A UK clinical trial investigating the use of puberty blockers for children with gender dysphoria has been paused after the Medicines and Healthcare products Regulatory Agency (MHRA) raised concerns about the age of participants. The MHRA warned that the trial should have a minimum age limit of 14 due to the 'unquantified risk' of 'long-term biological harms'.
The Pathways clinical trial, sponsored by King's College London, was announced following recommendations from the Cass review into children's gender care, which found weak evidence for the benefits of puberty blockers. The trial aimed to recruit around 226 young people over three years, with initial plans to include children as young as 10 to 11 for biological females and 11 to 12 for biological males.
The Department of Health and Social Care (DHSC) confirmed that discussions between the MHRA and King's College London will begin next week to address the wellbeing concerns. A DHSC spokesperson stated that the trial will only proceed if expert scientific and clinical evidence concludes it is safe and necessary, emphasising that the safety of children remains the priority.
King's College London expressed commitment to working with the MHRA, noting that the trial was designed with scientific rigour to build an evidence base for better-informed decisions. The MHRA's letter called for a 'graded/stepwise approach' starting with participants aged 14 as the lower limit, with potential to lower the threshold based on initial findings.
The pause follows the Cass review's 2024 recommendation to ban routine use of puberty blockers on the NHS, limiting their use to research settings. Professor Sir Jonathan Montgomery of University College London noted that the regulatory process is working properly, focusing on safety rather than stopping the trial entirely.
