Background: Attempts to improve the tolerability of combined oral contraceptives (COCs) have included the substitution of ethinylestradiol (EE) with 17beta-estradiol (E2). However, this has proved unsatisfactory, specifically in terms of cycle control. To improve upon the poor cycle control seen previously, E2 [in the form of estradiol valerate (E2V); 1 mg of E2V contains 0.76 mg of E2] was combined with dienogest (DNG) in a novel four-phasic regimen. In the current studies, the ovulation-inhibition potency of four variations of this regimen was assessed.

Study design: Two randomized, open-label, Phase II studies were performed. The first study compared two regimens (Regimens 1A and 2A) with similar dosages of DNG but different lengths of application. Having established in Study 1 that the length of application of Regimen 2A was most suitable, but that the dosages of DNG were too low for effective ovulation inhibition, a second study, which compared two regimens (Regimens 2B and 2C) with similar lengths of application but with increased dosages of DNG, was undertaken. The primary efficacy variable in both studies was the proportion of women with a Hoogland score of 5 or 6 during Cycle 2.

Results: The full analysis set comprised 192 and 203 women in Studies 1 and 2, respectively. In Study 1, 10 women (10.9%) in Regimen 1A and 6 women (6.4%) in Regimen 2A had a Hoogland score of 5 or 6. In Study 2, three women (3.1%) in Regimen 2B and one woman (1.0%) in Regimen 2C had a Hoogland score of 5 or 6. There were no safety concerns with any of the regimens.

Conclusion: The results of these studies identified a four-phasic COC preparation comprising E2V/DNG that provides efficient ovulation inhibition. It is expected that this regimen will lead to an innovative COC containing E2 instead of EE.