Patient description: A 53-year-old man presents with chronic HCV infection for the past 2 years. His past medical history is only significant for inguinal hernia surgery when he was 20 years old. He is on IFN (100 mg/week) plus RBV (400 mg/day) combination therapy for the past 9 months. Direct antiviral drugs were added to his treatment 6 months ago. His medical record shows previous positive HCV RNA tests as well as positive enzyme immunoassay for anti-HCV-antibodies. The recent biopsy was negative for hepatocellular carcinoma and was only remarkable for chronic inflammation compatible with a chronic viral hepatitis. There is no evidence of alcoholic liver disease, bleeding from esophageal varices, hemochromatosis, autoimmune hepatitis or metabolic liver disease. He is an alert male with no acute distress. His BP: 130/75, HR: 90/min and BMI: 27. His abdomen is soft with no ascites or tenderness. The lower extremities are normal with no edema.

Clinical trial eligibility criteria: eligible ages (years): 18.0-60.0,  Hepatitis B, Chronic Part 1 Healthy Volunteers only Absence of evidence of any active or chronic disease following a detailed medical and surgical history, a complete physical examination including vital signs, 12-lead Electrocardiogram (ECG), hematology, blood chemistry, serology and urinalysis A Body Mass Index (BMI) between 18 to 30 kilograms per square meter (kg/m^2) inclusive Female participants must be either surgically sterile or post-menopausal for at least one year For men: agreement to remain abstinent or use contraceptive measures, and agreement to refrain from donating sperm Part 2 Chronic HBV-infected participants only A BMI between 18 to 30 kg/m^2 inclusive Chronic Hepatitis B infection, defined as positive test for Hepatitis B surface antigen (HBsAg) for more than 6 months prior to randomization HBV DNA at screening greater than or equal to (>/=) 2 × 10^4 international units per milliliter (IU/mL) for Hepatitis B e antigen (HBeAg) positive participants, or >/=2 × 10^3 IU/mL for HBeAg-negative participants  Part 1 Healthy Volunteers only History or symptoms of any clinically significant gastrointestinal, renal, hepatic, broncho-pulmonary, neurological, psychiatric, cardio-vascular, endocrinological, hematological or allergic disease, metabolic disorder, cancer or cirrhosis History of Gilbert's syndrome Participants who have had significant acute infection, e.g., influenza, local infection, acute gastrointestinal symptoms or any other clinically significant illness within two weeks of dose administration Any confirmed significant allergic reactions (urticaria or anaphylaxis) against any drug, or multiple drug allergies Any clinically significant concomitant diseases or condition that could interfere with, or treatment of which might interfere with, the conduct of the study, or that would, in the opinion of the Investigator, pose an unacceptable risk to the participant in this study Positive test at screening of any of the following: Hepatitis A (HAV IgM Ab), Hepatitis B (HBsAg), Hepatitis C (HCV RNA or HCV Ab) or human immunodeficiency virus (HIV Ab) Acute narrow-angle glaucoma (for MAD-midazolam cohorts) Part 2 Chronic HBV-infected participants only