Building bridges for highly selective, potent and stable oxytocin and vasopressin analogs

Abstract

Oxytocin (OT) is an exciting potential therapeutic agent, but it is highly sensitive to modification and suffers extensive degradation at elevated temperature and in vivo. Here we report studies towards OT analogs with favorable selectivity, affinity and potency towards the oxytocin receptor (OTR), in addition to improving stability of the peptide by bridging the disulfide region with substituted dibromo-xylene analogs. We found a sensitive structure-activity relationship in which meta-cyclized analogs (dOT) gave highest affinity (50 nM K), selectivity (34-fold), and agonist potency (34 nM EC, 87-fold selectivity) towards OTR. Surprisingly, ortho-cyclized analogs demonstrated OTR and vasopressin V receptor subtype affinity (220 nM and 69 nM, respectively) and pharmacological activity (294 nM and 35 nM, respectively). V binding and selectivity for ortho-cyclized peptides could be improved 6-fold by substituting a neutral residue at position 8 with a basic amino acid, providing potent antagonists (14 nM IC) that displayed no activation of the OTR. Furthermore, xylene-bridged analogs demonstrated increased stability compared to OT at elevated temperature, demonstrating promising therapeutic potential for these analogs which warrants further study.

Oxytocin in the Male Reproductive Tract; The Therapeutic Potential of Oxytocin-Agonists and-Antagonists

“…They also suffer short pharmacokinetic half-lives necessitating continuous application by either intramuscular or intravenous application which is only reasonable for short periods of time. These routes of systemic delivery often lead to undesirable off-target side-effects (e.g., cardio-vasculature), with the exception of the central nervous system due to the blood-brain barrier (BBB) (213). Intranasal applications and antagonists with BBB-penetrating properties have been developed to affect the brain and central nervous system specifically.…”

Development of a Highly Potent Analogue and a Long-Acting Analogue of Oxytocin for the Treatment of Social Impairment-Like Behaviors

“…Frozen hOTRexpressed HEK cells were thawed and suspended in 20 mL of a cold lysis buffer containing 1 mM EDTA, 50 mM HEPES, 10 mM MgCl 2 , pH 7.4, with the addition of complete cocktail of protease inhibitor (Roche Diagnostics) as described previously. 66 The cells allowed to swell for 20 min and were homogenized with a Teflon-glass homogenizer. 67 Intact cells and nuclei pellets were removed by centrifugation at 500g for 10 min.…”

On‐Resin Preparation of Allenamidyl Peptides: A Versatile Chemoselective Conjugation and Intramolecular Cyclisation Tool

“…Satisfied with the ability to modify model peptide 7 with a diverse range of thiols in excellent conversions (>85 %), we turned our attention towards the intramolecular reactivity of an allenamidyl peptide. Oxytocin is a well‐studied disulfide bridged peptide with a particularly poor half‐life in vivo , at least in part due to reduction of the disulfide bond which is generally thought to precede its proteolytic degradation . Taking oxytocin as a model substrate, we envisioned replacing the disulfide bond with a vinyl sulfide bridge by first introducing an allenamide handle to the peptide on‐resin and then effecting an intramolecular thia‐Michael cyclisation with a Cys residue by use of aqueous buffer.…”