New UK clinical trials regulations

Last updated: 4 October 2025

Below is an attempt to provide information on the new clinical trials regulations. The information is by no means complete or exhaustive. Please use this post as a starting point and take the time to read all of the guidances and other information published on the MHRA website.

Click on the ‘+’ sign to access each section below.

DateUpdate(s)
4 Oct 2025Post updated and laid out in accordian style for ease of reading.
New section Quiz added.
2 Oct 2025Table updated further to add information and improve readability.

Added new section Types of modification to a clinical trial approval and sub sections.
1 Oct 2025Table updated to
i) add new column titled Information on latest draft guidance update
ii) Add new row with link to guidance on Clinical trials that include an in vitro diagnostic device.
27 Aug 2025The following new sections were added:
i) Changes to notification of Type A trials 
ii) Risk proportionate support for reviewing Route B substantial modifications
20 Aug 2025New section Route B substantial modification pilot added.
18 Aug 2025In the section Clinical trials for medicines: modifying a clinical trial approval, added information on the types of amendments including on Route B which was posted on the MHRA website today.
25 June 2025The following two sections were added:
i) Guidances published thus far
ii) Transitional arrangements.
26 May 2025Item no 3 added to the section Further Reading.
1 May 2025New link to an article titled Clinical trial reform gets underway added to the section Further Reading.
28 Apr 2025The following new sections were added:

1) What reforms proposed in the draft legislation have full implemented been implemented in the final approved regulations?
2) What key elements have also been confirmed in the final approved regulations?

A new reference No 7 Reforms to UK clinical trials framework passed into law was added.
25 Apr 2025New section Further reading added.
14 Apr 2025 Post updated substantially.
28 Mar 2025Section Webinars updated to add a link to the MHRA webinar of 25 Feb 2025 entitled Guidance accompanying the new clinical trials plus a summary of the webinar.
17 Jan 20251) Table added to the section Will there also be new guidance published in addition to the new clinical trials legislation?
2) New section When is it anticipated the the new regulation will come into force? added.
3) New reference no 3 added to the References section
19 Dec 2024New section References added.
13 Nov 2024Added new section Webinar.

The reforms were developed through a series of stakeholder workshops, seeking the views of a wide range of organisations and individuals from across the clinical research sector, including patient representatives.

A public consultation took place in January to March 2022, to which over 2,000 responses were received, and the Government response was published in March 2023. 

The New clinical trials draft legislation (Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2024) was laid in Parliament on 12 December 2024 to:

  • address the research sector’s need for a more efficient, streamlined and adaptable regulatory framework for clinical trials.
  • make the UK a more attractive place for innovators to conduct important research and to help to get potentially life-changing new treatments to patients and the NHS as quickly as possible.

Here is a link to the statement made in parliament by Baroness Merron on 12 Dec 2024 concerning laying of the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2024 before Parliament.

The New UK clinical trials regulations (The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025) were signed into law on 11 April 2025.

A 12-month roll-out began on 11 April 2025 to deliver the most significant update to UK clinical trials regulation in two decades – with the aim of:1

  • strengthening patient safety,
  • accelerating approvals,
  • enabling innovation and
  • helping more people benefit from taking part in vital research.1

The new legislation will take full effect from 10 April 2026 following a 12-month implementation period to ensure readiness, aims to reduce unnecessary administrative burdens on trial sponsors without compromising patient safety.

The reforms will1:

  • Put patients and their safety are at the focus of all clinical trials and bring the benefits of clinical trials to everyone.
  • Cut duplication and unnecessary delays, while maintaining robust oversight of the safety of trials.
  • Create a proportionate and flexible regulatory environment, reducing bureaucracy for lower-risk trials.
  • Cement the UK as a destination for international trials.
  • Provide a framework that is streamlined, agile and responsive to innovation.

