A Phase 1 Study of Novel GS-9973 Tablet Formulations to Evaluate the Effect of Acid Reducing Agents, Relative Bioavailability, and Food Effect on GS-9973 Pharmacokinetics

Inclusion Criteria: * Have the ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study procedures * Must have a body mass index (BMI) range of approximately 19 to 30 kg/m2 * Must have a minimum weight of 45 kg * Females of childbearing potential must have negative serum pregnancy tests at screening and baseline and must practice at least 1 reliable method of contraception as defined by the protocol * Female subjects who utilize hormonal contraceptive as 1 of their birth control methods must have used the same method for at least 3 months prior to study dosing * Male subjects must agree to use condoms during heterosexual intercourse and avoid sperm donation from Day -1 until 90 days following the last dose of study medication * Must refrain from blood donation throughout the study period * Must, in the opinion of the Investigator, be in good general * Must be a non- or light smoker, eg, less than 10 cigarettes per day Exclusion Criteria: * Pregnant or lactating subjects * Use of prescribed or over-the-counter medications that affect gastric pH * History of severe peptic ulcer disease, GERD, or other diseases requiring prolonged(\>6 weeks) medication or surgical therapy to modify gastric pH * Have a history of clinically significant cardiac abnormalities or presence of clinically significant abnormality on 12-lead ECG. * Have a history of any cancer requiring systemic chemotherapy or radiation * Have a history of bleeding disorders * Have a history of liver disorders * Current acute infection or history of acute infection within 7 days * Have a recent history of alcohol or illicit drug abuse and/or have a positive test for selected drugs of abuse * Have a positive hepatitis screen or positive Human Immunodeficiency Virus antibody test * Have participated in another clinical trial within 28 days * Have received transfusion of blood or plasma products within 6 months * Have donated \> 500 mL blood within 56 days * Are unable or unwilling to comply with study restrictions, return for follow-up appointments, or other considerations, which in the opinion of the Investigator, would make the candidate unsuitable for study participation * Current or historical medical condition that is deemed to be of medical significance by the Investigator * Have used prescription medications, over the counter products, herbal remedies and nutritional supplements within 7 days