ABT-450/r-ombitasvir and dasabuvir with ribavirin for hepatitis C with cirrhosis.

BACKGROUND: Interferon-containing regimens for the treatment of hepatitis C virus (HCV) infection are associated with increased toxic effects in patients who also have cirrhosis. We evaluated the interferon-free combination of the protease inhibitor ABT-450 with ritonavir (ABT-450/r), the NS5A inhibitor ombitasvir (ABT-267), the nonnucleoside polymerase inhibitor dasabuvir (ABT-333), and ribavirin in an open-label phase 3 trial involving previously untreated and previously treated adults with HCV genotype 1 infection and compensated cirrhosis. METHODS: We randomly assigned 380 patients with Child-Pugh class A cirrhosis to receive either 12 or 24 weeks of treatment with ABT-450/r-ombitasvir (at a once-daily dose of 150 mg of ABT-450, 100 mg of ritonavir, and 25 mg of ombitasvir), dasabuvir (250 mg twice daily), and ribavirin administered according to body weight. The primary efficacy end point was a sustained virologic response 12 weeks after the end of treatment. The rate of sustained virologic response in each group was compared with the estimated rate with a telaprevir-based regimen (47%; 95% confidence interval [CI], 41 to 54). A noninferiority margin of 10.5 percentage points established 43% as the noninferiority threshold; the superiority threshold was 54%. RESULTS: A total of 191 of 208 patients who received 12 weeks of treatment had a sustained virologic response at post-treatment week 12, for a rate of 91.8% (97.5% CI, 87.6 to 96.1). A total of 165 of 172 patients who received 24 weeks of treatment had a sustained virologic response at post-treatment week 12, for a rate of 95.9% (97.5% CI, 92.6 to 99.3). These rates were superior to the historical control rate. The three most common adverse events were fatigue (in 32.7% of patients in the 12-week group and 46.5% of patients in the 24-week group), headache (in 27.9% and 30.8%, respectively), and nausea (in 17.8% and 20.3%, respectively). The hemoglobin level was less than 10 g per deciliter in 7.2% and 11.0% of patients in the respective groups. Overall, 2.1% of patients discontinued treatment owing to adverse events. CONCLUSIONS: In this phase 3 trial of an oral, interferon-free regimen evaluated exclusively in patients with HCV genotype 1 infection and cirrhosis, multitargeted therapy with the use of three new antiviral agents and ribavirin resulted in high rates of sustained virologic response. Drug discontinuations due to adverse events were infrequent. (Funded by AbbVie; TURQUOISE-II ClinicalTrials.gov number, NCT01704755.).

Validation of diacyl glycerolacyltransferase I as a novel target for the treatment of obesity and dyslipidemia using a potent and selective small molecule inhibitor.

A highly potent and selective DGAT-1 inhibitor was identified and used in rodent models of obesity and postprandial chylomicron excursion to validate DGAT-1 inhibition as a novel approach for the treatment of metabolic diseases. Specifically, compound 4a conferred weight loss and a reduction in liver triglycerides when dosed chronically in DIO mice and depleted serum triglycerides following a lipid challenge in a dose-dependent manner, thus, reproducing major phenotypical characteristics of DGAT-1(-/-) mice.

Discovery of piperidine-aryl urea-based stearoyl-CoA desaturase 1 inhibitors.

A series of structurally novel stearoyl-CoA desaturase1 (SCD1) inhibitors has been identified via molecular scaffold manipulation. Preliminary structure-activity relationship (SAR) studies led to the discovery of potent, and orally bioavailable piperidine-aryl urea-based SCD1 inhibitors. 4-(2-Chlorophenoxy)-N-[3-(methyl carbamoyl)phenyl]piperidine-1-carboxamide 4c exhibited robust in vivo activity with dose-dependent desaturation index lowering effects.

Hepatic knockdown of stearoyl-CoA desaturase 1 via RNA interference in obese mice decreases lipid content and changes fatty acid composition.

