1. Background medical lipid modifying therapy that has not been stable for at least 4 weeks (6 weeks for fibrates) prior to the screening visit

2. Having undergone lipid apheresis within 4 weeks prior to the screening visit

3. Use of another investigational drug or therapy within 30 days or at least 5 half-lives (whichever is longer) prior to the screening visit

4. Previous participation in any clinical trial of REGN1500

Study of REGN1500 in Participants With Homozygous Familial Hypercholesterolemia (HoFH)