The primary objective of the study is to evaluate the pharmacokinetics (PK) of a single dose of olpasiran in participants with mild, moderate, or severe hepatic impairment compared to participants with normal hepatic function.

Inclusion Criteria:

• Male or female participants of nonchildbearing potential, between 18 and 75 years of age (inclusive) at the time of Screening.
• Body mass index between 18.0 and 40.0 kg/m^2 (inclusive) at the time of Screening.

Participants with Normal Hepatic Function Only:

• In good health, determined by no clinically significant findings from medical history, physical examination, 12-lead ECG, vital signs measurements, and clinical laboratory evaluations at Screening and Check-in as assessed by the Investigator (or designee).

Participants with Hepatic Impairment Only:

• Child-Pugh A (Group 2), B (Group 3), or C (Group 4) classification defined by both Screening (to determine participant group) and Check-in (to confirm participant group prior to dosing) clinical laboratory values and physical examination findings.

Exclusion Criteria:

• History of significant hypersensitivity, intolerance, or allergy to any drug compound, food, or other substance, unless approved by the Investigator (or designee).
• Estimated glomerular filtration rate < 60 mL/min/1.73m^2 (Groups 1-3) or < 50 mL/min/1.73m^2 (Group 4 only) by Modification of Diet in Renal Disease formula at Screening or Check-in.
• Receiving or has received any investigational drug within the 30 days or 5 half-lives (whichever is longer) before receiving olpasiran.
• Participants who were previously exposed to olpasiran.
• Female participants with a positive pregnancy test at Screening or Check-in.

Participants with Normal Hepatic Function Only:

• Positive hepatitis panel. Participants whose results are compatible with prior immunization may be included.
• Alanine aminotransferase and aspartate aminotransferase elevations > 3x upper limit of normal at Screening or Check-in.

Participants with Hepatic Impairment Only:

• Positive for hepatitis B surface antigen. Participants with positive hepatitis B core antibody may be included if hepatitis B surface antigen is negative. Participants with positive hepatitis B surface antibody may be included (consistent with prior vaccination).
• Active malignancy of any type. Participants with a history of malignancy that has been eradicated with supporting medical documentation indicating that there is no residual malignancy detected in the past 2 years will be allowed.
• Values outside the normal range for liver function tests that are not consistent with their hepatic condition, as determined by the Investigator (or designee).

De-identified individual patient data for variables necessary to address the specific research question in an approved data sharing request.

Data sharing requests relating to this study will be considered beginning 18 months after the study has ended and either 1) the product and indication have been granted marketing authorization in both the US and Europe or 2) clinical development for the product and/or indication discontinues and the data will not be submitted to regulatory authorities. There is no end date for eligibility to submit a data sharing request for this study.

Qualified researchers may submit a request containing the research objectives, the Amgen product(s) and Amgen study/studies in scope, endpoints/outcomes of interest, statistical analysis plan, data requirements, publication plan, and qualifications of the researcher(s). In general, Amgen does not grant external requests for individual patient data for the purpose of re-evaluating safety and efficacy issues already addressed in the product labelling. Requests are reviewed by a committee of internal advisors. If not approved, a Data Sharing Independent Review Panel will arbitrate and make the final decision. Upon approval, information necessary to address the research question will be provided under the terms of a data sharing agreement. This may include anonymized individual patient data and/or available supporting documents, containing fragments of analysis code where provided in analysis specifications. Further details are available at the URL below.