Just 6 percent of clinical trials used to approve new drugs in the United States reflect the nation’s racial and ethnic makeup, a new analysis warns, and an “increasing trend” of underrepresentation is shutting Black and Hispanic patients out of the data that shapes modern medicine. Researchers at the University of California, Riverside and UC Irvine examined 341 pivotal trials conducted between 2017 and 2023 and found Black and Hispanic enrollment has declined since 2021, even as calls for equity in science and medicine have grown louder. Asian representation rose and white participation remained largely stable, widening the gap
“Precision medicine relies on understanding how genetic differences influence treatment outcomes,” said geneticist Sophie Zaaijer, co-lead author of the study. When trials under-sample “large segments of human genetic variation, critical signals for safety and efficacy may be missed.” Co-author Simon “Niels” Groen put it bluntly: “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.”
The team also points to geography as a hidden driver of inequity. Sub-Saharan Africa and much of Latin America host less than 3 percent of pivotal trials, leaving the people who live there largely invisible in the evidence base for drugs used worldwide. The authors urge companies to set diversity goals early, choose testing locations that reflect local health needs and genetic backgrounds, and collect biological samples that reveal how different bodies metabolize medications. “Precision medicine becomes possible only when clinical trials map the biology of all patients, not just a subset,” Groen said.
See: “FDA drug trials exclude a widening slice of Americans” (December 12, 2025)
