The UK has delayed a clinical trial on puberty blockers for young people after a regulatory 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.
King’s College London sponsors the Pathways trial. It will not recruit participants until officials resolve the issues. The regulator and researchers will begin formal discussions next week.
The study followed the Cass review on gender care for children. That review found weak evidence for the benefits of puberty blockers. Dr Hilary Cass said only a controlled trial could clarify their effects.
The Department of Health and Social Care said safety remains the main condition. Experts will reassess the scientific evidence before the trial can proceed.
Researchers had planned to recruit 226 participants within three years. The original design allowed children as young as ten. The regulator now demands a stepwise approach that starts at 14.
King’s College London said it will work closely with the regulator. It stressed the study’s scientific rigour and its focus on young people’s wellbeing.
The Cass review had already led NHS England to stop routine prescriptions of puberty blockers. Their use is now limited to research.
Professor Sir Jonathan Montgomery said the regulator wants to improve the study design. He described the pause as a normal safety measure that protects participants.
