The UK has halted a clinical trial on puberty blockers for children after the medicines regulator raised safety concerns. The agency warned about unknown long-term biological risks and demanded a minimum age of 14.
The Medicines and Healthcare products Regulatory Agency will meet King’s College London next week. They will review participant wellbeing and the study design. The Pathways trial will not recruit children until they resolve these issues.
The Cass review had called for the trial. It found weak evidence for the benefits of puberty blockers in young people with gender dysphoria. Hilary Cass said only a controlled study could clarify the treatment’s effects.
The Department of Health and Social Care said safety remains the main condition. Experts are now examining the evidence. The trial will proceed only if they confirm it is safe and necessary.
King’s College London said it prioritises the health of young people and their families. The team will continue working with the regulator. Researchers designed the study to build a stronger evidence base for future decisions.
The project had planned to recruit 226 participants over three years. Earlier plans allowed children as young as ten. The regulator now wants a stepwise approach that begins at age 14 because of uncertain risks.
NHS England already restricts puberty blockers to research settings. The Cass review had recommended ending routine use.
Health law professor Sir Jonathan Montgomery said the regulator aims to improve the protocol, not cancel the trial. He said the pause shows the safety system working as intended.
