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Timeline of puberty blockers and cross-sex hormones for children 

This timeline tracks the series of political and regulatory steps leading to the approval of the puberty-blocker trial, and the expert, legal and campaigning challenges against it.

Boxes of prescription drugs, NHS logos, Tavistock & Portman clinic

Key documents

DateEventDocuments
19th July 2022Dr Hilary Cass writes to NHS England recommending a puberty-blocker trial.Letter
8th March 2024National Institute for Health and Care Research hosts a workshop to develop a trial.
13th March 2024National Children and Young People’s Gender Dysphoria Research Oversight Board members receives an update from Professor Simonoff:
“An outline protocol has been developed.

“Dr Cass remarked that her report is likely to recommend that there should also be a formal evaluation of non-medical interventions as a response to paediatric gender incongruence. While members were supportive of the proposition, Professor Simonoff’s view was that the group’s efforts should be focused on establishing the PSH study before reaching to other elements of the pathway.”		Minutes from a freedom of information request
10th April 2024 Cass Review published Cass Review
9th May 2024Temporary emergency order banning the supply of puberty blockers, which comes into force on 3rd June 2024.SI 2024/727
29th May 2024 National Children and Young People’s Gender Dysphoria Research Oversight Board meeting receives verbal update from Emily Simonoff, Professor of Child and Adolescent Psychiatry, King’s College, London.good progress on recruitment to the study team, and the draft study application.Minutes from an FOI request
8th July 2024National Children and Young People’s Gender Dysphoria Research Oversight Board meeting:
Emily Simonoff provides an update on the proposed study design and the membership of the study team.		Minutes from an FOI request
Unknown dateCommission on Human Medicines meets with Professor Emily Simonoff.
16th September 2024National CYP’s Gender Dysphoria Research Oversight Board meeting:
“Board members will receive a full study briefing ahead of their endorsement being sought.”

National Institute for Health and Care Research (planned) further study workshop in September.		Minutes from an FOI request
13th November 2024Wes Streeting, Secretary of State for Health and Social Care, receives advice from Commission on Human Medicines supporting a ban on the sale and supply of puberty blockers and the puberty-blocker trial. CHM report
11th December 2024Streeting announces intention to make the ban permanent.Announcement
Statement to the House of Commons
December 2024National Institute for Health and Care Research agrees £10m funding for “Pathways” study of puberty suppression.NIHR Award page
March 2025Clinical Advisory Network on Sex and Gender (CAN-SG) writes to “Pathways” trial investigators, National Children and Young People’s Gender Dysphoria Research Oversight Board, Health Research Authority, Medicines and Healthcare products Regulatory Agency, National Institute for Health and Care Research, NHS England, Commission on Human Medicines, King’s College Hospital, South London and Maudsley NHS Foundation Trust and the Secretary of State for Health and Social Care.CAN SG Letter
16th April 2025Judgment on For Women Scotland from the Supreme Court. FWS v Scottish Ministers
30th April 2025Sex Matters, LGB Alliance, Transgender Trend and Genspect write to Sir James Mackey, CEO of NHS England – and Wes Streeting, Secretary of State for Health and Social Care.Joint letter
21st August 2025King’s College London submits application for trial approval to Health Research Authority.Letter
REC application form
4th September 2025Meeting of London – City and East Research Ethics Committee with nine members in attendance: two “expert”, three “lay” and four “lay plus” agrees a “provisional opinion”REC minutes (4th September 2025)
11th September 2025Research Ethics Committee issues “provisional opinion” and asks trial sponsors to provide 16 items of further information before a final ethical opinion can be issued. HRA provisional opinion 
Unknown dateMedicines and Healthcare products Regulatory Agency raises concerns: 19 clinical grounds for non-acceptance (“GNA”) and three non-clinical GNAs.
18th September 2025Exceptional meeting of Commission on Human Medicines where members agree with the Medicines and Healthcare products Regulatory Agency’s GNAs, and conclude that: “on the evidence before them, the CHM had reason to think that on grounds relating to safety they might be unable to advise the grant of a Clinical Trial Authorisation for this trial at present”. FOI request submitted
9th October 2025Trial sponsors write with response to both Research Ethics Committee and Medicines and Healthcare products Regulatory Agency.Pathways response letter
29th October 2025Approvals manager of Research Ethics Committee issues request to trial sponsors for “a more complete response” to five of the issues raised in the 4th September 2025 provisional opinion, reflecting the five items discussed at the 28th October 2025 sub-committee meeting.Request for further information
28th October 2025Sub-committee of Research Ethics Committee with five members meets and identifies five further amendments or items of information required.Sub-REC minutes 29 Oct 2025
31st October 2025Trial sponsors provided a further response to these five issues. Response document 
6th November 2025Differently constituted sub-committee of the Research Ethics Committee meets and issues a favourable ethical opinion of the trial. Sub-REC minutes 6 Nov 2025
6th November 2025Research Ethics Committee gives a “favourable opinion” on the “Pathways” trial.REC favourable opinion 
7th November 2025Medicines and Healthcare products Regulatory Agency issues a written notice to the trial sponsors stating that it accepted the request for authorisation. Not disclosed
19/20th November 2025Final protocol and easy-read version of “Pathways” trial protocol published.Pathways trial protocol; Pathways easy-read trial protocol
22nd November 2025Regulatory approval announced. 
24th November 2025Sex Matters writes to Wes Streeting, Secretary of State for Health and Social Care.Sex Matters letter
26th November 2025Genspect writes to Streeting.Genspect letter
27th November 2025Patient information sheets finalised.Pathways information sheet for parents

