Clinical trials regulations: transitional arrangements
Guidance on transitional arrangements for applying for clinical trial approval.
This guidance accompanies 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.
These amendments come into force on 28 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.
We welcome your feedback on the new draft guidelines.
‘Old rules clinical trials’ and ‘new rules clinical trials’
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 (referred to as “the amended Clinical Trials Regulations”) come into force on 28 April 2026.
If an application to approve a clinical trial is submitted before this date (even if an outcome has not been received by 28 April 2026), that trial will be considered an ‘old rules clinical trial’, per schedule 14 of the amended Clinical Trials Regulations.
Any application for approval of a clinical trial submitted on or after 28 April 2026 will be considered a ‘new rules clinical trial’.
Please note that whether a trial was submitted through the combined review process or through separate applications to the licensing authority and ethics committee has no impact on its status as an old rules or new rules clinical trial. The transitional arrangements in this guidance apply regardless of the route of submission.
Transitional arrangements for applying for clinical trial approval
Old rules clinical trials
If an application to approval a clinical trial is submitted before 28 April 2026:
- the Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 (“old regulations”) apply to the whole process of requesting approval (even after 28 April 2026, if the licensing authority and ethics committee have not issued a decision or opinion by then)
- if the licensing authority issues a notice of grounds for non-acceptance after 28 April 2026, the old still apply following the applicant’s response to the grounds for non-acceptance
- the provision that a clinical trial approval will lapse two years from the date on which the trial was approved if no participants have been recruited to take part does not apply
New rules clinical trials
If an application to approve a clinical trial is submitted on or after 28 April 2026, the amended Clinical Trials Regulations apply to the whole process of requesting approval.
Transitional arrangements for transparency regulations
Old rules clinical trials
If an application to approve a clinical trial is submitted before 28 April 2026 and the trial ends prior to 28 April 2026, the transparency requirements in the amended Clinical Trials Regulations do not apply. However, if an application to approve a clinical trial is submitted before 28 April 2026 and the trial ends on or after 28 April 2026:
- it must be registered in a public registry, either before the date on which the first participant signs the consent form or within 90 calendar days of 28 April 2026 (or within 90 calendar days of 28 April 2026, if the first participant had already been recruited before 28 April 2026)
- a summary of the results of the clinical trial must be published in the same public registry that it was registered in
- the requirement to provide an accessible summary of results for participants does not apply, although sponsors of old rules clinical trials are still encouraged to do so
- the automatic deferral for phase I trials applies, provided that the sponsor registers the required minimum information in a public registry before the aforementioned deadline for registering the trial
New rules clinical trials
If an application to approve a clinical trial is submitted on or after 28 April 2026, all transparency provisions in the amended Clinical Trials Regulations will apply.
Transitional arrangements for applying for approval for modifications
The applicable regulations are determined by the date on which the application to approve the substantial modification was submitted, not by whether the trial to be modified is an old rules or a new rules trial.
This means that:
- if the sponsor submits an application to approve a substantial amendment (or receives notice of a proposed amendment by the licensing authority or ethics committee) prior to 28 April 2026, the old regulations apply to the whole process of requesting approval (even after 28 April 2026, if the authorities have not issued a decision by then)
- If an application to approve a substantial modification is submitted on or after 28 April 2026, the amended Clinical Trials Regulations apply to the approval process (even if the clinical trial approval to be modified is for an old rules clinical trial)
Transitional arrangements for Good Clinical Practice
Old rules clinical trials
From 28 April 2026, Part 4 (Good practice and the conduct of clinical trials) of the amended Clinical Trials Regulations will apply to old rules clinical trials (i.e. where the application to approve the trial was submitted before 28 April 2026), with the exception of the amended regulation 31A(7) (retention of the trial master file), which does not apply. Instead, regulation 31A(7) immediately in force before 28 April 2026 applies, which requires the trial master file to be retained for at least 5 years after the trial concludes.
New rules clinical trials
For new rules clinical trials (i.e. where the application to approve the trial was submitted on or after 28 April 2026), Part 4 of the amended Clinical Trials Regulations apply.
