Design of Oxytocin Antagonists, which are more Selective than Atosiban

Abstract

We report the solid phase synthesis of four pairs of L- and D-thienylalanine (Thi/D-Thi) position two modified analogues of the following four oxytocin (OT) antagonists: des-9-glycinamide [1-(beta-mercapto-beta,beta-pentamethylene propionic acid), 2-O-methyltyrosine, 4-threonine]ornithine-vasotocin (desGly(NH2)9,d (CH2)5[Tyr(Me)2,Thr4]OVT) (A); the Tyr-(NH2)9 analogue of (A), d(CH2)5[Tyr(Me)2,Thr4,Tyr-(NH2)9]OVT (B); the Eda9 analogue (where Eda = ethylenediamine) of (A), d(CH2)5[Tyr(Me)2, Thr4, Eda9]OVT (C); and the retro Tyr10 modified analogue of (C), d(CH2)5[Tyr(Me)2, Thr4, Eda9<--Tyr10]OVT (D). The eight new analogues of A-D are (1) desGly(NH2),d(CH2)5[Thi2,Thr4]OVT, (2) desGly(NH2),d(CH2)5[D-Thi2,Thr4]OVT, (3) d(CH2)5[Thi2, Thr4,Tyr-(NH2)9]OVT, (4) d(CH2)5[D-Thi2,Thr4,Tyr-(NH2)9]OVT (5) d(CH2)5[Thi2,Thr4Eda9]OVT, (6) d(CH2)5[D-Thi2,Thr4,Eda9]OVT, (7) d(CH2) [Thi2,Thr4,Eda9<--Tyr10]OVT, (8) d(CH2),[D-Thi2,Thr4,Eda9<--Tyr10]OVT. We also report the synthesis of (C). Peptides 1-8 and C were evaluated for agonistic and antagonistic activities in in vitro and in vivo OT assays, in in vivo vasopressor (V1a receptor) assays and in in vivo antidiuretic (V2 receptor) assays. None of the eight peptides nor C exhibit oxytocic or vasopressor agonism. Peptides 1-8 are extremely weak V2 agonists (antidiuretic activities range from < 0.0005 to 0.20 U/mg). Peptide C is a weak mixed V2 agonist/antagonist. Peptides 1-8 and C exhibit potent in intro (no Mg2+) OT antagonism (anti-OT pA2 values range from 7.76 to 8.05). Peptides 1-8 are all OT antagonists in vivo (estimated in vivo anti-OT pA2 values range from 6.54-7.19). With anti-V1a pA2 values of approximately 5-5.80, peptides 1-8 exhibit marked reductions in anti-V1a potencies relative to those of the parent peptides A-D (anti-V1a pA2 range from 6.48 to 7.10) and to l-deamino[D-Tyr(Et)2, Thr4]OVT (Atosiban, trade name Tractocile) (anti-V1a pA2-6.14). Atosiban has recently been approved in Europe for clinical use for the prevention of premature labour (Pharm. J. 264(7-100): 871). Peptides 1-8 exhibit striking gains in in vitro anti-OT/anti-V1a selectivities with respect to the parent peptides A, B, C and D and to Atosiban. Peptides 1-8 exhibit anti-OT (in vitro)/anti-V1a selectivities of 450, 525, 550, 450, approximately 1080, 116, 355, 227 respectively. The corresponding values for A-D and Atosiban are 30, 4.2, 4.3, 2.6 and 37. With the exception of peptide 6, the remaining seven peptides exhibit 3-18-fold gains in anti-OT (in vivo)/anti-V1a selectivity with respect to Atosiban, peptides 1-8 exhibit anti-OT (in vivo)/anti-V1a selectivities of 22, approximately 82, approximately 82, 147, approximately 83, 11, 31 and 42. By comparison, Atosiban exhibits an anti-OT (in vivo)/anti-V1a selectivity = 8. With an estimated in vivo anti-OT pA2 value = 7.19+/-0.06, peptide 4 is equipotent with Atosiban (pA2 = 7.05+/-0.05). However, with its significantly reduced anti-vasopressor potency, pA2 = approximately 5, it is approximately 18 times more selective for OT receptors with respect ...

Cardiac oxytocin receptor blockade stimulates adverse cardiac remodeling in ovariectomized spontaneously hypertensive rats

“…The OTA proposed in this study is selective for OTR but can also bind arginine-vasopressin receptor 1, albeit at a much lower affinity (28), and has been used previously in voles with differential effects on OT and arginine-vasopressin receptors (5,6).…”

Probing the Existence of G Protein-Coupled Receptor Dimers by Positive and Negative Ligand-Dependent Cooperative Binding

“…Typical experimental data are presented in Fig. 6a and are fitted (Manning et al, 2001(Manning et al, , 2005 (Fig. 6b).…”

SSR126768A (4-Chloro-3-[(3R)-(+)-5-chloro-1-(2,4-dimethoxybenzyl)-3-methyl-2- oxo-2,3-dihydro-1H-indol-3-yl]-N-ethyl-N-(3-pyridylmethyl)-benzamide, Hydrochloride): A New Selective and Orally Active Oxytocin Receptor Antagonist for the Prevention of Preterm Labor

“…The relatively selective distribution of OTR in the uterus, the cell/tissue specific uterine up-regulation for OTR at the time of parturition, the paracrine/autocrine stimulation of the OTR in the uterus with large local fetal and maternal OT production, and the OT-stimulating effect on prostaglandin secretion support the development of pure OTR antagonists for the prolongation of gestation and might make such antagonists superior to currently used tocolytics in terms of both efficacy and safety. Several synthetic OTR antagonists have been designed by chemical modification of the natural hormone producing potent OT ligands with various selectivity, able, for some of them, to delay or to interrupt labor process when administered to pregnant animals (Chen et al, 1994;Demarest et al, 1989;Kobayashi et al, 1999;Manning et al, 2001) and to pregnant women as well, after intravenous infusion (Akerlund et al, 1987;Romero et al, 2002;The Worldwide Atosiban versus Beta-Agonists Study Group, 2003). In this context, nonpeptide OTR antagonists with good oral bioavailability are eagerly awaited for acute and chronic treatment of premature labor.…”

“…For peptides, one of the most selective compounds for OTR is that with threonine in C4 position and ornithine in the C8 position (Chen et al, 1994;Manning et al, 2001). But, for nonpeptide molecules, no rule has been established, and the recently described pyrrolidine carboxamide derivative OTR antagonist exhibited very moderate OTR selectivity with only a 6-fold selectivity against V 1a R ( Cirillo et al, 2003).…”