The selective progesterone receptor modulator, telapristone acetate, is a mixed antagonist/agonist in the human and mouse endometrium and inhibits pregnancy in mice.

OBJECTIVE

To investigate the effect of the selective progesterone receptor modulator, telapristone acetate (CDB-4124), on endometrial biology and reproductive outcomes. Ovariectomized and hormone-treated CD1 female mice, CD1 female mice with xenotransplants of reconstructed human endometrial tissue, mated wildtype female mice, and cultured human endometrial stromal cells (hESCs) were treated with CDB-4124, followed by the assessment of endometrial cell deoxyribonucleic acid (DNA) proliferation, stromal decidual response, and embryo implantation.

DESIGN

Experimental study.

SETTING

Academic research laboratory.

PATIENTS

Healthy volunteer women from the community were recruited for endometrial biopsies.

ANIMALS

CD1 out-bred mice (Charles River Laboratories) and nude mice, NU/J (Jackson Laboratories, Bar Harbor, ME).

INTERVENTION

Treatment of mice and hESCs with CDB-4124.

MAIN OUTCOME MEASURE

The effect of CDB-4124 on endometrial cell morphology and DNA synthesis, decidual response, and mouse embryo implantation.

RESULTS

CDB-4124 inhibited estradiol-induced epithelial DNA synthesis in the mouse uterus and xenotransplanted human endometrium. This antiproliferative effect was less than that of progesterone (P4) and was observed when CDB-4124 was administered alone or concomitantly with P4. In the uterine epithelium, CDB-4124 acted as a P4 agonist and partial antagonist. In contrast, CDB-4124 acted as a complete P4 antagonist in the uterine stroma, where it blocked P4's action to induce a decidual response in the pseudopregnant mouse uterus and wildtype mouse uterus after copulation. In mated female mice, CDB-4124 impaired embryo implantation. Similarly, CDB-4124 inhibited the morphological and biochemical transformations of hESCs to decidual cells in vitro.

CONCLUSION

CDB-4124 exerts mixed P4 antagonistic/agonistic effects in the human and mouse endometrium, which result in failed embryo implantation because of the absence of stromal decidualization.