A new study from researchers at the University of California, Riverside and UC Irvine reviewed 341 pivotal clinical trials conducted between 2017 and 2023 and found that just 6% of trials used to approve new drugs in the United States reflect the country’s racial and ethnic makeup. The analysis shows an increasing trend of underrepresentation of Black and Hispanic individuals, with a decline in their enrollment beginning in 2021. Over the same period Asian representation rose, while white participation stayed largely stable.
The authors note that many pivotal trials follow International Council for Harmonisation (ICH) standards and are run across a few regions such as the US, Europe, China and Japan. This geographic focus concentrates the evidence available. Sub-Saharan Africa and much of Latin America host less than 3% of pivotal trials and are often left out of the data that informs medicines used by millions of Americans. The study also points out that Brazil joined ICH in 2016, Mexico in 2021 and Argentina in 2024, which may change where trials take place.
Sophie Zaaijer, a geneticist and co-lead author, said, "Precision medicine relies on understanding how genetic differences influence treatment outcomes." She warned that "If clinical trials under-sample large segments of human genetic variation, critical signals for safety and efficacy may be missed." Coauthor Simon "Niels" Groen added that ancestry should not be the only guide to treatment, but that genetic differences matter in early drug development. The study, published in Communications Medicine, recommends more diversity earlier in development and stronger, ancestry-aware data from the start.
- Set diversity goals beginning at the preclinical stage.
- Choose testing locations that reflect local health needs and genetic backgrounds.
- Collect biological samples such as blood or saliva to study drug responses.
Difficult words
- pivotal — very important or central in a process
- underrepresentation — smaller presence than expected or needed
- enrollment — act of signing up or joining a study
- ancestry — a person's family genetic or ethnic origins
- preclinical — research stage before testing in human participants
- efficacy — ability of a treatment to produce intended results
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How could low participation from Black and Hispanic populations affect the safety and effectiveness of new medicines?
- What practical steps could researchers take to increase diversity earlier in drug development, based on the article?
- How might joining the International Council for Harmonisation change where clinical trials are conducted in countries like Brazil, Mexico and Argentina?
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