valopicitabine and Hepatitis-C

Hepatitis C infection (HCV) remains a global problem and the current anti-HCV therapies available in the clinic have sustained virologic response rates (SVR) of only about 50%, especially in HCV genotype 1-infected subjects. The SVR is even lower in HIV-HCV co-infected patients, estimated at only about 30-40%. However, exciting new research is under way to find new anti-HCV therapies. Presently, efforts to develop new anti-HCV agents for HCV-infected persons who fail pegylated interferon and ribavirin-based therapies have focused on inhibitors of key HCV enzymes such as the HCV NS3 protease and the NS5B polymerase. There are two protease inhibitors, telaprevir (VX-950, Vertex) and boceprevir (SCH 503034, Schering-Plough); and three polymerase inhibitors, valopicitabine (NM283, Idenix), R1626 (Roche), and HCV-796 (Viropharma) that have advanced to late-stage clinical trials. Of these aforementioned agents, telaprevir is the most advanced in clinical development. Early trial results on efficacy, safety, and HCV drug-resistance profiles of these novel agents will be discussed in this review paper.

Topics: Antiviral Agents; Genotype; Hepacivirus; Hepatitis C; HIV Infections; Humans; Multicenter Studies as Topic; Oligopeptides; Proline; Protease Inhibitors; Pyrimidine Nucleosides; Randomized Controlled Trials as Topic

Idenix Pharmaceuticals Inc and Novartis AG are codeveloping valopicitabine dihydrochloride, a once-daily oral nucleoside for the potential treatment of HCV infection. In January 2005, a phase IIa clinical trial comparing valopicitabine dihydrochloride with pegylated IFN in treatment-naive HCV patients was ongoing, in addition to a phase IIb trial in patients that had previously failed pegylated IFN and ribavirin combination therapy. In January 2006, an international phase III trial in treatment-refractory patients was planned for the first half of the year, with a phase III trial in treatment-naive individuals planned for the second half of the year.

Topics: Animals; Clinical Trials, Phase II as Topic; DNA-Directed RNA Polymerases; Drugs, Investigational; Enzyme Inhibitors; Hepacivirus; Hepatitis C; Humans; Molecular Structure; Pyrimidine Nucleosides

Hepatitis C virus (HCV) infects an estimated 170 million individuals worldwide, and the current standard of care, a combination of pegylated interferon alpha and ribavirin, is efficacious in achieving sustained viral response in ~50% of treated patients. Novel therapies under investigation include the use of nucleoside analog inhibitors of the viral RNA-dependent RNA polymerase. NM283, a 3'-valyl ester prodrug of 2'-C-methylcytidine, has demonstrated antiviral efficacy in HCV-infected patients (N. Afdhal et al., J. Hepatol. 46[Suppl. 1]:S5, 2007; N. Afdhal et al., J. Hepatol. 44[Suppl. 2]:S19, 2006). One approach to increase the antiviral efficacy of 2'-C-methylcytidine is to increase the concentration of the active inhibitory species, the 5'-triphosphate, in infected hepatocytes. HepDirect prodrug technology can increase intracellular concentrations of a nucleoside triphosphate in hepatocytes by introducing the nucleoside monophosphate into the cell, bypassing the initial kinase step that is often rate limiting. Screening for 2'-C-methylcytidine triphosphate levels in rat liver after oral dosing identified 1-[3,5-difluorophenyl]-1,3-propandiol as an efficient prodrug modification. To determine antiviral efficacy in vivo, the prodrug was administered separately via oral and intravenous dosing to two HCV-infected chimpanzees. Circulating viral loads declined by ~1.4 log(10) IU/ml and by >3.6 log(10) IU/ml after oral and intravenous dosing, respectively. The viral loads rebounded after the end of dosing to predose levels. The results indicate that a robust antiviral response can be achieved upon administration of the prodrug.

Topics: Animals; Antiviral Agents; Cytidine; Cytidine Monophosphate; Female; Hepacivirus; Hepatitis C; Hepatocytes; Macaca mulatta; Male; Pan troglodytes; Prodrugs; Pyrimidine Nucleosides; Rats; Rats, Sprague-Dawley; Viral Load

The currently approved treatment for hepatitis C virus infections is a combination of Ribavirin and pegylated Interferon. It leads to a sustained virologic response in approximately only half of the patients treated. For this reason there is an urgent need of new therapeutic agents. 2'-C-Methylcytidine is the first nucleoside inhibitor of the HCV NS5B polymerase that was efficacious in reducing the viral load in patients infected with HCV. The application of a monophosphate prodrug approach based on unprecedented cyclic phosphoramidates is reported. Our SAR studies led to compounds that are efficiently converted to the active triphosphate in human hepatocytes.

Topics: Animals; Antiviral Agents; Cricetinae; Cytidine; Drug Stability; Hepacivirus; Hepatitis C; Hepatocytes; Humans; Prodrugs; Structure-Activity Relationship

The application of a phosphoramidate prodrug approach to 2'-C-methylcytidine (NM107), the first nucleoside inhibitor of the hepatitis C virus (HCV) NS5B polymerase, is reported. 2'-C-Methylcytidine, as its valyl ester prodrug (NM283), was efficacious in reducing the viral load in patients infected with HCV. Several of the phosphoramidates prepared demonstrated a 10- to 200-fold superior potency with respect to the parent nucleoside in the cell-based replicon assay. This is due to higher levels of 2'-C-methylcytidine triphosphate in the cells. These prodrugs are efficiently activated and converted to the triphosphate in hepatocytes of several species. Our SAR studies ultimately led to compounds that gave high levels of NTP in hamster and rat liver after subcutaneous dosing and that were devoid of the toxic phenol moiety usually found in ProTides.

Topics: Amides; Animals; Antiviral Agents; Cell Line; Cytidine; Hepacivirus; Hepatitis C; Hepatocytes; Humans; Phosphoric Acids; Polyphosphates; Prodrugs; Structure-Activity Relationship; Virus Replication

Topics: Antiviral Agents; Biomedical Research; Drug Design; Hepatitis C; Humans; Oligopeptides; Pyrimidine Nucleosides; Recombinant Fusion Proteins; Ribavirin; Toll-Like Receptors

In order to improve the oral bioavailability of 2-C-methylcytidine, a potent anti-HCV agent, the corresponding 3'-O-L-valinyl ester derivative (NM 283) has been synthesized Based on its ease of synthesis and its physicochemical properties, NM 283 has emerged as a promising antiviral drug for treatment of chronic HCV infection.

Topics: Animals; Antiviral Agents; Chemistry, Pharmaceutical; Deoxycytidine; Drug Design; Hepacivirus; Hepatitis C; Humans; Models, Chemical; Prodrugs; Pyrimidine Nucleosides