This is a single center, randomized, double-blind, placebo-controlled, single ascending dose study that will evaluate the safety, tolerability, pharmacokinetics and pharmacodynamic effects of single doses of RG7625 in healthy male and female volunteers.

The study will employ an interleaved cohort ('leapfrog') design in which dosing is alternated between two cohorts and each individual within a cohort will receive study drug dosing on four occasions - in effect giving a four treatment, four period, four-way crossover for each individual. The minimum duration for each participant is approximately 8 weeks.

Inclusion Criteria:

• Healthy male and female participants, 18 to 60 years of age, inclusive
• A body mass index between 18 to 30 kg/m2 inclusive
• Able to participate and willing to give written informed consent and to comply with the study restrictions

Exclusion Criteria:

• Any clinically relevant abnormalities, concomitant diseases or ongoing medical conditions, abnormal laboratory test results or a history of any other clinically significant disorders
• Any major illness within the one month preceding the screening visit, or any febrile illness within the two weeks preceding the screening visit
• Any significant allergic reaction to drugs
• Immunocompromised or with reduced immune function and/or immunization within 30 days before the first study drug administration or planning vaccination during the study
• Women who are pregnant or lactating or of childbearing potential
• Clinically significant abnormal ECG or other risk factors for QT prolongation
• Use of prescribed or over the counter medication
• Inability or unwillingness to comply with study requirements