Allergan Releases Setipiprant Male Hair Loss Treatment Trial Results

A 2017 Phase 2a clinical trial exploring twice-per-day oral doses of setipiprant as a potential treatment for Male Pattern Hair Loss has now published its findings.

Setipiprant is an investigational drug - originally developed as an allergy medication - currently being explored as an antagonist for the PGD2 receptor; the PGD2 receptor is an enzyme that was shown in 2012 to affect hair growth and be an area worthy of study in order for targeted treatments for various hair loss conditions to be developed.

The randomised, multi-centre study was sponsored by Allergan, and pitted setipiprant against finasteride 1mg - currently the only MHRA-licensed and FDA-approved oral men's hair loss treatment for androgenetic alopecia.

In the results, published on 9th April 2019, some of the data for the finasteride element of the trial has been omitted, however.

Three-arm trial

The double-blind American trial comprised 169 men aged between 18 and 49 years of age, all with a confirmed diagnosis of genetic hair loss.

These participants formed three separate groups, each of which was administered oral tablets for 24 weeks.

One group of 83 men was given setipiprant 1,000mg (2 x 500mg) to be taken at 12 hour intervals, another group of 12 men was given finasteride 1mg to be taken once per day, whilst a further 74 men took a placebo twice daily at 12 hour intervals.

There were a number of participants who did not complete the trial - 26 of those taking setipiprant, 26 of those taking the placebo and 4 from the finasteride group. Reasons ranged from withdrawing consent and not properly complying with the study drug, to adverse events.

As such, the numbers reduced to 78 taking setipiprant, 11 taking finasteride and 70 taking the placebo.

For these men, the following terminal hair counts were recorded in the target area being studied, described as being at the "anterior leading edge of vertex thinning area of scalp and centered with a semi-permanent microdot tattoo to ensure same target area was reproduced each visit".

Potentially insignificant results

The changes seen after 24 weeks of treatment, of each type, were measured using digital imaging and the recorded data can be seen in the bar chart, here.

On first appearance, these hair count results look impressive for setipiprant, however, it is only when taking into account the mean data that the true picture emerges. And it is certainly less compelling.

Given the mean is so varied - and the statistical analysis also had a P-value of 0.9239) - this effectively renders them insignificant. This is perhaps why the results were published without fanfare or press release - just yet, at least.

We believe that Allergan is currently waiting for its study to be federally evaluated so, this may also be a reason to delay comment.

To be clear, this does not mean that setipiprant does not show promise as a Male Pattern Hair Loss treatment; what it means is that further research - ideally using better matched participants - is needed to properly establish its potential.

"Although the mean number of hair count per square cm was the highest for setipiprant, the standard deviations were also the highest which suggests the particpants in this group had very different results from each other. Also, looking at the other tables they have provided in their results, their p values suggest the results did not have statistical significance," says Belgravia hair loss specialist, Rali Bozhinova. "Overall, I think they would need more research, ideally with more participants."

For now, it remains unproven and far more clinical trials are required if Allergan wishes to meet its current pipeline estimate of a 2021/22 release.