MHRA outlines PATHWAYS puberty blocker trial checks

If you’ve seen the headlines about puberty blockers and the PATHWAYS study, here’s the clear version. On 20 February 2026 the UK medicines regulator (MHRA) said it had raised concerns about participant wellbeing in the paediatric trial and would now hold scientific discussions with the sponsor, King’s College London. The Department of Health and Social Care added the same day that preparations are paused and recruitment will not begin until the issues are resolved.

This is how regulation works in practice. The MHRA’s job is to protect participants. It reviews trials before they start and keeps them under continuous review once approved. That means it can ask for extra safeguards at any time, especially in paediatric research. In its short statement, the agency stressed caution and “highest scrutiny” because children and young people could be involved.

Alongside the statement, the MHRA published a sponsor letter sent to King’s College London. The letter invites a meeting with the sponsor, the MHRA and the Health Research Authority (which oversees Research Ethics Committees) to discuss strengthening the trial protocol. It makes clear this is about tightening safety before any participant is enrolled, not about pushing a study through at speed.

One proposed change is a minimum age for participants. The MHRA suggests setting the lower age at 14 years at the point of consent. Age floors are common in paediatric trials when puberty stage, growth and the ability to report side effects can materially change risk. For readers checking sources, this 14+ point is set out in the published sponsor letter itself.

The letter also proposes tougher safety monitoring and clearer withdrawal rules. Examples include more frequent bone health checks using DEXA scans, setting automatic withdrawal if a low‑trauma fracture occurs, and adding specific rules around persistent vaginal bleeding. It also recommends using brain imaging data to flag any concerning cognitive or neurological changes, with a requirement to withdraw if adverse signals are seen-particularly at the 12‑month scan.

Another key ask is an “exit strategy”. In plain terms, if a young person finishes or leaves the trial and the agreed care pathway involves continuing gonadotropin‑releasing hormone (GnRH) agonists, there should be a plan for safe, continuous care and data collection on outcomes. This follows earlier advice from the Commission on Human Medicines in November 2024, which emphasised clear post‑trial pathways in this area.

So where does the trial stand today? According to the Department of Health and Social Care on 20 February 2026, preparatory work has been paused and recruitment will only begin if the MHRA’s concerns are addressed to the satisfaction of regulators and clinicians. In other words: no young people are being enrolled while these safety questions are worked through.

If you’re new to research language, here’s a quick primer you can use in class. The “sponsor” is the organisation legally responsible for the design, conduct and insurance of a study (here, King’s College London, co‑sponsoring with the South London and Maudsley NHS Foundation Trust). The Health Research Authority coordinates Research Ethics Committees, which review whether a study is ethical and safe to run. Regulators like the MHRA can request “substantial amendments” to a protocol before or during a study to tighten safety.

What will the research look like if and when it proceeds? King’s College London describes PATHWAYS as a randomised trial comparing starting puberty blockers immediately with starting after 12 months, alongside linked studies (CONNECT and HORIZON) that track brain development and outcomes over time. The Health Research Authority summary notes plans for 226 under‑16 participants recruited through NHS Children and Young People’s Gender Services, with independent oversight committees in place.

Context helps. NHS England confirmed on 12 March 2024 that puberty blockers would not be routinely prescribed for under‑18s outside research. In December 2024, following advice from the Commission on Human Medicines, government made indefinite restrictions on private and overseas prescriptions for this indication, with a review scheduled for 2027. PATHWAYS is the planned research route to gather better evidence.

What this means for families and teachers right now: nothing changes in clinics today except that the trial is not opening to participants yet. The regulator has asked for stronger guardrails first. That’s the system doing what it is meant to do-stress‑testing safety before inviting young people to take part.

How to read the next wave of headlines. “Paused” is not the same as “cancelled”. The MHRA has flagged improvements, proposed a meeting, and set out concrete safety asks. The sponsor can respond with amendments. If regulators and ethics committees are satisfied, recruitment could begin with those measures in place. Until then, official updates from the MHRA, the Department of Health and Social Care, King’s College London and the Health Research Authority are the sources to trust.