ONO-8815Ly, an EP2 agonist that markedly inhibits uterine contractions in women

To determine the effect of ONO-8815Ly on uterine contractions.

A randomised, double-blind, placebo-controlled, dose-ascending, cross-over study.

Department of Obstetrics and Gynaecology, University Hospital of Lund, Sweden.

Seventeen, healthy, parous and permanently sterilised women.

Intrauterine pressure was recorded on days 1-3 of bleeding of two menstruations. Subjects were intravenously treated with 4 or 8 microg/minute of ONO-8815Ly or placebo for 130 minutes. Intravenous bolus injections of oxytocin, 50 pmol/kg body weight, were given 10 minutes before, during infusion after 60 and 120 minutes and 60 minutes after completion of infusion. The plasma concentrations of ONO-8815Ly were measured in samples obtained immediately before each oxytocin injection.

Area under pressure recording curve (AUC) 10 minutes before and after each oxytocin injection.

Twelve women, six in each dose group, completed both recordings. Of these, two women of each group were not included in efficacy analysis due to non-responsiveness to oxytocin or missing baseline value. The AUC over 10 minutes before oxytocin injection after 60 minutes of infusion of ONO-8815Ly at 4 and 8 microg/minute was reduced to 21% and 37% of that before infusion, respectively. The AUC after oxytocin at that time amounted to 21% and 19%, respectively, of that before infusion. The activity and responsiveness remained low after 120 minutes but started to return to baseline 60 minutes after stopping infusion. Placebo had no effect.

ONO-8815Ly is a potent inhibitor of spontaneous uterine contractility in non-pregnant women and it reduces the uterine response to oxytocin injections.