No abstract

HCV NS3/4a protease inhibitors are proven therapeutic agents against chronic hepatitis C virus infection, with boceprevir and telaprevir having recently received regulatory approval as add-on therapy to pegylated interferon/ribavirin for patients harboring genotype 1 infections. Overcoming antiviral resistance, broad genotype coverage, and a convenient dosing regimen are important attributes for future agents to be used in combinations without interferon. In this communication, we report the preclinical profile of MK-5172, a novel P2-P4 quinoxaline macrocyclic NS3/4a protease inhibitor currently in clinical development. The compound demonstrates subnanomolar activity against a broad enzyme panel encompassing major hepatitis C virus (HCV) genotypes as well as variants resistant to earlier protease inhibitors. In replicon selections, MK-5172 exerted high selective pressure, which yielded few resistant colonies. In both rat and dog, MK-5172 demonstrates good plasma and liver exposures, with 24-h liver levels suggestive of once-daily dosing. When administered to HCV-infected chimpanzees harboring chronic gt1a or gt1b infections, MK-5172 suppressed viral load between 4 to 5 logs at a dose of 1 mg/kg of body weight twice daily (b.i.d.) for 7 days. Based on its preclinical profile, MK-5172 is anticipated to be broadly active against multiple HCV genotypes and clinically important resistance variants and highly suited for incorporation into newer all-oral regimens.C hronic hepatitis C virus (HCV) infection afflicts more than 170 million people worldwide and is the major etiological cause of fibrosis, liver cirrhosis, and hepatocellular carcinoma (20,53). Current treatment relies on a backbone of interferon and ribavirin, a regimen with poor tolerability and toxicity (31, 34). Efforts to develop novel therapies to improve treatment have focused largely on direct acting antiviral agents (DAAs) (19), which therapeutically intervene with virally encoded components essential for HCV replication.Hepatitis C virus, a member of the Flaviviridae family of viruses in the Hepacivirus genus, is encoded by a 9.6-kb positivestrand RNA genome (8). It is initially translated into a single polypeptide that is subsequently cleaved into individual protein components by a combination of both host-and virally encoded proteases (2, 38). HCV protease inhibitors currently in clinical development span a variety of structural classes. The most advanced of these are keto amide compounds, which covalently bind to the active-site serine of the protease in a slowly reversible manner. Boceprevir (29) and telaprevir (37), both from this class, recently received regulatory approval as add-on therapy to pegylated interferon/ribavirin in the treatment of genotype 1-infected patients. A number of rapidly reversible NS3/4a protease inhibitors, including the P1-P3 constrained macrocyclic inhibitors TMC 435 (23) and danoprevir (45), the P2-P4 constrained macrocyclic inhibitor vaniprevir (33), the linear inhibitors BI 201335 (52), BMS650032 (47), and ABT-450 ...

Novel potent and selective diarylimidazole inhibitors of p38 MAP (mitogen-activated protein) kinase are described which have activity in both cell-based assays of tumor necrosis factor-alpha (TNF-alpha) release and an animal model of rheumatoid arthritis. The SAR leading to the development of selectivity against c-Raf and JNK2alpha1 kinases is presented, with key features being substitution of the 4-aryl ring with m-trifluoromethyl and substitution of the 5-heteroaryl ring with a 2-amino substituent. Cell-based activity was significantly enhanced by incorporation of a 4-piperidinyl moiety at the 2-position of the imidazole which also enhanced aqueous solubility. In general, oral bioavailability of this class of compounds was found to be poor unless the imidazole was methylated on nitrogen. This work led to identification of 48, a potent (p38 MAP kinase inhibition IC50 0.24 nM) and selective p38 MAP kinase inhibitor which inhibits lipopolysaccharide-stimulated release of TNF-alpha from human blood with an IC50 2.2 nM, shows good oral bioavailability in rat and rhesus monkey, and demonstrates significant improvement in measures of disease progression in a rat adjuvant-induced arthritis model.

A new class of HCV NS3/4a protease inhibitors containing a P2 to P4 macrocyclic constraint was designed using a molecular modeling-derived strategy. Building on the profile of previous clinical compounds and exploring the P2 and linker regions of the series allowed for optimization of broad genotype and mutant enzyme potency, cellular activity, and rat liver exposure following oral dosing. These studies led to the identification of clinical candidate 15 (MK-5172), which is active against genotype 1−3 NS3/4a and clinically relevant mutant enzymes and has good plasma exposure and excellent liver exposure in multiple species.KEYWORDS: hepatitis C, HCV, MK-5172, macrocycle, genotype 3a, mutant enzymes H epatitis C virus (HCV) is a chronic liver infection that affects an estimated 130−170 million people worldwide. 1,2 HCV displays a high degree of genetic heterogeneity and can be classified into six major genotypes with different geographic distributions: genotypes 1, 2, and 3 account for more than 90% of the infections in the developed world. Treatment for HCV is based on combination therapy with pegylated interferon-α and ribavirin. 3 Sustained viral response is seen in ∼45% of HCV genotype 1-infected patients treated for 48 weeks and in ∼80% of genotype 2-and 3-infected patients treated for 24 weeks. Interferon and ribavirin therapy is also associated with a number of serious side effects, limiting the number of patients who may be treated. 4 There is a compelling medical need for new oral therapeutic agents with improved efficacy and tolerability. Several promising antiviral targets for HCV have emerged, 5 with NS3/4a protease inhibitors showing perhaps the most dramatic antiviral effects. 6 Clinical proof of concept for this mechanism was first achieved with BILN-2061. 7 Other compounds have entered clinical trials, including telaprevir 8 and boceprevir, 9 both of which are now marketed treatments for use in combination with a standard of care. Compounds currently in development include TMC-435 10 and We have disclosed a molecular modeling-derived strategy that led us to design HCV NS3/4a protease inhibitors that contain the P2 to P4 macrocyclic constraint. 12 This design arose from an analysis of the crystal structure of full-length NS3/4A with and without inhibitors docked in the active site. 13 Our strategy coupled with a modular synthetic approach, which relies on a key ring-closing metathesis (RCM) reaction, 14 allowed for the rapid exploration of these molecules and the identification of clinical candidates, vaniprevir (1) 15,16 and MK-1220 (2). 17 Herein, we describe the discovery of a clinical candidate with broad activity across genotypes (gt) and resistant HCV variants. 18,19 With the development of vaniprevir progressing, we set a goal for the ongoing discovery program to be the identification of a second generation NS3/4a protease inhibitor. We wanted to maintain or improve the PK profile seen with our previous compounds and make significant improvements in activity against the gt 3a enz...