50 eligible patients ( aged 12 years ) with homozygous familial hypercholesterolaemia , on stable lipid-regulating therapy for at least 4 weeks , and not receiving lipoprotein apheresis , were randomly allocated by a computer-generated randomisation sequence in a 2:1 ratio to receive subcutaneous evolocumab 420 mg or placebo every 4 weeks for 12 weeks .