Effect of the Novel Selective Progesterone Receptor Modulator Vilaprisan on Ovarian Activity in Healthy Women

This randomized, double‐blind, parallel‐group study in healthy young women investigated the effect of treatment with vilaprisan (0.5, 1, 2, or 4 mg/day for 12 weeks) on ovarian function by assessing the Hoogland score, which is based on the size of follicle‐like structures as determined by transvaginal ultrasound and on estradiol and progesterone serum concentrations. Ovulation inhibition (ie, Hoogland score <6 in treatment weeks 1‐4 and 8‐12) was observed in >80% of the subjects receiving vilaprisan ≥1 mg/day. The effect was dose dependent. With a Bayesian approach, the percentage of subjects with ovulation inhibition was estimated to increase from 37% in subjects receiving 0.5 mg/day vilaprisan to 76%, 86%, and 88% in subjects receiving 1, 2, and 4 mg/day, respectively. Follicle growth was not suppressed during treatment. The majority of subjects receiving ≥1 mg/day had a Hoogland score of 4 (active follicle‐like structures, ie, follicle diameter >13 mm, estradiol >27.2 pg/mL, no progesterone increase) both at beginning and end of treatment. Mean average estradiol as well as mean maximum progesterone concentrations were noticeably decreased during treatment with vilaprisan ≥1 mg/day compared to pretreatment, but estradiol concentrations remained >80 pg/mL. Both hormones returned to pretreatment levels after the end of treatment, indicating a rapid resumption of normal ovarian activity. Amenorrhea occurred in the majority of subjects during treatment at dosages ≥1 mg/day. The adverse events observed in this study confirm the known safety profile of vilaprisan. All in all, the results of this study support the development of vilaprisan for the long‐term treatment of uterine fibroids.