Primary Objective:

• To evaluate the effect of alirocumab (SAR236553/REGN727) on low-density lipoprotein cholesterol (LDL-C) levels after 12 weeks of treatment in comparison with placebo in participants with LDL-C ≥ 100 mg/dL (≥ 2.59 mmol/L) on ongoing stable atorvastatin therapy.

Secondary Objectives:

• To evaluate the effects of alirocumab on other lipid levels after 12 weeks of treatment in comparison with placebo
• To evaluate the safety and tolerability of alirocumab
• To evaluate the development of anti-alirocumab antibodies
• To evaluate the pharmacokinetics of alirocumab

The duration of study participation depended on the status of the participant at screening:

• For participants receiving atorvastatin 10 mg, 20 mg, or 40 mg at a stable dose for at least 6 weeks prior to screening, the study participation was to be approximately 21 weeks including a screening period of 1 week, a double-blind treatment period of 12 weeks and a follow-up period of 8 weeks.
• For participants receiving a lipid-lowering treatment other than atorvastatin or not at stable dose of atorvastatin 10 mg, 20 mg, or 40 mg for at least 6 weeks prior to screening, or drug naive participants, the study participation was to be approximately 27 weeks including a screening period of 1 week, a run-in treatment period with atorvastatin 10 mg, 20 mg, or 40 mg at a stable dose of 6 weeks, a double-blind treatment period of 12 weeks, and a follow-up period of 8 weeks.

Inclusion criteria:

• Participants with primary hypercholesterolemia receiving a lipid-lowering treatment other than atorvastatin or not at stable dose of atorvastatin 10 mg, 20 mg, or 40 mg for at least 6 weeks prior to screening period or drug naive participants if they are likely to have low-density lipoprotein cholesterol (LDL-C) ≥ 100 mg/dL (≥ 2.59 mmol/L) at the end of the 6-week run-in treatment period on atorvastatin therapy

OR

• Participants with primary hypercholesterolemia treated with atorvastatin at stable dose of 10 mg, 20 mg, or 40 mg for at least 6 weeks prior to screening period and likely to have LDL-C ≥ 100 mg/dL (≥ 2.59 mmol/L) at the screening visit

Exclusion criteria:

1. LDL-C < 100 mg/dL (< 2.59 mmol/L):

   • After the run-in period on atorvastatin (10 mg, 20 mg, or 40 mg) for participants receiving a lipid-lowering treatment other than atorvastatin or not at stable dose of atorvastatin 10 mg, 20 mg, or 40 mg for at least 6 weeks prior to the screening, or drug naive participant

   OR

   • At the first visit for participants who were being treated with stable dose of atorvastatin (10 mg, 20 mg, or 40 mg) for at least 6 weeks prior to screening

2. Participants not previously instructed on a cholesterol-lowering diet

3. Participants with type 1 diabetes

4. Participants with type 2 diabetes treated with insulin

5. Participants with type 2 diabetes and with an glycated hemoglobin (HbA1c) ≥ 8.5% at screening visit (considered poorly controlled)

6. Laboratory findings measured before randomization:

   • Triglycerides (TG) > 350 mg/dL (> 3.95 mmol/L) at screening visit
   • Positive serum or urine pregnancy test in females of childbearing potential

7. Pregnant or breast-feeding women

8. Women of childbearing potential with no effective contraceptive method

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.