Analysis of female enrollment in clinical trials for alcohol and substance use disorders: Is it time for sex-informed pharmacotherapy?

Background: Women represent an increasing number of individuals with alcohol and substance use disorders (ASUDs), and sex-differences might affect results of interventional clinical trials (CTs). We aim at assessing the proportion of women and the reporting of sex-stratified and female-specific data in CTs for ASUDs.

Methods: We extracted data from ClinicalTrials.gov on Phase 1-3 CTs of investigational drugs for ASUDs conducted from 2000 to 2021 and identified articles related to these trials. We determined the average proportions of women enrolled per trial overall, over time, and by disease area and trial phase. Next, we calculated the proportion of articles reporting sex-stratified and female-specific data.

Results: In the 234 CTs identified, the overall proportion of women was 33.4% [95% CI: 32.7%-33.9%]), with an increasing temporal trend. Women's participation was higher in CTs of investigational drugs for tobacco (43.5% [95% CI: 42.4% -44.5%]) and alcohol use disorder (35.9% [95% CI: 34.54%-37.21%]), and closely mirrored their representation in the disease populations (46% and 37%). Conversely, women were underrepresented in clinical trials of drugs for cocaine and stimulant use disorders (25.8% [95% CI: 24.6%-27.1%]) and opioid use disorders (25.9% [95% CI:24.2%-27.7%]). Nine publications reported sex-stratified data in the method and/or result section, whereas none documented female-specific data.

Conclusions: Enrollment of women in ASUDs CTs has increased over time but remains low in several disease areas. This, together with the low rates of reporting of sex-stratified data, calls for an adequate inclusion of sex in the design and analysis of CTs for ASUDs.