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Pyrilutamide (KX-826): A Promising Future Treatment For Hair Loss?

Pyrilutamide, also known as KX826, is an anti-androgenic drug with a similar mechanism of action to that of flutamide, albeit with potentially fewer side effects. Developed as a treatment for both androgenetic alopecia and acne vulgaris, pyrilutamide is currently in phase III clinical trials in China and phase II clinical trials in the US. In this ultimate guide, we’ll examine the available data on pyrilutamide: what it is, how it works, what the clinical studies show, and whom it might benefit.

Key Takeaways

  • Drug. Pyrilutamide is an androgen receptor antagonist developed for treating androgenetic alopecia and acne vulgaris. Topical pyrilutamide has completed phase III trials in China and phase II trials in the US and has recently gained approval for a trial using pyrilutamide in combination with minoxidil in China. 
  • Clinical Data. There have been five as yet unpublished trials that were conducted in either China or the US. We only have information about these trials from press releases or conference poster presentations. The key information we do have is bulleted below:
    • A 24-week trial with 160 women with female pattern hair loss was conducted in China. The participants were randomized to six treatment groups (0.25% pyrilutamide applied once daily, 0.25% applied twice daily, 0.5% applied once daily, 0.5% applied twice daily, or two placebo groups – once daily and twice daily treatments). The 0.5% once-daily treatment appeared to perform the best, with an increase of 11.39 hairs per cm2 from the baseline compared to the placebo groups.
    • A 24-week trial with 120 men with male-pattern hair loss was conducted in China. During the trial, the participants were randomized to four treatment groups (0.25% pyrilutamide applied twice daily, 0.5% applied once daily, 0.5% applied twice daily, or a placebo). This time, the 0.5% twice-daily treatment appeared to perform the best by the end of the 24 weeks, with an increase of 15.34 hairs per cm2 from the baseline compared to the placebo groups.
    • A 24-week phase 1 trial investigating the safety, tolerability, and pharmacokinetics of pyrilutamide was conducted in the US. 40 men aged 18-60 with male-pattern hair loss were treated with ascending dose treatments of pyrilutamide (0.3%, 1.2%, 4.8%, and 9.6%). The study showed that the only reported adverse effects were mild contact dermatitis. Furthermore, pyrilutamide treatment was found to have a low risk of systemic effects, with low concentrations found in the blood after treatment.
    • A 24-week phase 2 trial investigating the efficacy and safety of pyrilutamide was conducted in the US. 123 male patients with male-pattern hair loss were treated with either 0.25% once daily, 0.5% once daily, or 0.5% twice daily. The study showed that pyrilutamide improved hair counts by 10 hairs per cm2; however, no significant improvement was observed compared to the placebo.
    • A 24-week phase 3 trial investigating the efficacy and safety of pyrilutamide was conducted in China. The participants were treated with either 0.5% pyrilutamide or a placebo. Similar to the phase 2 trial above, the study showed that pyrilutamide significantly improved hair counts compared to the baseline, however, no significant improvement was observed compared to the placebo.
  • Evidence Quality. Pyrilutamide scored 37/100 for evidence quality by our metrics.
  • Safety. Based on the information available, topical pyrilutamide treatment appears to be well-tolerated. However, none of the studies have been published, and there is the possibility that important information might have been omitted from the data that is available.

Best Practices. From the limited data available, a concentration of 0.5% pyrilutamide (once daily for women and twice daily for men) appears to be the most effective pyrilutamide treatment regimen. It appears to be a well-tolerated treatment for androgenetic alopecia.

What is Pyrilutamide?

Pyrilutamide (also known as KX-826) is a topical nonsteroidal antiandrogen (NSAA) drug developed by Kintor Pharmaceuticals. It was developed as a treatment for androgenetic alopecia and acne vulgaris, and the drug is currently undergoing phase III trials in China and phase II trials in the US.

Molecular Structure
Figure 1: Pyrilutamide molecular structure. Adapted from:[1]Pubchem, (no date). Pyrilutamide. NIH. Available at: https://pubchem.ncbi.nlm.nih.gov/substance/469676781 (Accessed: 04 May 2023)

Testosterone and dihydrotestosterone (or DHT) are androgens that have been implicated in pattern hair loss. To exert their effects, androgens must bind to the androgen receptor, and although the exact mechanisms are unknown, activating the androgen receptor in certain types of hair follicles appears to cause them to undergo miniaturization and eventually cause total hair loss.[2]Trueb, R.M., (2021). Understanding pattern hair loss-hair biology impacted by genes, androgens, prostaglandins, and epigenetic factors. Indian Journal of Plastic Surgery, 54(4). 385-392. Available … Continue reading Because pyrilutamide binds to and blocks the androgen receptor, in theory, it should help to prevent the negative effects of androgens on hair follicles.

