A Novel Topical Dutasteride Lotion (FOL100) for Male Pattern Baldness in Israeli Men: A Phase I Study of Safety, Tolerability, Usability, and Exploratory Efficacy

Background Dutasteride, a potent 5α‐reductase inhibitor, has demonstrated efficacy in male pattern baldness (MPB) when administered orally, but concerns about systemic side effects limit its use. Topical formulations may offer a safer alternative. This Phase I trial evaluated the safety, local tolerability, usability, and exploratory efficacy of FOL100, a novel topical dutasteride lotion. Methods In this open‐label, multicenter study, 79 men with mild‐to‐moderate MPB received FOL100 ( n = 66) once daily for 24 weeks or oral finasteride (OF) 1 mg/day ( n = 13). The trial was registered at ClinicalTrials.gov. Assessments included clinical safety, laboratory parameters, pharmacokinetics, hair counts via phototrichograms, hair morphology, and investigator and participant global improvement scales. Follow‐up continued for 4 weeks post‐treatment. Results In the FOL100 group, treatment‐related adverse events occurred in 10.6% of participants and were all mild and transient (mainly pruritus and erythema), with no treatment‐related discontinuations. Serum dutasteride levels were undetectable in all FOL100‐treated participants, and systemic dihydrotestosterone suppression was minimal and not statistically significant. Usability and tolerability ratings were consistently favorable, supporting good adherence potential. Exploratory efficacy analysis in the FOL100 group at Week 28 showed, using a bootstrap model, a significant increase in total hair count median from baseline (+11 hairs/cm 2 ; −11.25, 27.50 Q1‐Q3 range), along with improvements in follicular unit density. Global assessments by both investigators and subjects indicated stabilization or improvement in most participants. The small sample size in the OF arm precluded meaningful efficacy analysis. Conclusions FOL100 demonstrated excellent safety, tolerability, and usability with promising signals of clinical benefit. These findings support further placebo‐controlled studies to establish the therapeutic value of topical dutasteride in MPB. Trial Registration: ClinicalTrials.gov identifier: NCT05611593