LOS ANGELES – Pelage Pharmaceuticals has announced promising Phase 2a clinical trial results for its lead drug candidate, PP405, a topical therapy designed to regenerate hair through stem cell reactivation. The trial marks a significant step forward in the development of what could become the first treatment to directly induce new hair growth by targeting dormant hair follicle stem cells.
PP405 is being developed as a non-invasive regenerative treatment for androgenetic alopecia, a common form of hair loss affecting more than 80% of men and 40% of women. Unlike existing therapies that focus on secondary causes like hormonal imbalances, PP405 works by activating hair follicle stem cells—cells that remain present even in balding areas but have become dormant due to age, stress, genetics, or environmental factors.
The randomized, controlled trial enrolled 78 men and women representing a diverse range of skin types and hair textures. Participants applied PP405 or a placebo topically for four weeks and were monitored for an additional eight weeks. The study met its safety and pharmacokinetic goals, showing no systemic absorption of the drug and a favorable safety profile. Exploratory endpoints also revealed encouraging signs of efficacy.
Among men with more advanced hair loss, 31% of those treated with PP405 showed a greater than 20% increase in hair density by week eight—just four weeks after completing the treatment. No such response was observed in the placebo group. These results are notable, as visible regrowth from most hair loss treatments typically takes six to twelve months. More significantly, PP405 appeared to stimulate new hair growth in areas previously devoid of active follicles, suggesting a regenerative effect rather than simple maintenance or enhancement of existing hair.
“These early clinical results reinforce the potential of our approach to go beyond slowing the hair loss process and directly drive hair follicle regeneration,” said Dr. Christina Weng, Chief Medical Officer at Pelage. “We see this as a milestone that expands the possibilities of regenerative medicine.”
Pelage plans to initiate Phase 3 trials in 2026 to further assess the safety and efficacy of PP405 in both men and women. An open-label extension study is currently underway for subjects who initially received placebo, to evaluate the long-term safety of the treatment.
Dr. Arash Mostaghimi, Vice Chair of Clinical Trials and Innovation at Brigham and Women’s Hospital and a member of Pelage’s advisory board, called the results a significant breakthrough. “What’s compelling about PP405 is that it brings scientific rigor to a space that’s needed it for decades,” he said. “A well-tolerated, topically delivered therapy that shows measurable biological activity this early is rare. This could reshape how we think about clinical progress in hair growth.”
The company’s technology stems from cutting-edge stem cell research conducted at UCLA, and its leadership includes experts in dermatology and regenerative biology from institutions such as Mass General Brigham. Pelage is backed by a prominent investor syndicate led by GV (Google Ventures), with support from Main Street Advisors, Visionary Ventures, and YK Bioventures.
With PP405, Pelage is positioning itself as a leader not just in hair loss treatment, but in the broader field of regenerative medicine and aging-related therapies.
