The principal aim of this study is to obtain safety and tolerability data when MRT-8102 is administered orally as single and multiple doses to healthy participants and participants at cardiovascular risk with elevated CRP. This information, together with the pharmacokinetic (PK) data, will help establish the dose and dosing regimen suitable for future studies. The study drug, MRT-8102, is experimental. This is the first study in which MRT-8102 will be given to humans. Part 1: Healthy participants will receive a single oral dose of MRT-8102 or placebo on Day 1 Part 2: Healthy participants will receive multiple oral doses of MRT-8102 or placebo for 7 consecutive days Part 3: Participants at cardiovascular risk with elevated CRP will receive multiple oral doses of MRT-8102 or placebo for 28 consecutive days