

That earlier trial, a phase 2 study in 404 men at six German centres, is the only source of published hair counts in men. After 12 months, men on the 5% lotion had about 14 more hairs than the dummy group in each cm² of scalp, a patch roughly the size of a fingernail. But most of that gap came from the dummy group losing about 9 hairs.

Those men used less lotion than in the phase 3 trials, but a stronger 7.5% version giving the same daily amount of drug did about the same. And on the men’s own rating of their hair growth, clascoterone wasn’t significantly better than the dummy lotion.^[7]

For a rough sense of scale, finasteride’s two main trials, published in 1998, followed 1,553 men for a year. Men on finasteride had 107 more hairs than men on placebo in a 1-inch circle at the crown, which works out at about 21 per cm². That isn’t a fair head-to-head: the trials were around 20 years apart, counted hairs differently and used different groups of men.^[9]

So before anyone can say how clascoterone compares with finasteride, we’d need the phase 3 hair counts, and ideally a trial testing the two side by side. Until then, 539% tells you it beat the dummy lotion but not how much hair you will actually grow from using it.

In April 2026, Cosmo announced results from the second half of the trials. Only men who said on the questionnaire at 6 months that their hair had improved could carry on. Those on clascoterone were then split again: two in three stayed on it, and one in three was switched to the dummy lotion without being told.^[11] [2]

According to Cosmo, men who stayed on clascoterone for the full year had hair counts 2.39 times better than men who were switched, and the switched men’s counts fell. But again the actual hair counts weren't published, so we don't know how much extra hairs the men ended up with.

Because only men who felt it was working carried on, it tells us nothing about men it didn’t help. And the second half was single-blind: the men didn’t know which lotion they had, but the study doctors did.^[2]

It does show us that the benefit fades when you stop, which is also true of finasteride and minoxidil. With clascoterone, keeping the benefit would mean applying it twice a day, every day, for as long as you want to keep the hair.

Cosmo says side effects in the hair loss trials were similar to the dummy lotion, with no significant hormonal effects. Its December 2025 announcement went further, saying clascoterone works “without systemic absorption”, meaning it doesn’t get into the bloodstream. Though none of the safety data behind either claim has been published.^[1]

The phase 2 trial in men does have published safety figures, and they’re reassuring as far as they go. Four of 78 men on the 5% lotion stopped because of side effects, as did 4 of 82 on the dummy lotion. None of the serious side effects in men on clascoterone were judged to be caused by it.^[7]

The acne cream’s UK label shows what to watch for. In a high-dose study, 1 in 20 adults and 2 in 22 teenagers had blood test signs that their adrenal glands, which make the hormone cortisol, were being suppressed. All were back to normal 4 weeks after stopping, and none had symptoms. The label also lists raised potassium as a common side effect, though in the acne trials that checked it, it was about as common on the dummy cream (3.9%) as on clascoterone (3.6%).^[4]

Normal acne use puts about 20mg of clascoterone on the skin each day, and the European label caps adults at 5g of cream a day, which is 50mg. The high-dose study used about 120mg a day for 2 weeks. The hair loss trials used 150mg a day, and hair loss treatment lasts years, not weeks.

A scalp lotion may not be absorbed in the same way as a cream, so these figures don’t tell you how much reaches the blood. But only 123 people in the acne trials were treated for up to 12 months.^[4] This is why we need to wait for the full safety data before deciding it can be used “without systemic absorption”.

The UK label also advises caution alongside other medicines that can suppress the adrenal glands, such as steroid creams and inhalers, and the European label describes clascoterone as structurally related to steroid creams. In pregnancy, animal studies showed harm to unborn young and the European label says not to use it. Men in the hair loss trials had to use contraception with female partners.^[4] [15]

In animal studies, 9 months of the 2.5% and 5% creams shrank the outer layer of minipigs’ adrenal glands, which didn’t fully reverse in males. The treated skin also had more hair follicles in their resting phase, though the UK label says these minipig findings weren’t considered adverse. In a 2-year rat study, the European label reports more benign (non-cancerous) tumours of the skin’s oil glands where the 5% cream was applied, in males only. Animal results don’t always apply to people.

