Britain’s closely watched puberty blocker study has been given the green light to proceed with new minimum age rules, a move that comes as the project faces mounting pressure from critics who say it should be scrapped entirely over fears of harm to young people.
The UK trial was paused in February after the Medicines and Healthcare products Regulatory Agency (MHRA) advised that participants should be at least 14 years old.
The study, led by King’s College London (KCL) and known as Pathways, began late last year after the 2024 Cass Review into children’s gender care called for stronger evidence. The review found the quality of research cited to support puberty blockers for children with gender dysphoria to be “poor”.
According to researchers, the UK-wide clinical trial is designed to generate data on how the timing of treatment may influence quality of life, mental health, physical development, cognitive function and gender-related distress.
When launched in November, the study was expected to include about 226 participants aged from 10 to almost 16.
The MHRA has now confirmed it has signed off on a “modified protocol” for the project, including what it described as “strengthened safeguards” such as setting minimum entry ages.
KCL researchers said the updated framework means birth-registered females must be at least 11 years old to enrol, while birth-registered males must be at least 12.
In February correspondence to the research team, the MHRA raised concerns about the trial’s minimum age and pressed for a higher threshold of 14.
The regulator’s letter said: “Since potentially significant and, as yet, unquantified risk of long-term biological harms is present to participants and biological safety has not been definitively demonstrated in this proposed cohort, at the very least, there should be a graded/stepwise approach starting with those aged 14 as the lower limit of eligibility.”
In an update issued today, the MHRA said it had “sought the advice of independent experts from the Commission on Human Medicines on participant safety and the adequacy of proposed strengthened safeguards”.
Meanwhile, legal action against the Government is continuing after politicians and public figures — including Harry Potter author JK Rowling — voiced opposition to the study.
Rowling, who has been outspoken on gender issues, called the project “an unethical experiment on children who can’t give meaningful consent”.
A campaign group and two individuals are seeking to take legal action against the Health Research Authority (HRA) and the Department of Health and Social Care, arguing that the trial’s ethical approval process “contained serious flaws”.
KCL researchers said today it remains a requirement that no child can participate without parental consent. They added that young people would still have to satisfy all other eligibility conditions, including “demonstrating a good understanding of the intervention and its possible benefits and risks”.
No children are expected to be recruited before 1 August because of the ongoing legal proceedings, the MHRA said.
Researchers, from KCL said: “Our priority remains to safely, and robustly, investigate the benefits and risks of puberty suppression for young people with gender incongruence to improve the evidence base and inform NHS healthcare.
“We have worked extensively and openly with the MHRA to understand and resolve the questions they raised about Pathways Trial in February, which were not based on the emergence of any new scientific evidence.
“We have strengthened patient information connected to the trial and introduced a minimum age requirement, however there are no major changes to the design or conduct of Pathways Trial.
“Approval of the modified protocol paves the way for the study to begin, subject to the ongoing judicial review challenge to the MHRA and HRA’s decisions which focuses on their regulatory processes. As a research team we will engage with this fully and openly.”
