Retosiban prevents stretch-induced human myometrial contractility and delays labor in Cynomolgus monkeys.

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Retosiban prevents stretch-induced human myometrial contractility and delays labor in Cynomolgus monkeys.

J Clin Endocrinol Metab. 2017 Dec 26;:

Authors: Aye ILMH, Moraitis AA, Stanislaus D, Charnock-Jones DS, Smith GCS

Abstract
Context: Stretch of the myometrium promotes its contractility and is believed to contribute to the control of parturition at term and to the increased risk of preterm birth in multiple pregnancies.
Objective: To determine the effects of the putative oxytocin receptor (OTR) inverse agonist retosiban on (i) the contractility of human myometrial explants, and (ii) labor in non-human primates.
Design: Human myometrial biopsies were obtained at planned term cesarean and explants were exposed to stretch in the presence and absence of a range of drugs, including retosiban. The in vivo effects of retosiban were determined in Cynomolgus monkeys.
Results: Prolonged mechanical stretch promoted myometrial Erk1/2 phosphorylation. Moreover, stretch-induced stimulation of myometrial contractility was prevented by Erk1/2 inhibitors. Retosiban (10nM) prevented stretch-induced stimulation of myometrial contractility and phosphorylation of Erk1/2. Moreover, the inhibitory effect of retosiban on stretch-induced Erk1/2 phosphorylation was prevented by co-incubation with a 100-fold excess of a peptide OTR antagonist, atosiban. Compared with vehicle treated Cynomolgus monkeys, treatment with oral retosiban (100 to 150 days of gestational age) reduced the risk of spontaneous delivery (hazard ratio = 0.07, 95% CI 0.01 to 0.60, P=0.015).
Conclusions: The OTR acts as a uterine mechanosensor, whereby stretch increases myometrial contractility through agonist-free activation of the OTR. Retosiban prevents this through inverse agonism of the OTR and, in vivo, reduced the likelihood of spontaneous labor in non-human primates. We hypothesize that retosiban may be an effective preventative treatment for preterm birth in high risk multiple pregnancies, an area of unmet clinical need.

PMID: 29293998 [PubMed - as supplied by publisher]

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