What is HMI-115 and how is it different from common treatments like minoxidil?

Hair loss affects millions of people worldwide, and treatments such as minoxidil have long been the standard option. Experimental drugs working through other mechanisms are now in trials, including HMI-115. Understanding what HMI-115 actually is, what has been tested, and how that compares with minoxidil is useful for anyone following where hair loss research is going.

HMI-115 (also identified as BAY 1158061) is an investigational monoclonal antibody that blocks the prolactin receptor. It is not a GnRH antagonist, and it does not act on the pituitary gland or lower sex hormone levels — earlier versions of this page described it that way, which was wrong. Prolactin signalling influences the hair follicle cycle, including the transition between the growth (anagen) and regression (catagen) phases, and blocking the prolactin receptor is the rationale for testing it in androgenetic alopecia. This is a different kind of intervention from minoxidil, a topical vasodilator applied to the scalp.

There is no published peer-reviewed study of HMI-115 in androgenetic alopecia, in humans or in animals. Descriptions of a 24-week macaque study with photographic analysis and hair density counts have circulated online attached to a citation that does not exist; that material has been removed from this page. What is published is a randomized placebo-controlled Phase 1 study of the antibody in postmenopausal women, run as a safety and tolerability study rather than a hair study (Nave et al., Reproductive Sciences, 2019).

How Minoxidil Works Compared to HMI-115

Minoxidil, approved by the U.S. Food and Drug Administration in the late 1980s, works in a different way. It is a vasodilator, which means it widens blood vessels. Applied to the scalp, it is thought to prolong the growth phase of the hair cycle. The exact mechanism is not fully understood; studies suggest minoxidil opens potassium channels in cells, which may stimulate follicle activity. Unlike HMI-115, minoxidil does not act on hormone signalling. This is one reason topical minoxidil is available over the counter as solutions and foams. Its limitation is that it does not work for everyone.

Published minoxidil trials report modest average increases in hair count over placebo. The share of participants rated as having moderate or dense regrowth varies widely between studies depending on which endpoint is used, and the figures often repeated online do not trace back to any specific FDA document. Evaluation in these studies typically involves hair counts in a marked scalp area plus photographic comparison. The recurring criticisms are variability in response, the requirement for indefinite continuous use, and results that are often modest rather than dramatic.

Why HMI-115 Is of Interest

Androgenetic alopecia is strongly linked to androgen signalling, particularly dihydrotestosterone (DHT), which is associated with progressive follicle miniaturization. Finasteride blocks the conversion of testosterone to DHT and carries a side-effect profile that includes reported sexual dysfunction. HMI-115 is of interest precisely because it is not an anti-androgen: it targets prolactin receptor signalling instead, a separate pathway. Whether a different pathway means a different or better side-effect profile in practice is an open question, and it is not something the published data can answer. Prolactin has functions well beyond the hair follicle, so long-term safety in a cosmetic indication is a genuine unknown rather than a formality.

Research on HMI-115 So Far

Four HMI-115 studies are registered on ClinicalTrials.gov, two of them in hair loss:

• NCT05324293 — a Phase 1 study in Australia, 16 participants with androgenetic alopecia, 24 weeks of treatment, started May 2022, completed. A company press release described a positive outcome; no peer-reviewed publication has followed, and a 16-person early-phase study cannot establish effectiveness.
• NCT06118866 — a Phase 2 study in Chinese men with androgenetic alopecia, 192 participants, started September 2023, recorded as completed. Its results have not been published.
• NCT05101317 and NCT07318688 — Phase 2 and Phase 3 studies in endometriosis-associated pain, a separate indication for the same antibody.

So the earlier statement on this page that HMI-115 "has not yet entered large-scale human clinical trials" was wrong: a completed 192-man Phase 2 exists. What is true is that none of the hair-loss results have been published in a peer-reviewed journal, and there is no registered Phase 3 hair-loss study.

Minoxidil, by contrast, has decades of published trial data and regulatory review behind it, which is the practical difference between the two: one is a marketed product with a known if modest effect size, the other is an unapproved antibody whose hair-loss results exist only as company announcements and registry entries.

The Future of Hair Loss Treatment

HMI-115 is not available to the public and is not approved by any regulator. For now, minoxidil and finasteride remain the treatments with published evidence and regulatory approval. The interest in HMI-115 reflects a broader shift in research toward pathways other than androgen blockade. Whether that shift produces a usable treatment depends on Phase 2 and Phase 3 results being published and reproduced, which has not happened.

In short: HMI-115 is an experimental monoclonal antibody against the prolactin receptor, given by subcutaneous injection in trials. Minoxidil is a topical vasodilator that acts locally on the scalp. The evidence bases are not comparable: minoxidil has published trials and approval; HMI-115 has completed trials whose results have not been published.