How Does Pyrilutamide Work?

Pyrilutamide works in a different way than other anti-androgenic drugs, such as finasteride or dutasteride. Instead of inhibiting the enzyme 5α-reductase that catalyzes the conversion of testosterone to dihydrotestosterone, it competitively binds to the androgen receptor. This stops dihydrotestosterone and testosterone from binding to the receptor and exerting their effects.[3]Kintor, (2021), Kintor Pharmaceuticals Announced Successful Dosing of the First Batch of Patients for Acne Vulgaris Phase I/II Clinical Trial of Pyrilutamide. News Center. Available at: … Continue reading

Does Pyrilutamide Work to Regrow Hair?

There are currently no published data demonstrating the effects of pyrilutamide on hair loss; however, Kintor Pharmaceuticals has made some press announcements where they mention results from their clinical trials. The problem with not publishing their results in peer-reviewed journals is that we don’t have access to all of the details of the study, nor do we have the confidence that the claims and methods have been looked at by independent scientists. This also means that there is the potential that researchers could omit details that could undermine their work or omit findings that do not align with the claims they wish to make. It’s important to note that all of the findings we will examine below have to be taken with a grain of salt because we only have information from press releases and brochures.

Study 1

The first study, looking at female androgenetic alopecia,  was a 24-week, multi-center, randomized, double-blind, placebo-controlled phase II trial conducted in China.[4]Cision PR Newswire, (2022), Kintor Pharma Announced the Primary Endpoint of Phase II Clinical Study for KX-826’s Treatment of Female Androgenetic Alopecia in China was Met. Available at: … Continue reading 160 female participants were randomly assigned to six treatment groups, including 0.25% pyrilutamide applied once daily, 0.25% applied twice daily, 0.5% applied once daily, and 0.5% applied twice daily, or placebo groups (one group for once daily, and one group for twice daily). The primary measured outcome was the change in hair growth, as measured by target area non-vellus hair count (TAHC). Essentially, the researchers were counting the number of thick, pigmented hairs (or ‘terminal’ hairs) in a given area, as opposed to the number of fine, unpigmented (vellus) hairs.

The researchers determined that the recommended dose for their phase III trial in China is 0.5% once daily, as it increased hairs by 11.39 counts per cm2 from baseline, compared to the placebo group. Furthermore, the researchers said that efficacy was seen as early as the end of week 12 of treatment. When it came to safety, the researchers mentioned that it was well tolerated, with mild adverse events seen that were similar to the placebo. Unfortunately, they do not mention what these adverse effects were.

Study 2

Another 24-week, randomized, double-blind, placebo-controlled, multi-regional study was conducted to evaluate the efficacy and safety of pyrilutamide in 120 men with androgenetic alopecia.[5]Cision PR Newswire, (2023), Kintor Pharma Announces Completion of Subject Enrollment in Phase III Clinical Trial of KX-826 for Treatment of Male Androgenetic Alopecia in China. Available at: … Continue reading For this study, the researchers presented a poster at the 6th National Hair Academic Conference in China and it has since been translated to English online.

The participants were randomized into four groups:

  • 0.25% pyrilutamide applied twice daily
  • 0.5% pyrilutamide applied once daily
  • 0.5% pyrilutamide twice daily
  • Placebo (most likely treatment with just the cream or emollient that pyrilutamide is suspended in).

The researchers found that the participants that used 0.5% pyrilutamide twice daily showed improvement in total hair count at the end of the 24 weeks, with an increase of 15.34 hairs per cm2 compared to the placebo-treated groups (Figure 2).[6]Kintor Pharmaceutical Limited, (2022). Interim Results Announcement for the six months ended 30 June 2022. Kintor Pharmaceutical. 1-50. Available at: … Continue reading

It’s worth noting that the study reports that all the treatment groups demonstrated significant improvement compared to the placebo groups, but it does not provide details on statistical testing or variability in each group.

