Structure-antigastrin activity relationships of new spiroglumide amido acid derivatives

Cholecystokinin antagonists: pharmacological and therapeutic potential

Cholecystokinin (CCK) is a regulatory peptide hormone, predominantly found in the gastrointestinal tract, and a neurotransmitter present throughout the nervous system. In the gastrointestinal system CCK regulates motility, pancreatic enzyme secretion, gastric emptying, and gastric acid secretion. In the nervous system CCK is involved in anxiogenesis, satiety, nociception, and memory and learning processes. Moreover, CCK interacts with other neurotransmitters in some areas of the CNS. The biological effects of CCK are mediated by two specific G protein coupled receptor subtypes, termed CCK(1) and CCK(2). Over the past fifteen years the search of CCK receptor ligands has evolved from the initial CCK structure derived peptides towards peptidomimetic or non-peptide agonists and antagonists with improved pharmacokinetic profile. This research has provided a broad assortment of potent and selective CCK(1) and CCK(2) antagonists of diverse chemical structure. These antagonists have been discovered through optimization programs of lead compounds which were designed based on the structures of the C-terminal tetrapeptide, CCK-4, or the non-peptide natural compound, asperlicin, or derived from random screening programs. This review covers the main pharmacological and therapeutic aspects of these CCK(1) and CCK(2) antagonist. CCK(1) antagonists might have therapeutic potential for the treatment of pancreatic disorders and as prokinetics for the treatment of gastroesophageal reflux disease, bowel disorders, and gastroparesis. On the other hand, CCK(2) antagonists might have application for the treatment of gastric acid secretion and anxiety disorders.

Neuropeptides in drug research

Neuropeptides have been a subject of considerable interest in the pharmaceutical industry over the last 20 years or more. Many drug discovery teams have contributed to our understanding of neuropeptide biology but no significant drugs that act selectively upon neuropeptide receptors have yet emerged from the clinic. There are, however, a plethora of clinically useful drugs that act at other classes of neurotransmitter and neuromodulator receptors, many of them discovered over the last 20 years. Nevertheless, we think that the future for the discovery of novel drugs acting at neuropeptide receptors looks bright for two reasons: (1) there has been a substantial increase in our understanding of the function of neuropeptides; and (2) high-throughput screening (HTS) against neuropeptide receptors has now begun to yield many interesting drug-like molecules, rather than peptides, that have the potential to become clinically useful drugs. The objective of this review is to summarise our current understanding of specific areas of neuropeptide biology and pharmacology in the CNS as well as the PNS. We will also speculate on where we think the new generation of neuropeptide agonists and antagonists could emerge from the clinic.

C-terminal anthranoyl-anthranilic acid derivatives and their evaluation on CCK receptors

A series of C-terminal anthranoyl-anthranilic acid derivatives arising from a strict bond disconnection approach of asperlicin were synthesized and examined for their CCK receptor affinities. These compounds represent the second step of our investigation directed toward the search for alternative substructures of asperlicin as a starting point for the development of a new class of CCK ligands. The obtained micromolar affinities for CCK-A rather than CCK-B receptor confirm that the anthranilic acid dimer represents a useful template for the development of selective CCK-A receptor ligands.

Therapeutic and chemical developments of cholecystokinin receptor ligands

Cholecystokinin (CCK) is an important 'brain-gut' hormone located both in the gastrointestinal (GI) system and in the CNS. At least two different G-coupled high affinity receptors have been identified: the CCK-A and the CCK-B receptors. Although the complex biological role of CCK is, as yet, not fully understood, its connection with many different physiological processes both at the GI level and at the CNS level is now well established. There is much potential for therapeutic use of CCK receptor ligands, however, clear investigations have yet to be completed. Several chemical families have been investigated over the last 20 years to find potent, subtype selective and stable CCK receptor agonists and antagonists. The main goal was to discover new therapeutic drugs acting on GI and/or on CNS diseases and also, to obtain powerful pharmacological tools that could permit a better understanding of the biological role of CCK. Despite promising results from investigations into medicinal chemistry of CCK receptor ligands, the therapeutical applications of these ligands still remains to be defined. This article reviews the main biological role of CCK, the therapeutic potential of CCK-A and CCK-B receptor agonists and antagonists and the common compounds from the different families of ligands.

Cytosolic Ca2+ evaluation in rabbit parietal cells: a novel method to screen gastrin receptor antagonists

We have evaluated the application of the fura-2 method to detect cytosolic Ca2+ increase in gastric cells expressing CCKB/gastrin receptors, in order to screen gastrin receptor antagonists, as an alternative to functional studies. We have characterized the receptors on parietal cell suspension from rabbit gastric mucosa and validated the method using both the CCKB and CCKA receptor agonists and antagonists. Human gastrin I (gastrin) (0.1 nM-4 microM) and sulfated cholecystokinin 26-33 (CCK-8) (0.01 nM-2 microM) dose-dependently augmented cytosolic Ca2+. The efficacies of the two agonists were similar, but the potency of CCK-8 (EC50 1.03 nM) was about 10-fold greater than that of gastrin (11 nM). Response to a submaximal dose of gastrin (50 nM) was dose-dependently blocked by the CCKB-receptor antagonists CAM-1028 (4-[[2-[[3-(1 H-indol-3-yl)-2-methyl-1-oxo-2-[[[1,7,7-trimethylbicyclo[2, 2,1]hept-2-yl)oxy]carbonyl]amino]propyl]amino]-1-phenylethyl]amino-4-oxo -[1 S-1 alpha, 2 beta [S'(S')4 alpha]]-butanoate-N-methyl-D-glucamine) (IC50 1.9 nM), L-365,260 (3 R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1 H-1, 4-benzodiazepin-3-yl)-N'-(3-methylphenyl)urea) (IC50 10 nM) and spiroglumide ((R)-4-(3,5-dichlorobenzamido)-5-(8-azaspiro[4.5]decan -8-yl)-5-oxopentanoic acid) (IC50 2 microM). The results were in agreement with those obtained from binding studies in guinea-pig cortical membranes. The model was employed to optimize the synthesis of a new class of spiroglumide analogues which led to a new molecule, (S)-4-¿(R)-4'-(3,5-dichlorobenzoylamino)-5'-(8-azaspiro[4.5] decan-8-yl)-5'-oxo)-pentanoylamino-5-(1-naphthylamino)-5-oxo pentanoic acid (CR 2622), whose potency was about 100-fold greater than that of spiroglumide. CR 2622, as well as the other CCKB receptor antagonists tested, exhibited no effect on basal [Ca2+]i. The simplicity and the reproducibility of this method suggest that it is a useful model to screen gastrin and antigastrin activity in parallel or as an alternative to binding studies.