In a step toward the wider use of gene editing, a treatment that uses Crispr successfully slashed high cholesterol levels in a small number of people. Though rare, some people are born with a mutation in this gene that protects against heart disease with no apparent adverse consequences. LDL cholesterol is the waxy substance in the blood that can clog and harden arteries over time. Participants were between the ages of 31 and 68 and had uncontrolled levels of LDL cholesterol and triglycerides. The man had a rare, inherited genetic form of high cholesterol and previously had several procedures to improve blood flow to his heart.