For decades, clinical trials have failed to adequately represent the patients who will ultimately use the medicines and treatments being tested. Gaps in enrolment across race, ethnicity, sex, age, and socioeconomic background have created an incomplete evidence base, leaving regulators, clinicians, and patients uncertain whether approved therapies will work equally well across populations. Now, with the United States retreating from diversity initiatives under the Trump administration, all eyes are turning to Europe and the United Kingdom to maintain momentum on one of medicine’s most persistent problems.
The Scale of the Problem
The underrepresentation of minority populations in clinical research is well documented. A 2022 Lancet paper analysing two decades of studies found that fewer than half of all US-based trials included race and ethnicity data. A 2022 NIHR Diversity Data Report analysing 148 UK randomised controlled trials initiated between 2007 and 2017 found that only 60% reported ethnicity data, and of those that did, 86% of participants identified as White.
The disparities are not uniform across disease areas, which makes the problem harder to address. In 2016, cardiovascular therapy trials included fewer than 3% Black patients, despite this group being disproportionately affected by severe cardiovascular disease. By contrast, trials for psychiatric conditions showed an over-representation of Black and African-American patients, who made up 24.2% of participants. Such imbalances raise serious questions about the quality and generalisability of clinical evidence and, ultimately, about patient safety.
The consequences extend beyond statistics. When a drug is approved based on data that does not reflect the population using it, adverse effects and reduced efficacy in underrepresented groups can go undetected until the product is already on the market. As Joshua Sharfstein, a former senior official at the US Food and Drug Administration (FDA), has put it:
“Diversity in clinical trials is not about an ideological position. It’s about scientific accuracy and medical progress.”
The US Reversal
For much of the past decade, the United States led global efforts to embed diversity requirements into clinical trial design. The Food and Drug Omnibus Reform Act (FDORA), signed into law by President Biden in 2022, required drug and device sponsors to submit Diversity Action Plans (DAPs) to the FDA ahead of pivotal clinical studies, setting out enrolment goals disaggregated by age, sex, race, and ethnicity, along with an explanation of how those goals would be met.
Draft guidance to support this requirement was issued in June 2024. However, days after President Donald Trump signed an executive order in January 2025 targeting diversity, equity, and inclusion programmes across federal agencies, the FDA quietly removed its DAPs guidance from its website without public notice. The removal was noted publicly on 23 January 2025 and raised immediate concerns across the life sciences sector about regulatory certainty.
A court order subsequently required the Department of Health and Human Services to restore the website to its state as of 29 January 2025. The reinstated page carries a memo from the Trump administration instructing readers to disregard content it deems to promote what it describes as “gender ideology.” The FDA’s Project Equity, launched in 2021 to ensure cancer drugs were evaluated using data from diverse study populations, was also removed from the agency’s website during the same period.
The statutory deadline for final DAP guidance under FDORA was 26 June 2025. Whether the FDA will meet that deadline, and how it will interpret its obligations under the law, remains uncertain. Samantha Artiga, director of racial equity at US health policy group KFF, warned that positive post-COVID momentum on diversity was at risk.
“We’re likely to continue to see under-representation of groups in trials, particularly people of colour and women and other historically underserved groups,” she said.
Dr Lindsay McNair, a clinical research consultant and research ethicist at Equipoise Consulting, was direct in her assessment.
“This wasn’t just kind of an effort to be woke,” she said. “This wasn’t just diversity for the sake of political correctness. This is diversity because it’s necessary for scientific reasons.”
Europe Moves Forward
As the US retreats, European regulators are stepping up. The European Medicines Agency (EMA) updated its Clinical Trials Regulation to require sponsors to justify any non-representative enrolment procedures, with an emphasis on ensuring study populations reflect real-world patient demographics. Sponsors must now provide justification for inclusion and exclusion criteria based on age and sex, and the EMA is increasingly leveraging real-world evidence to support and contextualise data from traditional trials.
In January 2025, a consortium of 73 public and private healthcare organisations launched Research in Europe and Diversity Inclusion (READI), a pan-European initiative aimed at building a more democratic and less fragmented ecosystem for clinical research across the continent. Led by the Servicio Madrileño de Salud (SERMAS), based at the Spanish University Hospital of La Paz, and co-led by Novartis as project lead, the initiative is backed by €66.8 million in funding over six years, with €31.5 million coming from the European Union’s Horizon Europe Innovative Health Initiative. Industry participants include Novo Nordisk, AbbVie, and Roche, alongside regulatory bodies including the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA).