Now none of this means clascoterone is unsafe, we just need to wait for the data surrounding its use in the lotion formulation at the dose and length of time you would use for hair loss treatment, which the acne data doesn not cover.

No, and we wouldn’t recommend trying. Winlevi does contain the same medicine, but it isn’t the same product that was used in the trials, it is a 1% cream, which a fifth of the strength of the 5% lotion used in the hair loss trials. In Cosmo’s phase 2 trial, the weakest strength tested was 2.5%, and no trial has tested Winlevi itself on the scalp. A cream is also a different product from a scalp lotion, and nobody has measured how it behaves on the scalp.

The safety questions from the last section apply too. The UK label warns that using it over large areas or for a long time increases how much is absorbed, and treating hair loss would mean both.

A prescriber can sometimes prescribe a medicine outside its licence. But MHRA guidance says they must be satisfied that a licensed medicine wouldn’t meet your needs, and that there’s enough evidence it’s safe and works.

We don’t prescribe Winlevi for hair loss. Lots of people search for it, so offering it would be good for business. But there’s no evidence it works on the scalp and better-tested treatments are available now, so the only reason to offer it would be to make a quick sale off someone wanting to try it which isn't how we work.

Probably not anytime soon, Cosmo hasn’t applied for a licence anywhere yet. In December 2025 it said it would apply in the US and Europe promptly after the 12-month results, which came in April 2026. It now plans to apply in the US between January and March 2027, and in Europe between April and June 2027.

The FDA’s standard target for reviewing an application like this, for a medicine it has already approved in another form, is 10 months. So an application in early 2027 points to a US decision around the end of 2027 or early 2028 at the earliest.

Under the MHRA’s International Recognition Procedure, it can rely on an approval from the US or Europe and aim to decide within 60 to 110 days.

A company can also apply to the MHRA directly, without waiting for another regulator. That route aims for a decision within 150 to 210 days of assessment, not counting the time the company spends answering questions, but it is unlikely they will go down this route as no UK application has been announced.

My personal estimate is that it’s unlikely to be licensed in the UK before 2028. And a licence isn’t the same as being able to get it, someone would also need to sell it here, and no UK partner has been announced for the hair loss lotion.

This massively depends on the full results holding up and the safety data holding up to their claims. If they do, the obvious fit is men who can’t or won’t take finasteride or dutasteride such as men who’ve had side effects on it, or who’d rather not take a tablet that lowers DHT around the body. The trials only included men with mild to moderate hair loss, though, so there’s no evidence yet for more advanced hair loss.

Clascoterone would be a lotion you apply twice a day, every day, for as long as you want to keep the hair. Sticking to that routine is the biggest problem people have with minoxidil lotion, as we cover in our oral and topical minoxidil guide.

Male pattern hair loss usually means a slowly receding hairline or thinning crown on an otherwise healthy scalp. Arrange to be seen by your GP if any of the following apply:

1. Your hair is coming out suddenly or getting worse quickly, rather than thinning gradually.
2. You have a completely bald patch, rather than general thinning.
3. Your scalp is red, scaly, crusted, sore or burning, rather than looking normal.
4. You’re also losing hair from your eyebrows, eyelashes, beard or body.
5. You’ve had heavy shedding for several months.
6. You have other new symptoms, such as tiredness or changes in your weight.

Our types of hair loss guide has the full list.

If you’re taking finasteride and notice low mood, depression or thoughts of suicide, stop taking it and speak to your prescriber or GP straight away. For urgent help that isn’t an emergency, call 111 and choose the mental health option. If you do not feel you can keep yourself safe, call 999 or go to A&E.