OT-R antagonist 1 is a new potent and selective nonpeptide low molecular weight OT-R antagonist. OT-R antagonist 1 inhibits oxytocin-evoked intracellular Ca2+ mobilization (IC50 = 8 nM).IC50 value: 8 nMTarget: oxytocin receptorin vitro: OT-R antagonist 1 inhibitis IP3-Synthesis, rat OT-R (IC50=0.03 uM). [4] OT-R antagonist 1 inhibits phosphodiesterase IV with IC50 = 6.1 μM, a value about 300-fold higher than the affinity for OT-R. OT-R antagonist 1 shows a very clean selectivity profile with specific interaction with OT-R. OT-R antagonist 1 competitively inhibits binding of [3H]oxytocin and the peptide antagonist 125I-ornithine vasotocin analog to human and rat oxytocin receptor expressed in human embryonic kidney 293-EBNA or Chinese hamster ovary cells with nanomolar potency. Selectivity against vasopressin receptor subtypes is >6-fold for V1a and >350-fold for V2 and V1b. [1]in vivo: Oxytocininduced contraction of isolated rat uterine strips is blocked by OT-R antagonist 1 (pA2 = 7.82). In anesthetized nonpregnant rats, single administration of OT-R antagonist 1 by i.v. or oral routes causes dose-dependent inhibition of contractions elicited by repeated injections of oxytocin with ED50 = 3.5 mg/kg i.v. and 89 mg/kg p.o., respectively. OT-R antagonist 1 significantly inhibits spontaneous uterine contractions in pregnant rats near term when administered intravenously or orally. [1]

[1]. Serge Halazy, et al. Pharmaceutically active pyrrolidine derivatives as bax inhibitors. WO/2001072705/A1. [2]. Cirillo R, et al. Pharmacology of (2S,4Z)-N-[(2S)-2-hydroxy-2-phenylethyl]-4-(methoxyimino) -1-[(2'-methyl[1,1'-biphenyl]-4-yl)carbonyl]-2-pyrrolidinecarboxamide, a new potent and selective nonpeptide antagonist of the oxytocin receptor. J Pharmacol Exp Ther. 2003 Jul;306(1):253-61. [3]. William Nadler, et al. Method for preparing pyrrolidine oximes. WO/2005082848/A2. [4]. Serge Halazy, et al. Pharmaceutically active pyrrolidine derivatives as bax inhibitors.WO/2001074769/A1.