Hershey, PA—Women of childbearing age are generally underrepresented in clinical trials for type 2 diabetes drugs, which leads to an incomplete understanding of the effects of the therapies on those who become pregnant unexpectedly, according to a new study.

The report, published recently in Diabetes Care, points out that women of childbearing potential are often excluded from participating in clinical trials because of concerns about adverse effects on the fetus, which might not be a realistic risk in some cases.

Penn State College of Medicine researchers sought to determine the prevalence of fertility-related exclusion criteria in clinical trials of type 2 diabetes medications and to determine whether these criteria are commensurate with drug risk.

To do that, the study team queried ClinicalTrials.gov for trials of type 2 diabetes medications that were phase 2 or 3, based in the United States and enrolled participants aged 18 to 40 years. Overall, 688 trials met that criteria and were analyzed for information about enrollment, trial length, exclusion and inclusion criteria, trial sponsor, and pregnancy category of drug(s) administered.

Results indicate that most studies (59%) included one or more fertility-related exclusion criteria, most commonly excluding current pregnancy (55%) and breast-feeding (44%). Yet, the study found that trials of medications with increased fetal risk were not necessarily more restrictive; trials of category C drugs (evidence of fetal risks in animals) were found to be less likely to exclude pregnancy compared with trials of category B drugs (no known human or animal fetal risks)—45.6% versus 69.8%, odds ratio [OR] 0.37) —or to require contraceptive use—29.9% versus 57.1%, OR 0.32.

The study points out that a 1993 National Institute of Health mandate prohibits the routine exclusion of women of childbearing potential from participation in NIH-funded clinical research.

More than 50 studies excluded all women of childbearing potential, study authors report, adding that especially restrictive criteria, such as excluding women planning to donate eggs, requiring two contraceptives and requiring contraceptives after the end of the trial, were not uncommon. Multiple pregnancy tests were required for continued participation in 29 of the trials.

The most restrictive criteria were found in trials initiated by investigators at academic health centers, as opposed to pharmaceutical companies, according to the report.

“There are still widespread restrictions placed on participation of women in clinical drug trials, often without justification,” lead researcher Richard S. Legro, MD, said in a Penn State Medical School press release. “Results from these trials may not be generalizable to the larger population. Up to half of pregnancies are unplanned, and we don't know what the effects of these drugs will be on women if they take them and conceive while on them or if they are pregnant.”

« Click here to return to Weekly News Update.