1222 NS3 GENETIC VARIABILITY IN HCV GENOTYPE IB ISOLATES FROM LIVER TISSUE OF NAIVE PATIENTS WITH CHRONIC HEPATITIS C

POSTERS performed in all patients. Phenotypic analysis was conducted using a chimeric genotype 1b replicon assay. Results: Emerging mutations at one or more of the NS3 amino acid positions 80, 155, 156, 168 were detected by population sequencing in all 6 patients during study C101. At baseline of the subsequent OPERA-1 study, population sequencing and phenotyping revealed similar NS3 sequences and EC50 values as those observed prior to TMC435 monotherapy in C101 for all 5 patients enrolled. However, in one patient a previouslyselected R155K mutation was detected at low frequency (<2%) using 454 sequencing. This patient showed an initial virologic response (<25 IU/mL detectable at week 4) followed by a viral breakthrough during PegIFN/RBV therapy which was associated with a R155K mutation. In another patient, who showed a slightly slower initial viral decline, mutations Q80R/D168E detected as minority variant during C101 using 454 sequencing, emerged as a major variant early upon re-treatment with TMC435. This patient discontinued treatment per protocol due to elevated plasma bilirubin levels. The remaining 3/5 patients showed fast initial virologic response, reached undetectable HCV RNA at week 4 and achieved an SVR24. Conclusions: Most viral variants that emerged during first exposure to TMC435 were no longer detected over time, while some persisted at low frequencies based on deep-sequencing analysis. Successful treatment after prior exposure to TMC435 with emergence of resistance variants was possible in 3/5 patients who had failed interferon-based therapy. 1222 NS3 GENETIC VARIABILITY IN HCV GENOTYPE 1B ISOLATES FROM LIVER TISSUE OF NAIVE PATIENTS WITH CHRONIC HEPATITIS C S. Maimone, C. Musolino, G. Squadrito, G. Raffa, T. Pollicino, G. Raimondo. Unit of Clinical and Molecular Hepatology University Hospital of Messina, Messina, Italy E-mail: [email protected] Background and Aim: Specifically Targeted Antiviral Therapy for HCV (STAT-C), are able to directly inhibit viral replication. Protease inhibitors (PIs) will be soon available for treatment of patients infected with HCV genotype 1. These molecules have potent antiviral efficacy, but the emergence of resistant variants, after very short time of treatment, represents a limitation for their use. Aim of this study was to investigate the possible presence of HCV variants resistant to PIs in viral isolates from liver and serum of untreated patients. Patients and Methods: Cloning and sequencing analyses of HCV NS3 domain (amino acid 1–185) were performed in viral isolates from both liver biopsy specimens and serum samples of 10 HCV genotype 1b chronic hepatitis patients naive to any treatment. In particular, the following mutations known to confer resistance to NS3 PIs were evaluated: V36A/M/C, T54S/A, V55A, Q80R/K, R155K/T/Q, A156S/T/V, V163L, D168A/V/T/H, V170 A/T. Results: By the analysis of 10–15 clones from liver isolates of each patient we found that 6 of 10 cases had a single or multiple mutations conferring resistance to PIs. On the contrary, the analysis of the corresponding serum samples excluded presence of these mutations in all cases but one, who had the Q80R mutation in all clones from both liver and serum samples. Conclusions: Naturally occurring HCV variants resistant to PIs are largely diffused and this clearly explains their very early emergence under treatment. However, this high prevalence is evident at intrahepatic level, whereas the identification of these variants as circulating viral populations might be occasional, thus rending questionable the utility of testing serum samples for their detection.

1223 NO EARLY VIROLOGIC BREAKTHROUGH OBSERVED WITH THE HCV NS3 PROTEASE INHIBITOR BMS-650032 IN MULTIPLE DOSE MONOTHERAPY STUDIES AND PHASE 2A COMBINATION STUDIES WITH PEGIFNa/RBV F. McPhee1 , A. Sheaffer1 , F. Yu1 , M. Lee1 , S. Chaniewski1 , P. Falk1 , C. Pasquinelli2 , C. Llasamo1 , E. Hughes3 , D. Hernandez1 . 1 Bristol-Myers Squibb Company, Wallingford, CT, 2 Bristol-Myers Squibb Company, Hopewell, 3 Bristol-Myers Squibb Company, Lawrenceville, NJ, USA E-mail: fi[email protected] Background: BMS-650032 is a potent, selective inhibitor of HCV NS3 protease that has demonstrated antiviral activity in monotherapy studies and in combination studies with the potent, first-in-class NS5A inhibitor BMS-790052 and/or pegIFNa/RBV in subjects chronically infected with HCV genotype (GT) 1a/b. Genotypic and phenotypic analysis from our previously reported single ascending dose studies revealed the emergence of polymorphisms at amino acid position 80. The impact of this polymorphism on the efficacy of BMS-650032 is unknown. Methods: Forty-eight serum samples from HCV-infected subjects administered 200, 400, or 600 mg BID BMS-650032 for 3 days or with either 200 or 600 mg BID or 600 mg QD BMS-650032 in combination with pegIFNa/RBV were collected at baseline, and at subsequent time-points where viral load was ≥1000 IU/mL. HCV RNA was isolated and the NS3 protease region was amplified and population sequenced. Clonal analysis was performed to assess the presence of major and minor variants. Patient-derived NS3 protease sequences were introduced into chimeric sub-genomic replicons and their susceptibility to BMS-650032 inhibition was compared with reference strains. Results: Population sequencing of the NS3 protease regions in all patient baseline isolates revealed the pre-existence of polymorphisms at amino acid positions 1a-80 (Q80K/L) and 1b-122 (S122R). In the 3-day monotherapy study, enrichment of known PI-resistant variants (substitutions at V36, R155, A156, and D168) was not detected at the doses tested. Emergence and disappearance of variants was observed in four of 12 subjects treated with BMS650032. Phenotypic analysis of these samples in chimeric replicon cell-based assays revealed that the polymorphisms did not appear to confer resistance. In the combination study of BMS-650032 with pegIFNa/RBV, no viral breakthrough was observed over 12 weeks of dosing suggesting that polymorphisms detected at NS3–80 in baseline isolates did not affect antiviral response to a BMS-650032containing regimen. Conclusions: In HCV-infected subjects administered BMS-650032 in a 3-day monotherapy or in combination with pegIFNa/RBV over 12 weeks, no viral breakthrough was observed. The lack of detectable emergent resistance variants to BMS-650032 when combined with pegIFNa/RBV supports the continued clinical development of BMS-650032 as an add-on to pegIFNa/RBV, or in combination with the BMS-790052 NS5A inhibitor. 1224 FACTORS AFFECTING HCV VIRAL LOAD RESPONSE TO THE NONNUCLEOSIDE POLYMERASE INHIBITORS ABT-072 AND ABT-333 T. Middleton1 , Y. He1 , J. Beyer1 , I.A. Gaultier2 , D.E. Cohen2 , T.J. Podsadecki2 , B. Bernstein2 , C. Collins1 . 1 Antiviral Research, 2 Antiviral Global Project Team, Abbott Laboratories, Abbott Park, IL, USA E-mail: [email protected] Introduction: ABT-333 and ABT-072 are nonnucleoside HCV NS5B polymerase inhibitors with potent in vitro activity against genotype 1a and 1b NS5B replicons and an excellent preclinical safety profile. Previous studies in HCV-infected untreated individuals suggest a higher prevalence of variants that are resistant to nonnucleoside

Journal of Hepatology 2011 vol. 54 | S363–S534

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