Mean Change
Figure 2: Mean change from the baseline in the number of non-vellus hairs in the target area (TAHC) after 24 weeks of treatment. * = p<0.05 compared to the baseline. QD = once daily, BID = twice daily. Adapted from:[7]Follicle Thought, (2022). Kintor Pharmaceutical KX-826 Phase 2 Results with Poster. Follicle Thought Hair Growth Treatment News. Available at: … Continue reading

According to the researchers, the safety profile was good in all dose groups with:

  • 5.9% of participants reported pruritus (itchy skin)
  • 2.5% of participants reported contact dermatitis
  • 2 patients showing hypertriglyceridemia (high volume of fats in the blood)

Study 3

A randomized, double-blind, placebo-controlled, dose-escalation phase 1 trial was completed in the US over 24 weeks to evaluate the safety, tolerability, and pharmacokinetics of different concentrations of pyrilutamide.[8]Kintor Pharmaceuticals, (2020), Results of Kintor’s Phase 1b Clinical Trials of Pyrilutamide in America. News Center. Available at: https://en.kintor.com.cn/news/129.html (Accessed: 03 May 2023) The participants included 40 healthy male patients, 18-60 years old with androgenetic alopecia, who were treated with multiple ascending dose applications of 0.3%, 1.2%, 4.8%, and 9.6% pyrilutamide.[9]Clinical Trials, (2019), Safety, tolerability, and pharmacokinetics of KX826 in healthy male subjects with androgenetic alopecia following topical single ascending dose administration. NIH. Available … Continue reading

The study showed no “severe” adverse drug events, with all adverse events relating to the drug application being mild contact dermatitis that healed in a short time.[10]Kintor Pharma, (no date), Developing Novel Drugs and Commercialization Platform. Available at: https://docs.publicnow.com/viewDoc?hash_primary=BFD6444A4669BD4BE0683A8BCC8B5E80F3D7E430 (Accessed: 03 … Continue reading Unfortunately, the amount of time taken to heal was not given. 

Furthermore, the researchers measured the concentration of the drug in the blood to measure the risk of any systemic effects. While we do not have the specific numbers, the researchers do mention that the concentration of pyrilutamide in the blood was low, indicating that the topical concentrations used were not enough to cause a systemic accumulation (i.e., it may not lead to effects around the rest of the body after being topically applied, at these concentrations and frequency).

Study 4

A subsequent phase 2 study was next conducted in the US, with results announced in May 2023. The randomized, double-blind, placebo-controlled, and parallel-group clinical study was conducted in 123 male AGA patients who were classified as stage III vertex, IV, or V using the Hamilton-Norwood scale. 93 patients were randomly assigned to either 0.25% once daily (“QD”), 0.5% QD, and 0.5% twice daily (“BID”) pyrilutamide. 30 patients were randomly assigned to placebo groups for each dose.[11]Kintor Pharma, (2023). Voluntary Announcement. Successful Completion of Phase II Clinical Trial of KX-826 for Treatment of AGA in the United States. Available at: … Continue reading 

According to Kintor, the 0.5% BID KX-826 group hair count increased by around 10 hairs per cm2 compared to the baseline after 24 weeks, which was statistically significant. An improvement was seen over the placebo. However, this was not found to be statistically significant. Similar to Study 3, a favorable safety profile was observed, with the only adverse events being mild and local scalp sensitivity.

Study 5

After a number of promising results, the next study showed a missed primary endpoint for a phase 3 study. This was a multicenter, randomized, double-blind, placebo-controlled study to evaluate the twice-daily use of 0.5% KX-826 in men with AGA in China.[12]Kintor Pharma, (2023). Results of KX-826 Phase III Clinical Trial for Treatment of Male AGA in China. Available at: … Continue reading Unfortunately, Kintor did not mention the number of participants in this study.

Pyrilutamide was found to be safe, with no serious adverse events reported. After 24 weeks, the total area hair count was statistically improved compared to the baseline (although no numbers were given), but once again, there was no significant change compared to the placebo. 

A few months later, Kintor announced that the NMPA in China had approved a trial for the combination treatment of pyrilutamide and minoxidil in male AGA patients. We will have to wait and see whether combination treatment leads to better results.

What are the Side Effects of Pyrilutamide?

As mentioned above, pyrilutamide treatment does not appear to lead to any serious side effects, with mild contact dermatitis being the only adverse event reported by the researchers. However, because we do not have the full study details or outcomes we do not know if there were any other side effects omitted. 

If this is the only side effect, however, pyrilutamide may present an alternative to oral androgen receptor antagonists like flutamide (which you can read about here) that have limited safety profiles in both men and women. Furthermore, because pyrilutamide is a topical treatment instead of an oral treatment this may reduce the risk of systemic effects.

However, as yet, we have no information on whether pyrilutamide can build up in the body and potentially cause systemic effects. Pyrilutamide is an anti-androgen, and therefore it is not unreasonable to hypothesize that,  if present at a high enough concentration, pyrilutamide will be associated with side effects like those of other anti-androgens (like erectile dysfunction and loss of sexual interest).

Is Pyrilutamide Right for Me?

