The acyclic CB1R inverse agonist taranabant mediates weight loss by increasing energy expenditure and decreasing caloric intake.

Cannabinoid 1 receptor (CB1R) inverse agonists are emerging as a potential obesity therapy. However, the physiological mechanisms by which these agents modulate human energy balance are incompletely elucidated. Here, we describe a comprehensive clinical research study of taranabant, a structurally novel acyclic CB1R inverse agonist. Positron emission tomography imaging using the selective CB1R tracer [(18)F]MK-9470 confirmed central nervous system receptor occupancy levels ( approximately 10%-40%) associated with energy balance/weight-loss effects in animals. In a 12-week weight-loss study, taranabant induced statistically significant weight loss compared to placebo in obese subjects over the entire range of evaluated doses (0.5, 2, 4, and 6 mg once per day) (p < 0.001). Taranabant treatment was associated with dose-related increased incidence of clinical adverse events, including mild to moderate gastrointestinal and psychiatric effects. Mechanism-of-action studies suggest that engagement of the CB1R by taranabant leads to weight loss by reducing food intake and increasing energy expenditure and fat oxidation.

Efficacy and Safety of 0.01% and 0.02% Atropine for the Treatment of Pediatric Myopia Progression Over 3 Years: A Randomized Clinical Trial.

Importance: The global prevalence of myopia is predicted to approach 50% by 2050, increasing the risk of visual impairment later in life. No pharmacologic therapy is approved for treating childhood myopia progression. Objective: To assess the safety and efficacy of NVK002 (Vyluma), a novel, preservative-free, 0.01% and 0.02% low-dose atropine formulation for treating myopia progression. Design, Setting, and Participants: This was a double-masked, placebo-controlled, parallel-group, randomized phase 3 clinical trial conducted from November 20, 2017, through August 22, 2022, of placebo vs low-dose atropine, 0.01% and 0.02% (2:2:3 ratio). Participants were recruited from 26 clinical sites in North America and 5 countries in Europe. Enrolled participants were 3 to 16 years of age with -0.50 diopter (D) to -6.00 D spherical equivalent refractive error (SER) and no worse than -1.50 D astigmatism. Interventions: Once-daily placebo, low-dose atropine, 0.01%, or low-dose atropine, 0.02%, eye drops for 36 months. Main Outcomes and Measures: The primary, prespecified end point was the proportion of participants' eyes responding to 0.02% atropine vs placebo therapy (<0.50 D myopia progression at 36 months [responder analysis]). Secondary efficacy end points included responder analysis for atropine, 0.01%, and mean change from baseline in SER and axial length at month 36 in a modified intention-to-treat population (mITT; participants 6-10 years of age at baseline). Safety measurements for treated participants (3-16 years of age) were reported. Results: A total of 576 participants were randomly assigned to treatment groups. Of these, 573 participants (99.5%; mean [SD] age, 8.9 [2.0] years; 315 female [54.7%]) received trial treatment (3 participants who were randomized did not receive trial drug) and were included in the safety set. The 489 participants (84.9%) who were 6 to 10 years of age at randomization composed the mITT set. At month 36, compared with placebo, low-dose atropine, 0.02%, did not significantly increase the responder proportion (odds ratio [OR], 1.77; 95% CI, 0.50-6.26; P = .37) or slow mean SER progression (least squares mean [LSM] difference, 0.10 D; 95% CI, -0.02 D to 0.22 D; P = .10) but did slow mean axial elongation (LSM difference, -0.08 mm; 95% CI, -0.13 mm to -0.02 mm; P = .005); however, at month 36, compared with placebo, low-dose atropine, 0.01%, significantly increased the responder proportion (OR, 4.54; 95% CI, 1.15-17.97; P = .03), slowed mean SER progression (LSM difference, 0.24 D; 95% CI, 0.11 D-0.37 D; P < .001), and slowed axial elongation (LSM difference, -0.13 mm; 95% CI, -0.19 mm to -0.07 mm; P < .001). There were no serious ocular adverse events and few serious nonocular events; none was judged as associated with atropine. Conclusions and Relevance: This randomized clinical trial found that 0.02% atropine did not significantly increase the proportion of participants' eyes responding to therapy but suggested efficacy for 0.01% atropine across all 3 main end points compared with placebo. The efficacy and safety observed suggest that low-dose atropine may provide a treatment option for childhood myopia progression. Trial Registration: ClinicalTrials.gov Identifier: NCT03350620.