Pathways information sheet for participants
2nd December 2025CAN-SG writes to the Health Research Authority. CAN-SG letter
5th December 2025Bayswater Group, Keira Bell and James Essess send letter before claim to Medicines and Healthcare products Regulatory Agency, Research Ethics Committee and Health Research Authority. Letter before claim
17th December 2025MPs write to Wes Streeting, Secretary of State for Health and Social Care.MPs’ letter
17th December 2025Streeting makes statement to House of Commons that trial will go ahead. BBC report
18th December 2025Open letter from clinicians to Streeting.Open Letter
18th December 2025Deborah Cohen interviews Emily Simonoff and Hilary Cass for the British Medical Journal: “This is why the trial is necessary.”BMJ article
19th December 2025Health Research Authority publishes further documents.HRA disclosures
5th January 2026Professor Jacob George starts as Chief Medical and Scientific Officer at Medicines and Healthcare products Regulatory Agency.Announcement
8th January 2026Petition to cancel the puberty-blockers trial launched by James Esses.Petition
12th January 2026Petition reaches 100,000 signatures.Petition
13th January 2026Streeting writes back to MPs.Wes Streeting letter
15th January 2026CAN-SG writes to Health Research Authority again.Article in The New Statesman
15th January 2026“Forensic” letter sent to Health Research Authority by concerned clinician and researcher on “Pathways” patient information sheets: “not just that critical information is missing, but that the information sheets as currently written violate the HRA’s own requirements”. Handled as a formal complaint.Article in The New Statesman
15th January 2026Health Research Authority publishes more documents.HRA disclosures
2nd February 2026Government responds to petition to cancel the puberty-blockers trial.Petition
6th February 2026Bayswater Support Group, Keira Bell and James Esses issue claim for judicial review.Claimant’s statement of facts and grounds
11th February 2026Medicines and Healthcare products Regulatory Agency sends letter to King’s College London asking for further amendments to trial, raising safety concernsLetter from MHRA 
12th February 2026Department for Education publishes new draft guidance Keeping Children Safe in Education which precludes allowing children to use opposite-sex facilities and requires that their sex be recorded accurately at school. KCSIE draft
15th February 2026Dr Hilary Cass is interviewed for the BBC by Laura Kunnesberg.BBC interview
19th February 2026Sex Matters writes to Wes Streeting, Secretary of State for Health and Social Care.Sex Matters letter
20th February 2026Medicines and Healthcare products Regulatory Agency publishes its letter to King’s College London and issues a statement saying it has raised concerns about the trial.MHRA statement
22nd February 2025Hilary Cass says “pausing puberty blockers trial seems political, not scientific” in Observer interview.Article in The Observer
23rd February 2026Streeting tells Parliament that the trial is paused.Wes Streeting statement
25th February 2026Sex Matters writes to the Medicines and Healthcare products Regulatory Agency asking whether parents and children could meaningfully consent or assent to medical treatment based on hoped-for outcomes that cannot be achieved within the framework of UK law.Sex Matters letter
25th February 2026Someone points Natasha Loder, health editor of The Economist, to gender critical X posts by Professor George.Loder’s X post
