This study is designed to evaluate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple doses of ARO-033 compared to placebo in adult normal healthy volunteers (NHVs).

Key Inclusion Criteria:

• Adults who are not pregnant, not breastfeeding, and do not plan to become pregnant (or impregnate their partners) during the study and for at least 90 days following the end of the study.
• Body mass index (BMI) between 18.0 and 35.0 kilograms (kg)/square meter (m^2), inclusive.
• No abnormal finding of clinical relevance at the Screening evaluation that in the opinion of the Investigator could adversely impact participant's safety during the study or adversely impact study results.

Key Exclusion Criteria:

• Human immunodeficiency virus (HIV) infection, as shown by the presence of anti-HIV antibody (seropositive).
• Seropositive for hepatitis B virus (HBV) (hepatitis B surface antigen positive at screening) or hepatitis C virus (HCV) (HCV antibody positive with reflex confirmation using HCV RNA amplification at Screening). Cured HCV (positive antibody test without detectable HCV RNA) is permitted if HCV RNA has been negative for at least 2 years.
• Uncontrolled hypertension (resting systolic blood pressure ≥160 millimeters of mercury [mmHg] or diastolic blood pressure ≥95 mmHg, confirmed by repeat measurement, at Screening).
• Evidence of clinically significant immunocompromising condition (for example, primary immunodeficiency syndrome, aplastic anemia, known or suspected complement factor deficiency, or any other condition resulting in significantly impaired immune response as evidenced by recurrent infections), or recent/ongoing treatment with immunosuppressive agents.
• History of major surgery within 90 days of Screening.
• Use of an investigational agent or device within 30 days or 5 half-lives (whichever is longer) prior to dosing or current participation in an investigational study. Participants recently participating in studies involving investigational agents with prolonged therapeutic effect (such as ribonucleic acid interference [RNAi] therapeutics, cell or gene therapies) should be discussed with the Medical Monitor.
• Any medical condition or clinically significant laboratory abnormality at Screening that in the opinion of the Investigator should exclude the participant from participation, preclude safe and successful completion of the study, or confound study results.

Note: Other protocol-defined inclusion and exclusion criteria may apply.