What is RU58841?
RU58841 (also written RU-58841 or RU 58841) is a synthetic, nonsteroidal antiandrogen that binds the androgen receptor. Roussel Uclaf scientists in Romainville, France, described it in 1994 as topically active and a candidate for androgen-dependent skin conditions such as acne, androgenetic alopecia and hirsutism (Battmann et al., 1994).
It is not an approved drug; a 2026 study describes it as lacking regulatory approval yet sold online (Okutan et al., 2026). Disguised Alpha supplies it only as Minoxidil 5% / RU58841 5% (50ML), a liquid dropper research blend that combines RU58841 5% and minoxidil 5% in one 50ML bottle, for laboratory research use only. Nothing on this page is guidance for use in people.
RU58841 reference data
| Property | Value |
|---|---|
| Name | RU58841 |
| Also called | RU-58841, RU 58841, PSK-3841, HMR-3841 |
| Structure | 5,5-Dimethylhydantoin ring carrying a 4-cyano-3-(trifluoromethyl)phenyl group and a 4-hydroxybutyl chain (IUPAC: 4-[3-(4-hydroxybutyl)-4,4-dimethyl-2,5-dioxoimidazolidin-1-yl]-2-(trifluoromethyl)benzonitrile) |
| Compound class | Nonsteroidal androgen receptor antagonist (N-substituted arylhydantoin); not a peptide |
| Molecular formula | C₁₇H₁₈F₃N₃O₃ |
| Molecular weight | 369.34 g/mol |
| Form | Minoxidil 5% / RU58841 5% (50ML): a liquid dropper research blend combining RU58841 5% and minoxidil 5% in one 50ML bottle |
| Testing | Third-party tested, with the certificate for each lot published on the product page and in the COA portal |
Identity data and aliases are from PubChem CID 132981; the FDA substance registry (UNII 0D8FJQ0ADW) lists the same substance. Name, strengths, volume, format and storage are from the product page, which lists no identity data.
See it beside the other compounds on this site in the peptide molecular weight reference table.
What the research covers
Published work on RU58841 falls into the five areas below. Nearly all of it is cell, tissue and animal data; the only study in people in PubMed is a small 2026 metabolism study.
Androgen receptor binding and antagonism in cells
Roussel Uclaf reported high affinity for androgen receptors from hamster prostate and flank organ (Battmann et al., 1994). In PC3 prostate cancer cells transfected with the wild-type receptor and a reporter, RU58841 did not activate the receptor at 10⁻¹¹ to 10⁻⁷ M and competitively suppressed activation by dihydrotestosterone (DHT), about as potently as hydroxyflutamide; the authors noted this could mean systemic effects after topical use (Pan et al., 1998).
In DU145 prostate cancer cells co-transfected with the receptor and its coactivator ARA70, it and other antiandrogens raised receptor-driven transcription, an agonist-like response (Miyamoto et al., 1998). Models: receptor binding assays and human prostate cancer cell lines.
Hamster and rat sebaceous gland models
In hamsters, topical RU58841 reduced flank organ area at as little as 1 microgram per animal, without antiandrogenic activity on deep accessory sex organs or a testosterone change up to 100 micrograms; 300 micrograms per animal given subcutaneously had only a small flank organ effect and weak systemic activity (Battmann et al., 1994).
On male Syrian hamster ears, four weeks of topical application at 10 micrograms per day shrank sebaceous glands by up to 60%; the opposite ear showed no inhibition, and glands returned to normal within four weeks of stopping (Matias et al., 1995). In male fuzzy rats, a 1% solution applied to the back for two months regressed sebaceous glands and ducts as much as castration without changing serum testosterone, DHT or prostate weight; finasteride, tested alongside, gave moderate regression and reduced prostate weight (Ye et al., 1997). Models: hamster and rat.
Hair follicle models: macaques, papilla cells and scalp grafts
Stumptailed macaques, which develop frontal balding after puberty, model androgenetic alopecia. In their cultured cells, testosterone inhibited outer root sheath cell proliferation only alongside dermal papilla cells from adult bald scalp, and RU58841 blocked this (Obana et al., 1997); with human keratinocytes, bald-scalp papilla cells likewise let testosterone inhibit keratinocyte proliferation, which RU58841 abolished (Pan et al., 1999).
In the animals, topical RU58841 increased hair density, thickness and length, with no systemic effects detected (Pan et al., 1998). On balding human scalp grafts kept on testosterone-conditioned nude mice, 8 of 29 active follicles (28%) on grafts given 1% RU58841 entered a second hair cycle, against 2 of 28 (7%) on ethanol controls, with a significantly higher linear hair growth rate (P < 0.04) (De Brouwer et al., 1997). Models: macaques, cell co-cultures and human scalp grafts on mice.
Skin penetration and prodrug studies
In hairless rat skin in vitro, 24-hour absorption was 3 to 4 times higher through normal skin than through scar skin lacking sebaceous glands; autoradiography placed the drug mainly in the stratum corneum and epidermis when applied in an alcoholic solution and mainly in sebaceous glands when applied in liposomes, and the authors concluded that sebaceous glands were the main pathway (Bernard et al., 1997).
An ester prodrug, RU 58841-myristate, had almost no receptor affinity and was rapidly converted to RU58841 by cultured human foreskin fibroblasts and keratinocytes, scalp dermal papilla cells and SZ95 sebocytes; in Franz cells, the prodrug formulation permeated reconstructed epidermis and excised pig skin only negligibly over 6 hours (Münster et al., 2005). Models: hairless rat skin, human skin cells, reconstructed epidermis and pig skin.