26th February 2026Hannah Barnes writes in The New Statesman that the MHRA’s U-turn raises questions over the regulatory process: “Other sources with connections to youth gender care have pointed out to me that the MHRA’s actions coincide with the introduction of a new role at the regulator in January: chief medical and scientific officer. Their remit is to ‘oversee the MHRA’s scientific, research and innovation activities’.”‘Inside the decision to pause the puberty blocker trial’, The New Statesman
26th February 2026Streeting lays a parliamentary order to facilitate the data-linkage study.Parliamentary statement
27th February 2026Cathy Newman publishes “news” about Professor George’s posts. “breaking news @TImes Radio”: “we’ve unearthed social media posts by a senior officer at the MHRA, the regulator overseeing the puberty blockers trial. Posts expressing gender critical views and mocking trans supporters appeared on the X account of Prof Jacob George, MHRA’s chief medical and scientific officer, who was only appointed last month”.Cathy Newman’s X post
27th February 2026Medicines and Healthcare products Regulatory Agency says Jacob George is recused. “Following the identification of social media posts made prior to his appointment, Professor Jacob George is recused from further involvement on the Pathways clinical trial as a precaution.”MHRA statement
28th February 2026Medicines and Healthcare products Regulatory Agency makes a further statement to Sonia Sodha: “Civil servants, like anyone else, hold personal views but must also carry out their roles in line with the Civil Service core values of integrity, honesty, objectivity and impartiality. While there is no evidence to suggest that decisions taken were not impartial, Professor Jacob George is recused from further involvement in the Pathways clinical trial as a precaution.”Sonia Sodha’s X post
28th February 2026Ben Spencer and Shaun Lintern report: “Professor who stopped Pathways puberty blocker trial recused over ‘bias’.”The Times
6th March 2026Judicial review initial hearing. Timetable proposed by Andrew Sharland, representing King’s College London is:
27th April – Medicines and Healthcare products Regulatory Agency and King’s College London complete their discussions and issue the new puberty-blocker trial protocol.
27th April – Judicial review re-starts; amended claim form prepared, along with statement of facts and further evidence.
15th May – four-hour hearing to to determine claimants’ application to rely on expert evidence.
6th July – Judicial review hearing. This will be two days if expert evidence is ruled inadmissible or three to four days if expert evidence is allowed.
31st July (latest) – Judgment. Trial either begins recruiting, or stops.		Nick Wallis report
9th March 2026NHS England announces it has paused new prescriptions of cross-sex hormones to 16 and 17 year olds who question their gender, after a review found previous research into how harmful or beneficial the drugs may be was “really weak”.
NHS England launches consultation.		BBC report
Consultation
Evidence reviews
10th March 2026Sex Matters, LGB Alliance and Women’s Rights Network lobby day.Sex Matters update
11th March 2026The Good Law Project writes to Streeting challenging the pause of the trial, claiming that his decision was solely based on the MHRA letter published on 20th February 2026, allegedly written by Professor Jacob George, and thus “infected by bias”.GLP letter
23rd March 2026Westminster Hall debate on the January 2026 petition to cancel the puberty-blockers trial. Hansard