UK officials have paused a clinical trial on puberty blockers for young people after a safety warning. The Medicines and Healthcare products Regulatory Agency raised concerns about unknown long-term biological risks. It called for a minimum participant age of 14.
The Department of Health and Social Care said the regulator will meet King’s College London next week. They will review the protocol and address wellbeing concerns. The Pathways trial will not recruit participants until they resolve these issues.
The study followed a recommendation from the Cass review. That review found weak evidence for the benefits of puberty blockers in children. Hilary Cass said a controlled trial offered the only reliable way to clarify outcomes.
Government officials stressed that child safety guides every decision. Experts are now examining the evidence. The trial will proceed only if they confirm that it is safe and necessary.
King’s College London said the health of young people remains its priority. The team will work with the regulator during the review. It described the project as scientifically rigorous and essential for future clinical decisions.
Researchers had planned to recruit about 226 participants over three years. The original design allowed children as young as ten. The regulator now wants a stepwise approach that begins at 14.
The Cass review had already led NHS England to end routine prescriptions of puberty blockers for minors. Their use is now limited to research.
Legal expert Sir Jonathan Montgomery said the regulator aims to strengthen the study, not cancel it. He said the pause shows the safety system working as intended.