By reducing red tape and simplifying approvals, the new framework supports the Prime Minister’s target to reduce the time from application to first participant from 250 to 150 days. It will speed up research and reduce the time it takes for promising treatments to reach patients, without compromising on safety.1

The Combined Review – a system that lets researchers apply for ethics and regulatory approval in one go – and notification scheme for some clinical trial initial applications and amendments will now be written into law as part of the changes.1

The key reforms to UK CTR proposed in the December 2024 draft legislation have been fully implemented in the final version of the amendment regulations and include:7

  • Risk-proportionate Regulation:
    • Regulatory requirements now align with the risk level of clinical trials.
    • Low-risk trials can receive faster approval through automatic authorisation without comprising patient safety.7
  • Streamlined Approval Process:
    • A combined review process integrates regulatory and ethics committee approvals, leading to a single UK decision for decision for clinical trials.
    • This aims to reduce duplication and unnecessary delays while maintaining robust oversight of trial safety.7
  • Enhanced Transparency Requirements:
    • New legal obligations mandate the registration of clinical trials in public registry and the publication of trial results within 12 months of the trail’s conclusion.
    • This initiative aims to build public trust in research by improving access to information about ongoing studies.7

The following key elements have also been confirmed in the final amendment regulations:7

  • Notification Scheme for Low-Risk Trials:
    • A notification scheme has been introduced for lower-risk clinical trials, enabling sponsors to notify the MHRA about eligible trials where the risk to participant is similar to standard medical care.
    • This streamlined process facilitates faster initiation of these trials without compromising safety.7
  • Extended Archiving Period:
    • The regulations now require the archiving of trial master files for 25 years, an extension from the previous 5-year requirement.
    • This change ensures long-term accessibility to trial data for future reference and analysis.7
  • Sunset Period for Trials Approvals:
    • Clinical trial approvals will now lapse after a proposed sunset period of two years if no participants have been enrolled.
    • This measure encourages timely initiation of trials and optimises resources allocation.7

Yes, alongside the regulations, the MHRA and HRA has published guidance to embed meaningful public involvement in clinical trials and increase the diversity of people taking part in research trials. This will ensure that research findings can improve everyone’s care, helping address health inequalities.

Draft Guidances published so far

The draft guidances in the table below accompany the Medicines for Human Use (Clinical Trials) Regulations 2004 (“the Clinical Trials Regulations”), as amended by The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025.

Draft Guidance TitleInformation on latest draft guidance update What the guidance is aboutWhen the amendment comes into force
Clinical trials regulations: transitional arrangementsGuidance on transitional arrangements for the Clinical Trials Regulations28 April 2026

Until this date, this guidance is in draft and should only be used to support sponsors in preparing for the implementation of the new regulations		Please see Clinical trials for medicines: apply for authorisation in the UK and Clinical trials for medicines: manage your authorisation, report safety issues for the guidance that should be followed prior to 28 April 2026.
Clinical trials for medicines: apply for approval in the UKMajor update of guidance wording with new links and attachments updated and added on 1 October 2025How to apply for a clinical trial from 28 April 2026, including eligibility, documentation and registration in a public registry.

As aboveAs above
Clinical trials that include an in vitro diagnostic deviceGuidance on submitting an application for approval of a clinical trial that includes an in vitro diagnostic deviceAs aboveAs Above
Clinical trials for medicines: expert adviceMajor update to guidance and diagram attachments on 1 October 2025Clinical trial applications that need expert advice from a specialist group or committee.As aboveAs above
Clinical trials for medicines: labellingMajor update to table 1 and Figure 1in guidance on 1 October 2025.Guidance on labelling for medicinal products used in clinical trialsAs aboveAs above
Clinical trials for medicines: notifiable trialsGuidance on clinical trials that are categorised as ‘notifiable’.

To enable a streamlined, risk-proportionate approach to its review of applications, the licensing authority is categorising certain clinical trials as ‘notifiable’. Applications to approve these trials will receive automatic authorisation from the licensing authority.		As aboveAs above
Clinical trials for medicines: modifying a clinical trial approvalUpdated on 1 October 2025 to add new documents on Route A and B for Modifying a Clinical Trial ApprovalGuidance on the various types of modifications that can be made to a clinical trial approval.

Further details provided below after this table.		As aboveAs above
Clinical trials: Non-investigational medicinal productsMajor update to guidance and diagram attachments on 1 October 2025.Guidance on using non-investigational medicinal products in a clinical trial.As aboveAs above
Clinical trials for medicines: ending a clinical trialMajor update to guidance and diagram attachments on 1 October 2025Guidance on the process for ending a clinical trial.As aboveAs above
Clinical trials for medicines: collection, verification, & reporting of safety eventsMajor update to table 1 and Figure 1 on 1 October 2025Guidance on the collection, verification, and reporting of safety events in clinical trials of an investigational medicinal product.As aboveAs above

As per regulation 20 of the Clinical Trials Regulations, a clinical trial approval may be modified by:

  • the trial’s sponsor,
  • the licensing authority, or the ethics committee.

