CB-03-01 is the development code for clascoterone, a topical androgen receptor antagonist structurally related to spironolactone. It was developed by Cassiopea (now Cosmo Pharmaceuticals) as a topical that blocks androgens at the skin level without systemic effects.

Is CB-03-01 an approved medicine?

Yes, in one indication. Clascoterone 1% cream is approved as Winlevi for acne: by the FDA in 2020 and by the EMA in 2022. The hair loss formulation, developed under the name Breezula, is not approved anywhere.

What is the difference between Winlevi and Breezula?

Same molecule, different concentrations and indications. Winlevi is the approved 1% acne cream. Breezula is the investigational higher-concentration topical for androgenetic alopecia, which has completed Phase 2 studies with published results and is progressing through later-stage development. It has no marketing authorisation.

Is clascoterone a research chemical?

No, not in the way RU-58841 and pyrilutamide are. Because an approved formulation exists (Winlevi), the molecule is a licensed medicine in that indication. Selling unlicensed clascoterone preparations crosses into territory the unapproved compounds do not: the authorities do not need to argue anything, a marketing authorisation already exists for the molecule.

Can I buy CB-03-01 from Norwood Labs?

No, and that is deliberate. We supply unlicensed research compounds with no marketing authorisation anywhere. Clascoterone has one, so it does not belong in that catalogue. The distinction is the reason our catalogue policy exists.

How does clascoterone compare to RU-58841 and pyrilutamide?

Mechanically similar in the broadest sense: all three are topical androgen receptor antagonists. Clascoterone has the strongest human evidence (approved acne indication, published hair-loss Phase 2 data), pyrilutamide has China Phase 3 company-reported data, and RU-58841 has no completed human trials. Evidence strength and regulatory status are two separate axes, and clascoterone scores highest on both, which is exactly why it is treated differently.

What Is CB-03-01 (Clascoterone)? Explained for 2026

Key facts (as of October 2026)

CB-03-01 is clascoterone, a topical androgen receptor antagonist.
The FDA approved clascoterone 1% cream (Winlevi) for acne in August 2020, with EMA approval following in 2022.
Two large Phase 3 acne programmes supported that approval.
The hair-loss formulation, Breezula, remains unapproved as of October 2026.
Published Phase 2 results in androgenetic alopecia reported statistically significant hair count improvements versus placebo.
Because an approved form exists, Norwood Labs does not sell clascoterone.

The short version

CB-03-01 is clascoterone, a topical androgen receptor antagonist.
Approved as Winlevi (1% acne cream, FDA 2020, EMA 2022).
Not approved as Breezula, the hair-loss formulation still in development.
Because an approved form exists, it is not a research-chemical category product, and we do not sell it.
Research use only framing applies to the unapproved compounds we do supply.

The compound that crossed the line

CB-03-01 is clascoterone, a topical androgen receptor antagonist. It is the one compound in this niche with a marketing authorisation: approved by the FDA as Winlevi 1% cream for acne in August 2020, with the hair loss formulation, Breezula, still unapproved as of October 2026. It blocks DHT signalling locally in skin, the same design brief as RU-58841.

Winlevi: the approved side

The FDA approved clascoterone 1% cream as Winlevi in August 2020 for acne, with the EMA following in 2022. Two large Phase 3 programmes supported the approval, and the product has real-world safety data accumulating since launch. This is what an approved topical antiandrogen looks like, and it is the reference point every other compound in this space is measured against.

Breezula: the unapproved side

For hair loss, clascoterone is formulated at higher concentration under the brand name Breezula. Its Phase 2 results in androgenetic alopecia have been published and are genuinely interesting: statistically significant hair count improvements versus placebo, with the expected local tolerability profile. But Breezula holds no approval anywhere, and no launch date is confirmed. Same molecule, two very different regulatory statuses, which is exactly why the acne and hair-loss claims about it must be kept separate.

Why we do not sell it

Our catalogue rule is simple and it is the same one from the RU-58841 legality page: we supply unlicensed research compounds with no marketing authorisation anywhere in the world. Clascoterone has one. Selling unlicensed preparations of an approved molecule is a different legal category, and it is not one we operate in. If you are researching topical antiandrogens, the honest comparison is between the approved molecule you cannot buy as a research product (clascoterone) and the unapproved ones you can (RU-58841, pyrilutamide), with the regulatory difference being the point, not a detail.

The evidence table, honestly

	Clascoterone (CB-03-01)	Pyrilutamide (KX-826)	RU-58841
Approval status	Approved for acne (Winlevi); hair-loss form unapproved	No marketing authorisation anywhere	No marketing authorisation anywhere
Human trial data	Two Phase 3 acne programmes; published Phase 2 hair-loss data	China Phase 3 (company-reported topline)	None completed
Research-category status	Not research-category (approved molecule)	Research compound	Research compound
Sold by Norwood Labs	No, by policy	Yes	Yes