The Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025, signed into law in April 2025 and entering into force on 28 April 2026, represent the most substantial revision to the UK clinical trial regulatory framework since the original 2004 Regulations transposed the European Clinical Trials Directive into UK law. For sponsors, contract research organisations (CROs), and principal investigators operating in the United Kingdom, the 28 April 2026 date is not an administrative milestone it is the point at which a set of operational requirements changes, and operations not aligned with those requirements become non-compliant.
The new regulations were developed by the MHRA and Health Research Authority (HRA) following a public consultation that drew over 2,000 responses, and they represent the UK's first opportunity since Brexit to depart from the EU Clinical Trials Regulation framework and build a regulatory environment shaped by domestic research priorities, NHS infrastructure, and the post-O'Shaughnessy review ambition to reestablish the UK as a leading clinical trials destination.
This article sets out what changes on 28 April 2026, what the notification scheme means in practice, and what the registration and transparency requirements demand of sponsors and investigators now.
The Notification Scheme for Lower-Risk Trials
The most operationally significant change for a large proportion of CTIMP sponsors is the introduction of a statutory notification scheme for lower-risk trials. Under the previous framework, every clinical trial of an investigational medicinal product required a full clinical trial authorisation (CTA) from the MHRA, regardless of the risk profile of the investigational product. The CTA process involves submission of an investigational medicinal product dossier (IMPD), protocol review, and MHRA scientific assessment a process that, at its slowest, extends the initiation timeline by weeks for studies where the product is well characterised and the modification to standard use is minimal.
Under the new regulations, trials involving a licensed medicine used within or close to its licensed indication, without substantial modification to dose or route of administration, may proceed through a notification process rather than a full CTA. The notification scheme allows approval within 14 days compared with the standard 30-day CTA assessment timeline and the 60-day target the MHRA committed to in its 2023 reform programme. This is not a deregulatory measure. It is a risk-stratified approach that redirects MHRA expert resource from lower-risk assessments to higher-risk reviews first-in-human studies, advanced therapy medicinal products, oncology agents, and complex innovative designs where scientific scrutiny adds the most value.
The boundary between notification-eligible and CTA-required trials is defined by the regulations with reference to the risk of the investigational product and the degree of modification from the authorised use. Sponsors who are uncertain about eligibility should seek early MHRA advice rather than default to a full CTA or, more problematically, attempt to self-classify as notification-eligible a trial that does not meet the criteria. Incorrect self-classification under the notification scheme is a regulatory compliance failure from the point the regulations enter force.
Registration and Results Disclosure Requirements
The new regulations introduce statutory obligations around trial registration and results publication that did not previously carry legislative force in the UK. From 28 April 2026, sponsors must register every new CTIMP on a World Health Organisation (WHO)-recognised public database within 30 days of receiving regulatory approval or recruiting the first participant, whichever occurs sooner. This registration obligation applies to all new CTIMPs; it does not retrospectively require registration of trials approved before the entry-into-force date, but sponsors of ongoing trials should audit their registration status as a matter of good practice.
Results disclosure is the second new statutory requirement with direct operational impact. Sponsors must publish a summary of results on the trial registry within 12 months of the trial end date defined as the date of the last participant's last visit for data collection purposes. This 12-month results disclosure window is more demanding than the current voluntary norm for many academic and commercial sponsors, particularly in therapeutic areas where the academic publication process runs on longer timescales. Sponsors who rely on peer-reviewed journal publication as their primary results disclosure mechanism will need to reconfigure their publication planning to ensure that registry summary results are posted within 12 months even where the full manuscript has not yet been published.
The regulations also require that sponsors provide a plain-language summary of results to participants who request it a requirement that formalises the shift from viewing trial participants as data sources to recognising them as stakeholders with a right to know what their participation contributed. The practical infrastructure for delivering participant-facing results summaries coordinated across multiple sites and in language accessible to lay readers is an operational challenge that many sponsors have not yet addressed.
Real fact: The UK's new clinical trials regulations require sponsors to publish trial results summaries within 12 months of trial completion a statutory obligation that applies from 28 April 2026 and that closes a gap in UK trial transparency that has existed since the original 2004 clinical trials legislation.
What Changes for Combined Review
The combined review process the single application route through which MHRA scientific assessment and Research Ethics Committee (REC) review are coordinated into a single UK decision was introduced as a policy initiative before being placed on a statutory footing by the new regulations. Combined review has been operational since 2022 through the Integrated Research Application System (IRAS) and the HRA's combined review section. The new regulations formalise the combined review pathway as the standard route for all new CTIMP applications and remove the legacy dual-submission pathway.
For sponsors accustomed to the legacy system, the practical change is that MHRA and ethics review are now formally coordinated from the point of submission, with a single decision timeline rather than two parallel but independently variable timelines. This reduces the administrative burden of managing two separate review processes but requires that the application submitted through IRAS is complete and accurate at submission partial or iterative submissions that relied on the flexibility of the legacy dual-pathway will not work as effectively in the combined review model.
The new regulations also address the process for complex innovative trial designs adaptive trials, platform trials, basket trials, and umbrella trials which have become increasingly common in oncology and rare disease development but whose structural features sit awkwardly within approval frameworks designed for fixed, two-arm, placebo-controlled studies. Sponsors seeking approval for complex innovative designs are strongly encouraged to engage with the MHRA's scientific advice service before submission; the regulations provide a formal pathway for pre-submission dialogue on complex design questions that the previous framework handled informally.
Implications for CROs and Academic Sponsors
For contract research organisations operating in the UK, the new regulations create an environment in which the notification scheme may significantly accelerate study initiation for a portion of their portfolio predominantly post-marketing studies of licensed medicines and studies involving well-characterised biologics. The operational challenge is accurate risk classification at the portfolio level: CROs managing large numbers of CTIMPs across multiple therapeutic areas and sponsor clients will need to develop systematic classification protocols that correctly identify notification-eligible studies and route them appropriately from 28 April 2026.
For academic sponsors university research offices, NHS trust research departments, and charity-funded investigators the registration and results disclosure requirements are the most consequential change. Academic clinical trial programmes have historically had lower rates of timely results publication than commercial sponsors, a disparity that the new regulations address through statutory obligation rather than voluntary commitment. Academic institutions receiving UK research funding will face compliance scrutiny from funders as well as from the MHRA, and the resource requirements for compliant results disclosure particularly the participant-facing plain-language summary should be built into research grant budgets from now.
What Sponsors Should Be Doing Now
With 28 April 2026 now the entry-into-force date, sponsors who have not yet reviewed their operational procedures against the new requirements are behind the preparation timeline that the MHRA and HRA have been signalling since 2023. The specific actions required before the entry-into-force date include: classification of the current active CTIMP portfolio against the notification scheme eligibility criteria; review and update of standard operating procedures for trial registration and results disclosure; assessment of participant-facing results summary capability and resource requirements; training of clinical operations, regulatory affairs, and data management teams on the new requirements; and engagement with IRAS system updates that reflect the formalisation of combined review.
The 2025 regulations are an opportunity as much as a compliance obligation. The UK's departure from the EU CTR framework creates the conditions for a genuinely differentiated research environment faster initiation for lower-risk studies, stronger scientific scrutiny for high-risk ones, and a transparency regime that builds public trust in clinical research at a time when that trust is a competitive asset. Sponsors who treat 28 April 2026 as a deadline rather than a starting point will be managing compliance reactively; those who have prepared will be initiating studies faster.
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