Source: MHRA

What are the categories of modifications to a clinical trials authorisation approval

Modifications to a clinical trial approval can be categorised into:

Substantial modifications categorised as Route A or Route B

Route A substantial modifications

  • These are likely to have a substantial impact on the safety or rights of the participants or on the reliability or robustness of the data generated in the trial
  • Approval to make substantial modifications must be received from the licensing authority and ethics committee before implementation.
  • The exception to this is for substantial modifications that relate to urgent safety measures. 
  • When considering implementing substantial modifications, sponsors should assess whether such modifications alter the original clinical trial approval to the extent that it should be considered a new clinical trial.
  • If this is the case, a new application for clinical trial approval should be submitted.

Route B substantial modifications

  • These are defined in regulation 11B of the Clinical Trial Regulations and the examples section of this guidance

Modifications of an important detail

  • These do not significantly impact the safety or rights of the participants but the authorities need to be aware of them for administrative or oversight purposes.
  •  Instructions for notifying the authorities about a modification of an important detail are provided on completion of the modification tool.

Minor modifications

  • These may be implemented at any time and without informing the licensing authority or ethics committee at the point of implementation (however, other approvals may be required, which can be determined using the modification tool).
  • The sponsor must keep records of any modifications implemented and, if requested, make them available to the licensing authority or ethics committee.

Source: MHRA

It is the sponsor’s responsibility to determine the modification type, using a risk-based approach, whether a modification is substantial, minor or a modification of an important detail.

Source: MHRA

The MHRA is also expanding its current risk proportionate approach to include the review of modifications to approved clinical trial applications.

  • Once implemented under the new regulations, substantial modifications which meet pre-defined criteria will be eligible for automatic approval from the MHRA through the Route B substantial modification process. 
  • This process will need to be followed by everyone submitting an eligible modification to a clinical trial.
  • Draft guidance supporting the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 is available in this post and in more detail on the Clinical Trials Hub.
  • The section on modifying a clinical trial covers the Route B substantial modifications criteria.

Source: MHRA

To ensure a smooth transition into the new Clinical Trials Regulations, the MHRA will be testing the Route B substantial modification process over the coming months and invite you to get involved. 

The MHRA is opening a pilot for Route B substantial modifications from 1 October 2025 until 31 March 2026, and encourages you to sign up to take part. More information is available on this MHRA page.

By joining the pilot, you will gain early insight into how the new process works and help the MHRA shape it, so it’s ready to support the new regulations from 28 April 2026.   

Click on this link for information on the transitional arrangements concerning the topics listed below or for a summary of the arrangements, click here.

Transitional arrangements for:

  • applying for clinical trial approval
  • transparency regulations
  • approval for modifications
  • Good Clinical Practice
  • pharmacovigilance
  • manufacture and importation of investigational medicinal products
  • labelling of investigational medicinal products
  • enforcement

Source: MHRA

Webinars
  1. Here is a link to the MHRA webinar of 15 October 2024 entitled Implementing the new UK Clinical Trials Regulations and a link to a blog post on the webinar.
  2. Here is a link to the MHRA webinar of 25 February 2025 entitled Guidance accompanying the new clinical trials regulations.

A summary of the webinar of 25 February 2025 has been provided below with the help of the chatbot Google Gemini.

This webinar, presented jointly by the MHRA and the HRA, focuses on the guidance supporting the new clinical trial regulations [00:08].

