Non-basic azolotriazinone MCHR1 antagonists for the treatment of obesity: An empirical brain-exposures-driven candidate selection for in vivo efficacy studies.

Non-basic azolotriazinones were explored using an empirical free brain exposures-driven approach to identify potent MCHR1 antagonists for evaluation in in vivo efficacy studies. An optimized lead from this series, 1j (rMCHR1 Ki=1.8 nM), demonstrated a 6.9% reduction in weight gain relative to vehicle in a rat model at 30 mg/kg after 4 days of once-daily oral treatment as a glycine prodrug. Despite a promising efficacy profile, an assessment of the biliary toxicity risk of this compound rendered this compound non-progressible.

Dihydropyrrolopyrazol-6-one MCHR1 antagonists for the treatment of obesity: Insights on in vivo efficacy from a novel FLIPR assay setup.

Our investigation of the structure-activity and structure-liability relationships for dihydropyrrolopyrazol-6-one MCHR1 antagonists revealed that off-rate characteristics, inferred from potencies in a FLIPR assay following a 2 h incubation, can impact in vivo efficacy. The in vitro and exposure profiles of dihydropyrrolopyrazol-6-ones 1b and 1e were comparable to that of the thienopyrimidinone counterparts 41 and 43 except for a much faster MCHR1 apparent off-rate. The greatly diminished dihydropyrrolopyrazol-6-one anti-obesity response may be the consequence of this rapid off-rate.

Synthesis and SAR of 2,3,3a,4-tetrahydro-1H-pyrrolo[3,4-c]isoquinolin-5(9bH)-ones as 5-HT2C receptor agonists.

A series of 2,3,3a,4-tetrahydro-1H-pyrrolo[3,4-c]isoquinolin-5(9bH)-ones is described, several examples of which exhibit potent 5-HT(2C) agonism with excellent selectivity over the closely related 5-HT(2A) and 5-HT(2B) receptors. Compounds such as 38 and 44 were shown to be effective in reducing food intake in an acute rat feeding model.

Synthesis and SAR of potent and selective tetrahydropyrazinoisoquinolinone 5-HT(2C) receptor agonists.

The 5-HT2C receptor has been implicated as a critical regulator of appetite. Small molecule activation of the 5-HT2C receptor has been shown to affect food intake and regulate body weight gain in rodent models and more recently in human clinical trials. Therefore, 5-HT2C is a well validated target for anti-obesity therapy. The synthesis and structure-activity relationships of a series of novel tetrahydropyrazinoisoquinolinone 5-HT2C receptor agonists are presented. Several members of this series were identified as potent 5-HT2C receptor agonists with high functional selectivity against the 5-HT2A and 5-HT2B receptors and reduced food intake in an acute rat feeding model upon oral dosing.

Characterization of a novel and selective CB1 antagonist as a radioligand for receptor occupancy studies.

Obesity remains a significant public health issue leading to Type II diabetes and cardiovascular disease. CB1 antagonists have been shown to suppress appetite and reduce body weight in animal models as well as in humans. Evaluation of pre-clinical CB1 antagonists to establish relationships between in vitro affinity and in vivo efficacy parameters are enhanced by ex vivo receptor occupancy data. Synthesis and biological evaluation of a novel and highly selective radiolabeled CB1 antagonist is described. The radioligand was used to conduct ex vivo receptor occupancy studies.

Tricyclic dihydroquinazolinones as novel 5-HT2C selective and orally efficacious anti-obesity agents.

Agonists of the 5-HT(2C) receptor have been shown to suppress appetite and reduce body weight in animal models as well as in humans. However, agonism of the related 5-HT(2B) receptor has been associated with valvular heart disease. Synthesis and biological evaluation of a series of novel and highly selective dihydroquinazolinone-derived 5-HT(2C) agonists with no detectable agonism of the 5-HT(2B) receptor is described. Among these, compounds (+)-2a and (+)-3c were identified as potent and highly selective agonists which exhibited weight loss in a rat model upon oral dosing.

Discovery of (R)-9-ethyl-1,3,4,10b-tetrahydro-7-trifluoromethylpyrazino[2,1-a]isoindol- 6(2H)-one, a selective, orally active agonist of the 5-HT(2C) receptor.

Robust pharmaceutical treatment of obesity has been limited by the undesirable side-effect profile of currently marketed therapies. This paper describes the synthesis and optimization of a new class of pyrazinoisoindolone-containing, selective 5-HT2C agonists as antiobesity agents. Key to optimization of the pyrazinoisoindolone core was the identification of the appropriate substitution pattern and functional groups which led to the discovery of (R)-9-ethyl-1,3,4,10b-tetrahydro-7-trifluoromethylpyrazino[2,1-a]isoindol-6(2H)-one (58), a 5-HT2C agonist with >300-fold functional selectivity over 5-HT2B and >70-fold functional selectivity over 5-HT2A. Oral dosing of 58 reduced food intake in an acute rat feeding model, which could be completely reversed by a selective 5-HT2C antagonist and caused a reduction in body weight gain in a 4-day rat model.

