The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 (UK CTR 2025) came into force on 28 April 2026, representing the most substantial reform of the UK's 'clinical trials ecosystem' in over twenty years.

The reforms are central to the UK's ambition to establish itself as a leading hub for life sciences innovation and help accelerate patients' access to innovative treatments whilst safeguarding their safety and providing ethical oversight. For sponsors, clinical trial organisations and research institutions, the changes will have practical implications across trial design, governance, approvals, transparency and compliance.

We explore the key factors behind this life sciences regulatory reform, what's changing under the new regime and key points businesses need to know.

Background to the reforms

Implementation of the UK CTR 2025, which gained approval in April last year, modernises the 2004 regulations and seeks to further strengthen UK policy in this area following extensive consultation. Developments during the UK's departure from the EU and the COVID-19 pandemic had highlighted the need for efficiency and flexibility in trial processes and provide some context to the reforms. In addition, with life sciences identified as one of eight high-growth sectors in the UK's Modern Industrial Strategy, the Life Sciences Sector Plan includes a focus on streamlining regulatory processes to help accelerate the development of new treatments and make it more attractive for companies to invest in the UK.

While the sector plan sets out measures to improve the speed and capacity to deliver commercial trials and research, these regulatory changes provide a supporting framework. Following approval in April 2025, the Medicines and Healthcare products Regulatory Agency (MHRA) in collaboration with the Health Research Authority, has issued detailed guidance to the amended clinical trials regulations. This guidance outlines changes to the Research Ethics Committee (REC) and MHRA review process for clinical trials involving investigational medicinal products in the UK.

What is a clinical trial? Scope of the regulations

The core definition of a clinical trial remains unchanged under the UK CTR 2025 – defined as any investigation in human participants, other than a non-interventional trial, intended:

  • to discover or verify the clinical, pharmacological or other pharmacodynamic effects of one or more medicinal products;
  • to identify any adverse reactions to one or more such products; or
  • to study absorption, distribution, metabolism and excretion of one or more such products.

with the object of determining the safety or efficacy of those products.

Therefore the definition continues to be rooted in whether the study involves an investigational medicinal product and is designed to assess safety or efficacy. While this is unchanged there are, notably, a number of changes to terminology used within the details of the Regulations which are highlighted in the section below.

The amended regulations apply to all clinical trials involving Investigational Medicinal Products (CTIMPs) in the UK.

Key changes under the UK Clinical Trials Regulations 2025

1. A single, streamlined approvals process

There is now a single application route for CTIMPs in the UK. Under the 2004 regime, sponsors were required to apply separately for regulatory authorisation from the MHRA and for a favourable opinion from a REC.

Under the new framework, these processes are formally combined into one application, one coordinated review and one UK regulatory decision. The aim is to reduce duplication, improve consistency and shorten approval timelines. For specific lower‑risk trials, a notification‑based pathway has been introduced that can result in automatic regulatory authorisation, helping to further accelerate trial start‑up where appropriate.

2. A new approach to trial changes: from "amendments" to "modifications"

There is a shift in terminology as the established terminology of "amendments" is replaced with "modifications", aligning the UK more closely with international regulatory practice. Changes to an approved trial will now be categorised as one of the following:

  • "Substantial modifications" – these are referred to as Route A and Route B and are essentially changes to a clinical trial that are likely to have a substantial effect on the safety or rights of participants, or on the reliability or robustness of the data generated by the clinical trial. Further details on Route A and Route B modifications can be found on the MHRA website.

    Some examples of substantial modifications include: changes to primary or secondary endpoints likely to have a significant impact on the safety or scientific value of the trial; addition of a trial arm or placebo group; withdrawal of an independent data monitoring committee; and change of insurance or indemnity arrangements for the trial and change of chief investigator.

     

  • "Modifications of an important detail" – examples would include, increase to the duration of a clinical trial, changes to contact details, change to the investigator (other than the Chief Investigator), addition of new trial locations, changes in a sponsor's legal representatives and change in sponsor. However, if the change in sponsor would require changes to insurance arrangements and/or study documents (beyond the name of the sponsor) then this would constitute a substantial modification.

  • "Minor modifications" – this would include changes to processes associated with record keeping, changes in technical equipment and minor changes to protocol, such as correcting of errors, updating contact details and minor clarifications.

If a sponsor has already submitted a modification request that is undergoing review and wished to submit another modification, they could do so under certain circumstances. Multiple modifications are permitted if they relate to changes to the project information and there is no overlap between the modifications. For example, a sponsor may submit two project‑information modifications concurrently, provided they do not relate to the same study documents.

Those conducting clinical trials will therefore need to ensure their internal change‑control processes, governance frameworks and contractual arrangements are aligned with the new classifications and approval routes.

3. Increased transparency and accountability

New transparency requirements are introduced to:

  • register clinical trials on a public register prior to recruitment of the first participant or within 90 days of approval (whichever is sooner);
  • publish a summary of trial results within 12 months of trial completion; and
  • share those results with trial participants.

This reflects a broader policy aim to strengthen public trust in clinical research and, from a business perspective, transparency requirements will need to be carefully balanced with commercial confidentiality, intellectual property considerations and global disclosure strategies.

4. Safety reporting

Suspected unexpected serious adverse reactions (SUSARs) and annual safety reports will now be submitted to the MHRA only.

