Synthesis and biological activity of novel 4,4-difluorobenzazepine derivatives as non-peptide antagonists of the arginine vasopressin V1A receptor

Vasopressin and Its Analogues: From Natural Hormones to Multitasking Peptides

Human neurohormone vasopressin (AVP) is synthesized in overlapping regions in the hypothalamus. It is mainly known for its vasoconstricting abilities, and it is responsible for the regulation of plasma osmolality by maintaining fluid homeostasis. Over years, many attempts have been made to modify this hormone and find AVP analogues with different pharmacological profiles that could overcome its limitations. Non-peptide AVP analogues with low molecular weight presented good affinity to AVP receptors. Natural peptide counterparts, found in animals, are successfully applied as therapeutics; for instance, lypressin used in treatment of diabetes insipidus. Synthetic peptide analogues compensate for the shortcomings of AVP. Desmopressin is more resistant to proteolysis and presents mainly antidiuretic effects, while terlipressin is a long-acting AVP analogue and a drug recommended in the treatment of varicose bleeding in patients with liver cirrhosis. Recently published results on diverse applications of AVP analogues in medicinal practice, including potential lypressin, terlipressin and ornipressin in the treatment of SARS-CoV-2, are discussed.

Molecular modeling of vasopressin receptor and in silico screening of V1b receptor antagonists

INTRODUCTION

G protein-coupled receptors (GPCRs) are integral membrane proteins which contain seven-transmembrane-spanning alpha-helices. GPCR-mediated signaling has been associated with various human diseases, positioning GPCRs as attractive targets in the drug discovery field. Recently, through advances in protein engineering and crystallography, the number of resolved GPCR structures has increased dramatically. This growing availability of GPCR structures has greatly accelerated structure-based drug design (SBDD) and in silico screening for GPCR-targeted drug discovery.

AREAS COVERED

The authors introduce the current status of X-ray crystallography of GPCRs and what has been revealed from the resolved crystal structures. They also review the recent advances in SBDD and in silico screening for GPCR-targeted drug discovery and discuss a docking study, using homology modeling, with the discovery of potent antagonists of the vasopressin 1b receptor.

EXPERT OPINION

Several innovative protein engineering techniques and crystallographic methods have greatly accelerated SBDD, not only for already-resolved GPCRs but also for those structures which remain unclear. These technological advances are expected to enable the determination of GPCR-fragment complexes, making it practical to perform fragment-based drug discovery. This paves the way for a new era of GPCR-targeted drug discovery.

Azetidinones as vasopressin V1a antagonists

The azetidinone LY307174 (1) was identified as a screening lead for the vasopressin V1a receptor (IC50 45 nM at the human V1a receptor) based on molecular similarity to ketoconazole (2), a known antagonist of the luteinizing hormone releasing hormone receptor. Structure-activity relationships for the series were explored to optimize receptor affinity and pharmacokinetic properties, resulting in compounds with Ki values <1nM and brain levels after oral dosing approximately 100-fold higher than receptor affinities.

Binding and signal transduction characteristics of the nonpeptide vasopressin V1A receptor-selective antagonist YM218 in cultured rat mesangial cells

Vasopressin (AVP) causes mesangial cell contraction, proliferation and hypertrophy. The present study investigated the effects of YM218, a potent, nonpeptide AVP V(1A) receptor-selective antagonist, on rat mesangial cells using binding, signal transduction and cell growth assays. Specific binding of (3)H-AVP to rat mesangial cell plasma membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with the expected V(1A) receptor profile. YM218 showed high affinity for V(1A) receptors, exhibiting a K(i) value of 0.19 nmol/l. AVP concentration-dependently increased intracellular Ca(2+) ([Ca(2+)](i)) levels, stimulated mitogen-activated protein (MAP) kinase and induced hyperplasia. Conversely, YM218 potently suppressed [Ca(2+)](i) elevation, activation of MAP kinase and hyperplasia induced by AVP. These results indicate that YM218 displays both high affinity for rat mesangial cell V(1A) receptors and high potency in inhibiting AVP-induced signal transduction and growth response. Therefore, YM218 is a useful pharmacologic tool for investigating the physiologic and pathophysiologic roles of AVP in kidney, and may have clinical application in the prevention or regression of mesangial cell growth.