Neuronal activation in the hypothalamus and brainstem during feeding in rats.

We trained rats to a regime of scheduled feeding, in which food was available for only 2 hr each day. After 10 days, rats were euthanized at defined times relative to food availability, and their brains were analyzed to map Fos expression in neuronal populations to test the hypothesis that some populations are activated by hunger whereas others are activated by satiety signals. Fos expression accompanied feeding in several hypothalamic and brainstem nuclei. Food ingestion was critical for Fos expression in noradrenergic and non-noradrenergic cells in the nucleus tractus solitarii and area postrema and in the supraoptic nucleus, as well as in melanocortin-containing cells of the arcuate nucleus. However, anticipation of food alone activated other neurons in the arcuate nucleus and in the lateral and ventromedial hypothalamus, including orexin neurons. Thus orexigenic populations are strongly and rapidly activated at the onset of food presentation, followed rapidly by activity in anorexigenic populations when food is ingested.

MK-7128, a novel CB1 receptor inverse agonist, improves scopolamine-induced learning and memory deficits in mice.

Cannabinoid receptors (CBRs) play an important role in a variety of physiological functions and have been considered drug targets for obesity and psychiatric disorders. In particular, the CB1R is highly expressed in brain regions crucial to learning and memory processes, and several lines of evidence indicate that pharmacological blockade of this receptor could have therapeutic applications in the treatment of cognitive disorders. In this study, we investigated whether MK-7128 (0.1, 0.3, and 1 mg/kg, orally), a novel and selective CB1R inverse agonist, could improve learning and memory deficits induced by scopolamine (1 mg/kg, subcutaneously) in mice. The investigators also assessed CB1R occupancy in the brain to ensure target engagement of MK-7128, and showed that MK-7128 significantly improved both Y-maze spontaneous alternation and object habituation performance in scopolamine-treated mice and inhibits the binding of radioiodinated AM251 in murine cortex and hippocampus. These data indicate that MK-7128 improves cognitive performance in a model of cholinergic hypofunction and suggest that efficacy is achieved at relatively low levels of CB1R occupancy in the brain. Our results extend earlier findings suggesting a role of CB1Rs in the modulation of memory processes and a potential therapeutic application for CB1R inverse agonists in cognitive disorders.

Discovery of a piperazine urea based compound as a potent, selective, orally bioavailable melanocortin subtype-4 receptor partial agonist.

We report the discovery of piperazine urea based compound 1, a potent, selective, orally bioavailable melanocortin subtype-4 receptor partial agonist. Compound 1 shows anti-obesity efficacy without potentiating erectile activity in the rodent models.

Genome-wide expression profiling revealed peripheral effects of cannabinoid receptor 1 inverse agonists in improving insulin sensitivity and metabolic parameters.

Inhibition of cannabinoid receptor 1 (CB1) has shown efficacy in reducing body weight and improving metabolic parameters, with the effects correlating with target engagement in the brain. The peripheral effects of inhibiting the CB1 receptor has been appreciated through studies in diet-induced obese and liver-specific CB1 knockout mice. In this article, we systematically investigated gene expression changes in peripheral tissues of diet-induced obese mice treated with the CB1 inverse agonist AM251 [1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-(1-piperidyl)pyrazole-3-carboxamide]. CB1 receptor inhibition led to down-regulation of genes within the de novo fatty acid and cholesterol synthetic pathways, including sterol regulatory element binding proteins 1 and 2 and their downstream targets in both liver and adipose tissue. In addition, genes involved in fatty acid beta-oxidation were up-regulated with AM251 treatment, probably through the activation of peroxisome proliferator-activated receptor alpha (PPARalpha). In adipose tissue, CB1 receptor inhibition led to the down-regulation of genes in the tumor necrosis factor alpha signal transduction pathway and possibly to the activation of PPARgamma, both of which would result in improved insulin sensitivity.

