Novel pharmacological MC4R agonists can efficiently activate mutated MC4R from obese patient with impaired endogenous agonist response.

Human melanocortin 4 receptor (hMC4R) mutations with in vitro functional effects are responsible for 0.5-2.5% of severe obesity. Designing ligands that are able to counteract this in vitro-associated molecular defect is crucial to develop specific anti-obesity drugs in these genetically associated cases. We analyzed the in vitro effect of two novel melanocortin agonists, IRC-022493 and IRC-022511, on typical hMC4R mutations chosen based on the nature of their functional alterations, i.e. intracytoplasmic retention and/or reduced basal activity and/or reduced α-MSH potency. We assessed the in vitro ability of IRC-022493 and IRC-022511 to bind and activate hMC4R mutants. These mutations were found earlier in 11 obese French patients (median age (range) was 17.6 years (5.7-48.0) and body mass index (BMI)-Z-score 4.2 s.d. (1.5-5.5). The MC4R agonists were responsible for a significant activation of mutated hMC4R depending on the functional characteristics of the mutations. Both agonists were able to activate mutated hMC4R with decreased α-MSH potency, associated with or without decreased basal activity, to the same extent than α-MSH in wild-type MC4R. This result suggests that those mutations would be the best targets for the MC4R agonists among MC4R mutation-bearing obese patients. No specific clinical phenotype was associated with the differential response to pharmacological agonists. We identified two novel melanocortin agonists that were able in vitro to efficiently activate mutated hMC4R with impaired endogenous agonist functional response. These results stimulate interest in the development of these drugs for hMC4R mutations-associated obesity.

Analysis of the therapeutic functions of novel melanocortin receptor agonists in MC3R- and MC4R-deficient C57BL/6J mice.

Melanocortin receptor agonists act in the brain to regulate food intake and body weight and, independently of these actions, affect insulin sensitivity. These experiments investigated the function of novel non-selective melanocortin receptor agonists (BIM-22493, BIM-22511) that cross the blood-brain barrier when administered peripherally. Treatment of diet induced obese C57BL/6J (B6) mice with melanocortin agonists administered peripherally improved obesity, hyperinsulinemia (approximately 50%) and fatty liver disease. Specificity of function was determined using B6 melanocortin-3 and melanocortin-4 receptor knockout mice (MC3RKO, MC4RKO). Chow fed MC4RKO but not MC3RKO used for these tests exhibited obesity, hyperinsulinemia and severe hepatosteatosis associated with increased expression of insulin-stimulated genes involved in lipogenesis. Reduced food intake associated with acute BIM-22493 treatment, and weight loss associated with 14 days of treatment with BIM-22511, required functional MC4R but not MC3R. However, while 14 days of treatment with BIM-22511 did not affect body weight and even increased cumulative food intake in MC4RKO, a significant reduction (approximately 50%) in fasting insulin was still observed. Despite lowering insulin, chronic treatment with BIM-22511 did not improve hepatosteatosis in MC4RKO, and did not affect hepatic lipogenic gene expression. Together, these results demonstrate that peripherally administered melanocortin receptor agonists regulate body weight, liver metabolism and glucose homeostasis through independent pathways. MC4R are necessary for melanocortin agonist-induced weight loss and improvements in liver metabolism, but are not required for improvements in hyperinsulinemia. Agonists with activity at MC4R improve glucose homeostasis at least partially by causing weight loss, however other melanocortin receptors may have potential for treating aberrations in glucose homeostasis associated with obesity.

Identification of a novel series of benzimidazoles as potent and selective antagonists of the human melanocortin-4 receptor.

A novel series of benzimidazoles was identified and optimized, leading to the discovery of potent and selective antagonists of the human melanocortin-4 receptor. In addition, compound 5i was shown to cross the blood-brain barrier after intravenous dosing in rats.

Anticancer activity of BIM-46174, a new inhibitor of the heterotrimeric Galpha/Gbetagamma protein complex.

A large number of hormones and local agonists activating guanine-binding protein-coupled receptors (GPCR) play a major role in cancer progression. Here, we characterize the new imidazo-pyrazine derivative BIM-46174, which acts as a selective inhibitor of heterotrimeric G-protein complex. BIM-46174 prevents the heterotrimeric G-protein signaling linked to several GPCRs mediating (a) cyclic AMP generation (Galphas), (b) calcium release (Galphaq), and (c) cancer cell invasion by Wnt-2 frizzled receptors and high-affinity neurotensin receptors (Galphao/i and Galphaq). BIM-46174 inhibits the growth of a large panel of human cancer cell lines, including anticancer drug-resistant cells. Exposure of cancer cells to BIM-46174 leads to caspase-3-dependent apoptosis and poly(ADP-ribose) polymerase cleavage. National Cancer Institute COMPARE analysis for BIM-46174 supports its novel pharmacologic profile compared with 12,000 anticancer agents. The growth rate of human tumor xenografts in athymic mice is significantly reduced after administration of BIM-46174 combined with either cisplatin, farnesyltransferase inhibitor, or topoisomerase inhibitors. Our data validate the feasibility of targeting heterotrimeric G-protein functions downstream the GPCRs to improve anticancer chemotherapy.

3-Thio-1,2,4-triazoles, novel somatostatin sst2/sst5 agonists.

Novel 3-thio-1,2,4-triazoles have been obtained via a solution-phase parallel synthesis strategy, affording potent non-peptidic human somatostatin receptor subtypes 2 and 5 agonists.