Metabolism and systemic exposure
In rats given 10 mg/kg intravenously, RU58841 left the plasma with a half-life of about 1 hour. Only about 1% of it became the slowly cleared N-desalkyl metabolite RU 56279, which was clearly antiandrogenic on prostate and seminal vesicle weight; the authors linked that low conversion to its local action without systemic effects (Cousty-Berlin et al., 1994).
In 2026, a Cologne doping-control laboratory found six metabolites in human liver fractions, formed by hydroxylation, oxidation, glucuronidation and N-dealkylation, which yields cyanonilutamide (RU 56279; PubChem CID 11162285). Six healthy men then received one scalp application of an RU 58841 hair serum: five metabolites appeared in their urine, and the parent compound and its oxidized metabolite in dried blood spots, which the authors called considerable systemic exposure; urinary steroid profile markers were unchanged (Okutan et al., 2026). Models: rats, human liver fractions and six volunteers.
Key studies
- Battmann T, et al. "RU 58841, a new specific topical antiandrogen: a candidate of choice for the treatment of acne, androgenetic alopecia and hirsutism." J Steroid Biochem Mol Biol. 1994. PMID 8136306. DOI 10.1016/0960-0760(94)90250-x. Hamsters: flank organ regression after topical application, with no deep accessory sex organ or testosterone effect up to 100 micrograms and weak systemic activity when given subcutaneously; rats: no effects up to 1 microgram per animal by either route.
- Cousty-Berlin D, et al. "Preliminary pharmacokinetics and metabolism of novel non-steroidal antiandrogens in the rat: relation of their systemic activity to the formation of a common metabolite." J Steroid Biochem Mol Biol. 1994. PMID 7947350. DOI 10.1016/0960-0760(94)90114-7. Rat plasma kinetics: fast clearance; antiandrogenic metabolite RU 56279.
- De Brouwer B, et al. "A controlled study of the effects of RU58841, a non-steroidal antiandrogen, on human hair production by balding scalp grafts maintained on testosterone-conditioned nude mice." Br J Dermatol. 1997. PMID 9415227. Scalp grafts on nude mice, randomized and blinded: more second hair cycles, faster linear growth.
- Pan HJ, et al. "Evaluation of RU58841 as an anti-androgen in prostate PC3 cells and a topical anti-alopecia agent in the bald scalp of stumptailed macaques." Endocrine. 1998. PMID 9798729. DOI 10.1385/ENDO:9:1:39. PC3 cells and macaques: competitive receptor antagonism; denser, thicker, longer hair.
- Okutan A, et al. "Investigation Into the Metabolism and Elimination Behavior of RU 58841, and Its Influence on the Steroid Profile in Humans." Biomed Chromatogr. 2026. PMID 42615108. DOI 10.1002/bmc.70602. Liver fractions and six volunteers: metabolites and systemic exposure.
Handling and storage of RU58841 and minoxidil dropper solution
General laboratory practice for this material:
- Store at 15 to 25°C with the cap closed, away from direct light and heat; do not freeze (storage guidance on the product page).
- Close the dropper after each use, and log each lot number with its certificate.
- The solution holds two actives, so analytical methods must resolve RU58841 (C₁₇H₁₈F₃N₃O₃, 369.34 g/mol) from minoxidil.
Frequently asked questions
What is the RU58841 mechanism of action?
RU58841 binds the androgen receptor and competes with androgens. In PC3 cells it suppressed DHT-driven receptor activity without activating the receptor (Pan et al., 1998). In DU145 prostate cancer cells co-transfected with the coactivator ARA70, it showed agonist activity (Miyamoto et al., 1998).
Is RU58841 a peptide?
No. RU58841 is a small synthetic molecule (C₁₇H₁₈F₃N₃O₃, 369.34 g/mol, PubChem CID 132981) built on a hydantoin ring, not a chain of amino acids. Papers place it among N-substituted arylhydantoin antiandrogens (Cousty-Berlin et al., 1994).
Is RU58841 FDA approved?
No. RU58841 has never been FDA approved: Drugs@FDA lists no product containing it (checked October 2026). The FDA substance registry lists it as UNII 0D8FJQ0ADW and notes that a UNII "does not imply any regulatory review or approval." A 2026 study describes it as lacking regulatory approval yet sold online (Okutan et al., 2026).
RU58841 vs finasteride: how do the mechanisms differ?
They act on different targets. RU58841 is an androgen receptor antagonist that blocks androgen signaling at the receptor (Pan et al., 1998). Finasteride inhibits the type II isozyme of steroid 5-alpha reductase instead, as described in a fuzzy rat study that tested both (Ye et al., 1997).
What RU58841 side effects have studies reported?
Apart from one small metabolism study, PubMed lists no study in people and no case report (searched October 2026), so the record is animal, cell and metabolism data. Subcutaneous RU58841 had weak systemic activity in hamsters (Battmann et al., 1994), and its metabolite RU 56279 was clearly antiandrogenic in rats (Cousty-Berlin et al., 1994).
One group warned that its receptor potency could mean systemic side effects after topical use (Pan et al., 1998). In six healthy men, RU58841 from one scalp application was detected in blood, which the authors said gives it potential for systemic effects; repeated use was not studied (Okutan et al., 2026).
Where can researchers buy RU58841?
Disguised Alpha sells RU58841 only combined with minoxidil, as a liquid dropper research blend for laboratory research, with each lot's certificate on the product page: Minoxidil 5% / RU58841 5% (50ML).
Related compounds and guides
- Minoxidil 5% / RU58841 5% (50ML)
- KY-19382 research guide
- PP405 research guide
- AHK-Cu research guide
- GHK-Cu research guide
- Research library
- COA portal: every published certificate, by lot
This product is for research use only. It has not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.