Hair loss can be deeply distressing, so it is natural that many people search online for a “cure for baldness.” The new PP405 hair regrowth treatment from UCLA has attracted attention because it tries something different: instead of just slowing loss, it aims to wake up dormant hair follicles so they start growing full hairs again. Early trials are encouraging, but PP405 is still experimental, and it will not work for everyone.
PP405 hair regrowth: how the new molecule works
For most people with androgenetic alopecia, or pattern baldness, the follicles do not die. They shrink and switch into a long resting state, producing thin, short hairs instead of thick strands. Standard treatments like minoxidil and finasteride try to nudge this cycle, but they often give modest gains and must be used for many months before results appear.
PP405 takes another path. UCLA scientists studying stem cells in mouse and human hair follicles found a metabolic “switch” that keeps these cells dormant. In a 2017 paper, the same lab showed in mice that pushing follicle stem cells to produce lactate wakes them up. By designing a small molecule that hits this switch, they found a way to coax follicle stem cells back into an active state so the follicle can enter a new growth phase.
From UCLA lab discovery to Pelage Pharmaceuticals
The PP405 story began in William Lowry’s lab at UCLA, where researchers looked at how hair follicle stem cells decide when to rest and when to grow. They identified a target in the cells’ energy pathways and developed PP405 to act on it. UCLA then licensed the intellectual property around PP405 and related compounds to a startup, Pelage Pharmaceuticals, in 2018.
Pelage, backed by Google Ventures and other investors, had raised $16.4 million by 2024 according to the UCLA magazine, to move the drug through clinical trials. The company describes PP405 as a novel, non-invasive topical molecule that is applied to the scalp to reactivate dormant hair follicle stem cells and restart hair growth.
A metabolic switch in hair follicle stem cells
Hair follicle stem cells sit in a small niche in the skin and cycle between rest and activity. In pattern baldness, the growth phase gets shorter, the resting phase gets longer, and hairs become thinner over time. PP405 appears to work by shifting how these stem cells handle energy, pushing them out of dormancy. In lab studies and early human biopsies, treatment with PP405 increased markers of stem cell activation in the follicles.
Unlike hormone-blocking drugs, PP405 does not target testosterone or dihydrotestosterone (DHT) directly. That is important, because hormonal drugs such as finasteride can have sexual and mood side effects in a small share of users.
PP405 vs older drugs like minoxidil and finasteride
Today, only two medicines, minoxidil and finasteride, are approved by the US Food and Drug Administration for androgenetic alopecia. They can slow further loss and regrow some hair, but many people find the effect limited, especially if their baldness is already advanced. Minoxidil must be applied twice a day, and finasteride is taken daily as a pill. Stopping either drug usually leads to renewed shedding.
PP405 is applied as a topical liquid once a day. Instead of changing blood hormones or simply improving blood flow, it targets the follicle stem cells themselves. If it continues to prove safe and effective, it could become a first-in-class regenerative treatment that helps some people grow new terminal hair, not just thicker “peach fuzz.” But it would still likely require ongoing use to maintain gains, just like other medical hair-loss treatments.
PP405 hair loss trials: what the studies show so far
Any new drug must move step by step through human trials. PP405 is currently in Phase 2a studies, which means it has passed initial safety tests but still needs larger trials before regulators can decide on approval.
Phase 1 safety and stem cell activation results
In its first human trial, PP405 was tested mainly for safety and biological activity. Volunteers with pattern hair loss applied the topical treatment on their scalp for a short period. According to Pelage, the Phase 1 results showed that PP405 was well tolerated and caused statistically significant activation of hair follicle stem cells in treated areas, without serious side effects.
Because this early study focused on lab markers and safety, it did not yet tell doctors how much visible hair regrowth people might expect. That requires larger, longer trials with careful counts of hair density and thickness.
Phase 2a early signs of thicker, denser hair
In 2024, Pelage launched a randomized, placebo-controlled Phase 2a trial, registered as NCT06393452, in 78 adults with androgenetic alopecia, including both women and men. Participants applied PP405 or a matching placebo to their scalp once per day for four weeks and were then followed for 12 weeks.
The company’s June 2025 results release reports that the trial met its primary safety and pharmacokinetic goals. No PP405 was detected in blood samples, which supports the idea that the drug stays local to the skin. For exploratory hair growth outcomes, early data showed that 31% of men with more advanced hair loss who used PP405 achieved more than a 20% increase in hair density at week 8, compared with 0% in the placebo group.
A 20% density gain means that if a patch had 100 hairs per square centimetre at baseline, it might have around 120 after treatment. That may not sound dramatic, but for many people it can change how the scalp looks in daily life, especially when combined with styling.
Who joined the PP405 androgenetic alopecia studies
The Phase 2a study made a point of enrolling people across a wide range of skin tones and hair textures, which has not always been the case in hair loss research. Both women and men with mild to moderate pattern baldness could join, as long as their follicles were still present and capable of growth.
This matters, because androgenetic alopecia is extremely common in every group. The same StatPearls review reports that by age 70, up to 80% of men and about half of women show signs of pattern hair loss, and the condition can have strong effects on self-esteem and mood, especially for women.
