If you follow the world of hair loss research closely, you might’ve seen a new name cropping up recently: PP405.
PP405 is an experimental topical treatment being investigated as a regenerative approach to hair loss, with early trial results that have caught a lot of attention.
But before getting carried away, it’s worth looking at what the science actually says so far, what stage the research is at, and what it might (and might not) mean for people dealing with hair loss today.
Where Is PP405 in Clinical Testing?
PP405 has completed Phase 2a clinical trials in 2025 and is expected to move into Phase 3 trials in 2026, provided everything continues to go smoothly.
If upcoming trials are successful and the treatment passes regulatory review, PP405 could become available around 2028 or 2029. Since development is currently US-based, UK approval through the MHRA would likely follow later, potentially adding another year or so.
How Does PP405 Work?
PP405 is a topical treatment thought to work by reactivating hair follicle stem cells. These stem cells play a key role in the hair growth cycle, which naturally moves through phases of growth and rest.
In dormant hair follicles, the stem cells are inactive, but still present. PP405 may help switch these cells back on, reactivating the follicle and encouraging hair growth in areas where growth has slowed or stopped.
This potentially sets it apart from most existing treatments for androgenetic alopecia, which mainly focus on slowing or stopping hair loss rather than reversing it.
Early lab data from Phase 1 trials showed that applying PP405 to human scalp skin activated stem cells within 24 hours. This was measured by an increase in Ki67, a marker linked to cell growth, suggesting follicles were becoming more active again.
Results from the Phase 2a trial, completed in 2025, add further context. While the study was designed to assess safety and pharmacokinetics rather than effectiveness, it included 78 participants with androgenetic alopecia and looked at early signs of hair growth as an exploratory outcome.
Participants applied PP405 or a placebo once daily for four weeks and were followed for up to 12 weeks. Early findings suggested that after one month, 31% of those using PP405 saw more than a 20% increase in hair density.
That’s notable, as most established treatments tend to take at least three months before visible results begin to appear.
In simple terms, the early research suggests PP405 may help restart the hair growth process by switching follicles back on, although this is still at an early stage.
What Are the Potential Limitations?
PP405 is often positioned as being different from current treatments, with claims that existing options only target indirect causes of hair loss. However, that may be an oversimplification.
Male pattern baldness is primarily driven by DHT, a hormone that binds to sensitive hair follicles and causes them to shrink over time.
Treatments like finasteride directly address this root cause by reducing DHT levels.
Based on current data, PP405 does not appear to target DHT. Instead, it may help reactivate follicles that have already become dormant.
Because of this, if PP405 proves effective, it will likely need to be used alongside DHT-blocking treatments like finasteride to properly tackle male pattern baldness.
That said, the company behind PP405 is also exploring its potential for other forms of hair loss, such as telogen effluvium or drug-induced alopecia, where treatment options are currently limited.
What Should You Do About Hair Loss Now?
While the early trial results for PP405 are promising, male pattern baldness is a progressive condition, meaning it worsens over time.
Starting treatment early gives you the best chance of maintaining your existing hair.
Right now, a combination of finasteride and minoxidil remains the most effective and well-studied approach to treating hair loss.
If you’re unsure which treatment plan is right for you, you can take our free consultation to get personalised recommendations based on your stage of hair loss.
All of our blog articles are reviewed by our Medical Director before publication.
