MHRA Publishes Final Transitional Rules for UK Clinical Trials Regulations

London, United Kingdom — 15 July 2026

The Medicines and Healthcare products Regulatory Agency (MHRA) has published definitive guidance on transitional arrangements for the amended Medicines for Human Use (Clinical Trials) Regulations, which came into full effect on 28 April 2026. This intelligence outlines the critical distinctions between 'old rules' and 'new rules' clinical trials, impacting approval processes, transparency obligations, Good Clinical Practice (GCP), pharmacovigilance, and the manufacture and labelling of Investigational Medicinal Products (IMPs).

Applications for clinical trial approval submitted prior to 28 April 2026 are categorised as 'old rules' trials and will continue under the 2004 regulations for the approval phase, even if decisions are pending post-deadline. Conversely, applications submitted on or after 28 April 2026 are 'new rules' trials and immediately fall under the amended regulations. This dual system necessitates careful tracking of submission dates to determine the applicable regulatory framework for individual trials.

Regarding transparency, 'old rules' trials ending on or after 28 April 2026 must be publicly registered within 90 calendar days of that date or first participant recruitment, with results summaries also published in the same registry. However, the requirement for an accessible summary for participants does not apply, offering a slight compliance reprieve. For 'new rules' trials, all enhanced transparency provisions apply, mirroring the European Union's Clinical Trials Regulation (CTR) principles.

All IMPs manufactured or imported into the UK after 28 April 2026 are subject to the new Part 6 of the amended Clinical Trials Regulations, regardless of whether they are for an 'old rules' or 'new rules' trial. The exception is regulation 37A concerning radiopharmaceuticals for diagnostic use, which does not apply to 'old rules' trials. IMPs manufactured under old regulations in approved countries, with EU Qualified Person (QP) certification completed by 28 April 2026, can still be imported. Manufacturers must also risk assess labelling changes for new IMP batches produced post-28 April 2026; substantial modifications require MHRA approval via an amendment.

What this means for United Kingdom

UK supplement manufacturers involved in any form of clinical investigation must audit their ongoing and planned trials against these revised MHRA regulations. Companies managing 'old rules' trials must ensure pharmacovigilance systems are updated by the first annual safety report post-28 April 2026, or risk non-compliance. Procurement and manufacturing teams must update Standard Operating Procedures for IMP production and labelling to adhere to new Part 6 requirements, especially for batches certified after 28 April 2026, which impacts lead times and costs. Regulatory teams must evaluate all substantial modifications to trials and IMP labels, ensuring correct submission pathways are followed under either old or new regulations to avoid delays in study progression.

Part 4 (Good Clinical Practice) and Part 5 (Pharmacovigilance) of the amended regulations apply to 'old rules' trials from 28 April 2026, with a temporary opt-out option for old pharmacovigilance rules for a limited period. The amended regulations also clarify that the lapse provision for trial approval (two years without participant recruitment) does not apply to 'old rules' trials, providing greater flexibility for studies initiated under the previous framework.

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