Synthesis and cannabinoid-1 receptor binding affinity of conformationally constrained analogs of taranabant.

The design, synthesis, and binding activity of ring constrained analogs of the acyclic cannabinoid-1 receptor (CB1R) inverse agonist taranabant 1 are described. The initial inspiration for these taranabant derivatives was its conformation 1a, determined by (1)H NMR, X-ray, and molecular modeling. The constrained analogs were all much less potent than their acyclic parent structure. The results obtained are discussed in the context of a predicted binding of 1 to a homology model of CB1R.

Furo[2,3-b]pyridine-based cannabinoid-1 receptor inverse agonists: synthesis and biological evaluation. Part 1.

The synthesis, SAR and binding affinities of cannabinoid-1 receptor (CB1R) inverse agonists based on furo[2,3-b]pyridine scaffolds are described. Food intake, mechanism specific efficacy, pharmacokinetic, and metabolic evaluation of several of these compounds indicate that they are effective orally active modulators of CB1R.

Dihydro-pyrano[2,3-b]pyridines and tetrahydro-1,8-naphthyridines as CB1 receptor inverse agonists: synthesis, SAR and biological evaluation.

Synthesis and structure-activity relationships of cannabinoid-1 receptor (CB1R) inverse agonists based on dihydro-pyrano[2,3-b] pyridine and tetrahydro-1,8-naphtyridine scaffolds are presented. Rat food intake and pharmacokinetic evaluation of 13g, 13i, 13k and 17a revealed these compounds to be highly efficacious orally active modulators of CB1R.

Discovery of a spiroindane based compound as a potent, selective, orally bioavailable melanocortin subtype-4 receptor agonist.

We report the design, synthesis and properties of spiroindane based compound 1, a potent, selective, orally bioavailable, non-peptide melanocortin subtype-4 receptor agonist. Compound 1 shows excellent erectogenic activity in the rodent models.

Discovery of highly potent and efficacious MC4R agonists with spiroindane N-Me-1,2,4-triazole privileged structures for the treatment of obesity.

We report an SAR study of MC4R analogs containing spiroindane heterocyclic privileged structures. Compound 26 with N-Me-1,2,4-triazole moiety possesses exceptional potency at MC4R and potent anti-obesity efficacy in a mouse model. However, the efficacy is not completely mediated through MC4R. Additional SAR studies led to the discovery of compound 32, which is more potent at MC4R. Compound 32 demonstrates MC4R mediated anti-obesity efficacy in rodent models.

Optimization of privileged structures for selective and potent melanocortin subtype-4 receptor ligands.

Design, syntheses and structure-activity relationships of N-acetylated piperazine privileged structures containing MC4R agonist compounds were described. The most potent derivatives were low nM MC4R selective full agonists. Several compounds from the series had modest pharmacokinetic properties.

Spiroindane based amides as potent and selective MC4R agonists for the treatment of obesity.

We report a series of potent and selective MC4R agonists based on spiroindane amide privileged structures for potential treatments of obesity. Among the synthetic methods used, Method C allows rapid synthesis of the analogs. The series of compounds can afford high potency on MC4R as well as good rodent pharmacokinetic profiles. Compound 1r (MK-0489) demonstrates MC4R mediated reduction of food intake and body weight in mouse models. Compound 1r is efficacious in 14-day diet-induced obese (DIO) rat models.

Discovery of potent, selective, and orally bioavailable 3H-spiro[isobenzofuran-1,4'-piperidine] based melanocortin subtype-4 receptor agonists.