READI’s stated aim is to map the characteristics of underserved populations using real-world data, develop standardised descriptors for their inclusion, and use those findings to inform regulatory and Health Technology Assessment policies. As the consortium stated at launch, it intends to “help underserved and underrepresented communities overcome barriers to clinical study participation, such as lack of information or awareness, mistrust, poor communication, geographic limitations, and prejudice.”
Sonia Anand, a professor of medicine and epidemiology at McMaster University in Canada, has welcomed these European developments but remains concerned about the direction of travel in the US.
“I’m worried that the US is not talking about equity, diversity and inclusion anymore,” she said. “I really hope that these other governments will continue along the path to promoting the importance of equitable inclusion into clinical trials.”
The UK’s Approach
In the United Kingdom, the Health Research Authority (HRA) and the MHRA have developed joint guidance requiring researchers to consider underserved groups from the point of trial design, rather than at later stages when recruitment is already underway. The centrepiece of this approach is the Inclusion and Diversity Plan (IDP), a set of structured questions that sponsors must address as part of their applications to the Integrated Research Application System (IRAS).
Following an informal consultation in 2024, a pilot was launched in which sponsors were invited to submit an IDP alongside their IRAS application. The pilot closed in December 2025 and the HRA has indicated it is reviewing feedback from sponsors, researchers, and Research Ethics Committee members before publishing findings and setting out next steps.
Importantly, the updated Medicines for Human Use (Clinical Trials) (Amendment) Regulations 2025 have been approved by Parliament and, following a twelve-month implementation period, will come into force on 28 April 2026. The reforms are intended to align UK processes with international standards, reduce unnecessary administrative burdens, and enhance transparency in clinical research. However, the HRA has been clear that the diversity and inclusion guidance itself does not form part of the mandatory regulations; it remains guidance rather than a legal requirement.
Operational Challenges Remain
Even with a supportive regulatory environment, achieving representative enrolment is an operationally complex task. Structural barriers including geographic distance from academic research sites, language differences, historic mistrust of medical institutions, and financial constraints continue to limit participation from underserved groups.
A recent survey found that only 24% of clinical trial professionals reported that their organisations were currently benchmarking disease demographics against enrolled populations. Katrina Rice, chief delivery officer at eClinical Solutions, a clinical data software and biometric services firm, noted that intent to act and actual measurement of outcomes have often diverged.
“Because trial diversity was important, companies were highlighting that they were going to do that. But did they have the data to show they were achieving it? There was already a lot of room for growth,” she said.
Rice has called for a more visible community presence from pharmaceutical and biotechnology companies as a marker of genuine commitment. “I want to see pharma and biotech companies at health fairs and other events talking about research and being visible in the community,” she said. “Progress is not just producing numbers, but showing that you’re there in the community you want to serve.”
The challenge of keeping participants engaged once enrolled adds a further layer of complexity, as explored in the analysis of how behavioural science and machine learning can transform trial adherence.
Decentralised and hybrid trial models, which combine remote participation with in-clinic elements, are increasingly cited as a practical mechanism for broadening access, particularly for populations who would face significant barriers to attending specialist research centres. Compounding this is a growing shortage of qualified investigators at trial sites, a structural problem examined in depth in The Physician Gap That’s Slowing Life Sciences. Real-world evidence is also becoming a more prominent complement to traditional trial data, helping regulators evaluate medicines across broader patient groups than those typically enrolled.
A Question of Scientific Integrity
The debate over clinical trial diversity is, at its core, a debate about the quality and applicability of medical evidence. Trials that consistently enrol non-representative populations produce findings of limited generalisability, increasing the risk that approved therapies will perform differently in the real world than clinical data suggests. The consequences for patient safety, healthcare costs, and public trust in medical research are considerable.
Former FDA Commissioner Robert Califf, who served under President Biden, summarised the position plainly.
“It’s hard for me to understand why anyone would be opposed to clinical trials including the variety of people for whom the drug or device is intended,” he told NPR. “That’s the essence of the FDA guidances.”
As the United States navigates a period of regulatory uncertainty, Europe and the United Kingdom face an opportunity to consolidate their positions as global leaders in inclusive clinical research. Whether the regulatory commitments now being formalised on both sides of the Atlantic translate into measurable progress in trial participation will depend as much on operational execution as on policy intent.
