This study will be a placebo-controlled, double-blind, randomized, phase 3 study in participants with HeFH to evaluate the efficacy, safety, and tolerability of obicetrapib as an adjunct to diet and maximally tolerated lipid-lowering therapy. The screening period for this study will take up to 14 days. Afterwards, patients will be randomized to placebo or 10 mg obicetrapib for an 365-day treatment period. After the treatment period, participants will have an end-of-study follow-up visit.