The date 28 April 2026 is an important milestone for clinical trial regulation in Europe. On this day, the transition period for the EU Clinical Trials Regulation (CTR) officially comes to an end. From that point onward, all clinical trials conducted within the European Union must operate fully under the CTR framework.
For organisations involved in clinical research, this date represents more than an administrative deadline. It marks the point at which the regulatory landscape across the EU becomes fully aligned with the system introduced by the Clinical Trials Regulation. At the same time, the UK continues to operate under its own regulatory framework. Understanding how these two systems differ is essential for sponsors, CROs and research teams running multinational studies.
The End of the CTR Transition Period
The EU Clinical Trials Regulation, Regulation (EU) No 536/2014, was introduced to harmonise the way clinical trials are authorised and managed across EU Member States. Under the previous system, trials were submitted separately to each country. This often resulted in duplicated work, inconsistent timelines and delays in starting clinical research.
The CTR was designed to simplify this process by introducing a coordinated assessment system and a single submission platform called the Clinical Trials Information System, or CTIS. Through this system, sponsors can submit one application covering multiple EU countries and regulators coordinate the scientific assessment.
Since January 2022 there has been a transition period allowing clinical trials approved under the earlier Clinical Trials Directive to move into the CTR system. That transition period ends on 28 April 2026. From that date forward, all EU clinical trials must operate under CTR and be managed through CTIS. Trials that have not transitioned to the CTR system will no longer be legally authorised to continue in EU Member States.
Does the UK follow the CTR?
A common misconception in clinical research is that the United Kingdom follows the EU Clinical Trials Regulation. In reality this is not the case. Following the UK’s departure from the European Union, the UK now operates under its own national regulatory framework for clinical trials.
Clinical trials conducted in the UK are authorised through national processes using the Integrated Research Application System, known as IRAS. Applications are reviewed by the Medicines and Healthcare products Regulatory Agency (MHRA) together with Research Ethics Committees coordinated through the Health Research Authority.
While the UK regulatory system shares many underlying principles with the EU framework, particularly around participant safety and Good Clinical Practice, the legal frameworks and submission systems are different. Organisations running multinational studies must therefore manage two regulatory systems when trials involve both EU and UK sites.
What Is Changing in the UK?
Although the UK is not adopting the EU Clinical Trials Regulation, regulatory changes are also taking place in the UK around the same time. Updated UK clinical trial regulations are expected to come into force to modernise the national framework and maintain the UK’s position as a leading location for clinical research.
The updated UK framework is designed to streamline approvals, support innovative trial designs and strengthen participant protections. Regulators are also aligning expectations with the latest global Good Clinical Practice guideline, ICH GCP E6 (R3).
E6 (R3) places greater emphasis on risk based quality management, proportionate monitoring strategies and stronger oversight of service providers and electronic systems. These principles reflect the way modern clinical trials are conducted, including the increasing use of digital technologies, decentralised trial approaches and complex global study designs.
Old Rules and New Rules
Another important concept organisations must understand is the transition between older trials approved under previous regulations and trials operating under updated rules.
Some clinical trials that began before 28 April 2026 may still be ongoing when the updated UK framework takes effect. These studies are often referred to as old rules trials because they were originally authorised under the previous regulatory requirements.
Even though these trials may continue under their original approval, certain activities that occur after the regulatory changes may need to follow the updated requirements. For example, substantial modifications submitted after the transition date may be assessed under the updated framework. Investigational medicinal products manufactured after the transition must comply with updated manufacturing and labelling expectations. Safety reporting processes may also follow the updated pharmacovigilance requirements.
This creates a situation where compliance depends not only on when the trial was approved, but also on the activity being performed.
Why This Matters
For sponsors and research teams, the regulatory changes around April 2026 require careful planning. Organisations must ensure that they clearly understand which regulatory framework applies to each trial and each activity within that trial.
This is particularly important for multinational studies involving both EU and UK sites. In these cases the same scientific protocol may need to be submitted through two different regulatory systems with different submission platforms and oversight processes.
Failure to follow the correct regulatory pathway can lead to delays in trial approval, regulatory findings during inspections or the invalidation of clinical trial data.
Preparing for the New Regulatory Landscape
As the April 2026 milestone approaches, organisations should review their clinical trial portfolios and ensure that internal procedures are aligned with the evolving regulatory environment. This includes confirming whether trials are conducted in the EU, the UK or both, ensuring regulatory submissions are made through the correct systems, and reviewing safety reporting and oversight procedures.
Teams should also ensure that trial processes align with the updated expectations introduced through ICH GCP E6 (R3), particularly around risk based quality management and oversight of outsourced activities.
Preparing teams early will help ensure clinical trials continue to run smoothly after the regulatory changes take effect.
Supporting Your Teams Through the Transition
The regulatory changes coming into effect around 28 April 2026 represent one of the most significant shifts in the clinical trial landscape in recent years. In the EU, the end of the transition period means all trials must operate under the Clinical Trials Regulation and be managed through the CTIS platform. In the UK, updated legislation will modernise the national framework for clinical trials involving medicinal products, introducing streamlined approvals, risk proportionate regulation and greater transparency.
For organisations running multinational studies, this creates a more complex environment. The same protocol may need to move through two different regulatory systems, each with its own processes, oversight mechanisms and reporting expectations. At the same time, teams must understand how newer regulatory principles, including the latest Good Clinical Practice guideline ICH GCP E6 (R3), influence trial oversight, safety monitoring and data reliability.
Ensuring that clinical development teams, regulatory professionals and investigators understand these differences is essential to maintaining compliance and avoiding operational delays.
To help organisations navigate these changes, we have developed two dedicated training courses:
Conducting Clinical Trials in the UK After 28 April 2026
This course explains how the updated UK clinical trial framework operates, the roles of the MHRA and Research Ethics Committees, and how to manage submissions, modifications and safety reporting using the IRAS system.
Clinical Trials Regulation EU CTR 536/2014
This course provides a comprehensive overview of the EU Clinical Trials Regulation framework, including CTIS submissions, coordinated assessment across Member States, safety reporting obligations and transparency requirements.
Together, these courses provide a clear understanding of how to conduct clinical trials across both regulatory environments. Whether your organisation runs trials exclusively in the UK, across the EU or globally, ensuring your teams understand the evolving regulatory landscape will help support compliant and successful clinical research.
If these courses aren’t quite what you need, take a look at our GCP R3 Training course or learn about our other Good Clinical Practice Training services.