Stearoyl-CoA desaturases (SCDs) catalyze the biosynthesis of monounsaturated fatty acids from saturated fatty acids. Four scd genes have been identified in mice and three in human (including one pseudogene). Among the four mouse SCD isoforms, SCD1 is predominantly expressed in liver and adipose tissue. Mice null for the scd1 gene have reduced adiposity, increased energy expenditure and altered lipid profiles. To further evaluate the specific role of hepatic SCD1 and the potential to achieve similar desirable phenotypic changes in adult obese mice, adenovirus-mediated short hairpin interfering RNA (shRNA) was used to acutely knock down hepatic scd1 expression in ob/ob mice. Robust reductions in hepatic SCD1 mRNA and SCD1 enzymatic activity were achieved, sustained up to 2 weeks. Reduced hepatic content of neutral lipids and robust lowering of lipid desaturation indexes, but increased content of liver phosphotidylcholine were observed with SCD1 knockdown. Increased total plasma cholesterol levels were also observed. No significant changes in body weight were observed. Expression levels of several lipogenic and lipid oxidation genes were not significantly altered by short term SCD1 reduction, but UCP2 expression was increased. Our results demonstrate that significant changes to both hepatic and systemic lipid profiles can be achieved through specific knockdown of liver-expressed SCD1 in the ob/ob mouse model. However, hepatic SCD1 knockdown does not result in significant changes in body weight in the short term.

Discovery of potent, selective, orally bioavailable stearoyl-CoA desaturase 1 inhibitors.

Stearoyl-CoA desaturase 1 (SCD1) catalyzes the committed step in the biosynthesis of monounsaturated fatty acids from saturated, long-chain fatty acids. Studies with SCD1 knockout mice have established that these animals are lean and protected from leptin deficiency-induced and diet-induced obesity, with greater whole body insulin sensitivity than wild-type animals. In this work, we have discovered a series of potent, selective, orally bioavailable SCD1 inhibitors based on a known pyridazine carboxamide template. The representative lead inhibitor 28c also demonstrates excellent cellular activity in blocking the conversion of saturated long-chain fatty acid-CoAs (LCFA-CoAs) to monounsaturated LCFA-CoAs in HepG2 cells.

Characterization of a neuronal cell line expressing native human melanin-concentrating hormone receptor 1 (MCHR1).

Melanin-concentrating hormone (MCH), an orexigenic neuropeptide in mammals, activates a G-protein coupled receptor, MCHR1. It is expected that antagonists of MCHR1 function will prove therapeutically useful as anti-obesity agents. Intracellular signaling by MCHR1 has been investigated primarily using non-neural cell lines expressing the recombinant receptor, in which MCHR1 has been shown to couple to G alpha(i/o) and G alpha(q) G-proteins. While these cell lines have been widely utilized to discover and optimize small molecule antagonists, it is unknown whether the intracellular signaling pathways in these cells accurately reflect those in neurons. Thus, we sought to develop a neurally derived cell line endogenously expressing MCHR1. IMR32, a human neuroblastoma cell line, has been shown to express MCHR1 mRNA; however, we were unable to detect either MCH-binding or MCH-stimulated Ca++-mobilization in these cells. Following transfection of IMR32 cells with a plasmid encoding human G alpha(16) G-protein, we isolated a cell line, I3.4.2, which responded to MCH in Ca++-mobilization assays. We found that the expression level of MCHR1 mRNA in I3.4.2 cells was 2000-fold higher than in the parent cell line. Using [125I]MCH saturation-binding to I3.4.2 cell membranes, we estimated the Bmax as 0.72 pmol/mg protein and the Kd as 0.35 nM. We report that Ca++-mobilization in I3.4.2 cells was insensitive to pertussis toxin (Ptx) treatment, indicating that signaling was via G alpha(q) G-proteins. Furthermore, negative results in cAMP accumulation assays confirmed the lack of signaling via the G alpha(i/o) G-proteins. Our results suggest that the I3.4.2 cell line may be useful for characterization of MCHR1 activity in a neural-derived cell line.

Characterization of ghrelin receptor activity in a rat pituitary cell line RC-4B/C.