Design, synthesis, and SAR of a series of 3H-spiro[isobenzofuran-1,4'-piperidine] based compounds as potent, selective and orally bioavailable melanocortin subtype-4 receptor (MC4R) agonists are disclosed.

Synthesis and evaluation of N-[(1S,2S)-3-(4-chlorophenyl)-2-(3-cyanophenyl)-1-methylpropyl]-2-methyl-2-aminopropanamide as human cannabinoid-1 receptor (CB1R) inverse agonists.

Obesity is a chronic medical condition that is affecting large population throughout the world. CB1 as a target for treatment of obesity has been under intensive studies. Taranabant was discovered and then developed by Merck as the 1st generation CB1R inverse agonist. Reported here is part of our effort on the 2nd generation of CB1R inverse agonist from the acyclic amide scaffold. We replaced the oxygen linker in taranabant with nitrogen and prepared a series of amino heterocyclic analogs through a divergent synthesis. Although in general, the amine linker gave reduced binding affinity, potent and selective CB1R inverse agonist was identified from the amino heterocycle series. Molecular modeling was applied to study the binding of the amino heterocycle series at CB1 binding site. The in vitro metabolism of representative members was studied and only trace glucuronidation was found. Thus, it suggests that the right hand side of the molecule may not be the appropriate site for glucuronidation.

Pyridopyrimidine based cannabinoid-1 receptor inverse agonists: Synthesis and biological evaluation.

The synthesis, SAR and binding affinities are described for cannabinoid-1 receptor (CB1R) specific inverse agonists based on pyridopyrimidine and heterotricyclic scaffolds. Food intake and pharmacokinetic evaluation of several of these compounds indicate that they are effective orally active modulators of CB1R.

The triple uptake inhibitor (1R,5S)-(+)-1-(3,4-dichlorophenyl)-3-azabicyclo[3.1.0] hexane hydrochloride (DOV 21947) reduces body weight and plasma triglycerides in rodent models of diet-induced obesity.

Selective inhibitors of biogenic amine (e.g., serotonin, norepinephrine, and dopamine) uptake exhibit varying degrees of safety and efficacy as antiobesity agents. Moreover, preclinical findings suggest that the combined inhibition of monoamine neurotransmitter transporters synergistically enhances antiobesity activity. (1R,5S)-(+)-1-(3,4-Dichlorophenyl)-3-azabicyclo-[3.1.0] hexane hydrochloride (DOV 21947) inhibits norepinephrine, 5-hydroxytryptamine, and dopamine uptake, and it reduces body weight in rodent models of diet-induced obesity (DIO). DIO rats treated orally with DOV 21947 for 1 to 24 days showed significantly lower body weights than vehicle-treated DIO rats. The decrease in body weight resulted specifically from a loss of retroperitoneal and mesenteric depots of white adipose tissue. DOV 21947 also reduced daily food intake in DIO rats, but consumption returned to control levels after 11 days of treatment. With the exception of a decrease in triglyceride levels, blood chemistry was unaltered after 24 days of DOV 21947 treatments. DOV 21947 had no effect on motor activity. Although DOV 21947 increased respiratory rate and decreased the tidal volume of normal rats, it did not alter the minute volume. In addition, DOV 21947 did not significantly affect blood pressure, heart rate, electrocardiographic indices or body temperature in telemeterized dogs. However, it caused a sustained, but reversible reduction in the rate of body weight gain for as long as 6 months in normal rats, and for up to 1 year in normal dogs. In summary, DOV 21947 is effective in causing a sustained and selective reduction in fat content and triglyceride levels in animal models of obesity without significantly altering vital organ function.

Conformational analysis and receptor docking of N-[(1S,2S)-3-(4-chlorophenyl)-2-(3-cyanophenyl)-1-methylpropyl]-2-methyl-2-{[5-(trifluoromethyl)pyridin-2-yl]oxy}propanamide (taranabant, MK-0364), a novel, acyclic cannabinoid-1 receptor inverse agonist.

