The answer is provided by the FDA’s 2025 Drug Trial Snapshot Summary Report. The report covers approximately 26,000 participants in 46 new drug approvals and pivotal trials, organized by therapeutic area rather than a single overall narrative. Half of these approvals (23 of 46) were for the treatment of rare or orphan diseases (ie, diseases affecting <200,000 individuals in the US). For health economists, clinical trial composition matters: age, gender, and the mix of US versus non-US enrollment directly shape how we interpret a clinical trial's external validity and equity considerations.
Looking at the data by disease area, some patterns emerge. Autoimmune, inflammatory, and pulmonary disease events are older than many other categories, consistent with the epidemiology of conditions such as severe asthma, idiopathic pulmonary fibrosis, and bronchiectasis. In contrast, the share of US trial participants in many oncology programs is significantly lower, reflecting a potentially growing gap between global development strategies and US practice patterns and trial populations. By comparison, infectious disease trials show that US enrollment is relatively higher than expected; Whereas the gender balance predictably varies where signs are gender-specific (for example, vasomotor symptoms due to menopause) versus mixed.
While these summary statistics are interesting from an academic perspective, policymakers must understand that “testing diversity” is not a single headline metric. Clinical trials should be representative of populations affected by diseases and the distribution of age, sex, geography, and disease context of clinical trial participants should be highly informed by disease epidemiology. Nevertheless, these data provide a useful overview of the types of patients who participate in clinical trials or drugs that have been approved by the FDA. You can read the full report here.
