Clinical trials regulations: transitional arrangements

‘Old rules clinical trials’ and ‘new rules clinical trials’

The Medicines for Human Use (Clinical Trials) Regulations 2004 (“the(‘the Clinical Trials Regulations”)Regulations’), as amended by the Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 (referred to as “the‘the amended Clinical Trials Regulations”)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’.

PleaseNote 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(‘old regulations”)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 rules 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)
• Ifif 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 viaby email (clintrialhelpline@mhra.gov.uk)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 partPart 6 of the amended Clinical Trials Regulations.Regulations regardless of whether they are for use in an old rules clinical trial or a new rules clinical trial. 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.

Note that where an IMP has been manufactured under the old regulations in an approved country for import, the UK QP responsible for importation oversight can continue to accept the importation of this IMP after 28 April 2026 as long as the EU Qualified Person (QP) certification is completed by 28 April 2026.

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. IMPsuse. 

IMPs manufactured after 28 April 2026 must be labelled according to the amended Clinical Trials Regulations. The date of manufacture for this purpose is considered to be the date of QP batch certification of the finished IMP.

Note that UK QP importation oversight does not have to have been completed before 28 April 2026 for these transitional arrangements to apply. Where an IMP manufactured in an approved country for import and labelled according to the old regulations has been certified by an EU Qualified Person (QP) prior to 28 April 2026, this IMP can continue to be used in a UK trial for which it is for use even though the UK QP importation oversight has not been completed before 28 April 2026.

Note that these transitional arrangements do not apply to non-investigational medicinal products (NIMPs). From 28 April 2026, all NIMPs must be labelled in accordance with the amended Clinical Trials Regulations regardless of the date of manufacture.

Sponsors of existing trials including NIMPs that are not labelled according to the amended Clinical Trials Regulations (these will be unauthorised NIMPs in most cases, as licensed products used according to the marketing authorisation can be labelled in accordance with the existing UK requirements for prescribed medicines dispensed by pharmacies) will need to submit a substantial amendment to the licensing authority either requesting approval for the new NIMP label or requesting approval to vary or disapply the new labelling requirements.

This substantial amendment should be submitted at least 35 calendar days before 28 April 2026.

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 manufactured before that date can continue to be used with labelling under the old rules 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