Abstract
BACKGROUND: Gender disparities persist in clinical trial leadership, with women underrepresented as principal investigators (PIs). While previous studies have documented these disparities, they have largely relied on limited datasets focused on specific therapeutic areas. Previous studies have also neglected potential gender differences in trialist career trajectories. This study examines gender representation in clinical trial leadership using the most comprehensive dataset available, assessing trends over time and gender differences in trialist career trajectories. METHODS: I analyzed a large sample of clinical trials submitted to ClinicalTrials.gov from 2010 to 2023. PI gender was inferred using algorithmic classification based on first names. I estimated the probability of female PI leadership for each trial year using logistic regression, adjusting for trial characteristics. To assess career trajectories, I examined the number of trials led by male and female PIs within fixed time horizons and assessed gender differences and their evolution in time using Poisson regression models. RESULTS: Among nearly 160,000 trials analyzed, female representation increased from 32 % in 2010 to 41 % in 2023. Female PI leadership remained lowest in cardiovascular trials (20 %) and highest in behavioral intervention trials (50 %). Although male PIs lead more trials than female PIs over all horizons after entering the field, the gap has narrowed over time. In 2010, male PIs led 7 % more trials than female PIs within their first three years after entering the field; by 2020, this difference had declined to 1 % and become statistically insignificant. CONCLUSIONS: Although female PIs remain underrepresented in clinical trial leadership, the gap is narrowing, particularly in terms of early-career progression. Future research should explore the underlying causes of these trends, including bias, career-family trade-offs, and the structural and behavioral mechanisms that shape sorting across medical specialties. Additionally, recent evidence suggests that female PIs may positively influence trial performance-particularly in patient recruitment diversity and safety outcomes, which highlights the broader significance of gender equity in clinical research.