Novel analogues of arginine vasopressin containing α-2-indanylglycine enantiomers in position 2

Continuing our efforts to obtain potent and selective analogues of AVP we synthesized and pharmacologically evaluated ten new compounds modified at position 2 with α‐2‐indanylglycine or its D‐enantiomer (Igl or D‐Igl, respectively). All the peptides were tested for pressor, antidiuretic, and in vitro uterotonic activities. We also determined the binding affinity of these compounds to human OT receptor. The Igl2 substitution resulted in a significant change of the pharmacological profile of the peptides. The new analogues were moderate or potent OT antagonists (pA2 values ranging from 7.19 to 7.98) and practically did not interact with V1a and V2 receptors. It is worth emphasizing that these new peptides were exceptionally selective. On the other hand, the D‐Igl2 substituted counterparts turned out to be weak antagonists of the pressor response to AVP and displayed no antidiuretic activity. Some of the results were unexpected, e.g. dual activity in the rat uterotonic test in vitro: the D‐Igl peptides showed a strong antioxytocic potency (pA2 values ranging from 7.70 to 8.20) at low concentrations and full agonism at high concentrations. The results provided useful information about the SAR of AVP analogues. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. The present study describes the synthesis and some pharmacological properties of ten new analogues of arginine vasopressin (AVP) modified at position 2 with α− 2‐indanylglycine or its D‐enantiomer (Igl or D‐Igl, respectively). The Igl2 substitution resulted in a significant change of the pharmacological profile of the peptides. The new analogues were moderate or potent oxytocin antagonists and practically did not interact with V1a and V2 receptors.