This randomized, double-blind, placebo-controlled, ascending-dose, parallel-group study will evaluate the pharmacodynamic effects, pharmacokinetics, safety, and tolerability of one week of RG7625 dosing in healthy male and female volunteers. Each participant will receive a single dose of RG7625 or placebo followed by one week of dosing with the same treatment. Each participant will also receive intradermal administration of 4 recall antigens at Screening and on Day 7 of treatment to assess study drug effects on delayed-type hypersensitivity (DTH).

Inclusion Criteria:

• Healthy adult males and females 18 to 60 years of age, inclusive
• Body mass index 18.0 to 30.0 kilograms per meter-squared (kg/m^2), inclusive

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 electrocardiogram (ECG) or other risk factors for QT prolongation
• Use of prescribed or over-the-counter medication
• Inability or unwillingness to comply with study requirements