We have discovered a novel class of endothelin (ET) receptor antagonists through pharmacophore analysis of the existing non-peptide ET antagonists. On the basis of this analysis, we determined that a pyrrolidine ring might replace the indian ring in SB 209670. The resultant compounds were readily prepared and amenable to extensive SAR studies. Thus a series of N-substituted trans,trans-2-(4-methoxyphenyl)-4-(1,3-benzodioxol-5-yl)pyrroli din e-3- carboxylic acids (8) have been synthesized and evaluated for binding at ET(A) and ET(B) receptors. Compounds with N-acyl and simple N-alkyl substituents had weak activity. Compounds with N-alkyl substituents containing ethers, sulfoxides, or sulfones showed increased activity. Much improved activity resulted from compounds where the N-substituents were acetamides. Compound 17u (A-127722) with the N,N-dibutylacetamide substituent is the best of the series. It has an IC(50)=0.36 nM for inhibition of ET-1 radioligand binding at the ET(A) receptor, with a 1000-fold selectivity for the ET(A) vs the ET(B) receptor. It is also a potent inhibitor (IC(50)=0.16 nM) of phosphoinositol hydrolysis stimulated by ET-1, and it antagonized the ET-1-induced contraction of the rabbit aorta with a pA(2)=9.20. The compound has 70% oral bioavailability in rats.

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.

A-837093 is a potent and specific nonnucleoside inhibitor of the hepatitis C virus (HCV) nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase. It possesses nanomolar potencies in both enzymatic and replicon-based cell culture assays. In rats and dogs this compound demonstrated an oral plasma half-life of greater than 7 h, and its bioavailability was >60%. In monkeys it had a half-life of 1.9 h and 15% bioavailability. Its antiviral efficacy was evaluated in two chimpanzees infected with HCV in a proof-of-concept study. The design included oral dosing of 30 mg per kg of body weight twice a day for 14 days, followed by a 14-day posttreatment observation. Maximum viral load reductions of 1.4 and 2.5 log 10 copies RNA/ml for genotype 1a-and 1b-infected chimpanzees, respectively, were observed within 2 days after the initiation of treatment. After this initial drop in the viral load, a rebound of plasma HCV RNA was observed in the genotype 1b-infected chimpanzee, while the genotype 1a-infected chimpanzee experienced a partial rebound that lasted throughout the treatment period. Clonal analysis of NS5B gene sequences derived from the plasma of A-837093-treated chimpanzees revealed the presence of several mutations associated with resistance to A-837093, including Y448H, G554D, and D559G in the genotype 1a-infected chimpanzee and C316Y and G554D in the genotype 1b-infected chimpanzee. The identification of resistance-associated mutations in both chimpanzees is consistent with the findings of in vitro selection studies, in which many of the same mutations were selected. These findings validate the antiviral efficacy and resistance development of benzothiadiazine HCV polymerase inhibitors in vivo.Hepatitis C virus (HCV) is a small, enveloped virus that contains a single-stranded, positive-sense RNA (2). The World Health Organization estimates that approximately 170 million people worldwide are infected with HCV (25). Of these, 130 million are chronic HCV carriers at risk for the development of liver cirrhosis and/or liver cancer. In the United States, HCV infection leading to liver failure is the major indication for liver transplantation (4, 12). The current standard of care, which consists of a combination of pegylated interferon and ribavirin, provides good clinical efficacy for patients infected with genotype 2 and 3 viruses but is less effective for patients infected with genotype 1 viruses. Subgenotypes 1a and 1b constitute the most commonly found isolates in the United States, Japan, and Western Europe; and thus, the development of effective treatments against genotype 1 viruses presents a pressing need.HCV nonstructural protein 5B (NS5B) encodes a viral RNA-dependent RNA polymerase, an essential enzyme responsible for the replication of the viral genome. NS5B shares very limited sequence homology with cellular polymerases; hence, it is an attractive target for the development of antiviral therapy. Several classes of inhibitors, including nucleosides, nonnucleosides, and pyrophosphate mimics, that target t...

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.

The benzodioxole ((methylenedioxy)benzene) group is present in a number of endothelin (ET) receptor antagonists thus far reported. As part of our own endothelin antagonist program we have developed (2R*,3R*,4S*)-1-(N,N-dibutylacetamido)-4-(1,3-benzodioxol-5- yl)-2-(4-methoxyphenyl)pyrrolidine-3-carboxylic acid (A-127722). This is a potent antagonist, binding to the ETA and ETB receptor subtypes with affinities (IC50) of 0.4 and 520 nM, respectively, and also contains the aforementioned benzodioxole. While this compound was seemingly optimized at its N-terminus, no effort had been directed toward understanding the contributions to binding affinity or receptor subtype selectivity conferred by the benzodioxole. Substitution by 1- or 2-naphthyl yielded weak antagonists. Oxygenated benzenes, such as p-anisyl, were potent compounds with IC50s in the low-nanomolar range. Simple deletion of either of the two oxygen atoms (dihydrobenzofurans) yielded extremely potent agents, possessing subnanomolar affinity for the ETA receptor. Additionally, the compounds showed enhanced selectivity, binding to the ETB receptor subtype in the micromolar range. This paper describes the development of this novel class of compounds.