Peripheral arterial disease (PAD) is characterized by lower limb arterial obstruction due to atherosclerosis. Magnetic resonance imaging (MRI) methods can accurately quantify atherosclerotic plaque in the superficial femoral artery (SFA) in patients with PAD. Such techniques have demonstrated plaque regression with statin therapy over 1 year. Alirocumab is a PCSK9 inhibitor that effectively reduces LDL cholesterol up to 70% in patients on statins or intolerant to statins. The investigators hypothesize that effective low density lipoprotein (LDL) lowering with Alirocumab 150m subcutaneously (SQ) every 2 weeks will regress atherosclerotic plaque in the SFA in patients with PAD over one year compared to placebo. 54 patients with mild-moderate PAD (ankle brachial index or ABI 0.4-0.9) will be randomized to alirocumab 150 mg SQ every 2 weeks or matching placebo at the University of Virginia (UVA) (n=34) and Northwestern (n=20). The primary endpoint is change in atherosclerotic plaque volume in the superficial femoral artery over the 1 year treatment period. Secondary endpoints include changes in peak calf muscle perfusion after thigh cuff occlusion/hyperemia, 6-minute walk distance, and blood biomarkers (LDL cholesterol, fibrinogen, high sensitivity c-reactive protein (hs-CRP), and lipoprotein(a).