414. The contraceptive potential of a long-acting IL-11 inhibitor

Abstract

Interleukin 11 (IL-11) signalling is essential for the establishment of pregnancy in mice, through its action on the differentiation of uterine endometrial stromal cells (decidualisation), a critical process during embryo implantation. IL-11Rα deficient mice are infertile due to defective decidualisation1. IL-11 expression peaks between days (D) 4.5–9.5 of pregnancy (D0: day of plug) in mouse decidua. We examined the effect of administering (intraperitoneal [IP] injection or vaginal gel) a PEGylated IL-11 antagonist (PEGIL-11A) on decidualisation and pregnancy outcome in mice. The sera half-life of PEGIL-11A (IC50 2.8nM) following IP injection was 24h, compared with <1 h for the non-PEGylated antagonist (IC50 0.26nM). Following IP injection, PEGIL-11A localised to decidual cells and blocked the IL-11 decidual target protein, cyclin D3. IP injection of 600µg/application PEGIL-11A (or PEG control) at 1000 h and 1600 h on D3 and 1000 h on D4 (n = 4/group), resulted in smaller implantation sites than controls on D6 due to retarded mesometrial decidual formation. On D10, severe decidual destruction was visible: implantation sites contained regions of haemorrhage and the uterine luminal epithelium had reformed, suggesting a return to oestrous cycling. Following vaginal application in aqueous placebo gel, PEGIL-11A localised to decidual cells. Vaginal application of 200µg/application PEGIL-11A (or control) twice daily from D2 to D5 (n = 4/group), resulted in smaller implantation sites than controls on D6 due to partial inhibition of mesometrial decidual formation. This study demonstrates that PEGIL-11A blocked IL-11 action in the uterus, resulting in total pregnancy loss, equivalent to the IL-11Rα deficient mouse. In women, IL-11 and its receptor are produced by the uterine luminal and glandular epithelium during the period of uterine receptivity2, suggesting that IL-11 may act during initial blastocyst attachment to the luminal epithelium as well as stromal decidualisation. This study provides proof-of-principle for the development of a novel, non-hormonal contraceptive for women. (1) Robb L et al. Nature Medicine 1998; 4: 303–308. (2) Dimitriadis E et al. Molecular Human Reproduction 2000; 6: 907–914.