Study in Participants With Homozygous Familial Hypercholesterolemia (HoFH)

The primary objective of the study is to demonstrate the reduction of low-density lipoprotein cholesterol (LDL-C) with alirocumab subcutaneous (SC) every 2 weeks (Q2W) in comparison to placebo after 12 weeks of treatment.

The secondary objectives of the study are:

* To evaluate the effect of alirocumab Q2W on other lipid parameters (ie, apolipoprotein \[Apo\] A-1 and B, non-high-density lipoprotein cholesterol \[non-HDL-C\], total-cholesterol \[TC\], proportion of participants with 15%, 30%, and 50% LDL-C reductions, Lp(a), HDL-C, triglycerides \[TG\]) in participants with HoFH
* To evaluate the safety and tolerability of alirocumab SC Q2W in participants with HoFH
* To assess the pharmacokinetics of alirocumab SC Q2W in participants with HoFH
* To assess the potential development of anti-drug (alirocumab) antibodies


Eligibility Criteria:
Note: The information listed below is not intended to contain all considerations relevant to a patient's potential participation in this clinical trial, therefore not all inclusion/exclusion criteria are listed.

Key Inclusion Criteria

1. Diagnosis of HoFH by at least 1 of the following genotype or clinical criteria (all patients on LDL apheresis must be diagnosed based on genotype):

   1. Documented homozygous or compound heterozygous mutations in both low-density lipoprotein receptor (LDLR) alleles
   2. Presence of homozygous or compound heterozygous mutations in Apo B, PCSK9 or LDL receptor adaptor protein 1 (LDLRAP1)
   3. Presence of double heterozygous mutations, i.e, mutations on different genes in the LDLR, Apo B or PCSK9 alleles
   4. Untreated TC \>500 mg/dL (12.93 mmol/L) and TG \<300 mg/dL (3.39 mmol/L) AND Both parents with history of TC \>250 mg/dL (6.46 mmol/L) OR cutaneous or tendinous xanthoma before age 10
2. Receiving a stable dose of a statin at the screening visit (documentation if statin ineffective or patient unable to tolerate statin)
3. If undergoing LDL apheresis, must have initiated LDL apheresis at least 3 months prior to screening and must have been on a stable weekly (every 7 days) or every other week (every 14 days) schedule or stable settings for at least 8 weeks

Key Exclusion Criteria:

1. Documented evidence of a null mutation in both LDLR alleles
2. Use of a PCSK9 inhibitor within 10 weeks from screening visit
3. Background medical lipid modifying therapy (LMT) that has not been stable for at least 4 weeks (6 weeks for fibrates, 24 weeks for mipomersen, 12 weeks for maximum tolerated dose of lomitapide) before the screening visit.
4. LDL apheresis schedule/apheresis settings that have not been stable for at least 8 weeks before the screening visit or an apheresis schedule/settings that is not anticipated to be stable over the next 24 weeks.
5. Use of nutraceuticals or over-the-counter (OTC) therapies known to affect lipids, at a dose/amount that has not been stable for at least 4 weeks prior to the screening visit or between the screening and randomization visits.
6. Chronic use of systemic corticosteroids, unless on a stable regimen of 10 mg daily prednisone equivalent or less for at least 6 weeks prior to randomization. Note: topical, intra-articular, nasal, inhaled and ophthalmic steroid therapies are not considered as 'systemic' and are allowed
7. Systolic blood pressure \>160 mmHg or diastolic blood pressure \>100 mmHg at the screening visit (1 repeat measurement is allowed).
8. LDL-C level \<70 mg/dL (1.81 mmol/L) at the screening visit
9. History of a myocardial infarction (MI), unstable angina leading to hospitalization, coronary artery bypass graft surgery, percutaneous coronary intervention , uncontrolled cardiac arrhythmia, carotid surgery or stenting, stroke, transient ischemic attack, valve replacement surgery, carotid revascularization, endovascular procedure or surgical intervention for peripheral vascular disease within 3 months prior to the screening visit.