The UK has suspended 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 hold talks with King’s College London next week. The Department of Health and Social Care said the study will not recruit participants until they resolve the concerns.
The government launched the Pathways trial after the Cass review. That review found weak evidence for the benefits of puberty blockers in young people. Dr Hilary Cass said only a clinical trial could clarify the effects.
Officials said child safety remains the main condition for approval. Clinicians will now examine the evidence in detail. The trial will proceed only if experts confirm that it is safe and necessary.
King’s College London said participant wellbeing remains its priority. The university will work with the regulator during the review. It described the project as a rigorous effort to build a reliable evidence base.
Researchers had planned to recruit 226 young people over three years. The original design allowed children as young as ten. The regulator has now asked for a step-by-step approach that starts at 14.
The study is one of two projects on puberty blockers. NHS England already limits the drugs to research settings. Health law expert Sir Jonathan Montgomery said the pause strengthens the protocol and protects participants.
