The UK has delayed a clinical trial on puberty blockers after the medicines regulator demanded a higher minimum age. Officials warned about unknown long-term biological risks and called for stricter safeguards.
The Medicines and Healthcare products Regulatory Agency will hold talks with King’s College London next week. The Department of Health and Social Care confirmed that recruitment will not start until they resolve the concerns.
The Pathways trial followed a recommendation from the Cass review. That review found weak evidence for the benefits of puberty blockers in young people. Dr Hilary Cass said a controlled trial was the only way to clarify the treatment’s effects.
Government officials said participant safety remains the priority. Clinicians will now examine the new scientific questions. The study will proceed only if experts judge it safe and necessary.
King’s College London said the health of affected young people guides its work. The team will continue discussions with the regulator. It stressed the trial’s scientific rigour and its goal of improving future clinical decisions.
Researchers had planned to enrol about 226 participants over three years. The original design allowed children as young as ten. The regulator has now asked researchers to start with a minimum age of 14 and consider younger groups later.
NHS England already limits puberty blockers to research settings. The Cass review had advised ending routine treatment.
Professor Sir Jonathan Montgomery said the pause aims to improve the study design. He described it as a normal safety step in the regulatory process.
