Imagine a world where groundbreaking new medicines could potentially fail or even harm millions of people simply because they're not tested on a diverse enough group – and astonishingly, that's the stark truth revealed in a shocking new study about drug trials in the U.S.!
A fresh investigation reveals that only 6% of the clinical trials used to approve new drugs in America truly mirror the nation's racial and ethnic diversity. What's more, there's a worrying pattern: these trials are increasingly leaving out Black and Hispanic participants, even as the push for personalized medicine – which tailors treatments to an individual's unique genetic profile – gains momentum.
To break this down for those new to the topic, clinical trials are the rigorous, step-by-step experiments scientists conduct to ensure a drug is safe and effective before it hits the market. Pivotal trials are the big, final-phase studies that lead to FDA approval. Researchers from UC Riverside and UC Irvine dove into data from 341 such trials conducted between 2017 and 2023. They spotted a troubling drop in Black and Hispanic enrollment starting in 2021, right when demands for fairness in science and healthcare were ramping up. On the flip side, Asian participation ticked up, while white involvement stayed pretty steady.
But here's where it gets controversial: Why is this underrepresentation happening, and what does it really mean for equity in medicine? Critics might argue that focusing on ancestry in drug development could lead to stereotypes or discrimination, while others firmly believe it's essential for true inclusivity.
“Personalized medicine depends on grasping how genetic variations impact how treatments work,” explained Sophie Zaaijer, a geneticist affiliated with both UCR and UC Irvine, who co-led the study. “If trials overlook huge chunks of human genetic diversity, we might miss vital clues about a drug's safety and effectiveness.”
Zaaijer and her co-author, Simon “Niels” Groen, also a UCR geneticist, emphasize that ancestry shouldn't be the sole factor in treatment choices. However, it plays a pivotal role early in drug creation. People from various backgrounds often have different gene versions, known as alleles, which can influence medication responses. For instance, think of how some folks metabolize caffeine quickly due to their genes, while others feel jittery from just a small amount – similar variations can affect drug efficacy or side effects.
“When trials only capture a limited segment of the population, we can't guarantee the drug will function properly or safely for all intended users,” Groen pointed out.
These U.S. drug approval trials aren't just domestic; they're often carried out in other nations adhering to International Council for Harmonisation (ICH) guidelines. This standardization speeds up approvals and ensures reliability, but it also clusters evidence in places like the U.S., Europe, China, and Japan. Regions such as Sub-Saharan Africa and large parts of Latin America, hosting fewer than 3% of these crucial trials, get sidelined – even though their populations use the resulting medicines.
And this is the part most people miss: things might be improving for Hispanic communities. Brazil signed on to ICH in 2016, Mexico in 2021, and Argentina in 2024. By broadening trial networks to these and other underserved areas, future studies could better represent global genetic diversity.
Zaaijer kicked off this research as a postdoctoral fellow at Cornell Tech, exploring how preclinical drug development – the early testing phase using cells from patients to simulate diseases and try out therapies – often ignores human genetic variety. “If our early models are this biased, what happens when those drugs enter human trials?” she wondered. Biases in preclinical steps are like red flags, but in clinical trials, they turn into real-world medical practices.
Her partnership with Groen's team was a natural fit. His lab at UCR examines how tiny worms process plant poisons, drawing parallels to human biology. “Many genes worms use to detoxify chemicals are ancient and shared with humans,” Groen noted. “Yet even slight natural differences in these genes can have major effects.”
The study, published in Communications Medicine, proposes actionable steps: Establish diversity targets right from the preclinical phase of drug development, select trial sites that match local health needs and genetic profiles, and gather samples like blood or saliva to study bodily reactions to drugs.
As DNA testing becomes routine in doctors' offices, the experts stress that unlocking personalized medicine's full potential requires robust, ancestry-informed data from the outset.
“Personalized medicine only thrives when trials cover the biology of every patient, not just a select few,” Groen concluded. “Our findings could serve as a blueprint for achieving that.”
Reference: Zaaijer S, Groen SC. Longitudinal clinical trial enrollment trends across 341 US FDA-approved drugs and their guiding role in precision medicine strategies. Commun Med. 2025;5(1):514. doi:10.1038/s43856-025-01270-2 (https://doi.org/10.1038/s43856-025-01270-2)
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What do you think – should ancestry play a bigger role in drug development, or could it risk oversimplifying complex health issues? Do you believe underrepresentation in trials is a systemic oversight, or something more intentional? Share your thoughts in the comments below; I'm curious to hear agreements and disagreements!
