UK officials have paused a clinical trial on puberty blockers for children after the medicines regulator raised safety concerns. The regulator warned about unknown long-term biological risks and called for a minimum age of 14.
The Medicines and Healthcare products Regulatory Agency will hold talks with King’s College London next week. The Department of Health and Social Care confirmed that the study will not recruit participants until they resolve the concerns.
The government launched the Pathways trial after the Cass review criticised existing research. The review found weak evidence for the benefits of puberty blockers in young people with gender dysphoria. Dr Hilary Cass said only a clinical trial could provide reliable answers.
The health department said patient safety remains the main condition for approval. Clinicians will examine the evidence before the trial can continue. Experts must confirm that the study is safe and necessary.
King’s College London said it will work closely with the regulator. The university described the project as scientifically rigorous and focused on young people’s wellbeing.
Researchers had planned to recruit 226 participants within three years. The original protocol allowed children as young as ten. The regulator has now demanded a stepwise approach that starts at age 14.
NHS England already restricts puberty blockers to research settings. The Cass review had advised ending routine use.
Health law expert Sir Jonathan Montgomery said the pause aims to improve the study design. He stressed that safety concerns, not legal action, caused the delay. He called the decision a sign of proper regulatory oversight.
