Discovery of 1-(2,4-dichlorophenyl)-N-(piperidin-1-yl)-4-((pyrrolidine-1-sulfonamido)methyl)-5-(5-((4-(trifluoromethyl)phenyl)ethynyl)thiophene-2-yl)-1H-pyrazole-3-carboxamide as a novel peripherally restricted cannabinoid-1 receptor antagonist with significant weight-loss efficacy in diet-induced obese mice.

After extensive synthetic efforts, we found that many structurally diverse bioisosteres could be generated via derivatizing the C-4 alkyl chain on the pyrazole ring of compound 3 (B/P = 1/33) with different electronegative groups. Especially when a sulfonamide or sulfamide moiety was added, resulting compounds exhibited not only potent CB1R activity but also a desired tPSA value over 90 Å(2), a threshold considered to possess a low probability to cross BBB, leading to the identification of compound 4 (B/P = 1/64) as a peripherally restricted CB1R antagonist. Apart from its significant weight-loss efficacy in DIO mice, compound 4 also displays 163 clean off-target profiles and is currently under development for treating obesity and the related metabolic syndrome.

Biphasic suppression of appetite by cannabinoid CB1 receptor antagonists with distinct functional activities.

A novel alkynylthiophene series of cannabinoid CB1 receptor antagonists has been described to exhibit distinct intrinsic activities with minimal substructure modifications. The three representatives, BPR0432, BPR0568 and BPR0569, functioning as a neutral antagonist, an inverse agonist and a partial agonist, respectively, in GTP binding assay, were further characterized for their downstream signaling activities in relation to in vivo efficacy in appetite suppression to diets of different macronutrients. Interestingly, these three derivatives all behaved as inverse agonists with the potency of BPR0432>BPR0568>BPR0569 in cAMP assay. After administered to non-deprived rats, the potency in appetite suppression was positively related to their strength in intrinsic activity in the first hour of intake. The preferential suppression to high fat and high carbohydrate diets was revealed after 6h and only appeared in the treatment of BPR0568, presumably due to its metabolic stability in addition to its intrinsic activity. These results indicated the suppression of appetite was controlled in a biphasic manner, and these three structurally close but functionally distinct compounds are invaluable tools in elucidating the mechanism of neuronal response to appetite and palatability.

Discovery of 2-[5-(4-chloro-phenyl)-1-(2,4-dichloro-phenyl)-4-ethyl-1H-pyrazol-3-yl]-1,5,5-trimethyl-1,5-dihydro-imidazol-4-thione (BPR-890) via an active metabolite. A novel, potent and selective cannabinoid-1 receptor inverse agonist with high antiobesity efficacy in DIO mice.

By using the active metabolite 5 as an initial template, further structural modifications led to the identification of the titled compound 24 (BPR-890) as a highly potent CB1 inverse agonist possessing an excellent CB2/1 selectivity and remarkable in vivo efficacy in diet-induced obese mice with a minimum effective dose as low as 0.03 mg/kg (po qd) at the end of the 30-day chronic study. Current SAR studies along with those of many existing rimonabant-mimicking molecules imply that around the pyrazole C3-position, a rigid and deep binding pocket should exist for CB1 receptor. In addition, relative to the conventional carboxamide carbonyl, serving as a key hydrogen-bond acceptor during ligand-CB1 receptor interaction, the corresponding polarizable thione carbonyl might play a more critical role in stabilizing the Asp366-Lys192 salt bridge in the proposed CB1-receptor homology model and inducing significant selectivity for CB1R over CB2R.

Bioisosteric replacement of the pyrazole 5-aryl moiety of N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A). A novel series of alkynylthiophenes as potent and selective cannabinoid-1 receptor antagonists.

Replacing the conventional pyrazole 5-aryl substituent of 1 (SR141716A) with the 2-thienyl moiety appended with an appropriate alkynyl unit, a novel class of 5-(5-alkynyl-2-thienyl)pyrazole derivatives, behaving as highly potent CB1 receptor antagonists with good CB1/2 selectivity, was discovered, many of which, as typified by compound 18, showed significant weight reduction in diet-induced obese mouse model, thus pharmacologically validating that the bioisosteric replacement described above is viable. Also encouraging was the finding that a subtle structural modification of the newly developed series could result in a distinct difference in the intrinsic property, as demonstrated by compounds 12 (NA) and its methylated structural isomers 15 (PA) and 18 (IA). Moreover, current structure-activity relationship studies revealed that around the pyrazole 5-position of 1, a deep and flat crevice surrounded by a sequence of hydrophobic/aromatic residues as indicated by the CB1-receptor homology model might exist in the binding site.

Cocaine-but not methamphetamine-associated memory requires de novo protein synthesis.

Context-induced drug craving and continuous drug use manifest the critical roles of specific memory episodes associated with the drug use experiences. Drug-induced conditioned place preference (CPP) in C57BL/6J mouse model, in this regard, is an appropriate behavioral paradigm to study such drug use-associated memories. Requirement of protein synthesis in various forms of long-term memory formation and storage has been phylogenetically demonstrated. This study was undertaken to study the requirement of protein synthesis in the learning and memory aspect of the conditioned place preference induced by cocaine and methamphetamine, two abused drugs of choice in local area. Since pCREB has been documented as a candidate substrate for mediating the drug-induced neuroadaptation, the pCREB level in hippocampus, nucleus accumbens, and prefrontal cortex was examined for its potential participation in the formation of CPP caused by these psychostimulants. We found that cocaine (2.5 and 5.0 mg/kg/dose)-induced CPP was abolished by the pretreatment of anisomycin (50 mg/kg/dose), a protein synthesis inhibitor, whereas methamphetamine (0.5 or 1.0 mg/kg/dose)-induced CPP was not affected by the anisomycin pretreatment. Likewise, cocaine-induced CPP was mitigated by another protein synthesis inhibitor, cycloheximide (15 mg/kg/injection) pretreatment, whereas methamphetamine-induced CPP remained intact by such pretreatment. Moreover, anisomycin treatment 2h after each drug-place pairing disrupted the cocaine-induced CPP, whereas the same treatment did not affect methamphetamine-induced CPP. An increase of accumbal pCREB level was found to associate with the learning phase of cocaine, but not with the learning phase of methamphetamine. We further found that intraaccumbal CREB antisense oligodeoxynucleotide infusion diminished cocaine-induced CPP, whereas did not affect the methamphetamine-induced CPP. Taken together, these data suggest that protein synthesis and accumbal CREB phosphorylation are essential for the learning and consolidation of the cocaine-induced CPP, whereas methamphetamine-induced CPP may be unrelated to the synthesis of new proteins.