Ghrelin, a 28 amino acid, octanoylated peptide, is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). In addition to various endocrine functions, including stimulation of GH release, ghrelin has been characterized as an important regulator of energy homeostasis. Ghrelin administration has been shown to increase adiposity in rodents and stimulate food intake in humans. Studies suggest that these orexigenic effects are mediated primarily through GHS-R expression in hypothalamic and pituitary neuronal pathways. In this context, GHS-R has been recognized as a potential target for the treatment of GH deficiency and body weight disorders. Cell lines provide convenient in vitro systems to identify and characterize potential pharmacophores and to analyze GHS-R functional activity. While recombinant cell lines that overexpress GHS-R have served as effective research tools for these studies, such cell lines may differ in signaling response to ghrelin compared with hypothalamic or pituitary cells expressing GHS-R. We show here that a cell line derived from a rat anterior pituitary adenoma, RC-4B/C, expresses endogenous GHS-R as judged by reverse transcriptase-PCR. In a Ca(2+)mobilization assay, RC-4B/C cells demonstrate a dose-dependent increase in intracellular [Ca(2+)] on stimulation with rat ghrelin and a related peptide agonist, hexarelin (EC(50), 1.0 nM and 1.7 nM respectively), but are unresponsive to treatment with inactive des-octanoyl rat ghrelin. A subclone, RC-4B/C.40, with a more robust and stable ghrelin response, was isolated from the parental population of cells to allow further analysis of GHS-R signal transduction. Using pertussis toxin and the phospholipase C inhibitor U-73122, we show that ghrelin signals through the Gq pathway in the RC-4B/C.40 cells. We also demonstrate that the ghrelin-induced rise of intracellular [Ca(2+)] in RC-4B/C.40 cells involves initial Ca(2+)release from intracellular stores followed by a sustained elevation that occurs via influx of extracellular Ca(2+) through ion channels. In addition, unlike observations reported in recombinant cell systems, the RC-4B/C.40 cells do not exhibit a high level of GHS-R constitutive activity as determined in a phosphatidylinositol hydrolysis assay. Overall, the data presented here suggest that the RC-4B/C parental and RC-4B/C.40 cells provide novel in vitro systems for the characterization of GHS-R pharmacophores and ghrelin signaling.

Discovery and pharmacological evaluation of growth hormone secretagogue receptor antagonists.

The discovery and pharmacological evaluation of potent, selective, and orally bioavailable growth hormone secretagogue receptor (GHS-R) antagonists are reported. Previously, 2,4-diaminopyrimidine-based GHS-R antagonists reported from our laboratories have been shown to be dihydrofolate reductase (DHFR) inhibitors. By comparing the X-ray crystal structure of DHFR docked with our GHS-R antagonists and GHS-R modeling, we designed and synthesized a series of potent and DHFR selective GHS-R antagonists with good pharmacokinetic (PK) profiles. An amide derivative 13d (Ca2+ flux IC50 = 188 nM, [brain]/[plasma] = 0.97 @ 8 h in rat) showed a 10% decrease in 24 h food intake in rats, and over 5% body weight reduction after 14-day oral treatment in diet-induced obese (DIO) mice. In comparison, a urea derivative 14c (Ca2+ flux IC50 = 7 nM, [brain]/[plasma] = 0.0 in DIO) failed to show significant effect on food intake in the acute feeding DIO model. These observations demonstrated for the first time that peripheral GHS-R blockage with small molecule GHS-R antagonists might not be sufficient for suppressing appetite and inducing body weight reduction.

Screening for cardiovascular safety: a structure-activity approach for guiding lead selection of melanin concentrating hormone receptor 1 antagonists.

An inactin-anesthetized rat cardiovascular (CV) assay was employed in a screening mode to triage multiple classes of melanin-concentrating hormone receptor 1 (MCHr1) antagonists. Lead identification was based on a compound profile producing high drug concentration in both plasma (>40 microM) and brain (>20 microg/g) with <15% change in cardiovascular endpoints. As a result of these stringent requirements, lead optimization activities on multiple classes of MCHr1 antagonists were terminated. After providing evidence that the cardiovascular liabilities were not a function of MCHr1 antagonism, continued screening identified the chromone-substituted aminopiperidine amides as a class of MCHr1 antagonists that demonstrated a safe cardiovascular profile at high drug concentrations in both plasma and brain. The high incidence of adverse cardiovascular effects associated with an array of MCHr1 antagonists of significant chemical diversity, combined with the stringent safety requirements for antiobesity drugs, highlight the importance of incorporating cardiovascular safety assessment early in the lead selection process.

2,4-diaminopyrimidine derivatives as potent growth hormone secretagogue receptor antagonists.

Ghrelin, a gut-derived orexigenic hormone, is an endogenous ligand of the growth hormone secretagogue receptor (GHS-R). Centrally administered ghrelin has been shown to cause hunger and increase food intake in rodents. Inhibition of ghrelin actions with ghrelin antibody, peptidyl GHS-R antagonists, and antisense oligonucleosides resulted in weight loss and food intake decrease in rodents. Here we report the effects of GHS-R antagonists, some of which were potent, selective, and orally bioavailable. A structure-activity relationship study led to the discovery of 8a, which was effective in decreasing food intake and body weight in several acute rat studies.

