Minimum age set for UK puberty blocker trial

A minimum age of 11 has been agreed for children recruited to a puberty blocker trial in the UK which some campaigners have said should be axed completely amid concerns around harm to young people.

The trial was paused in February with the Medicines and Healthcare products Regulatory Agency (MHRA) recommending participants should be at least 14 years old.

The research, led by King's College London (KCL) and known as Pathways, was launched late last year following a recommendation by the 2024 Cass Review into children's gender care, which concluded that the quality of research claiming to show the benefits of puberty blockers for youngsters with gender dysphoria was "poor".

Researchers said the UK-wide clinical study aims to provide evidence on how the timing of treatment affects quality of life, mental health, physical development, cognitive function, and gender-related distress.

The trial was originally intended to involve around 226 people aged between 10 and almost 16 when it was launched in November.

The MHRA has confirmed it had agreed a "modified protocol" to the trial, including "strengthened safeguards" such as the introduction of minimum ages of entry.

Researchers from KCL said it had been agreed that birth-registered females must be at least 11 years old while birth-registered males must be at least 12 to take part.

In a letter from the MHRA to researchers in February, the regulator expressed concern about the minimum age limit of the trial, asking for it to be raised to 14.

The letter stated: "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 its update 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".

Legal action is ongoing against the Government following politicians and public figures including Harry Potter author JK Rowling expressing their opposition to the trial.

The writer, who has been outspoken on gender issues, described the trial as "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, claiming the ethical approval process for the trial "contained serious flaws".

Researchers said today that it remains the case that no child can take part without parental consent and added that young people will continue to need to meet all the other eligibility criteria including "demonstrating a good understanding of the intervention and its possible benefits and risks".

No children are expected to be recruited to the trial before 1 August, due to 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."