The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of ALN-PCSSC in subjects with elevated LDL-C.

Inclusion Criteria:

• Adequate complete blood counts, liver and renal function
• Female subjects must be of non-childbearing potential; e.g. post-menopausal or pre-menopausal with surgical sterilization
• Male subjects agree to use appropriate contraception
• Willing to provide written informed consent and willing to comply with study requirements.
• Non-smokers and non-nicotine users for at least 90 days before screening
• On stable statin co-medication [for designated multiple dose cohorts only]

Exclusion Criteria:

• Any uncontrolled or serious disease, or any medical or surgical condition, that may interfere with participation in the clinical study and/or put the subject at significant risk
• Received an investigational agent within 90 days before the first dose of study drug or are in follow-up of another clinical study
• History of multiple drug allergies or intolerance to subcutaneous injection
• Received any medication or nutraceutical to alter serum lipids within 30 days before screening (non-statin cohorts only)