The current status of oral contraceptive clinical development in Japan

Since the oral contraceptive guideline was issued in April 1987, Japanese pharmaceutical firms have been asking physicians to perform clinical studies of the low-dose OCs. At present, eight products from six companies are under clinical development. Ethinyl estradiol (30-35 micrograms per tablet) as an estrogen component is common to all the test drugs. The progestin component in each OC is norethindrone, levonorgestrel, or desogestrel. Phase I clinical studies on small numbers of healthy volunteers showed that they could tolerate the test drugs without any serious complaints. The effects on endocrine systems, including the inhibition of ovulation, were also examined. Pharmacokinetic parameters of active ingredients were comparable to those of Western women, and no substantial difference seemed to exist between Japanese and Western women. As an example, the results of phase I studies of OJK-777 (Ortho-Novum 7/7/7) are mentioned. Phase III clinical studies, which are "open studies," are now under progress with more than 3,000 women. The major objectives are to examine (1) how well the drugs are tolerated, and the dropout rates; (2) the effects on cycle control, especially bleeding patterns; (3) effects on the cardiovascular system, including coagulation and lipid metabolism; (4) effects on hormone secretions. Although some women have been taking the test drugs for more than 12 cycles, overall statistics are not yet available, because the guideline requires long-term administration (for more than 24 cycles). However, some characteristic features observed thus far are discussed.