Optimization of chromone-2-carboxamide melanin concentrating hormone receptor 1 antagonists: assessment of potency, efficacy, and cardiovascular safety.

Evaluation of multiple structurally distinct series of melanin concentrating hormone receptor 1 antagonists in an anesthetized rat cardiovascualar assay led to the identification of a chromone-2-carboxamide series as having excellent safety against the chosen cardiovascular endpoints at high drug concentrations in the plasma and brain. Optimization of this series led to considerable improvements in affinity, functional potency, and pharmacokinetic profile. This led to the identification of a 7-fluorochromone-2-carboxamide (22) that was orally efficacious in a diet-induced obese mouse model, retained a favorable cardiovascular profile in rat, and demonstrated dramatic improvement in effects on mean arterial pressure in our dog cardiovascular model compared to other series reported by our group. However, this analogue also led to prolongation of the QT interval in the dog that was linked to affinity for hERG channel and unexpectedly potent functional blockade of this ion channel.

Lack of efficacy of melanin-concentrating hormone-1 receptor antagonists in models of depression and anxiety.

The aim of this study was to validate melanin-concentrating hormone (MCH)-1 receptor antagonism as a potential treatment of mood disorders. We attempted to replicate the effects previously reported with SNAP-7941 and expanded the investigation to three other orally bioavailable MCH-1 receptor antagonists with good brain penetration. SNAP-7941 (3-30 mg/kg, i.p.) and T-226296 (5-60 mg/kg, p.o.) (+/- racemate), were evaluated in the rat forced swim and mouse tail suspension tests. (+)SNAP-7941 (3-10 mg/kg, p.o.) was also tested in a modified 5-min rat forced swim protocol as previously reported. A-665798 (3-30 mg/kg, p.o.) and A-777903 (3-30 mg/kg, p.o.) were tested in mouse tail suspension and rat Vogel tests. None of the compounds showed meaningful efficacy in the paradigms tested. The lack of efficacy with four structurally different MCH-1 receptor antagonists does not support a role for therapeutic treatment of depression/anxiety via this mechanism of action.

Identification of 2-(4-benzyloxyphenyl)-N- [1-(2-pyrrolidin-1-yl-ethyl)-1H-indazol-6-yl]acetamide, an orally efficacious melanin-concentrating hormone receptor 1 antagonist for the treatment of obesity.

Optimization of a high-throughput screening hit against melanin-concentrating hormone receptor 1 (MCHr1) led to the discovery of 2-(4-benzyloxy-phenyl)-N-[1-(2-pyrrolidin-1-yl-ethyl)-1H-indazol-6-yl]acetamide (7a). This compound was found to be a high-affinity ligand for MCHr1 and a potent inhibitor of MCH-mediated Ca(2+) release, showed good plasma and CNS exposure upon oral dosing in diet-induced obese mice, and is the first reported MCHr1 antagonist that is efficacious upon oral dosing in a chronic model of weight loss.

Discovery and characterization of aminopiperidinecoumarin melanin concentrating hormone receptor 1 antagonists.

4-(1-Benzo[1,3]dioxol-5-ylmethylpiperidine-4-ylmethyl)-6-chlorochromen-2-one (7) is a potent, orally bioavailable melanin concentrating hormone receptor 1 (MCHr1) antagonist that causes dose-dependent weight loss in diet-induced obese mice. Further evaluation of 7 in an anesthetized dog model of cardiovascular safety revealed adverse hemodynamic effects at a plasma concentration comparable to the minimally effective therapeutic concentration. These results highlight the need for scrutiny of the cardiovascular safety profile of MCHr1 antagonists.

Discovery of tetralin carboxamide growth hormone secretagogue receptor antagonists via scaffold manipulation.

A case study of rational design of an efficient, specific, and proprietary molecular scaffold based on the structure-activity relationship (SAR) information on a screening hit is described. Potent, selective, and orally bioavailable tetralin carboxamide growth hormone secretagogue receptor (GHS-R) antagonists were discovered. Union of rational design and high throughput synthesis provided a quick access to high quality chemical leads.

Prospects for obesity treatment: MCH receptor antagonists.

