Puberty blockers: Controversial trial paused over safety concerns
The controversial Pathways trial assessing the effect of puberty blockers on young people with gender incongruence has been paused owing to “concerns related to the wellbeing of participants.”
The UK medicines watchdog the Medicines and Healthcare Products Regulatory Agency (MHRA) has written to King’s College London, which is leading the trial, “to discuss potential amendments that we believe will strengthen the trial protocol.”
The move comes after a concerted effort by campaigners to stop the trial going ahead. In December the Bayswater Support Group, which represents 800 parents of children and young adults who identify as transgender, sent a pre-action letter to the MHRA threatening judicial review unless the study is halted.
But the MHRA emphasised that the pause is related to scientific and wellbeing issues and not a direct result of the potential legal action.
The Pathways study was set up after a review of gender services for children and adolescents by the paediatrician Hilary Cass in 2024 found extremely limited data on the harms of puberty blockers and recommended further research.
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Source: BMJ, 24 February 2026