In the case of urgent safety measures, the timeframe for sponsors to provide written notification to the REC and the MHRA has been extended from three to seven calendar days. That notification must explain both the measures taken and the reasons for them.

Where urgent safety measures necessitate amendments to the study documentation, those amendments must be submitted as a substantial modification as soon as practicable, clearly stating that the changes arise from an urgent safety measure. A copy of the urgent safety measure notification should be submitted alongside the substantial modification.

The move to report SUSARs and annual safety reports solely to the MHRA is intended to streamline regulation, reduce administrative burden, and harmonise reporting standards. The MHRA will liaise directly with the REC on any ethical issues that arise.

5. Changes to certain terminology

The amended regulations introduce a number of changes to terminology, as set out below.

Authorised healthcare professional

The term "authorised healthcare professional" is replaced by "health care professional". Under the amended regulations, the Chief Investigator must now be a healthcare professional.

Chief Investigator

The definition of Chief Investigator has been broadened. Instead of being limited to an authorised healthcare professional (namely a doctor, dentist, pharmacist or nurse), the Chief Investigator must now be a UK‑registered healthcare professional. This expanded category includes doctors, dentists, pharmacists and nurses, as well as other UK‑registered healthcare professionals; including, in particular, ophthalmic opticians, HCPC‑registered healthcare professionals, osteopaths, chiropractors, anaesthesia associates and physician associates.

The Chief Investigator must be registered with an appropriate professional regulatory body. This requirement ensures professional accountability, provides additional assurance to the REC, and confirms that the Chief Investigator meets recognised professional standards. This change is intended to increase flexibility, reflect modern clinical trial roles and widen the pool of eligible candidates, while maintaining appropriate professional oversight.

Subject

The term "subject" is replaced with "participant". The definition remains substantively unchanged: a participant is an individual, whether a patient or not, who takes part in a clinical trial either as a recipient of an investigational medicinal product (or other treatment or product), or as a control without receiving any treatment or product.

Trial site

The term "trial site" has been replaced with "trial location", which is defined as a hospital, health centre, surgery or other establishment, facility or premises at or from which a clinical trial, or any part of it, is conducted.

This change reflects the evolution of clinical trial delivery, recognising that trial activities take place across a range of settings and are no longer confined to traditional hospital or clinical settings. For example, trial activities may be conducted in participants’ homes or via mobile units.

6. Updated good clinical practice and digital responsibilities

Under the UK CTR 2025 there is an update to the statutory reference point for good clinical practice (GCP), aligning more closely with international standards and clarifying sponsor responsibilities. This relates largely to section 28 of the 2004 Regulations which required sponsors and investigators to ensure trials are conducted in accordance with GCP and with the protection of trial participants a central concern.

A key change is to the terminology applied in this section, with "subject" consistently replaced with "participant", as mentioned above. While this is a subtle change, it provides for a broader definition to include individuals receiving treatment or acting as controls and highlights a shift towards a more risk-based, participant-centred GCP.

Broader amendments within this section introduce an expansion of digital and data-related responsibilities. With a focus on streamlining the regulation of clinical trials and supporting cross-border, data-driven trials, sponsors will need to ensure that digital systems demonstrably meet GCP standards. So systems used in trials for data capture, monitoring and reporting, for example, will require robust auditability, traceability and data integrity controls.

The revised framework provides greater flexibility and a more decentralised, digitally-enabled approach that will ultimately aid recruitment to trials and improve timeframes to results. Sponsors will need to navigate their wider responsibilities and ensure appropriate governance and controls are in place to align with the new regime. This will involve, but is not limited to, updating contractual terms and Standard Operating Procedures (SOPs) to reflect the revised definitions, as well as ensuring digital platforms and third-party suppliers meet the required GCP-compliant standards.

7. Manufacturing, labelling and non‑investigational medicinal products

The reforms also address operational aspects of clinical trials, including:

  • updated approaches to labelling for both investigational and non‑investigational medicinal products, broadly aligning with EU practice;
  • ·new provisions governing non‑investigational medicinal products (NIMPs) used in trials; and
  • a specific exemption from manufacturing authorisation requirements for certain diagnostic radiopharmaceuticals.

These changes will be particularly relevant to companies managing complex supply chains or multi-national trials.

Key takeaways for businesses

  • The UK is moving to a faster and more coordinated clinical trials approval system.
  • The new Regulations provide a strengthened framework but with some flexibility built in, taking a risk-proportionate approach.
  • SOPs, contracts and governance frameworks should be updated to reflect new terminology and processes.
  • Transparency is a core compliance obligation.
  • Sponsors face clearer responsibilities for safety reporting, digital systems, pharmacovigilance and supply chain oversight.
  • Early preparation and portfolio management will be essential to avoid disruption as the new regime comes into force.

How will the UK Clinical Trials Regulations affect your trial pipeline?

Overall, the UK CTR 2025 represents a shift towards a more agile and internationally aligned regulatory framework. For life sciences and pharmaceutical companies, it offers opportunities to accelerate innovation by reducing start-up times, making trial design more agile and risk-proportionate, and streamlining approval processes – but only where governance, compliance and operational readiness keep pace with regulatory change.

For more insight on what the changes under the new clinical trials regime will mean for your organisation and IP portfolio, and for sector-specific legal advice, contact Sharmela Kalmer in our Life Sciences team.

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