Olivier Nicolas

Evaluation of VCH-759 monotherapy in hepatitis C infection

BACKGROUND/AIMS VCH-759 is a non-nucleoside inhibitor of HCV RNA-dependent polymerase with sub-micromolar IC(50) values versus genotype 1a/1b replicons. METHODS The antiviral activity, pharmacokinetics and tolerability of VCH-759 administered as monotherapy for 10 days with a 14 day follow-up period were evaluated in 31 treatment-nai ve genotype 1 participants. Three cohorts received: 400mg thrice (t.i.d.), 800 mg twice (b.i.d.), 800 mg t.i.d or placebo. RESULTS VCH-759 was well tolerated with the most frequent adverse event being gastrointestinal upset in both the active and placebo groups attributable, in part, to the dosing vehicle. VCH-759 was rapidly absorbed and trough plasma levels were at or above the IC(90) (non protein-adjusted) for all dosing regimens. The mean maximal decrease in HCV RNA log(10) (IU/mL) was 1.97, 2.30 and 2.46 for 400mg t.i.d., 800 mg b.i.d. and 800 mg t.i.d. doses. Viral polymerase genotypic sequencing revealed emergence of HCV variants in a majority of participants that coincided with on-treatment viral rebound. CONCLUSIONS VCH-759 was well tolerated and achieved a> or =2 log(10) decline in HCV RNA with 800 mg b.i.d. and t.i.d doses. In a subset of participants, viral rebound was observed and associated with resistant variants. This data supports further evaluation of VCH-759 in combination with interferon-ribavirin treatment.

In vitro phenotypic characterization of hepatitis C virus NS3 protease variants observed in clinical studies of telaprevir.

ABSTRACT Telaprevir is a linear, peptidomimetic small molecule that inhibits hepatitis C virus (HCV) replication by specifically inhibiting the NS3·4A protease. In phase 3 clinical studies, telaprevir in combination with peginterferon and ribavirin (PR) significantly improved sustained virologic response (SVR) rates in genotype 1 chronic HCV-infected patients compared with PR alone. In patients who do not achieve SVR after treatment with telaprevir-based regimens, variants with mutations in the NS3·4A protease region have been observed. Such variants can contribute to drug resistance and limit the efficacy of treatment. To gain a better understanding of the viral resistance profile, we conducted phenotypic characterization of the variants using HCV replicons carrying site-directed mutations. The most frequently observed (significantly enriched) telaprevir-resistant variants, V36A/M, T54A/S, R155K/T, and A156S, conferred lower-level resistance (3- to 25-fold), whereas A156T and V36M+R155K conferred higher-level resistance (>25-fold) to telaprevir. Rarely observed (not significantly enriched) variants included V36I/L and I132V, which did not confer resistance to telaprevir; V36C/G, R155G/I/M/S, V36A+T54A, V36L+R155K, T54S+R155K, and R155T+D168N, which conferred lower-level resistance to telaprevir; and A156F/N/V, V36A+R155K/T, V36M+R155T, V36A/M+A156T, T54A+A156S, T54S+A156S/T, and V36M+T54S+R155K, which conferred higher-level resistance to telaprevir. All telaprevir-resistant variants remained fully sensitive to alpha interferon, ribavirin, and HCV NS5B nucleoside and nonnucleoside polymerase inhibitors. In general, the replication capacity of telaprevir-resistant variants was lower than that of the wild-type replicon.

Pharmacological Properties of a New Antimalarial Bisthiazolium Salt, T3, and a Corresponding Prodrug, TE3

