Reports of significant laboratory abnormalities and adverse events in a number of clinical study participants.

This is a Phase 2b, randomized, double-blind, parallel-group, placebo-controlled, multicenter study investigating the safety, tolerability and efficacy of two oral doses of GS-9450 in adults with chronic Hepatitis C Virus (HCV). Approximately 240 subjects 18-65 years of age who meet study entry criteria will be randomized (in other words, selected at random, like flipping a coin) to one of three treatment groups (80 subjects per treatment group) as follows:GS-9450 10 mg once daily,GS-9450 40 mg once daily, or matching placebo once daily.

Following randomization, subjects will return within seven business days for a Baseline (Day 1) visit, at which time study medication will be dispensed and subjects will enter a 26 week treatment phase. During the treatment phase, subjects will receive study drug once daily for 24 weeks and then taper off of study drug over the following 2 weeks by receiving study drug once every other day for one week and then every 3 days for one week. Following completion of the treatment phase, subjects will enter a 4-week off-treatment follow-up phase.

Inclusion Criteria:

• Adult subjects, ages 18-65
• Chronic HCV infection, defined as having documented HCV infection (antibody or RNA positivity) at least 6 months prior to Baseline (Day 1) with HCV viremia at screening
• Screening Knodell necroinflammatory score >= 3 based on liver biopsy evaluation (as determined by local pathologist) conducted anytime during the 45-day screening period
• ALT > the upper limit of the normal range (ULN) but < 10 X ULN at the screening visit
• Previously failed pegylated interferon-based HCV therapy in combination with ribavirin therapy, or is unable to tolerate or has contraindications to receiving interferon or ribavirin therapy
• BMI between 19 and 36 kg/m2 (inclusive)
• Creatinine clearance >= 70 mL/min
• absolute neutrophil count >= 1000/mm3
• Hemoglobin > 10 g/dL
• Have no clinical or laboratory evidence of hepatic decompensation

Exclusion Criteria:

• Decompensated liver disease
• Child-Pugh grade B or C cirrhosis
• Evidence of hepatocellular carcinoma
• Positive urine drug screen for cocaine or amphetamines
• Infection with HCV genotype 3
• Co-infection with hepatitis B virus or human immunodeficiency virus
• Pancreatitis
• Recent significant infection or symptoms of infection
• Autoimmune disorders
• Any history of seizure
• Is a public transportation operator (pilot of airplane or ship; air traffic controller; bus, train or subway driver) or operates heavy construction machinery
• Transplantation
• History of malignancy
• Current excessive alcohol ingestion, averaging > 3 drinks/day for females and > 4 drinks/day for males
• History of or current binge drinking