The convergence of the orphan G protein-coupled receptor SLC-1 with its orexigenic neuropeptide ligand melanin-concentrating hormone (MCH) in 1999 stimulated considerable research activity aimed at characterizing the role of this receptor system in the regulation of body weight. A solid body of genetic and pharmacological evidence now supports a role for MCH in the modulation of food intake and energy expenditure. High-throughput screening efforts have led to the identification of small molecule MCH receptor antagonists with diverse structural features and drug-like properties. In vivo results with two of these antagonists indicate efficacy in several animal models of body weight regulation and feeding behavior. Based on these preclinical findings, it is likely that reports from clinical studies of MCH antagonists will soon be forthcoming.

Cloning and characterization of the glucagon receptor from cynomologous monkey.

The glucagon receptor was cloned from cynolomologous monkey. A frame-shift mutation at the 3' end of the monkey transcript results in a C-terminal extension of 14 amino acids. This extension is not observed in either the human or rodent glucagon receptors. Monkey glucagon receptor was expressed in CHO cells, either with (mkGCGR) or without (mkGCGRDelta14) the 14-amino acid C-terminal extension to approximate the human receptor. Both forms of the monkey receptor bound glucagon with similar affinity and showed glucagon-stimulated cAMP production, however the full-length form of the monkey receptor (mkGCGR) was less sensitive to glucagon in its ability to stimulate cAMP than the shortened form (mkGCGRDelta14). PCR of genomic DNA from baboon and rhesus monkeys suggests that they express a form of the receptor similar to that of cynomologous monkey, while in chimpanzee, the receptor is similar to the human form.

Identification and preliminary characterization of a potent, safe, and orally efficacious inhibitor of acyl-CoA:diacylglycerol acyltransferase 1.

A high-throughput screen against human DGAT-1 led to the identification of a core structure that was subsequently optimized to afford the potent, selective, and orally bioavailable compound 14. Oral administration at doses ≥0.03 mg/kg significantly reduced postprandial triglycerides in mice following an oral lipid challenge. Further assessment in both acute and chronic safety pharmacology and toxicology studies demonstrated a clean profile up to high plasma levels, thus culminating in the nomination of 14 as clinical candidate ABT-046.

In vivo efficacy of acyl CoA: diacylglycerol acyltransferase (DGAT) 1 inhibition in rodent models of postprandial hyperlipidemia.

Postprandial serum triglyceride concentrations have recently been identified as a major, independent risk factor for future cardiovascular events. As a result, postprandial hyperlipidemia has emerged as a potential therapeutic target. The purpose of this study was two-fold. Firstly, to describe and characterize a standardized model of postprandial hyperlipidemia in multiple rodent species; and secondly, apply these rodent models to the evaluation of a novel class of pharmacologic agent; acyl CoA:diacylglycerol acyltransferase (DGAT) 1 inhibitors. Serum triglycerides were measured before and for 4h after oral administration of a standardized volume of corn oil, to fasted C57BL/6, ob/ob, apoE(-/-) and CD-1 mice; Sprague-Dawley and JCR/LA-cp rats; and normolipidemic and hyperlipidemic hamsters. Intragastric administration of corn oil increased serum triglycerides in all animals evaluated, however the magnitude and time-course of the postprandial triglyceride excursion varied. The potent and selective DGAT-1 inhibitor A-922500 (0.03, 0.3 and 3 mg/kg, p.o.), dose-dependently attenuated the maximal postprandial rise in serum triglyceride concentrations in all species tested. At the highest dose of DGAT-1 inhibitor, the postprandial triglyceride response was abolished. This study provides a comprehensive characterization of the time-course of postprandial hyperlipidemia in rodents. In addition, the ability of DGAT-1 inhibitors to attenuate postprandial hyperlipidemia in multiple rodent models, including those that feature insulin resistance, is documented. Exaggerated postprandial hyperlipidemia is inherent to insulin-resistant states in humans and contributes to the substantially elevated cardiovascular risk observed in these patients. Therefore, by attenuating postprandial hyperlipidemia, DGAT-1 inhibition may represent a novel therapeutic approach to reduce cardiovascular risk.

Discovery of 1-(4-phenoxypiperidin-1-yl)-2-arylaminoethanone stearoyl-CoA desaturase 1 inhibitors.

A series of novel stearoyl-CoA desaturase 1 (SCD1) inhibitors were identified by scaffold design based on known SCD1 inhibitors. Large structural changes were made leading to multiple analogs with comparable or improved potency. This approach is valuable for generation of proprietary compounds without conducting a costly high-throughput screening.