A Study to Investigate the Safety, Tolerability and Pharmacokinetics of RO6889678 and the Combination of RO6889678 With Ritonavir in Healthy Participants

A Single-Center, Randomized, Double-Blind, Single and Multiple Ascending Dose, Placebo-Controlled Study to Investigate the Safety, Tolerability and Pharmacokinetics of RO6889678 and the Combination of RO6889678 With Ritonavir Following Oral Administration, the Effect of Food on the Pharmacokinetics of RO6889678 and the Effect of Multiple Oral Dosing of RO6889678 and the Combination of RO6889678 With Ritonavir on the Pharmacokinetics of Midazolam in Healthy Subjects

This study is a single-center, double-blind, randomized, placebo-controlled, single-ascending dose (SAD) and multiple-ascending dose (MAD) study that will evaluate the safety, tolerability and pharmacokinetics (PK) of RO6889678 and the combination of RO6889678 with Ritonavir (RTV) following oral administration in healthy volunteers. The effect of food on the PK of RO6889678 and the effect of multiple dosing of RO6889678 and the combination of RO6889678 with RTV on the PK of a single oral microdose of midazolam will be evaluated.

Healthy participants will be screened up to 28 days before randomization and sequentially enrolled into SAD and MAD unboosted and RTV-boosted cohorts, then randomly assigned to RO6889678 or matching placebo. In RTV-boosted cohorts participants will take RO6889678 in combination with RTV. To explore the effect of food on RO6889678 PK, a cohort of volunteers will participate in a two-period food effect sub-study. Participants enrolled in the MAD cohorts will be given an oral microdose of midazolam before and after the repeat treatment with RO6889678 to evaluate the drug-drug interaction potential of RO6889678.

Inclusion Criteria:

• 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 (by means of hysterectomy and/or bilateral oophorectomy) or post-menopausal for at least one year (defined as amenorrhea greater than or equal to [>/=] 12 consecutive months without another cause, and confirmed by follicle stimulating hormone level greater than [>] 35 milli-international units per milliliter [mIU/mL])
• Male participants must agree to use two adequate methods of contraception with their female partners of childbearing potential, including a barrier method during the treatment period and for at least 2 months after the last dose of study drug

Exclusion Criteria:

• History or symptoms of any significant disease
• Pregnant or lactating
• Personal or family history of congenital long QT syndrome or sudden death
• Significant acute infection, e.g. influenza, local infection, acute gastrointestinal symptoms or any other clinically significant illness within two weeks of dose administration
• Clinically relevant ECG abnormalities on screening ECG
• Participation in an investigational drug or device study within 90 days prior to screening
• Medical or social conditions that would potentially interfere with the participant's ability to comply with the study visit schedule or the study assessments