On 28 April 2026, the amended Medicines for Human Use (Clinical Trials) Regulations took full legal effect across England, Wales, Scotland and Northern Ireland. Together with a UK-specific implementation of the international ICH E6(R3) Good Clinical Practice principles, this is the biggest change to clinical trial regulations UK-wide in over two decades. For research offices, sponsors and Research Ethics Committees, the transition period is now over — every application, modification and transparency obligation submitted from this date is assessed against the new framework.
- What changed on 28 April 2026
- Risk-proportionate approvals and modification categories
- Transparency duties and the transition timeline
- Answer-first Q&A
- What research offices must do now
- Outlook: bedding in the new regime
What changed on 28 April 2026
The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 were signed into law on 11 April 2025 and, following a 12-month implementation period led jointly by the Medicines and Healthcare products Regulatory Agency (MHRA) and the Health Research Authority (HRA), came into force on 28 April 2026. The Health Research Authority describes it as the largest package of clinical trial regulatory reform in more than 20 years, shaped by a 2022 public consultation with patients, researchers, healthcare professionals and industry.
Six changes matter most for day-to-day research administration:
- New terminology. “Amendment” is replaced by “modification”; “subject” becomes “participant”; “trial site” becomes “trial location”; and the role of “authorised health care professional” is removed in favour of a broader health care professional definition for chief investigators and investigators.
- A codified notification scheme. A new streamlined notification route for the lowest-risk trials and initial applications is now written into law, alongside the existing Combined Review service.
- UK-specific ICH E6(R3) GCP. All CTIMPs must now adhere to the principles of the latest international Good Clinical Practice guideline, ICH E6(R3), with trials intended to support a marketing authorisation required to comply with the full guideline.
- A recruitment deadline. Trials are expected to recruit their first UK participant within two years of approval; if recruitment has not started and no extension has been granted, the approval lapses.
- Simplified consent options. Sponsors of qualifying low-intervention trials may use newly published simplified arrangements for seeking and evidencing informed consent.
- Alignment for non-CTIMP studies. The HRA has issued parallel changes to how non-CTIMP health and social care research is processed, to keep the wider UK research-governance landscape consistent with the new CTIMP rules.
Updated model Clinical Trial Agreement (mCTA) forms are also being rolled out to reflect the new definitions and modification categories; research offices negotiating agreements under the old templates should check for the current version before signature.
Risk-proportionate approvals and modification categories
The reform’s central aim is proportionality: fewer administrative burdens for low-risk research, without loosening oversight of higher-risk trials. Modifications to an approved trial are now sorted into three statutory categories, each carrying a different regulatory pathway through the MHRA and the relevant Research Ethics Committee.
| Modification category | What it covers | Typical regulatory action |
|---|---|---|
| Substantial modification | Changes likely to affect participant safety, physical or mental integrity, or the scientific value of the trial | Full MHRA and/or REC review before implementation |
| Modification of an important detail | Changes to trial conduct that fall short of “substantial” but still need regulatory visibility | Notification-based route, streamlined against the 2004 regime |
| Minor modification | Administrative or low-impact changes with no bearing on safety or scientific validity | Recorded rather than formally reviewed |
Research Ethics Committees have also been restructured to align with ICH-GCP E6: each REC must now have at least five members with the collective expertise to assess a trial’s scientific, medical and ethical aspects, must retain an appointed Chair, and must include at least one lay member.
Transparency duties and the transition timeline
For the first time, UK law requires sponsors of CTIMPs to register their trial in a public registry, publish a summary of results within 12 months of trial completion, and offer participants a summary of results in an accessible format (with limited deferral provisions, for example for Phase 1 healthy-volunteer studies). This closes a long-standing transparency gap that UK research bodies had previously addressed only through voluntary commitments.
The reform followed a multi-year statutory process, set out below.
| Date | Milestone |
|---|---|
| March–April 2022 | Public consultation on proposed reforms |
| December 2024 | Statutory Instrument laid before Parliament |
| February 2025 | Approved by the Westminster Parliament and House of Lords |
| April 2025 | Northern Ireland Assembly approval and final ministerial sign-off; 12-month implementation period begins |
| June–October 2025 | HRA and MHRA guidance published and finalised |
| 28 October 2025 | Six-month countdown to implementation |
| 28 April 2026 | Amended regulations and UK ICH E6(R3) GCP come into force |
Diversity and public involvement remain guidance-led rather than statutory. The HRA’s Public Perceptions of Research work found that 88% of respondents believe trials should involve a diverse group of participants, 70% support this even where it increases cost, and 74% support it even where it extends timelines — evidence the HRA and MHRA cite in the (non-legal) inclusion and diversity guidance now being piloted alongside the statutory reforms.
Answer-first Q&A
What are the UK clinical trial regulations?
The UK clinical trial regulations are the Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the 2025 Regulations in force from 28 April 2026. They govern authorisation, ethical review, conduct, safety reporting and transparency for CTIMPs across all four UK nations, jointly overseen by the MHRA and HRA-recognised Research Ethics Committees.
What is the regulatory body for clinical trials in the UK?
The Medicines and Healthcare products Regulatory Agency (MHRA) authorises and inspects clinical trials of medicines, while the Health Research Authority (HRA) coordinates Research Ethics Committee review, most commonly through the Combined Review service that gives sponsors a single joint application route for both bodies.
What are the regulatory requirements for clinical trials in the UK?
Sponsors must obtain MHRA authorisation and REC approval, correctly classify each modification as substantial, important-detail or minor, register the trial in a public registry, recruit a first participant within two years of approval, and publish a results summary within 12 months of trial completion.
What research offices must do now
With the transition period closed, institutional research offices, sponsors and trial teams need to move from preparation to operation. Priority actions include:
- Update standard operating procedures, protocol templates and delegation logs to use the new terminology — “modification” not “amendment”, “participant” not “subject”, “trial location” not “trial site”.
- Retrain staff who classify trial changes, since misclassifying a substantial modification as minor risks a compliance breach with the MHRA or REC.
- Confirm registry and results-publication workflows exist and are resourced, given the new 12-month statutory deadline for posting result summaries.
- Check that any Clinical Trial Agreement in use is the current mCTA version, and flag legacy templates for replacement.
- Build recruitment-milestone tracking into trial management systems so the two-year first-participant deadline — and any extension request — is never missed.
- Review whether qualifying low-intervention studies can adopt the simplified consent arrangements, and update ethics submissions accordingly.
Research administration offices coordinating these changes across multiple trials and faculties may find it useful to revisit institutional research administration workflows and governance documentation as part of this update, since the reform touches sponsorship, contracting and compliance functions simultaneously rather than a single office alone.
Outlook: bedding in the new regime
The MHRA and HRA have signalled this is implementation, not a one-off event: guidance will continue to be refined, including on Phase 1 healthy-volunteer trials, diversity and inclusion, and public involvement, none of which are statutory requirements but all of which the regulators expect sponsors to engage with. Early inspection and audit activity through 2026 and 2027 will show how consistently the risk-proportionate approach — and the new modification categories in particular — are applied in practice. Research offices that treat 28 April 2026 as the start of an embedding period, rather than a single compliance deadline already met, will be best placed to avoid later remediation.