X-ray crystallographic, NMR spectroscopic, and computational studies of taranabant afforded similar low-energy conformers with a significant degree of rigidity along the C11-N13-C14-C16-C17 backbone but with more flexibility around bonds C8-C11 and C8-O7. Mutagenesis and docking studies suggested that taranabant and rimonabant shared the same general binding area of CB1R but with significant differences in detailed interactions. Similar to rimonabant, taranabant interacted with a cluster of aromatic residues (F(3.36)200, W(5.43)279, W(6.48)356, and Y(5.39)275) through the two phenyl rings and with F(2.57)170 and L(7.42)387 through the CF 3-Pyr ring. The notable distinction between taranabant and rimonabant was that taranabant was hydrogen-bonded with S(7.39)383 but not with K(3.28)192, while rimonabant was hydrogen-bonded with K(3.28)192 but not with S(7.39)383. The strong hydrogen bonding between the amide NH of taranabant and hydroxyl of S(7.39)383 was key to the superior affinity of taranabant to CB1R.

Cyclic analogs of alpha-melanocyte-stimulating hormone (alphaMSH) with high agonist potency and selectivity at human melanocortin receptor 1b.

Alpha-melanotropin (alphaMSH), Ac-Ser1-Tyr2-Ser3-Met4-Glu5-His6-Phe7-Arg8-Trp9-Gly10-Lys11-Pro12-Val13-NH2,(1) has been long recognized as an important physiological regulator of skin and hair pigmentation in mammals. Binding of this peptide to the melanocortin receptor 1 (MC1R) leads to activation of tyrosinase, the key enzyme of the melanin biosynthesis pathway. In this study, interactions of the human MC1bR (an isoform of the receptor 1a) with the synthetic cyclic analogs of alphaMSH were studied. These ligands were analogs of MTII, Ac-Nle4-cyclo-(Asp5-His6-D-Phe7-Arg8-Trp9-Lys10)-NH2, a potent pan-agonist at the human melanocortin receptors (hMC1,3-5R). In the structure of MTII, the His6-D-Phe7-Arg8-Trp9 segment has been recognized as "essential" for molecular recognition at the human melanocortin receptors (hMC1,3-5R). Herein, the role of the Trp9 in the ligand interactions with the hMC1b,3-5R has been reevaluated. Analogs with various amino acids in place of Trp9 were synthesized and tested in vitro in receptor affinity binding and cAMP functional assays at human melanocortin receptors 1b, 3, 4 and 5 (hMC1b,3-5R). Several of the new peptides were high potency agonists (partial) at hMC1bR (EC50 from 0.5 to 20 nM) and largely inactive at hMC3-5R. The bulky aromatic side chain in position 9, such as that in Trp, was found not to be essential to agonism (partial) of the studied peptides at hMC1bR.

GABAB receptors are required for galanin modulation of membrane properties of neurons in the arcuate nucleus of rats.

Galanin-mediated modulation of the arcuate nucleus (Arc) neurons is thought to be involved in the regulation of feeding behavior, hormone secretion, and reproduction. We previously reported that galanin perfusion significantly hyperpolarized the resting membrane potential and suppressed the spontaneous firing in the Arc neurons in slice preparation. In this study, we focused on the cellular and molecular mechanisms underlying the galanin effect. The galanin action is mediated by the galanin receptors (GAL1/2/3R). We found that activation of galanin receptors alone is not sufficient to mediate the galanin effect on resting membrane potential and spontaneous firing; co-activation of GABA(B) receptors is required for galanin to accomplish its modulation on the membrane properties of Arc neurons. In more details, the effect of galanin on the membrane properties of Arc neurons is blocked by either lowering the extracellular Ca(2+) or the inhibition of GABA(B) receptors with the selective GABA(B) antagonist, saclofen. In addition, activation of GABA(B) receptors by baclofen restored the galanin effect under low Ca (2+) conditions. These results suggest that GABA(B) receptors may serve as a molecular gate for galanin signaling, and thus can be targeted to manipulate the galanin-mediated physiological and behavioral responses.