Enrollment of female participants in United States drug and device phase 1-3 clinical trials between 2016 and 2019.

BACKGROUND

Historically, females have been underrepresented in clinical trials evaluating the safety and efficacy of investigational drugs and devices. We assessed participation by sex in recent clinical trials.

METHODS

We extracted data over a 4-year period (2016-2019) from ClinicalTrials.gov on US-based, pharmaceutical industry or government-funded Phase 1-3 clinical trials of drugs and devices. We included trials with adult cardiovascular, psychiatric, and cancer endpoints whose protocol planned to enroll both sexes. Average proportions of females enrolled per trial were described overall and by disease area.

RESULTS

Across 1433 trials including 302,664 participants in our analysis, on average, 41.2% were female. Females were underrepresented compared with their proportion of the disease population in cardiovascular disease trials (41.9% female participants vs. 49% female population with cardiovascular disease). In psychiatry, where females comprise 60% of patients, the mean participation of females in clinical trials was 42.0%. Similarly, for cancer trials, where 51% of patients are female, only 41.0% of cancer clinical trial participants were female. For each therapeutic area analyzed, the participation of females in clinical trials fell short of the benchmark derived from national prevalence data.

CONCLUSIONS

While the participation of females in clinical trials has improved compared to previous reports, sex-based gaps still persist between trial populations and those expected to use these drugs/devices based on distributions of diseases in the population. Given potential sex-based differences in treatment responses and toxicities, adequate inclusion of females in clinical trials remains critical.