RU58841 vs Pyrilutamide

RU58841: human research exists, but it does not establish a treatment winner#

Historical studies under the name PSK-3841 include a four-week safety study and a six-month hair-growth study. Both registry records are marked completed, but their results/publications sections provide no outcome report as checked for this review. Trial registration is evidence that research was undertaken, not proof of a successful treatment. Safety registry, hair-growth registry.

A 2026 study of six healthy men detected RU58841 in blood after a single scalp application. It investigated metabolism and antidoping detection, not hair regrowth or repeated-use safety. Unchanged urinary steroid-profile markers in that experiment cannot establish general endocrine safety. These human findings contradict a promise that topical RU58841 stays entirely local. Okutan and colleagues, full paper.

Pyrilutamide: distinguish the trials and the source of the results#

Kintor's 2023 annual report describes a 740-man Chinese phase III study of a 0.5% formulation in which the improvement over vehicle was not statistically significant. Improvement from a group's own baseline was a different result. 2023 annual report, page 19.

In March 2026, Kintor reported positive results from a newer, 666-man phase III stage. At 24 weeks, the 1.0% and 0.5% twice-daily trial arms increased target-area non-vellus hair counts by 15.33 and 14.46 hairs/cm² from baseline, versus 4.68 with vehicle. The reported differences from vehicle were 10.65 and 9.78 hairs/cm². These concentrations describe study groups, not instructions for use. The sponsor reported no drug-related serious adverse events; that does not mean adverse effects are impossible or long-term safety is settled. March 18 announcement.

Those are sponsor disclosures, not a complete independent assessment of the trial data. Neither study compared pyrilutamide with RU58841. The sponsor's August 2026 report separately describes cosmetic sales and a planned Chinese drug application in the second half of 2026; a plan is not an approval. August 19 interim results.

Use the evidence to frame a clinical discussion#

• For a regrowth claim: ask whether it comes from a controlled human study, which formulation was tested, and whether the difference was against vehicle or only baseline. The current sources do not justify choosing RU58841 for faster results or pyrilutamide for guaranteed safety.
• For systemic-risk concerns: topical application alone does not establish negligible absorption. The RU58841 blood findings cannot quantify the risk of every formulation, and separate studies cannot establish a safety ranking between these compounds.
• For a seller's product: do not assume it is equivalent to the trial formulation. In the six-person RU58841 paper, the tested serum's measured concentration differed from its label; that finding concerns one product, not every vendor. A purity certificate cannot establish clinical safety or effectiveness.
• For a personal next step: discuss the diagnosis and established treatment options with a dermatologist. These sources do not validate DIY mixing, dose escalation, use with AAS, or application after microneedling.

For more source detail, read our RU58841 and pyrilutamide evidence guide and pyrilutamide trial interpretation. Product links elsewhere on this page are commercial listings, not evidence that a research product is suitable for human treatment.