The UK has paused a clinical trial on puberty blockers after the medicines regulator demanded stricter safety measures. It warned about unknown long-term biological risks and called for 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 confirmed that recruitment will stay on hold 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. Hilary Cass said only a controlled trial could clarify their effects.
Officials said participant safety remains the priority. Experts will review the scientific evidence before the study can proceed. The government will approve the trial only if it proves both safe and necessary.
King’s College London said it will work closely with the regulator. It stressed that the study uses strict scientific methods and aims to guide future clinical decisions.
Researchers had planned to recruit more than 200 participants over three years. The original design allowed children as young as ten. The regulator now wants a step-by-step approach that begins at 14.
NHS England has already stopped routine prescriptions of puberty blockers for gender dysphoria. It limits their use to research settings.
Health law professor Sir Jonathan Montgomery said the pause strengthens the study rather than ends it. He called the move a proper focus on participant safety.
