Topical latanoprost acid for female androgenetic alopecia: a pilot proof-of-concept trial with mechanistic evidence of FP-receptor activation

Background Prostaglandin F2α (FP) receptor signaling is a plausible target for promoting hair growth, but clinical data on topical latanoprost acid (the active free-acid FP agonist) in hair loss are lacking. Methods In an investigator-initiated, randomized, double-blind, single-center, dose-ranging pilot trial, adult women with hair loss predominantly consistent with female androgenetic alopecia applied once-daily topical latanoprost acid 0.01%, 0.05%, or 0.1% for 6 months; a small vehicle group was included to support masking. The primary endpoint was within-participant change in target-area hair count (TAHC, hairs/cm²) from baseline to Month 6; trichoscopic activity markers (yellow dots) and follicular-unit (FU) remodeling were secondary/exploratory outcomes. Human hair dermal papilla cells were assessed for FP-linked signaling (intracellular Ca²⁺ flux) and proliferation (EdU) after exposure to latanoprost acid versus equimolar latanoprost. Results TAHC increased across active arms, with the most consistent multi-endpoint signal in the 0.05% group (mean ± SD ΔTAHC 23.5 ± 21.2 hairs/cm²), accompanied by reduced yellow dots and a shift from single-hair to multi-hair FUs; between-dose comparisons were not powered. Safety was favorable with no serious adverse events. In mechanistic assays, latanoprost acid triggered rapid, concentration-dependent Ca²⁺ flux, whereas equimolar latanoprost produced delayed signals; neither compound increased EdU incorporation. Conclusions Topical latanoprost acid showed a coherent clinical-trichoscopic bioactivity signal with supportive FP-linked signaling in human hair dermal papilla cells, warranting larger PK/PD-integrated trials centered on 0.05%. Trial registration: ClinicalTrials.gov, NCT07412587; registered on February 2, 2026.