RU58841

It is often proposed as a topical alternative to finasteride, but the published human evidence is a metabolism study, not a hair-growth result. The registry trail is real; the efficacy claim is not.

Binds the androgen receptor and was designed as a rapidly metabolised topical drug to limit systemic exposure. A 2026 human study detected parent drug in blood after a topical dose, so the local-only assumption needs qualification.

Key Distinction: An investigational or unapproved compound has no approved indication, and a proposed mechanism is not a demonstrated clinical effect.

Two completed human trials registered under PSK-3841 in the early 2000s, with no published results. A 2026 study in six men characterised metabolism and systemic exposure.

Any published efficacy result from the completed trials. A human safety dataset and long-term outcomes. Whether the demonstrated systemic exposure has meaningful hormonal effects. Independent quality standards for commercially supplied material.

Publication span: 2005–2026

What Has Actually Been Studied

• Investigation into the metabolism and elimination behavior of RU 58841, and its influence on the steroid profile in humans (Biomedical Chromatography, 2026) — Single-dose human metabolism and excretion study.
• Hair regrowth with topical PSK 3841 2.5% and 5% in male androgenetic alopecia (ISRCTN registry, 2005) — Multicentre, double-blind, randomised, vehicle-controlled trial (registry record).
• Safety and tolerance of topical PSK 3841 5% in men with androgenetic alopecia (ISRCTN registry, 2005) — Double-blind, randomised, vehicle-controlled safety and tolerability study (registry record).

Preparation and Handling

Lyophilized peptides ship as freeze-dried powders; whatever happens next involves diluents, concentrations and storage conditions that are compound- and product-specific.

United States Regulatory Status

No FDA-approved product

• No approved product in Drugs@FDA or any other regulator identified at this review.
• ISRCTN49873657 registered a four-week, double-blind, vehicle-controlled safety and tolerability study of 5% PSK-3841 in men with androgenetic alopecia.
• ISRCTN71083772 registered a six-month, multicentre, double-blind, vehicle-controlled hair-regrowth study of 2.5% and 5% PSK-3841 in men with androgenetic alopecia.
• Both registry records are marked completed. Neither has posted published results, so there is no human efficacy estimate to cite.
• A 2026 study in six healthy men detected five urinary metabolites and measurable parent drug in dried blood after a single 30 mg topical dose, demonstrating systemic exposure.
• RU58841 is sold as a research chemical, not as a pharmaceutical product. Purity, identity and sterility of commercial material are not guaranteed by any approval.