What PP405 could change for pattern baldness
If future Phase 3 trials confirm the early results, PP405 could shift the hair-loss landscape in several ways. Still, it is important not to confuse “promising new option” with “cure for everyone.”
Benefits compared with current hair loss treatments
Because PP405 is non-hormonal and stays in the skin, it may avoid some of the systemic side effects linked to oral finasteride, though this will need long-term confirmation. It also appears to work faster than many existing options: visible gains were reported a few months after just four weeks of use, while many current treatments require six to twelve months of continuous therapy before changes are easy to see.
If PP405 truly reactivates follicles that had stopped producing visible hair, it could help people who feel they have run out of options after trying minoxidil, finasteride, or even hair transplant surgery. That said, early trials have been short, and it is not yet known how well results hold up over years.
Limits: scarring, late-stage baldness, long-term use
PP405 can only act where follicles and stem cells are still present. In areas of long-standing, shiny baldness where the follicles have scarred or disappeared, no topical treatment is likely to restore hair. Reports also suggest that the best responses so far have been in people with mild to moderate hair loss rather than those with the most advanced thinning.
Like almost all hair-loss medicines, PP405 will probably need to be used indefinitely to keep its benefits. The hair cycle is ongoing; once the drug is stopped, the underlying genetic and hormonal forces that drive pattern baldness will still be there. This is similar to how minoxidil and finasteride must be continued to maintain results.
Side effects, costs and access questions
So far, trials report that PP405 has been well tolerated, with no serious safety signals and no drug detected in the bloodstream. But larger and longer studies are needed to rule out rare side effects. Regulators typically require multi-year data before approving a new chronic-use medicine.
Cost and access also remain open questions. Hair-loss drugs and procedures can be expensive, and many insurance plans treat them as cosmetic. If PP405 reaches the market, it may be priced like other branded dermatology treatments, and availability could vary by country. Newer treatments often reach wealthier patients first, as commenters and patient advocates rightly worry.
Other emerging hair regrowth treatments
PP405 is not the only new idea in this field. Several other approaches, each covered in its own Gromeus article, aim to regrow hair by acting on the follicle rather than on hormones.
A sugar found naturally in the body, 2-deoxy-D-ribose, may help hair regrow without drugs, according to a mouse study. For alopecia areata, the autoimmune form of hair loss, the arthritis drug baricitinib is the first proven pill. Platelet-rich plasma (PRP) injections and scalp microneedling, with or without minoxidil, are covered in the Gromeus guide to scalp tools for hair regrowth. Low-level laser devices and lab-grown hair follicles are also under study, though the strength of evidence varies.
Sources and related information
UCLA – Did UCLA just cure baldness? PP405 breakthrough treatment – 2025
This UCLA Magazine piece explains how researchers identified PP405 as a small molecule that can wake up dormant hair follicle stem cells, describes early human trial results, and stresses that the treatment will not work for everyone and still needs years of testing. The article also describes the creation of Pelage Pharmaceuticals to develop PP405 into a drug.
Nature Cell Biology – Lactate dehydrogenase activity drives hair follicle stem cell activation – 2017
The paper from William Lowry’s and Heather Christofk’s labs at UCLA showed in mice that shifting follicle stem cells toward lactate production activates them and speeds up the hair cycle, the metabolic mechanism PP405 was later designed around. Evidence type: animal study.
Pelage Pharmaceuticals / UCLA TDG – Pelage advances PP405 into Phase 2a trial – 2024
A joint release from Pelage and UCLA Technology Development Group outlines Phase 2a trial for PP405, including the goal of reactivating dormant hair follicle stem cells, inclusive recruitment of women and men of many skin and hair types, and the company’s Series A-1 funding round.
ClinicalTrials.gov – Safety, Pharmacokinetics and Efficacy of PP405 in Adults With AGA – 2024
The official registration of the Phase 2a trial, NCT06393452, sponsored by Pelage Pharmaceuticals, lists the study design, eligibility and outcome measures.
Businesswire – Positive Phase 2a clinical trial results for PP405 – 2025
This Businesswire press release reports early Phase 2a results in 78 participants, stating that PP405 is a topical, non-invasive small molecule that was well tolerated, showed statistically significant activation of hair follicle stem cells in Phase 1, and delivered early signs of clinically meaningful hair regrowth in people with androgenetic alopecia.
The Dermatology Digest – Regenerative medicine in action: topical PP405 shows promise in androgenetic alopecia – 2025
A feature in The Dermatology Digest summarises the Phase 2a trial, noting that PP405 met safety and pharmacokinetic endpoints, caused no detectable systemic exposure, and led about 31% of certain patients to gain more than 20% hair-density at eight weeks, with Phase 3 studies planned for 2026.
StatPearls – Androgenetic alopecia – 2024
This reference article reviews how common androgenetic alopecia is in men and women, explains its causes, and confirms that minoxidil and finasteride remain the only FDA-approved drugs for this condition, with low-level laser therapy also used.
Medscape – Androgenetic alopecia overview – 2023
A clinical overview with similar conclusions on causes, prevalence and approved treatments, noting that newer treatments like PP405 are still investigational.