Investigational vasopressin receptor modulators in the pipeline

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.

Monocyclic beta-lactams for therapeutic uses: a patent overview (2010-2020)

INTRODUCTION

Monocyclic beta-lactams are four-membered cyclic amides with various structural modifications of the nucleus that determine their chemical reactivity and target specificity. Their historical use is based on their antibacterial activity, but they have recently appeared in other areas as well.

AREAS COVERED

This review summarizes the relevant patent development on monocyclic beta-lactams in various therapeutic areas over the last 10 years. The majority of patents describe compounds with antibacterial activity, while there are some recent patents describing the neuroprotective, anti-inflammatory, anti-cancer, anticoagulant and antihyperlipidemic effects of 2-azetidinones.

EXPERT OPINION

Monocyclic beta-lactams can be considered safe and nontoxic drugs, as they have been used in the clinic for almost half of the century. Recently, monocyclic beta-lactams have been increasingly recognized for their non-antibiotic activity, which has led to some promising new clinical candidates in the field of neurodegenerative diseases and coagulation therapy. With regard to their antibacterial activity, there is still room for improvement of their activity and broadening of their spectrum of action, especially in Gram-positive bacteria and on drug-insensitive penicillin-binding proteins, and in increasing their beta-lactamase stability.

Hybrid peptide-small molecule oxytocin analogs are potent and selective agonists of the oxytocin receptor

Oxytocin (OT) is a peptide hormone agonist of the oxytocin receptor (OTR) that has been proposed as a therapeutic to treat a number of social and emotional disorders in addition to its current clinical use to induce labor and treat postpartum bleeding. OT is administered intravenously and intranasally rather than orally, in part because its low passive permeability causes low oral bioavailability. Non-peptidic OTR agonists have also been reported, but none with the exquisite potency of the peptide based agonists. In this report, we describe the OTR agonist activity and exposed polarity of a set of truncated OT analogs as well as hybrid peptide-small molecule analogs of OT. Examples of both truncated analogs and peptide-small molecule hybrid analogs are potent and selective OTR agonists. Hybrid agonist 13, which is 232 Da smaller than OT, still retains subnanomolar potency, full agonist activity, and selectivity over V1a. While these compounds were designed to address the low permeability of OT and other full length analogs, we found that reduction in molecular weight and the removal or replacement of the three amino acid tail of OT did not have a significant effect on passive permeability.

GPCR Signaling and Trafficking: The Long and Short of It

Emerging findings disclose unexpected components of G protein-coupled receptor (GPCR) signaling and cell biology. Select GPCRs exhibit classical signaling, that is restricted to cell membranes, as well as newly described persistent signaling that depends on internalization of the GPCR bound to β-arrestins. Termination of non-canonical endosomal signaling requires intraluminal acidification and sophisticated protein trafficking machineries. Recent studies reveal the structural determinants of the trafficking chaperones. This review summarizes advances in GPCR signaling and trafficking with a focus on the parathyroid hormone receptor (PTHR) as a prototype, and on the actin-sorting nexin 27 (SNX27)-retromer tubule (ASRT) complex, an endosomal sorting hub responsible for recycling and preservation of cell surface receptors. The findings are integrated into a model of PTHR trafficking with implications for signal transduction, bone growth, and mineral ion metabolism.

Peripheral Administration of a Long-Acting Peptide Oxytocin Receptor Agonist Inhibits Fear-Induced Freezing

