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The dominant narrative on equity, diversity, and inclusion in U.S. medical research emphasises the underrepresentation of Black and Hispanic participants in clinical trials, largely based on therapeutic phase 2 and 3 trials. Far less attention has been paid to phase 1 trials—particularly those involving healthy volunteers who assume health risks without therapeutic benefit, often for money. Focusing on inequalities in the distribution of research participation, risks, and potential benefits, this study analyses secondary data from 429 U.S. industry-involved phase 1 trials with 18,217 participants registered on ClinicalTrials.gov between January 2018 and October 2024. We examined trial-level demographics—race, ethnicity, sex—by phase 1 trial type and U.S. geographic region, comparing enrolment with U.S. Census estimates. Quasi-binomial regression models were used to identify trial-level factors associated with enrolment patterns. Black and Hispanic individuals were overrepresented in healthy-volunteer trials by 14 and 16 percentage points, but underrepresented in oncology trials by 7 and 8 percentage points. Overrepresentation in healthy-volunteer trials was especially pronounced for Hispanic participants in the U.S. West and South and for Black participants in the Northeast and Midwest. Female participants were underrepresented, except in non-oncology disease trials. We found a strong association between higher male and Black participation but not Hispanic participation. These findings highlight intersecting race, ethnicity, and gender inequalities in the distribution of research risks and rewards. Promoting equity in medical research requires moving beyond one-dimensional underrepresentation narratives to address the structural inequalities shaping racialised and gendered patterns of inclusion and exclusion across clinical trial phases, types, and locations.
Mulinari et al. (Fri,) studied this question.