Got bald spots from stress? Here is what PP405 actually is — and what it is not.

If you've ever noticed a coin-sized bald spot on your scalp, someone might have told you, "That's from stress." Some people do develop small, round areas with no hair during difficult periods. Round, sharply defined patches are the classic presentation of alopecia areata, an autoimmune condition — not the same thing as the diffuse shedding (telogen effluvium) that often follows a stressful event. A dermatologist can tell the two apart, and that matters, because they are treated differently. If you have patches like this, get them looked at rather than self-treating.

PP405 comes up a lot in hair-loss forums, and it is often described as a spray for stress-related patches. That description is wrong, and it is worth correcting, because the drug is real and the trials it is actually in are for something else.

What does stress have to do with hair loss?

There is published work linking stress hormones to hair follicle dormancy. A 2021 study in Nature reported that corticosterone — the mouse equivalent of cortisol — acts on the dermal papilla to suppress a signaling molecule called GAS6, and that this keeps hair follicle stem cells in a resting state; removing the stress hormone let the follicles cycle again (Choi et al., 2021). That is mouse work, and it describes prolonged resting phases rather than the round patches of alopecia areata.

Alopecia areata is different: it is understood as an immune attack on the hair follicle. Stress is often reported by patients around the onset, but it is not established as the cause. Telogen effluvium — a temporary, diffuse shedding a few months after a physical or emotional shock — is a third, separate thing. Lumping all three together as "stress hair loss" is the mistake that leads people to reach for the wrong product.

So, what exactly is PP405?

PP405 is an experimental drug from Pelage Pharmaceuticals. It is not a spray, it is not botanical, it is not anti-inflammatory, and it is not for sale anywhere — including Korea. It is a topical gel containing a small molecule that inhibits the mitochondrial pyruvate carrier (MPC).

The idea comes from University of California, Los Angeles research on follicle metabolism. A 2017 paper in Nature Cell Biology reported that hair follicle stem cells rely on glycolysis and lactate production, and that shifting their metabolism in that direction activated dormant follicle stem cells in mice (Flores et al., 2017). Blocking the MPC is one way to force that shift. PP405 is the attempt to turn that finding into a topical drug; the 2017 paper did not test PP405 itself.

Whether that works in people is not yet established. The compound is in clinical trials; it has not been approved by any regulator; and no efficacy result from a completed, published trial is available to summarize here.

What has actually been tested?

The registered Phase 2 trial (NCT06393452, sponsored by Pelage Pharmaceuticals) enrolled 78 adults with androgenetic alopecia — pattern hair loss — not alopecia areata and not stress-related patches. Participants applied a 0.05% PP405 topical gel, or a matching vehicle gel, once daily. Part 1 was a randomized, quadruple-masked 28-day period whose stated primary outcomes were treatment-related adverse events and local skin tolerability; Part 2 was an open-label extension of about three months. The registry lists the study as completed in October 2025.

Note what that trial was designed to measure: safety, tolerability and pharmacokinetics — not regrowth. Pelage's press release (17 June 2025) says that at week 8, 31% of men with more advanced hair loss who used PP405 had a more than 20% rise in hair density, compared with 0% on placebo. That is a company-reported subgroup result from a trial whose registered outcomes were safety and pharmacokinetics; it has not been peer-reviewed. A 24-week Phase 2/3 efficacy trial in about 600 men with pattern hair loss (NCT07819435, first posted 15 September 2026) is listed as not yet recruiting.

Where can I find PP405? And why talk about it if it is not on the market?

PP405 is not for sale. You will not find it on Amazon or in a pharmacy, and it has not been approved by the FDA (U.S. Food and Drug Administration). Anything sold online under that name is not the trial drug.

It is worth knowing about because it is a genuinely different approach — targeting follicle stem cell metabolism rather than hormones or blood flow — and because the forum description of it is so far off that people are shopping for the wrong thing. Whether it becomes a treatment depends on larger efficacy trials that have not yet reported.

User Experiences

Community discussion of PP405 on Tressless is anticipation, not experience. Because the drug is only available inside clinical trials, there are no user results to report: nobody outside a trial site has used it. Threads track the Pelage announcements, the funding rounds and the trial registry, and speculate about timelines.

Two things recur in those threads and are worth repeating. First, several users point out that any product sold as "PP405" is not the trial compound — the name is being used by sellers who have no access to it. Second, users who have tried unrelated topicals for round bald patches generally report that the patches came and went on their own, which is consistent with what is known about alopecia areata: spontaneous regrowth is common, and it makes any single person's before-and-after very hard to read.

What the community does not have — and cannot have yet — is anyone reporting whether PP405 grew their hair.

Is it worth keeping an eye on?

It is a compound to watch rather than a treatment to plan around. The mechanism is novel, the early-stage work is published, and the Phase 2 safety study has finished — but there is no approved product, no published efficacy result, and no data at all in alopecia areata or stress-related shedding.

If you have round bald patches, see a dermatologist rather than waiting for PP405. Alopecia areata has treatments now, including options that need a prescription and monitoring, and the earlier a patch is assessed the more the options are worth. Talk to a doctor or pharmacist before starting, stopping or combining any hair-loss treatment.

References

• Flores, A., Schell, J., Krall, A. S., Jelinek, D., Miranda, M., et al. (2017). Lactate dehydrogenase activity drives hair follicle stem cell activation. Nature Cell Biology, 19(9), 1017–1026. https://pubmed.ncbi.nlm.nih.gov/28812580/

• Choi, S., Zhang, B., Ma, S., Gonzalez-Celeiro, M., et al. (2021). Corticosterone inhibits GAS6 to govern hair follicle stem-cell quiescence. Nature, 592(7854), 428–432. https://pubmed.ncbi.nlm.nih.gov/33790465/

• ClinicalTrials.gov. Safety, Pharmacokinetics and Efficacy of PP405 in Adults With AGA. NCT06393452. https://clinicaltrials.gov/study/NCT06393452

• ClinicalTrials.gov. Phase 2/3 Efficacy and Safety of PP405 in Adult Males. NCT07819435. https://clinicaltrials.gov/study/NCT07819435

• Pelage Pharmaceuticals. (17 June 2025). Pelage Pharmaceuticals Announces Positive Phase 2a Clinical Trial Results for PP405 in Regenerative Hair Loss Therapy [press release; not peer-reviewed]. https://pelagepharma.com/press-releases/pelage-pharmaceuticals-announces-positive-phase-2a-clinical-trial-results-for-pp405-in-regenerative-hair-loss-therapy/

• Tressless. Community discussion on PP405. https://tressless.com/search/community/PP405/1?sort=relevance