Here’s a summary of the key topics discussed:

  • Application for Clinical Trial Approval: This includes a new notification approach [04:42]. The MHRA will provide more clarity on timelines, trials not submitted through combined review, and documentation requirements [06:23]. For notifiable trials, the inclusion/exclusion criteria will be clarified, and more information will be provided on the process if a trial is objected to [11:03].
  • Applying for Approval to Modify Clinical Trials: The term “modification” replaces “amendment” in the new regulations [04:56]. The criteria table for Route B modifications will be separated, and a decision tree/flowchart will be included to help identify the most appropriate submission route [13:29].
  • Safety Reporting: The final guidance will include specific guidance on reporting placebo-related events, align with ICH E2F guidelines, provide more DSUR example scenarios, clarify the DSUR submission process, detail how to notify urgent safety measures, and include a section on reporting serious breaches [16:26].
  • End of a Clinical Trial and Transitional Arrangements: The updated guidance will include a section on temporary halts, clarify the definition of a temporary halt, include reasons for temporary halts, clarify that a trial cannot restart until a substantial modification is approved, and include a diagram to explain the process [18:10]. For transitional arrangements, the guidance will reword references to trials submitted under old vs. new rules, clarify processes for trials assessed or migrated into combined review vs. those still ongoing under non-combined review, and clarify labeling aspects [20:21].
  • Transparency Requirements and HRA Guidance: The HRA guidance will cover aspects such as research ethics committee constitution and membership, transparency requirements (registration of trials, publishing summary results, sharing results with participants), and the deferrals process [22:02].

The MHRA and HRA are working together to ensure consistent guidance, with the HRA planning to publish its guidance in sync with the MHRA [22:21]. Stakeholder feedback is being incorporated into the guidance, with opportunities for further input [24:50]. The next steps involve waiting for approval, updating the guidance based on feedback, and publishing it [28:10].

1. Clinical trial reform gets underway, Charlotte Radcliffe et al, 1 May 2025, DAC BeachCroft

2. New Clinical Trials Regulations will bring UK closer to EU regime, Rory Trust, Burges Salmon, 22 April 2025

3. New Measures to Encourage Clinical Trials in the United Kingdom, Paul Ransom, 22 May 2025, Morgan Lewis.

Find below, a link to a quiz on the New Clinical Trials Regulations.

 

Results

#1. The New Clinical Trials Regulations were signed into law on which date?

#2. On what date will the New Clinical Trials Regulations come into force?

#3. Which of the following are included in the New clinical trials regulations? There may be more than one correct answer.

Select all that apply:

#4. All clinical trials can start once they have received a joint ‘clinical trial approval’ consisting of both, a favourable opinion from an ethics committee and an authorisation from the licensing authority, the UK MHRA. Is this true of false?

#5. A sponsor disagrees with the conditions attached to the approval by the licensing authority and wishes to appeal a licensing authority decision. How many days do they have to send written notice of their intention to appeal?

#6. A sponsor submits a CTA application. Within how many days of submission will the outcome of the validation checks be communicated by email and through IRAS?

#7. If the licensing authority does not approve a CTA application or the applicant disagrees with the conditions attached to the approval by the licensing authority, which of the following statements is FALSE?

#8. Valid CTA applications are reviewed by the licensing authority and ethics committee. A combined decision will be issued to the applicant:

#9. If a CTA application is not approved and the applicant needs more than 60 calendar days from the date on which the decision letter was issued, to provide the requested further information in order for the application to be reconsidered, which of the following are false?

Select all that apply:

#10. When must a clinical trial be registered in a public registry according to regulation 25(1)?

Previous
Finish

Once you complete the quiz and click Finish, You will see:

  • The questions that you have answered correctly with a Green band around the answers
  • The questions that you have answered incorrectly with a red dotted line around them and a Green band around the correct answers for these questions.

References

1. Clinical Trials regulations signed into law, 11 April 2025, MHRA

2. New Year Update: incoming changes to UK regulation of clinical trials, Jackie Mulryne et al, 13 January 2025, Arnold & Porter.

3. Framework amending the UK clinical trial regulations laid before Parliament, Jane Summerfield et al, 17 December 2024, Hogan Lovells

4. Patients, the NHS and the Life Sciences sector set to benefit from new clinical trials framework being laid in parliament today, Press release, 12 December 2024, MHRA

5. New clinical trials regulations laid in parliament today, Health Research Authority, 12 December 2024

6. MHRA webinar of 15 October 2024 entitled Implementing the new UK Clinical Trials Regulations (see link above in section Webinar.)

7. Reforms to UK clinical trials framework passed into law, Jane Summerfield et al, 24 April 2025, Hogan Lovells