ABSTRACT A new approach to malarial chemotherapy based on quaternary ammonium that targets membrane biogenesis during intraerythrocytic Plasmodium falciparum development has recently been developed. To increase the bioavailability, nonionic chemically modified prodrugs were synthesized. In this paper, the pharmacological properties of a bisthiazolium salt (T3) and its bioprecursor (TE3) were studied. Their antimalarial activities were determined in vitro against the growth of P. falciparum and in vivo against the growth of P. vinckei in mice. Pharmacokinetic evaluations were performed after T3 (1.3 and 3 mg/kg of body weight administered intravenously; 6.4 mg/kg administered intraperitoneally) and TE3 (1.5 and 3 mg/kg administered intravenously; 12 mg/kg administered orally) administrations to rats. After intraperitoneal administration, very low doses offer protection in a murine model of malaria (50% efficient dose [ED50] of 0.2 to 0.25 mg/kg). After oral administration, the ED50 values were 13 and 5 mg/kg for T3 and TE3, respectively. Both compounds exerted antimalarial activity in the low nanomolar range. After TE3 administration, rapid prodrug-drug conversion occurred; the mean values of the pharmacokinetic parameters for T3 were as follows: total clearance, 1 liter/h/kg; steady-state volume of distribution, 14.8 liters/kg; and elimination half-life, 12 h. After intravenous administration, T3 plasma concentrations increased in proportion to the dose. The absolute bioavailability was 72% after intraperitoneal administration (T3); it was 15% after oral administration (TE3). T3 plasma concentrations (8 nM) 24 h following oral administration of TE3 were higher than the 50% inhibitory concentrations for the most chloroquine-resistant strains of P. falciparum (6.3 nM).

Genotypic and Phenotypic Analyses of Hepatitis C Virus Variants Observed in Clinical Studies of VX-222, a Nonnucleoside NS5B Polymerase Inhibitor

ABSTRACT VX-222, a thiophene-2-carboxylic acid derivative, is a selective nonnucleoside inhibitor of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase. In phase 1 and 2 clinical studies, VX-222 demonstrated effective antiviral efficacy, with substantial reductions in plasma HCV RNA in patients chronically infected with genotype 1 HCV. To characterize the potential for selection of VX-222-resistant variants in HCV-infected patients, the HCV NS5B gene was sequenced at baseline and during and after 3 days of VX-222 dosing (monotherapy) in a phase 1 study. Variants with the substitutions L419C/I/M/P/S/V, R422K, M423I/T/V, I482L/N/T, A486S/T/V, and V494A were selected during VX-222 dosing, and their levels declined over time after the end of dosing. Phenotypic analysis of these variants was conducted using HCV replicons carrying site-directed mutations. Of the 17 variants, 14 showed reduced susceptibility to VX-222 compared with the wild type, with the L419C/S and R422K variants having higher levels of resistance (>200-fold) than the rest of the variants (6.8- to 76-fold). The M423I and A486S variants remained susceptible to VX-222. The 50% effective concentration (EC50) for the L419P variant could not be obtained due to the poor replication of this replicon. The majority of the variants (15/17) were less fit than the wild type. A subset of the variants, predominately the L419S and R422K variants, were observed when the efficacy and safety of VX-222- and telaprevir-based regimens given for 12 weeks were investigated in genotype 1 HCV-infected patients in a phase 2 study. The NS3 and NS5B variants selected during the dual combination therapy showed reduced susceptibility to both telaprevir and VX-222 and had a lower replication capacity than the wild type. The phase 1b study has the ClinicalTrials.gov identifier NCT00911963, and the phase 2a study has ClinicalTrials.gov identifier NCT01080222.

844 GENOTYPIC ANALYSIS OF HCV NS5B VARIANTS SELECTED FROM PATIENTS TREATED WITH VCH-759

Background: VCH-759 is a novel orally bioavailable non-nucleoside inhibitor of hepatitis C virus RNA-dependent RNA polymerase. In a phase Ib clinical study involving genotype 1a and 1b-infected subjects, VCH-759 has achieved a 2 log10 or greater decline in HCVRNA levels. During the 10-day dosing period, an initial rapid reduction of viral load was observed in all patients dosed with VCH-759. Some patients have experienced a sustained anti-viral response during treatment but viral breakthrough was noticed for others. The aim of this study was to genotypically and phenotypically characterize the selection of resistant variants and to investigate a potential correlation with the viral kinetics observed. Methods: Selected samples collected at day 1 (pre-dosing), day 11 (day after last dose), and days 17 and 24 (short term follow-up) were used for analysis. The entire NS5B gene was amplified by RT-PCR and directly sequenced. In order to determine the prevalence of each mutation within the population, the region corresponding to the compound binding pocket (amino acids 340–539) was also amplified, cloned, and numerous clones sequenced. The phenotypic and the in vitro replication capacity analysis of variants were performed using the HCV replicon system. Results: Analysis of pre-dosing sera has revealed a wild-type genotype for the positions 419, 423, and 482 of the NS5B when compared to the consensus sequence of genotypes 1a and 1b. A mixture of wild-type and M423T/V/I substitution was the common feature found by population sequencing in samples at day 11, 17, and 24. The M423T and M423V mutants were associated with a respective 18 to 21-fold increase in replicon EC50 values when compared to the wild-type. A less predominant mutation namely, L419M was detected by clonal analysis and was found to confer a 23-fold reduction in VCH-759 susceptibility. Overall, the selected mutants were found to have a reduced replication capacity when compared to the wild-type. Conclusions: HCV variants with mutations conferring resistance to VCH759 were selected during the course of a 10-day treatment. This study illustrates that VCH-759 should be used in a combination therapy to maintain viral suppression and prevent emergence of resistance.