Synthesis and Antiobesity Properties of 6-(4-Chlorophenyl)-3-(4-((3,3-difluoro-1-hydroxycyclobutyl)methoxy)-3-methoxyphenyl)thieno[3,2-d]pyrimidin-4(3H)-one (BMS-814580): A Highly Efficacious Melanin Concentrating Hormone Receptor 1 (MCHR1) Inhibitor.

The potent MCHR1 in vitro and in vivo antagonist activity of a series of cyclic tertiary alcohols derived from compound 2b is described. Subsequent pharmacokinetic and pharmacodynamic studies identified BMS-814580 (compound 10) as a highly efficacious antiobesity agent with a relatively clean in vitro and in vivo safety profile.

Disconnection between the early onset anorectic effects by C75 and hypothalamic fatty acid synthase inhibition in rodents.

In order to explore the relationship between the anorectic effect of 3-carboxy-4-octyl-2-methylenebutyrolactone (C75) and its pharmacokinetic properties, studies of in vivo and in vitro pharmacological characterization of C75 were performed in Fischer rats. In a quantitative measurement of food intake, we determined that appetite suppression by C75 takes place within 4 h. The C(max) for C75 of 2.6+/-1.5 microM was reached within 1-4 h after intraperitoneal administration at 30 mg/kg, a drug level that causes complete blockade of food intake. However, this concentration is substantially lower than the effective concentration used to inhibit rat fatty acid synthase enzyme activity in vitro (IC50: approximately 200 microM) and hypothalamic enzyme activity was found not to be inhibited by intraperitoneal administration of C75 at 30 mg/kg. Instead, a dramatic induction of c-Fos expression was found in area postrema. Collectively, these data indicate that the anorectic effect of C75 is independent of its inhibition of fatty acid synthase in the hypothalamus.

Monoamine reuptake site occupancy of sibutramine: Relationship to antidepressant-like and thermogenic effects in rats.

Sibutramine was formerly marketed as an anti-obesity agent. The current study investigated the relationships between monoamine reuptake site occupancy for sibutramine and both its antidepressant-like efficacy and thermogenic effects. Sibutramine's effects on locomotor activity (LMA) and food intake were also evaluated. Sibutramine occupied monoamine reuptake binding sites with the rank order of potency of NET>SERT>DAT; at 10mg/kg, po, occupancy was 95% NET, 81% SERT and 73% DAT. Sibutramine produced antidepressant-like behavior in the forced swim test; at the lowest effective dose (3mg/kg, po) occupancy was 61%, 90% and 23% at SERT, NET and DAT sites, respectively. Sibutramine also increased body core temperature in a dose- and time-dependent manner; at the lowest effective dose (30mg/kg) SERT, NET and DAT occupancies were respectively 78%, 86% and 59%. A significant decrease in food consumption was observed at 3 and 10mg/kg, po. LMA was increased at ≥10mg/kg, sc. The relationship between efficacy in the FST and occupancy was also determined for citalopram, fluoxetine and reboxetine. Similarly, the relationship between thermogenesis and target occupancy for several single or double/triple reuptake inhibitors was measured and showed that >40-50% DAT binding was required for thermogenesis. Thermogenesis was blocked by the D1 antagonist SCH39166 (3mg/kg, sc). Our findings indicate that the antidepressant-like effect of sibutramine may result from additive or synergistic actions on the three reuptake binding targets. At higher doses, sibutramine produces thermogenesis; DAT inhibition and activation of dopamine D1 receptors are required for this effect.

Identification of a nonbasic melanin hormone receptor 1 antagonist as an antiobesity clinical candidate.

Identification of MCHR1 antagonists with a preclinical safety profile to support clinical evaluation as antiobesity agents has been a challenge. Our finding that a basic moiety is not required for MCHR1 antagonists to achieve high affinity allowed us to explore structures less prone to off-target activities such as hERG inhibition. We report the SAR evolution of hydroxylated thienopyrimidinone ethers culminating in the identification of 27 (BMS-819881), which entered obesity clinical trials as the phosphate ester prodrug 35 (BMS-830216).

Reductions in log P improved protein binding and clearance predictions enabling the prospective design of cannabinoid receptor (CB1) antagonists with desired pharmacokinetic properties.

Several strategies have been employed to reduce the long in vivo half-life of our lead CB1 antagonist, triazolopyridazinone 3, to differentiate the pharmacokinetic profile versus the lead clinical compounds. An in vitro and in vivo clearance data set revealed a lack of correlation; however, when compounds with <5% free fraction were excluded, a more predictable correlation was observed. Compounds with log P between 3 and 4 were likely to have significant free fraction, so we designed compounds in this range to give more predictable clearance values. This strategy produced compounds with desirable in vivo half-lives, ultimately leading to the discovery of compound 46. The progression of compound 46 was halted due to the contemporaneous marketing and clinical withdrawal of other centrally acting CB1 antagonists; however, the design strategy successfully delivered a potent CB1 antagonist with the desired pharmacokinetic properties and a clean off-target profile.