Transitional arrangements for pharmacovigilance
Old rules clinical trials
By default, Part 5 (Pharmacovigilance) of the amended Clinical Trials Regulations will apply to old rules clinical trials from 28 April 2026.
However, sponsors of old rules clinical trials may elect to temporarily continue the trial under old pharmacovigilance regulations (i.e. Part 5 of the Medicines for Human Use (Clinical Trials) Regulations 2004 as in force prior to 28 April 2026) by contacting the licensing authority via email (clintrialhelpline@mhra.gov.uk) to request this either within 60 calendar days of 28 April 2026 or when making a notification or safety report under the old pharmacovigilance rules, whichever is earlier. The old pharmacovigilance regulations may then be followed until the first annual safety report after 28 April 2026 is submitted, after which Part 5 of the amended Clinical Trials Regulations must be followed.
New rules clinical trials
For new rules clinical trials, Part 5 of the amended Clinical Trials Regulations apply.
Transitional arrangements for manufacture and importation of investigational medicinal products
All investigational medicinal products (IMPs) manufactured or imported into the UK after the 28 April 2026 will be subject to the amended Clinical Trials Regulations. The exception to this is regulation 37A (exemption from the requirement to hold a manufacturing authorisation for radiopharmaceuticals used for diagnostic purposes), which does not apply to old rules clinical trials.
Transitional arrangements for labelling of investigational medicinal products
Part 7 (Labelling of investigational medicinal products) of the amended Clinical Trials Regulations will apply to IMPs used in both old rules and new rules clinical trials. However, IMPs manufactured under the old regulations before 28 April 2026 can continue to be used in the clinical trial for which they are for use. IMPs manufactured after 28 April 2026 must be labelled according to the amended Clinical Trials Regulations.
Transitional arrangements for enforcement
The enforcement measures that apply after 28 April 2026 depend on the provision that was breached:
- if the provision that has been breached is in the amended Clinical Trials Regulations, the enforcement measures in Part 8 (Enforcement and related provisions) of the amended Clinical Trials Regulations apply
- if the provision that has been breached is in the old regulations (i.e. the Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026), for example, where an old rules clinical trial is exempt from particular aspects of the amended Clinical Trials Regulations, the enforcement measures in the old regulations apply
In some cases, provisions in the old regulations may be applied with modifications made by virtue of the transitional provisions in the amended Clinical Trials Regulations. In such cases, an enforcement authority may include those modifications in the infringement notice.
Summary
The table below summarises the transition arrangements for old rules and new rules clinical trials.
Regulations which apply on and after 28 April 2026
| Area | Old rules clinical trials (application for clinical trial approval submitted before 28 April 2026) | New rules clinical trials (application for clinical trial approval submitted on or after 28 April 2026) |
|---|---|---|
| Applying for approval of a clinical trial | The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Applying to modify a clinical trial approval |
If the modification application was submitted before 28 April 2026: The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 If the modification application was submitted on or after 28 April 2026: the Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Registering a clinical trial in a public registry |
If the trial ends before 28 April 2026: The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 If the trial ends on or after 28 April 2026: The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Publishing the results of a clinical trial in a public registry |
If the trial ends before 28 April 2026: The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 If the trial ends on or after 28 April 2026: The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Offering an accessible summary of results to participants | The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 (meaning that this is not required) | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Lapse of clinical trial approval after 2 years where no participants are recruited | The Medicines for Human Use (Clinical Trials) Regulations 2004 as in force immediately before 28 April 2026 (meaning that this does not apply) | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Good Clinical Practice | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025, except regulation 31A(7) | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Pharmacovigilance | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 by default but sponsor can apply to continue under regulations in force immediately before 28 April 2026 until the first annual safety report is submitted | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Manufacture and importation of IMPs | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025, except regulation 37A | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Labelling of IMPs | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025; however, IMPs labelled before date can continue to be used in the clinical trial for which they are for use | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |
| Enforcement | Depends on the provision breached | The Medicines for Human Use (Clinical Trials) Regulations 2004, as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 |