This study is a Phase II, placebo-controlled, double-blind, randomized trial in 480 participants with atherosclerotic cardiovascular disease (ASCVD) or ASCVD-risk equivalents (for example, diabetes and familial hypercholesterolemia) and elevated LDL-C despite maximum tolerated dose of LDL-C lowering therapies to evaluate the efficacy, safety, and tolerability of ALN-PCSSC injection(s).