Historically, women have been significantly excluded from clinical drug trials. But according to a new study led by Sophie Zaaijer, a research specialist at the University of California, Irvine School of Medicine and the University of California, Riverside’s Institute for Integrative Genome Biology, the majority of clinical trials in the United States now adequately enroll women participants relative to their disease prevalence.
With her colleague Simon C. Groen of the University of California, Riverside, Dr. Zaaijer analyzed data from 195 drugs across 98 indications approved by the U.S. Food and Drug Administration between 2015 and 2023. Their analysis found that women’s participation met or exceed their disease prevalence in 67 percent of the studied clinical trials. Furthermore, therapies for addressing indications specific to women were more likely to receive FDA approval than those addressing male-predominant indications.
However, women’s representation in clinical trials varies significantly by medical discipline. In oncology, 83 percent of trials met or exceeded benchmarks for women’s participation, and in neurology, representation often exceeded expectations. Conversely, nearly three-quarters of cardiovascular disease trials and over two-thirds of autoimmune and inflammatory disease trials under-enrolled women.
“Many of the methods and benchmarks used in clinical research were developed around male physiology, which can unintentionally disadvantage women throughout the clinical trial process,” said Dr. Zaaijer. “As a result, we may be missing female-specific biological variables that influence diagnosis, eligibility for clinical trials, treatment response and toxicity, which could explain the under-enrollment in certain disease areas.”
Dr. Zaaijer is a graduate of Hanzer University in the Netherlands. She received a master’s degree in biotechnology from Wageningen University & Research in the Netherlands and a Ph.D. in molecular biology and genetics from University College London. She completed postdoctoral research at the New York Genome Center and Columbia University.