Pharmacological evaluation of analgesic effects of the cholecystokinin2 receptor antagonist Z-360 in mouse models of formalin- and cancer-induced pain

CCK2R antagonists: from SAR to clinical trials

The widespread involvement of the cholecystokinin-2/gastrin receptor (CCK₂R) in multiple (patho)physiological processes has propelled extensive searches for nonpeptide small-molecule CCK₂R antagonists. For the past three decades, considerable research has yielded numerous chemically heterogeneous compounds. None of these entered into the clinic, mainly because of inadequate biological effects. However, it appears that the ultimate goal of a clinically useful CCK₂R antagonist is now just around the corner, with the most promising compounds, netazepide and nastorazepide, now in Phase II clinical trials. Here, we illustrate the structure-activity relationships (SARs) of stablished CCK₂R antagonists of various structural classes, and the most recent proof-of-concept studies where new applicabilities of CCK₂R antagonists as visualizing agents are presented.

Cholecystokinin-2/gastrin antagonists: 5-hydroxy-5-aryl-pyrrol-2-ones as anti-inflammatory analgesics for the treatment of inflammatory bowel disease

Arylated 5-hydroxy-pyrrol-2-ones were prepared in 2 synthetic steps from mucochloric acid and optimised as CCK2-selective ligands using radiolabelled binding assays. CCK antagonism was confirmed for the ligands in isolated tissue preparations. DSS (dextran sulfate sodium)-induced inflammation was analysed for derivative 7 and PNB-001 with L-365,260 as a standard. The IC50 of PNB-001 was determined to be 10 nM. Subsequent in vivo evaluation confirmed anti-inflammatory activity with respect to IBD assays. The best molecule, PNB-001, showed analgesic activity in the formalin test and in the hotplate assay, in which the analgesic effect of 1.5 mg kg-1 PNB-001 was equivalent to 40 mg kg-1 tramadol. The CCK2-selective antagonist PNB-001 protected rats against indomethacin-induced ulceration at similar doses. The GI protection activity was found to be more potent than that of the 10 mg kg-1 dose of prednisolone, which served as a standard.

Opioid adjuvant strategy: improving opioid effectiveness

Opioid analgesics continue to be the mainstay of pharmacologic treatment of moderate to severe pain. Many patients, particularly those suffering from chronic pain, require chronic high-dose analgesic therapy. Achieving clinical efficacy and tolerability of such treatment regimens is hampered by the appearance of opioid-induced side effects such as tolerance, hyperalgesia and withdrawal syndrome. Among the therapeutic options to improve the opioid effectiveness, this current review focuses on strategies combining opioids to other drugs that can modulate opioid-mediated effects. We will discuss about experimental evidences reported for several potential opioid adjuvants, including N-methyl-d-aspartate receptor antagonists, 5-HT7 agonists, sigma-1 antagonists, I2-R ligands, cholecystokinin antagonists, neuropeptide FF-R antagonists and toll-like receptor 4 antagonists.

Gastrin receptor pharmacology

C-terminally amidated gastrins act at cholecystokinin-2 receptors (CCK2R), which are normally expressed by gastric parietal and enterochromaffin-like (ECL) cells and smooth muscle; there is also extensive expression in the CNS where the main endogenous ligand is cholecystokinin. A variety of neoplasms express CCK2R, or splice variants, including neuroendocrine, pancreatic, medullary thyroid and lung cancers. Other products of the gastrin gene (progastrin, the Gly-gastrins) may stimulate cell proliferation but are not CCK2R ligands. Depending on the cell type, stimulation of CCK2R evokes secretion, increases proliferation and cell migration, inhibits apoptosis, and controls the expression of various genes. These effects are mediated by increased intracellular calcium and activation of protein kinase C, MAPkinase and other protein kinase cascades. There has been recent progress in developing CCK2R ligands that can be used for imaging tumours expressing the receptor. New antagonists have also been developed, and there is scope for using these for suppression of gastric acid and for treatment of neuroendocrine and other CCK2R-expressing tumours.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Z-360, a novel therapeutic agent for pancreatic cancer, prevents up-regulation of ephrin B1 gene expression and phosphorylation of NR2B via suppression of interleukin-1 β production in a cancer-induced pain model in mice

BACKGROUND

Z-360 is an orally active cholecystokinin-2 (CCK2)/gastrin receptor antagonist currently under development as a therapeutic drug for pancreatic cancer. It was previously reported that Z-360 treatment in combination with gemcitabine prolonged the survival period in a lethal pancreatic cancer xenograft model in mice. In a phase Ib/IIa clinical study, Z-360 treatment displayed a trend of reduced pain in patients with advanced pancreatic cancer in combination with gemcitabine including analgesics such as opioids. Here, we investigated the mechanism of analgesic action of Z-360 in a severe cancer-induced pain model in mice, which is considered to be opioid-resistant, by examining ephrin B1 gene expression, N-methyl-D-aspartate receptor NR2B subunit phosphorylation, and interleukin-1β (IL-1β) production.

RESULTS

In a mouse model of cancer-induced pain, ephrin B1 gene expression in dorsal root ganglia (DRGs) and the phosphorylation of NR2B in the spinal cord were induced. Z-360 treatment inhibited both ephrin B1 gene expression and the phosphorylation of NR2B. In addition, IL-1β production increased in the cancer-inoculated hind paw of mice, but could be suppressed by treatment with Z-360. Moreover, we observed that the CCK1 receptor antagonist devazepide similarly suppressed up-regulation of ephrin B1 gene expression and IL-1β production, and that the intraperitoneal injection of sulfated CCK-8 induced the production of IL-1β in the cancer-inoculated region.

CONCLUSIONS

We have identified a novel pain cascade, in which IL-1β production in cancer-inoculated regions induces ephrin B1 gene expression in DRGs and then ephrin B1 enhances the tyrosine phosphorylation of NR2B via Eph B receptor in the spinal cord. Notably, Z-360 relieves cancer-induced pain by preventing this pain cascade through the suppression of IL-1β production, likely via the blockade of CCK1 receptor. The pre-clinical results presented here support the analgesic action of Z-360 in pancreatic cancer patients with severe, opioid-resistant pain. Pre-clinical and clinical results have demonstrated that Z-360 combined with gemcitabine represents a promising pancreatic cancer therapy approach with characteristic analgesic effects in addition to the prolongation of survival.