You may want to experiment with pyrilutamide if:

  • You accept the risk of potential side effects associated with the use of anti-androgen drugs
  • You suffer from male or female pattern hair loss
  • Are ok buying a product with no published (in peer-reviewed journals) data available for it
  • Want to try a topical androgen receptor antagonist

Where Can I Get Pyrilutamide?

Although this product is still in its clinical trial phase, you can buy it online at certain retailers. However, if you do decide to try it, it will set you back around $100 – $110 for a 2 FL OZ bottle. 

Final Thoughts

At a dose of 0.5% once daily in women and twice daily in men, topical pyrilutamide appears to be well-tolerated and may lead to an increase in hair number compared to the baseline. However, few of the studies that used a placebo found any statistically significant differences between the two groups. At this point in time, we would recommend not buying this product until more information from the currently ongoing trials is published.

References

References
1 Pubchem, (no date). Pyrilutamide. NIH. Available at: https://pubchem.ncbi.nlm.nih.gov/substance/469676781 (Accessed: 04 May 2023)
2 Trueb, R.M., (2021). Understanding pattern hair loss-hair biology impacted by genes, androgens, prostaglandins, and epigenetic factors. Indian Journal of Plastic Surgery, 54(4). 385-392. Available at: https://doi.org/10.1055/s-0041-1739252
3 Kintor, (2021), Kintor Pharmaceuticals Announced Successful Dosing of the First Batch of Patients for Acne Vulgaris Phase I/II Clinical Trial of Pyrilutamide. News Center. Available at: https://en.kintor.com.cn/news/172.html (Accessed: 03 May 2023)
4 Cision PR Newswire, (2022), Kintor Pharma Announced the Primary Endpoint of Phase II Clinical Study for KX-826’s Treatment of Female Androgenetic Alopecia in China was Met. Available at: https://www.prnewswire.com/news-releases/kintor-pharma-announced-the-primary-endpoint-of-phase-ii-clinical-study-for-kx-826s-treatment-of-female-androgenetic-alopecia-in-china-was-met-301691321.html (Accessed: 02 May 2023)
5 Cision PR Newswire, (2023), Kintor Pharma Announces Completion of Subject Enrollment in Phase III Clinical Trial of KX-826 for Treatment of Male Androgenetic Alopecia in China. Available at: https://www.prnewswire.com/news-releases/kintor-pharma-announces-completion-of-subject-enrollment-in-phase-iii-clinical-trial-of-kx-826-for-treatment-of-male-androgenetic-alopecia-in-china-301783455.html (Accessed: 03 May 2023)
6 Kintor Pharmaceutical Limited, (2022). Interim Results Announcement for the six months ended 30 June 2022. Kintor Pharmaceutical. 1-50. Available at: https://www1.hkexnews.hk/listedco/listconews/sehk/2022/0829/2022082902004.pdf (Accessed: 03 May 2023)
7 Follicle Thought, (2022). Kintor Pharmaceutical KX-826 Phase 2 Results with Poster. Follicle Thought Hair Growth Treatment News. Available at: https://folliclethought.com/kintor-pharmaceutical-kx-826-phase-2-results-with-poster/ (Accessed: 04 May 2023)
8 Kintor Pharmaceuticals, (2020), Results of Kintor’s Phase 1b Clinical Trials of Pyrilutamide in America. News Center. Available at: https://en.kintor.com.cn/news/129.html (Accessed: 03 May 2023)
9 Clinical Trials, (2019), Safety, tolerability, and pharmacokinetics of KX826 in healthy male subjects with androgenetic alopecia following topical single ascending dose administration. NIH. Available at: https://clinicaltrials.gov/ct2/show/NCT04984707 (Accessed: 03 May 2023)
10 Kintor Pharma, (no date), Developing Novel Drugs and Commercialization Platform. Available at: https://docs.publicnow.com/viewDoc?hash_primary=BFD6444A4669BD4BE0683A8BCC8B5E80F3D7E430 (Accessed: 03 May 2023)
11 Kintor Pharma, (2023). Voluntary Announcement. Successful Completion of Phase II Clinical Trial of KX-826 for Treatment of AGA in the United States. Available at: https://staticpacific.blob.core.windows.net/press-releases-attachments/1520008/HKEX-EPS_20230511_10734339_0.PDF (Accessed: 09 May 2024)
12 Kintor Pharma, (2023). Results of KX-826 Phase III Clinical Trial for Treatment of Male AGA in China. Available at: https://staticpacific.blob.core.windows.net/press-releases-attachments/1591631/HKEX-EPS_20231127_10979479_0.PDF (Accessed: 09 May 2024)

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