Ulipristal acetate administration at mid-cycle changes gene expression profiling of endometrial biopsies taken during the receptive period of the human menstrual cycle

•Ulipristal acetate administration at mid-cycle has anti PR effects on endometrium.•Genomic data in Ulipristal-treated subjects are compatible with a non-receptive endometrium.•Ulipristal is a potent emergency contraceptive due to its effects on endometrium.

The aim of this study was to analyze the effects of mid-cycle administration of Ulipristal acetate (UPA) on gene expression in endometrial biopsies taken during the receptive phase of the cycle. Fourteen healthy menstruating women were studied during 14 control non-treated and 12 treated cycles with a single dose of 30 mg UPA when follicle diameter reached 20 mm. Ovulation in both treated and control cycles was confirmed by serial determinations of serum LH, progesterone and vaginal ultrasound. An endometrial biopsy at day LH+7, in each cycle, was taken for RNA microarray and qPCR analysis or prepared for histological and immunohistochemistry studies. Functional analysis of differentially expressed genes showed the presence of changes compatible with a non-receptive endometrial phenotype, further confirmed by qPCR and immunohistochemistry. This study suggests the effects of UPA on endometrial receptivity, offering a plausible explanation for the higher contraceptive efficacy of this method compared to that of levonorgestrel.