Synthesis and evaluation of NS5A inhibitors containing diverse heteroaromatic cores.

Inhibitors of the HCV NS5A nonstructural protein are showing promising clinical potential in the treatment of hepatitis C when used in combination with other direct-acting antiviral agents. Current NS5A clinical candidates such as daclatasvir, ledipasvir, and ombitasvir share a common pharmacophore that features a pair of (S)-methoxycarbonylvaline capped pyrrolidines linked to various cores by amides, imidazoles and/or benzimidazoles. In this Letter, we describe the evaluation of NS5A inhibitors which contain alternative heteroaromatic replacements for these amide mimetics. The SAR knowledge gleaned in the optimization of scaffolds containing benzoxazoles was parlayed toward the identification of potent NS5A inhibitors containing other heteroaromatic replacements such as indoles and imidazopyridines.

Discovery of Novel Thiophene-Based, Thumb Pocket 2 Allosteric Inhibitors of the Hepatitis C NS5B Polymerase with Improved Potency and Physicochemical Profiles

The hepatitis C viral proteins NS3/4A protease, NS5B polymerase, and NS5A are clinically validated targets for direct-acting antiviral therapies. The NS5B polymerase may be inhibited directly through the action of nucleosides or nucleotide analogues or allosterically at a number of well-defined sites. Herein we describe the further development of a series of thiophene carboxylate allosteric inhibitors of NS5B polymerase that act at the thumb pocket 2 site. Lomibuvir (1) is an allosteric HCV NS5B inhibitor that has demonstrated excellent antiviral activity and potential clinical utility in combination with other direct acting antiviral agents. Efforts to further explore and develop this series led to compound 23, a compound with comparable potency and improved physicochemical properties.

Benzimidazole-containing HCV NS5A inhibitors: effect of 4-substituted pyrrolidines in balancing genotype 1a and 1b potency.

The treatment of HCV with highly efficacious, well-tolerated, interferon-free regimens is a compelling clinical goal. Trials employing combinations of direct-acting antivirals that include NS5A inhibitors have shown significant promise in meeting this challenge. Herein, we describe our efforts to identify inhibitors of NS5A and report on the discovery of benzimidazole-containing analogs with subnanomolar potency against genotype 1a and 1b replicons. Our SAR exploration of 4-substituted pyrrolidines revealed that the subtle inclusion of a 4-methyl group could profoundly increase genotype 1a potency in multiple scaffold classes.

Discovery of thienoimidazole-based HCV NS5A inhibitors. Part 2: Non-symmetric inhibitors with potent activity against genotype 1a and 1b

The discovery of non-symmetric thienoimidazole-containing HCV NS5A inhibitors is described. The inhibitors herein reported display high potencies against both genotype 1a and 1b. In this follow-up manuscript, we discuss the importance of the linker aromaticity to achieve high potency, particularly against genotype 1a.

Discovery of thienoimidazole-based HCV NS5A inhibitors. Part 1: C2-Symmetric inhibitors with diyne and biphenyl linkers

The discovery of C2-symmetric bis-thienoimidazoles HCV NS5A inhibitors is herein reported. Two straightforward approaches to access the requisite diyne and biphenyl linker moieties are described. This study revealed the paramount importance of the aromatic character of the linker to achieve high genotype 1a potency.