The UK has paused a clinical trial on puberty blockers for young people after a regulator raised safety concerns. The Medicines and Healthcare products Regulatory Agency warned about unknown long-term biological risks. It called for a minimum participant age of 14.
The agency will hold talks with the sponsor, King’s College London, next week. The Department of Health and Social Care confirmed the delay. The Pathways trial will not recruit participants until experts resolve the issues.
The study followed a recommendation from the Cass review into gender care for children. The review found weak evidence for the benefits of puberty blockers. Dr Hilary Cass said only a controlled trial could provide clear answers.
The health department said safety remains the main condition for approval. Clinicians will now examine the evidence in detail. The trial will proceed only if experts judge it safe and necessary.
King’s College London said the wellbeing of young people guides the project. It will continue working with the regulator. The university described the study as scientifically rigorous and essential for better future decisions.
Researchers had planned to recruit 226 participants over three years. The original design allowed children as young as ten. The regulator has now asked for a stepwise approach that begins at 14.
NHS England already restricts puberty blockers to research settings. Professor Sir Jonathan Montgomery said the pause aims to strengthen the protocol. He stressed that the process focuses on participant safety.
