Study of the Safety and Efficacy of REGN727/SAR236553 in Patients With HeFH Hypercholesterolemia

Inclusion Criteria:

1. Must meet the World Health Organization criteria for heFH

2. Participants must be on a stable statin dose, with or without ezetimibe, for at least
6 weeks before screening

3. Serum LDL-C levels ≥ 100 mg/dL at screening

4. Willing to follow the NCEP ATPIII TLC diet, or an equivalent diet plan, starting at
screening and continuing until the last study visit

5. A negative urine/serum pregnancy test at each screening visit and start of the study,
for women of childbearing potential

Key Exclusion Criteria:

1. Participants with homozygous FH (clinically or by previous genotyping)

2. Use of a medication (other than a statin or EZE) to alter serum lipids within 42 days
(6 weeks) before screening including, but not limited to:

- Fibrates

- Niacin (>500 mg/day)

- Omega-3 fatty acids (>1000 mg/day of DHA/EPA)

- Bile acid resins

3. Use of nutraceuticals or OTC medications that may alter lipid levels that are not
stable for at least 6 weeks before screening and are not planned to remain constant
throughout the study. Examples include:

- Omega-3 fatty acids (≤1000 mg/day of DHA/EPA)

- Niacin (≤500 mg/day)

- Plant stanols, such as found in Benecol, flax seed oil, psyllium

- Red yeast rice

4. Disorders known to influence lipid levels, such as nephrotic syndrome, significant
liver disease, Cushing's disease, untreated hypothyroidism (patients on stable
thyroid replacement for at least 12 weeks before the full screening visit, who are
metabolically euthyroid by thyroid-stimulating hormone (TSH) testing are allowed)

5. Use of thyroid medications (except for replacement therapy which has been stable for
at least 12 weeks before the full screening visit)

6. Fasting serum TG >350 mg/dL screening

7. LDL apheresis within 12 months before screening