Oxytocin (OT) modulates the expression of social and emotional behaviors and consequently has been proposed as a pharmacologic treatment of psychiatric diseases, including autism spectrum disorders and schizophrenia; however, endogenous OT has a short half-life in plasma and poor permeability across the blood-brain barrier. Recent efforts have focused on the development of novel drug delivery methods to enhance brain penetration, but few efforts have aimed at improving its half-life. To explore the behavioral efficacy of an OT analog with enhanced plasma stability, we developed PF-06655075 (PF1), a novel non–brain-penetrant OT receptor agonist with increased selectivity for the OT receptor and significantly increased pharmacokinetic stability. PF-06478939 was generated with only increased stability to disambiguate changes to selectivity versus stability. The efficacy of these compounds in evoking behavioral effects was tested in a conditioned fear paradigm. Both central and peripheral administration of PF1 inhibited freezing in response to a conditioned fear stimulus. Peripheral administration of PF1 resulted in a sustained level of plasma concentrations for greater than 20 hours but no detectable accumulation in brain tissue, suggesting that plasma or cerebrospinal fluid exposure was sufficient to evoke behavioral effects. Behavioral efficacy of peripherally administered OT receptor agonists on conditioned fear response opens the door to potential peripheral mechanisms in other behavioral paradigms, whether they are mediated by direct peripheral activation or feed-forward responses. Compound PF1 is freely available as a tool compound to further explore the role of peripheral OT in behavioral response.

A comparative protease stability study of synthetic macrocyclic peptides that mimic two endocrine hormones

Peptide therapeutics have traditionally faced many challenges including low bioavailability, poor proteolytic stability and difficult cellular uptake. Conformationally constraining the backbone of a peptide into a macrocyclic ring often ameliorates these problems and allows for the development of a variety of new drugs. Such peptide-based pharmaceuticals can enhance the multi-faceted functionality of peptide side chains, permitting the peptides to bind cellular targets and receptors necessary to impart their role, while protecting them from degrading cellular influences. In the work described here, we developed three cyclic peptides, VP mimic1, VP mimic2 and OT mimic1, which mimic endocrine hormones vasopressin and oxytocin. Making notable changes to the overall structure and composition of the parent hormones, we synthesized the mimics and tested their durability against treatment with three proteases chosen for their specificity: pepsin, alpha-chymotrypsin, and pronase. Vasopressin and oxytocin contain a disulfide linkage leaving them particularly vulnerable to deactivation from the reducing environment inside the cell. Thus, we increased the complexity of our assays by adding reducing agent glutathione to each mixture. Subsequently, we discovered each of our mimics withstood protease treatment with less degradation and/or a slower rate of degradation as compared to both parent hormones and a linear control peptide.

In vitro and in vivo pharmacological characterisation of the potent and selective vasopressin V(1A) receptor antagonist 4-[4-(4-Chloro-phenyl)-5-[1,2,3]triazol-2-ylmethyl-4H-[1,2,4]triazol-3-yl]-piperidin-1-yl-(3,5-difluoro-phenyl) methanone (PF-00738245)

The dysregulation of arginine vasopressin (AVP) release and activation of vasopressin receptors plays an important role in disease conditions including polycystic kidney disease, congestive heart failure and dysmenorrhoea. The development of potent and selective vasopressin receptor ligands is needed to help dissect the function of the specific subtypes in disease pathogenesis. Here we report the pharmacological characterisation of PF-00738245 in in vitro binding and functional assays using cells expressing vasopressin V(₁A), V(₁B) or V₂ receptors. PF-00738245 inhibited AVP binding to the recombinant human vasopressin V(₁A) receptor (K(i)=2.85 nM) and blocked AVP-induced rat aortic ring and human myometrial contraction (pK(B)=7.35 and 8.62 respectively). PF-00738245 was selective for the vasopressin V(1A) receptor by demonstrating minimal binding to vasopressin V(₁B) (3.6% inhibition at 10 μM) or functional activity at vasopressin V₂ receptors (8.1% agonist and -8.4% antagonist activity at 10 μM) as well as the oxytocin receptor (46.3% antagonist activity at 10 μM). The in vivo pharmacological properties were tested orally in the rat and PF-00738245 dose dependently blocked the effect of AVP on a capsaicin-induced cutaneous flare response. Taken together the data support the use of PF-00738245 as a potent and selective vasopressin V(₁A) receptor antagonist which may have utility in the treatment of disease conditions which are propagated by elevation in vasopressin V(₁A) receptor signalling.