We’ve published our final guidance to support researchers and sponsors ahead of legal changes to how clinical trials are run in the UK.
New clinical trials regulations were signed into law in April 2025 and we’re now almost halfway through a 12-month implementation period.
The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 will come into effect on 28 April 2026, and from that date researchers and sponsors must follow the updated legislation.
Over the last year we’ve engaged with a range of people and organisations, including researchers, sponsors and industry, to make sure our guidance is simple, clear and easy to follow.
The final guidance we’ve produced should be used by anyone involved in setting up and conducting clinical trials to update their processes and policies before the regulations come into force.
What are the main changes to the legislation?
The amended clinical trials regulations represent the most significant overhaul to the regulations in 20 years.
The updates, delivered in partnership with the Medicines and Healthcare products Regulatory Agency (MHRA), will help create a faster, more efficient, more accessible and more innovative clinical research system – making the UK a world leader in clinical trials.
The amended legislation is intended to support more streamlined and flexible regulation of clinical trials, removing unnecessary administrative burdens on trial sponsors, while protecting the interests of trial participants.
These updates will play a crucial role in supporting the aims of the government’s 10 Year Health Plan and in meeting the Prime Minister’s target to reduce how long it takes to set up clinical trials in the UK.
Updates to the legislation include:
New and updated definitions
The term ‘amendment’ to describe changes to approved trials will be replaced with ‘modification’. This term is already used by European Union nations to describe changes to clinical trials of investigational medicinal products (CTIMPs). This change will make sure there is better alignment between the UK and the international research community.
From 28 April 2026, modifications will be categorised as ‘substantial modifications’, ‘modification of an important detail’ or ‘minor modifications’.
The updated regulations introduce new definitions including ‘non-investigational medicinal product’, ‘notifiable trial’ and ‘public registry’.
There are also changes to existing definitions including the removal of the term ‘authorised health care professional’. Instead, the updated regulations say that chief investigators and investigators should be a health care professional as defined in the amended legislation.
The updated regulations also replace the term ‘subject’ with ‘participant’ and ‘trial site’ with ‘trial location’.
Read our final guidance on definitions and terminology.
Research transparency requirements
For the first time, it will be a legal requirement to:
- register clinical trials in a public registry
- publish a summary of trial results within 12 months of completion
- offer to share a summary of results with participants (or their representative) in a format they can easily understand
Provisions for deferrals and waivers in specific circumstances will be available under the updated regulations.
Read our guidance on research transparency requirements for clinical trials.
The approvals process for clinical trials
Combined Review – the system that lets researchers apply for ethics and regulatory approval in one go – and a new streamlined notification scheme for some clinical trial initial applications and amendments, will also now be written into law as part of the changes.
The updated regulations will result in changes to how Research Ethics Committees (RECs) and the MHRA process applications and amendments (modifications from 28 April 2026) for CTIMPs, including for Phase 1 healthy volunteer trials.
Under the amended regulations, the MHRA and RECs will be able to request that sponsors modify their trials in certain circumstances.
The legislation also sets the expectation that all CTIMPs should recruit their first participant in the UK within 2 years of the trials being approved, with extensions available. If there is no recruitment within 2 years and an extension has not been granted, the approval will lapse.
Read our guidance on the approvals process for clinical trials.
Research Ethics Committees
Changes to RECs will improve flexibility while aligning with international good clinical practice. When the new regulations come into force RECs will:
- need at least five members that collectively possess the qualifications and experience to review and evaluate any proposed trial's scientific, medical, and ethical aspects
- still be expected to have an appointed Chair
- include one lay member
Read our guidance on Research Ethics Committees that review clinical trials.
Simplified arrangements for consent in clinical trials
The new clinical trials regulations will offer sponsors of clinical trials that meet certain conditions the option to use simplified arrangements for seeking and evidencing informed consent.
As part of this work, we’re establishing an advisory group, made up of a range of people with appropriate expertise, skills and experience, to help us develop a set of principles that:
- provides guidance for sponsors and researchers looking to use simplified arrangements
- sets HRA expectations on the use of simplified arrangements that maintain people’s trust
- supports REC members to evaluate the ethical considerations of using simplified consent arrangements in specific types of clinical trials
Read our guidance on simplified arrangements for consent in clinical trials.
Pharmacovigilance
Safety reporting requirements for CTIMPs will change.
When the new regulations come into force, suspected unexpected serious adverse reactions and annual safety reports for all CTIMPs (including those which were not submitted through Combined Review) will only be reported to the MHRA.
The timeline to give written notice for urgent safety measures will also change, however the process will remain the same.
Read our guidance on pharmacovigilance.
What the guidance applies to
Our final guidance explains what will change in terms of processes, legal requirements, and expectations when the amended regulations come into force, and covers updates to the regulations which have been a key focus for the HRA.
The guidance outlines the review and assessment processes for CTIMPs by RECs and the MHRA through Combined Review.
It does not cover changes to other reviews, for example study wide review (HRA and HCRW Approval), and reviews of non-CTIMP applications. This is because the amended regulations do not apply to these types of studies.
The MHRA has also published separate guidance to accompany the amended regulations which you can read on their clinical trials hub. Their guidance covers updates to the regulations which have been a key focus for the MHRA.
Janet Messer, Director of Approvals"The HRA and MHRA are grateful to all who have been involved in helping us to create this suite of guidance for use across the UK. The publication of the guidance marks the start of implementing new ways of working.
“We encourage the clinical trial community to take time to understand what changes they should start implementing now, and what they need to plan to have in place for 28 April 2026.
“The amended regulations and supporting guidance will improve how clinical trials are set up and run in the UK, making it easier to do high-quality research that people can trust.”
Matt Westmore, Chief Executive“The updated regulations are a major milestone for UK clinical research. The HRA and MHRA have worked closely to ensure our guidance is aligned and clear, helping researchers and sponsors prepare.
“Clinical trials drive innovation in health and care, and this new guidance will support faster, more inclusive, and transparent research - making it easier to do research that people can trust, strengthening the UK’s global leadership in life sciences, and advancing the 10 Year Health Plan.”
Developing our clinical trials guidance
Find out more about the journey over the last year to develop our guidance and the work behind the scenes in this blog post from Catherine Blewett, Senior Development Manager, and Chris Cole, Guidance and Advice Manager.
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