The representation of women in clinical trials should be increased. Sponsors can start by conducting more trials at sites that treat large numbers of women. If studies continue to run primarily at centers that serve mostly men, then little will change. This may require investment in training and capacity to develop new research sites, but it's a small price to pay if we can better generalize the results. Our commitment to community-based research also needs to be reaffirmed -- even as our expectations for its performance are increased.
But simply (or not so simply) increasing the proportion of women enrolled in trials does not address the call for statistically significant results. The sample sizes of drug efficacy trials are chosen to yield convincing results with the contribution of data from every participant. Unless the study drug is a blockbuster, conclusions that rely on only a subset of the data can never be as sure as those from a full analysis. The only way to have equal confidence in the results for both men and women is to enroll equal numbers of each.
That's not likely to happen. Clinical trials for efficacy are expensive and slow going. Doubling the sample size of a trial will double its cost and probably double the time to get results -- something neither sponsors nor the community want. Still, we need to get better information about the effects of drugs on women. Body weight, hormonal variation, and menstruation are understudied variables. The nature, frequency and severity of toxicities seem to be different for women. Women may typically have lower viral loads than men. Add to these genetic factors and differences in immunological response -- which we understand even less -- and our ignorance seems appalling.
Efficacy data from HIV drug trials in the U.S. are unlikely to ever provide statistically significant results when stratified for female gender. Industry should take proactive steps to develop supplementary data on two key areas where woman-specific information is lacking: pharmacokinetics and safety. Patients and doctors will have more confidence extrapolating efficacy data to women if there are studies to reassure them that a drug is biologically available and that it is safe.
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