Are There Any Common Side Effects or Scalp Reactions to Watch For When Applying Pyrilutamide?

Understanding the potential side effects of pyrilutamide (KX-826) is essential for anyone considering its use. Because this medication is still under clinical investigation, publicly available evidence remains limited, fragmented, and largely derived from pharmaceutical filings, conference abstracts, and partial clinical disclosures. This means that while early data suggest a favorable safety profile, we must interpret these results cautiously. In this article, I explore what the research truly shows, what remains unclear, and what I would personally need to know before applying a topical anti-androgen like pyrilutamide to my own scalp.

Pyrilutamide is a topical androgen-receptor antagonist. In simple terms, androgens—particularly dihydrotestosterone (DHT)—bind to receptors in hair follicles and contribute to the gradual miniaturization characteristic of androgenetic alopecia. Pyrilutamide attempts to block that binding directly at the follicular level. Unlike oral anti-androgens, it aims to act mostly at the site of application. This local mechanism theoretically reduces systemic hormone disruption and lowers the risk of widespread side effects.

However, this theoretical advantage depends on how much of the drug is absorbed into the bloodstream. Early pharmacokinetic disclosures from Kintor Pharmaceutical suggest low systemic exposure, but without full peer-reviewed data, this assumption should be treated carefully.

What Clinical Trials Reveal: A Critical Look at Safety Data

A Phase I trial conducted in 2020 (NCT04502901) tested ascending topical doses of pyrilutamide in 40 healthy men with androgenetic alopecia. The study was randomized, double-blind, and placebo-controlled, which is considered the gold standard for early safety evaluations. Over the course of treatment, investigators monitored participants for local reactions, systemic absorption, and treatment-emergent adverse events. While full peer-reviewed data are not publicly available, the Purdue CDEK registry confirms the methodology and population parameters.

The absence of published detailed adverse-event tables limits interpretation. Without direct access to the full dataset, we cannot determine how many participants experienced redness, itching, or other forms of irritation. This lack of transparency is an important limitation.

Phase II Trials: Findings From Men and Women

In a 24-week Phase II trial in China involving 120 men with moderate androgenetic alopecia, Kintor Pharmaceutical reported no serious adverse events and emphasized a favorable safety profile. These statements come from official filings to the Hong Kong Stock Exchange rather than peer-reviewed journals. Such filings summarize results but do not provide detailed safety breakdowns or numerical incidence of scalp reactions.

A separate 24-week Phase II trial in 160 women showed statistically significant increases in hair count at a 0.5% concentration applied once daily. Adverse events were described as mild and comparable to placebo. These results were presented in abstract form at the 2023 EADV Congress. As with the male trial, limited methodological transparency restricts our ability to critically evaluate the exact frequency and severity of scalp reactions.

Scalp Reactions Reported in Studies and Real‑World Use

The most commonly mentioned reaction across research summaries and informal user reports is mild skin irritation. This includes redness, itching, burning sensations, and slight flaking. These symptoms are consistent with the behavior of many topical solutions, especially those containing alcohol‑based vehicles.

Published summaries also mention contact dermatitis. In dermatology, contact dermatitis refers to an inflammatory skin reaction triggered either by irritation or allergy. Irritant dermatitis typically results from repeated exposure to a solution that disrupts the skin barrier, while allergic dermatitis involves an immune‑mediated response. Without detailed patch‑testing data or incidence tables, we cannot determine how common these reactions truly are in pyrilutamide users.

Community reports, while anecdotal and not verified scientifically, consistently mention temporary increases in shedding within the first weeks of use. This is plausible because when follicles transition from a resting state into active growth, older hairs may shed more rapidly. Although not documented in official clinical records, this phenomenon mirrors the early shedding seen with other follicle‑stimulating or androgen‑blocking treatments.

Some online users have reported systemic symptoms such as headaches or fatigue. These accounts are subjective and do not appear in any of Kintor’s disclosed data. However, they remind us that low systemic absorption does not mean zero absorption. Without peer‑reviewed pharmacokinetic data and long‑term follow‑up, I must remain cautious about assuming systemic neutrality.

What We Still Do Not Know: The Limitations of Current Evidence

The most significant limitation in understanding pyrilutamide’s safety is the lack of complete published data. Company press releases and investor filings highlight successful endpoints but do not present full safety tables, raw adverse‑event counts, or dropout reasons. These omissions matter because safety evaluation requires detail, not summaries. Long‑term safety is also unknown. Most existing trials last 24 weeks, and while Kintor has initiated longer Phase III studies, final results are not yet publicly accessible. Without data covering one year or more, the possibility of chronic irritation, allergenic sensitization, or longer‑term systemic effects remains uncertain.

Furthermore, because pyrilutamide is not yet FDA‑approved, there is no publicly available FDA review detailing its safety assessments. In the absence of this, independent verification is limited.

If I were considering using pyrilutamide, I would note that current evidence suggests mostly mild scalp reactions, but the lack of comprehensive data means I would remain observant of any irritation, sensitivity, or shedding changes. I would want transparent, peer‑reviewed studies that clearly document adverse events including their frequency, severity, and long‑term outcomes. Until then, I would approach the treatment cautiously, not because the available evidence indicates high risk, but because the full picture is simply not yet available.

References

Clinical Trials Center, Purdue University. (2020). NCT04502901: A study to evaluate the safety, tolerability, and pharmacokinetics of KX‑826 topical solution in healthy male subjects with androgenetic alopecia. https://cdek.pharmacy.purdue.edu/trial/NCT04502901/

European Academy of Dermatology and Venereology. (2023). EADV Congress 2023 scientific abstracts: Hair and nail disorders. https://eadv.org/wp-content/uploads/scientific-abstracts/EADV-congress-2023/Hair-and-nail-disorders.pdf

Hong Kong Stock Exchange. (2022). Kintor Pharmaceutical interim results announcement. https://www1.hkexnews.hk/listedco/listconews/sehk/2022/0829/2022082902004.pdf

Hong Kong Stock Exchange. (2023). Kintor Pharmaceutical Phase II and Phase III clinical disclosures. https://www1.hkexnews.hk/listedco/listconews/sehk/2023/0328/2023032801491.pdf

Kintor Pharmaceutical. (2022). Phase II clinical study for KX‑826 in female androgenetic alopecia meets primary endpoint. 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

Kintor Pharmaceutical. (2022). KX‑826 Phase II enrollment completion announcement. https://www.prnewswire.com/news-releases/kintor-pharma-announces-completion-of-patient-enrollment-in-phase-ii-clinical-trial-of-kx-826-for-treatment-of-androgenetic-alopecia-in-the-us-301598969.html

Kintor Pharmaceutical. (2021). First patient dosed in Phase III trial of KX‑826 in China. https://en.kintor.com.cn/news_details/1803365190745829376.html