New Study Reveals Widening Racial Gap in FDA Drug Trials Despite Diversity Pushes

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December 15, 2025

RIVERSIDE, Calif. — Despite years of intensified calls for health equity and federal initiatives aimed at diversifying medical research, a troubling new study has revealed that the racial gap in U.S. clinical trials is not closing—it is widening.

The research, published December 12 in the journal Communications Medicine, analyzed hundreds of pivotal drug trials pivotal to FDA approvals over a seven-year period. The findings paint a stark picture: only 6% of these trials accurately reflected the racial and ethnic makeup of the United States. More concerningly, the study identified a specific regression in the enrollment of Black and Hispanic participants starting in 2021, creating a growing “blind spot” in modern medicine just as the era of personalized precision therapies aims to take flight.

“When a trial includes only a narrow slice of humanity, we can’t be confident a drug will work—or be safe—for everyone it’s meant to help,” said Simon “Niels” Groen, a geneticist at the University of California, Riverside (UCR) and co-author of the study.

The Data: A Step Backward

Researchers from UC Riverside and UC Irvine examined data from 341 pivotal clinical trials conducted between 2017 and 2023. These trials are the final, critical hurdles new medications must clear to gain approval from the Food and Drug Administration (FDA).

While the medical community has ostensibly prioritized diversity following the COVID-19 pandemic’s spotlight on health disparities, the data suggests these efforts have yet to translate into systemic change for certain groups. The study found that while the representation of Asian participants has increased and White participation has remained stable, enrollment rates for Black and Hispanic individuals have effectively slid backward since 2021.

This trend is particularly alarming given the rapid advancement of “precision medicine”—treatments tailored to an individual’s specific genetic profile. Without diverse trial data, the promise of these targeted therapies may remain out of reach for large segments of the population.

The “Genetic Blind Spot”

The implications of this exclusion go beyond fairness; they are a matter of patient safety and drug efficacy. Sophie Zaaijer, a researcher formerly at Cornell Tech and co-author of the study, noted that the problem often begins long before a drug reaches human trials.

“Bias in preclinical models is an early warning sign, but bias in clinical trials becomes medical practice,” Zaaijer explained.

Different populations often carry unique variants of genes, known as alleles, which can significantly influence how the body metabolizes medications. A drug that is effective and safe for a patient of European descent might be ineffective or even toxic for a patient of African or Latin American descent due to these subtle genetic differences.

By consistently under-sampling these genetic variations, pharmaceutical companies risk missing critical safety signals. The study highlights that this data gap renders the “universal” approval of many drugs scientifically shaky when applied to the diverse American populace.

A Global Disconnect

The study also points to the geography of clinical trials as a major contributing factor. To streamline approvals and maintain consistency, many drug developers rely on standards set by the International Council for Harmonisation (ICH). While this facilitates cooperation between the U.S., Europe, China, and Japan, it often inadvertently excludes the rest of the world.

The researchers found that Sub-Saharan Africa and Latin America—regions with vast genetic diversity—hosted less than 3% of the pivotal trials analyzed. This concentration of research in specific wealthy regions means the biological data shaping global medicine is drawn from a limited genetic pool.

“Precision medicine becomes possible only when clinical trials map the biology of all patients, not just a subset,” Groen added. “Our analysis could offer a roadmap for how to get there.”

Moving Forward

The authors of the study argue that fixing this issue requires a fundamental shift in how drugs are developed, not just how participants are recruited at the final stage. Their recommendations include:

Early Diversity Goals: Establishing diversity targets at the preclinical stage of drug development.
Strategic Locations: Choosing clinical trial sites that inherently reflect the health needs and genetic backgrounds of underrepresented populations.
Biological Sampling: Proactively collecting biological samples from diverse groups to better understand genetic variances early in the pipeline.

While the study noted progress in the inclusion of Asian participants, the widening exclusion of Black and Hispanic communities remains a critical hurdle. As the FDA continues to approve increasingly complex and targeted therapies, the cost of this exclusion—measured in ineffective treatments and overlooked side effects—may continue to rise.

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.