(4-(Bis(4-Fluorophenyl)Methyl)Piperazin-1-yl)(Cyclohexyl)Methanone Hydrochloride (LDK1229): A New Cannabinoid CB₁Receptor Inverse Agonist from the Class of Benzhydryl Piperazine Analogs

Abstract

Some inverse agonists of cannabinoid receptor type 1 (CB 1 ) have been demonstrated to be anorectic antiobesity drug candidates. However, the first generation of CB 1 inverse agonists, represented by rimonabant (SR141716A), otenabant, and taranabant, are centrally active, with a high level of psychiatric side effects. Hence, the discovery of CB 1 inverse agonists with a chemical scaffold distinct from these holds promise for developing peripherally active CB 1 inverse agonists with fewer side effects. We generated a new CB 1 inverse agonist, (4-(bis(4-fluorophenyl)methyl)piperazin-1-yl)(cyclohexyl)methanone hydrochloride (LDK1229), from the class of benzhydryl piperazine analogs. This compound binds to CB 1 more selectively than cannabinoid receptor type 2, with a K i value of 220 nM. Comparable CB 1 binding was also observed by analogs 1-[bis (4-fluorophenyl)methyl]-4-cinnamylpiperazine dihydrochloride (LDK1203) and 1-[bis(4-fluorophenyl)methyl]-4-tosylpiperazine hydrochloride (LDK1222), which differed by the substitution on the piperazine ring where the piperazine of LDK1203 and LDK1222 are substituted by an alkyl group and a tosyl group, respectively. LDK1229 exhibits efficacy comparable with SR141716A in antagonizing the basal G protein coupling activity of CB 1 , as indicated by a reduction in guanosine 59-O-(3-thio)triphosphate binding. Consistent with inverse agonist behavior, increased cell surface localization of CB 1 upon treatment with LDK1229 was also observed. Although docking and mutational analysis showed that LDK1229 forms similar interactions with the receptor as SR141716A does, the benzhydryl piperazine scaffold is structurally distinct from the first-generation CB 1 inverse agonists. It offers new opportunities for developing novel CB 1 inverse agonists through the optimization of molecular properties, such as the polar surface area and hydrophilicity, to reduce the central activity observed with SR141716A.

Discovery of Selective Cannabinoid CB2 Receptor Agonists by High-Throughput Screening

“…31,32 In brief, nine different concentrations of the test compounds (from 100 pM to 100 µM) were incubated with cell membranes and the tracer [ 3 H]CP 55,940 (150.2 Ci/mmol; PerkinElmer) at 1.5 nM to achieve a robust signal while staying lower than the K D determined for this system. 33 Nonspecific binding was determined using 1 µM unlabeled CP 55,940. Experiments were performed in duplicate three times, and only two times when no binding was detected.…”