UK Puberty Blocker Trial Paused After Regulator Raises Safety Concerns
A major clinical trial investigating the use of puberty blockers for children has been paused in the United Kingdom following intervention by the Medicines and Healthcare products Regulatory Agency (MHRA). The regulator has expressed serious concerns about the potential for long-term biological harms, leading to a halt in recruitment until safety issues are resolved.
Regulator Calls for Higher Age Limit
The MHRA has recommended that the minimum age for participants in the Pathways trial be raised from 10 to 14 years old. In a formal letter, the agency highlighted the unquantified risk of significant long-term biological harms, stating that biological safety has not been definitively demonstrated for the proposed cohort. The letter emphasised a need for a graded approach, starting with older adolescents to better assess risks before considering younger participants.
Originally, the trial planned to recruit participants as young as 10 to 11 years old for biological females and 11 to 12 for biological males, though researchers noted that rigorous selection might result in older participants. The trial aimed to enrol approximately 226 young people over three years to build an evidence base for treating gender dysphoria.
Background and Context of the Trial
The Pathways trial was announced in response to the Cass review, a comprehensive investigation into children's gender care. The review, led by Hilary Cass, found that existing research on the benefits of puberty blockers was of poor quality and uncovered a very weak evidence base. Cass advocated for a clinical trial as the only way to clarify the effects, given strong beliefs among clinicians and families about potential benefits.
Following the Cass review's recommendations, NHS England restricted the use of puberty blockers to research settings, ending routine practice for children with gender dysphoria. The paused trial is one of two studies intended to explore the impact of these medications in a controlled environment.
Official Statements and Next Steps
The Department of Health and Social Care (DHSC) confirmed that discussions between the MHRA and the trial sponsor, King's College London, will begin next week to address wellbeing concerns. A DHSC spokesperson reiterated that safety and clinical evidence are paramount, stating that the trial will only proceed if expert advice concludes it is both safe and necessary.
King's College London affirmed its commitment to the wellbeing of young people with gender incongruence, noting that the trial was designed with scientific rigour by world-leading academics. The institution pledged to collaborate with the MHRA during the review process to ensure robust evidence for future decision-making.
This development underscores ongoing debates about medical interventions for transgender youth, balancing potential benefits against unknown risks. The pause reflects heightened scrutiny in the wake of the Cass review, aiming to prioritise child safety in clinical research.
