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Gender Differences in Clinical Registration Trials: Is There a Real Problem?

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Gender Differences in Clinical Registration Trials: Is There a Real Problem?

Geert Labots et al. Br J Clin Pharmacol.

Abstract

Aims: Several studies have reported the under-representation of women in clinical trials, thereby challenging the external validity of the benefit/risk assessments of launched drugs. Our aim was to determine the extent to which women have been included in clinical trials used for drug registration and to analyse the fraction of women participating in phases I, II and III.

Methods: We conducted cross-sectional, structured research into publicly available registration dossiers of Food and Drug Administration (FDA)-approved drugs that are prescribed frequently. Furthermore, we analysed compounds with high hepatic clearance and a known gender-related difference in drug response. In a sensitivity analysis, we compared figures with US disease prevalence data.

Results: For 38 of the initial 137 drugs (28%), sufficient data were reported and publicly available. For these drugs, 185 479 trial participants were included, of whom 47% were female and 44% were male; gender was not reported for 9% of participants. However, the number of female participants varied with the phase of the trial, with 22% females in phase I trials vs. 48% and 49%, respectively, in phase II and III trials. When compared with US disease prevalence data, 10 drugs (26%) had a greater than 20% difference between the proportion of females affected with the disease compared with representation in clinical trials.

Conclusions: From these publicly available data, there was no evidence of any systematic under-representation of women in clinical trials.

Keywords: adverse event; clinical trials; disease prevalence; efficacy; gender; gender subgroup analysis; safety.

Figures

Figure 1
Figure 1
Bar graph representing the percentages of females participating in clinical trials (green bars) vs. the proportion of females with the disease, and the proportion for whom no gender was reported (yellow). The drugs are listed alphabetically, from A–L (A) and Li–Z (B)
Figure 2
Figure 2
Pie chart representing the outcomes of the qualitative gender analysis. Subgroup analysis of the retrieved drug data was performed for efficacy (purple), safety (green), and efficacy and safety (yellow). For a small proportion, no subgroup analysis was performed (red)
Figure 3
Figure 3
Pie chart representing the outcome of the qualitative efficacy analysis, with the green area representing no difference between men and women; the yellow area representing higher efficacy in women than in men; and the blue area representing higher efficacy in men than in women
Figure 4
Figure 4
Pie chart representing the outcome of the qualitative safety analysis, with the purple area representing no difference between men and women, the red area representing more adverse events reported in women than in men, and the grey area representing more adverse events reported in men than in women

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