User Experiences

HMI-115 has drawn attention in the hair loss community as a treatment under investigation. Unlike minoxidil or finasteride, which target blood flow and androgen conversion respectively, HMI-115 is a monoclonal antibody designed to block the prolactin receptor. Community discussions reveal a mix of cautious optimism and skepticism. Some users point out that HMI-115 looks different from past "hyped" compounds like pyrilutamide or cosmeRNA, which disappointed many (Reddit, 2024a). Others question whether it will deliver anything beyond incremental improvement.

Reports from the Chinese trial have generated interest. Community members have said that after around two months, volunteers reported visible thickening and new growth, a faster timeline than minoxidil, which usually takes six months or more to show results (Reddit, 2024b). Photographs circulating from trial leaks appeared to support these accounts. These are unverified second-hand reports of an unpublished trial: leaked photographs are not trial data, they carry no information about which arm a participant was in, and they should not be read as results.

Other discussions focus on practicalities. Unlike minoxidil (a daily topical or oral vasodilator) or finasteride (a daily oral 5-alpha reductase inhibitor), HMI-115 is given as a series of subcutaneous injections in the trials. Some users hope this could mean longer-lasting effects with less daily compliance burden, while others raise accessibility and cost, since monoclonal antibodies are expensive to produce. Material sold online under the name is unregulated and of unverified identity, purity and concentration.

Several community members note that HMI-115 is not another anti-androgen, and that it works on prolactin signalling, which influences transitions between the anagen and catagen phases of the hair cycle (Reddit, 2023b). This has led some to speculate that it could produce regrowth in more advanced cases where minoxidil and finasteride are better at maintenance. That is speculation, not a finding from any published study.

The tone across user experiences is far from unanimous. Many emphasise patience, recalling past disappointments in hair loss research. Some think the early reports are overstated; others see one of the more interesting developments in years. Until trial results are published and larger studies are complete, HMI-115 remains an experimental compound, and community sentiment about it is not evidence either way.

Before You Act on Any of This

HMI-115 is an experimental injectable antibody. It cannot be prescribed, it is not sold as a medicine, and anything offered online under that name is unregulated. Talk to a doctor or pharmacist before starting, stopping or combining any hair loss treatment, including minoxidil and finasteride, and before acting on trial reports from this page or anywhere else.

References

Nave, R., et al. (2019). Monoclonal Antibody Against Prolactin Receptor: A Randomized Placebo-Controlled Study Evaluating Safety and Tolerability in Postmenopausal Women. Reproductive Sciences. PMID 29806538. https://pubmed.ncbi.nlm.nih.gov/29806538/

Agrawal, A., et al. (2026). Emerging pharmacotherapies for androgenetic alopecia. Expert Opinion on Pharmacotherapy. PMID 42290527. https://pubmed.ncbi.nlm.nih.gov/42290527/

ClinicalTrials.gov. To Evaluate the Safety, Tolerability and Efficacy in Male and Female with AGA Treated with HMI-115 Over a 24-week Treatment Period (Phase 1, Australia, 16 participants). NCT05324293. https://www.clinicaltrials.gov/study/NCT05324293

ClinicalTrials.gov. A Study to Assess the Efficacy and Safety of HMI-115 in Male Subjects With Androgenetic Alopecia (Phase 2, China, 192 participants). NCT06118866. https://www.clinicaltrials.gov/study/NCT06118866

ClinicalTrials.gov. A Study to Assess the Efficacy and Safety of HMI-115 in Subjects With Endometriosis-Associated Pain (Phase 2, 142 participants). NCT05101317. https://www.clinicaltrials.gov/study/NCT05101317

ClinicalTrials.gov. Evaluate the Efficacy and Safety of HMI-115 in Women With Moderate to Severe Endometriosis-associated Pain (Phase 3, China, 540 participants, recruiting). NCT07318688. https://www.clinicaltrials.gov/study/NCT07318688

Reddit. (2024a). Is hmi 115 the cure? Or is it just like cosmerna, brezula, pyrilutamide, and other ies. Retrieved from https://reddit.com/r/tressless/comments/1djrrpd/is_hmi_115_the_cure_or_is_it_just_like_cosmerna/

Reddit. (2024b). 2-month HMI-115 results from the Chinese trial. Retrieved from https://reddit.com/r/tressless/comments/1ctjjfy/2month_hmi115_results_from_the_chinese_trial/

Reddit. (2024c). HMI 115 Phase 2 - Leaked pics from Discord. Retrieved from https://reddit.com/r/tressless/comments/1cj63dg/hmi_115_phase_2_leaked_pics_from_discord/

Reddit. (2023a). HMI-115 question about potential earliest access. Retrieved from https://reddit.com/r/tressless/comments/12nelu3/hmi115_question_about_potential_earliest_access/

Reddit. (2023b). What do we actually know about HMI-115?. Retrieved from https://reddit.com/r/tressless/comments/14m8cr2/what_do_we_actually_know_about_hmi115/

Reddit. (2024d). HMI-115: What We Know So Far. Retrieved from https://reddit.com/r/tressless/comments/1d1tffj/hmi115_what_we_know_so_far_hmi115_also_known_as/