This randomized, open-label, multiple-treatment multiple-dose, 2-period, 2-sequence study will evaluate potential drug-drug interactions between danoprevir (DNV) when coadministered with low-dose ritonavir (r) and tenofovir disoproxil fumarate (TDF) or atazanavir (ATZ) in healthy volunteers. Subjects will be randomized to receive in Period 1 either single oral doses of TDF and multiple oral doses of DNV/r or multiple oral doses of ATZ/r. In Period 2, all subjects will receive multiple oral doses of DNV/r plus ATZ. Anticipated time on study treatment is up to 20 days.

Inclusion Criteria:

• Male and female volunteers, 18 to 55 years of age, inclusive
• Body weight >/= 55 kg
• Body mass index (BMI) 18.0 - 32.0 kg/m2
• Healthy non-smoking subjects. Healthy status will be defined by absence of evidence of any active or chronic disease following a detailed medical and surgical history and a complete physical examination
• Medical history without major recent or ongoing pathology
• Females of childbearing potential and males and their female partners of childbearing potential must agree to use 2 forms of contraception, 1 of which must be a barrier method, during the study and for 90 days after the last drug administration

Exclusion Criteria:

• Pregnant or lactating women or males with female partners who are pregnant or lactating
• Any history of clinically significant disease or condition
• Positive for drugs of abuse at screening or prior to admission to the clinical site
• Positive for hepatitis B, hepatitis C or HIV infection
• Current smokers or subjects who have discontinued smoking less than 6 months prior to first dose of study medication
• Use of hormonal contraceptives (e.g. birth control pill, patches, or injectable, implantable devices) within 30 days before the first dose of study medication
• Use of an investigational drug or device within 30 days of the first dose of study medication (6 months for biologic therapies) or 5 half-lives of the investigational drug, whichever is longer
• History of drug-related allergy reaction
• History (within 3 months of screening) of alcohol consumption exceeding 2 standard drinks per day on average