Relationship Between Low-Density Lipoprotein Cholesterol, Free Proprotein Convertase Subtilisin/Kexin Type 9, and Alirocumab Levels After Different Lipid-Lowering Strategies

Background-Alirocumab undergoes target-mediated clearance via binding of proprotein convertase subtilisin/kexin type 9 (PCSK9). Statins increase PCSK9 levels; the effects of nonstatin lipid-lowering therapies are unclear. Every-4-weeks dosing of alirocumab may be appropriate for some patients in absence of background statin but is not yet approved. Methods and Results-Low-density lipoprotein cholesterol (LDL-C), PCSK9, and alirocumab levels were assessed in subjects (LDL-C >130 mg/dL, n=24/group) after a 4-week run-in taking oral ezetimibe, fenofibrate, or ezetimibe placebo, when alirocumab 150 mg every 4 weeks (days 1, 29, and 57) was added. Maximal mean LDL-C reductions from day -1 baseline (prealirocumab) occurred on day 71 in all groups: alirocumab plus placebo, 47.4%; alirocumab plus ezetimibe, 56.6%; and alirocumab plus fenofibrate, 54.3%. LDL-C reductions were sustained through day 85 with alirocumab plus placebo (47.0%); the duration of effect was slightly diminished at day 85 versus day 71 with ezetimibe (49.6%) or fenofibrate combinations (43.2%). Free PCSK9 concentrations were lowest at day 71 in all groups, then increased over time; by day 85, free PCSK9 concentrations were higher, and alirocumab levels lower, with alirocumab plus fenofibrate, and to a lesser extent alirocumab plus ezetimibe, versus alirocumab plus placebo. Conclusions-Alirocumab 150 mg every 4 weeks produced maximal LDL-C reductions of 47% in combination with placebo and 54% to 57% in combination with ezetimibe or fenofibrate. The oral lipid-lowering therapies appear to increase PCSK9 levels, leading to increased alirocumab clearance. Although the duration of effect was modestly diminished with alirocumab plus ezetimibe/fenofibrate versus placebo, the effect was less than observed in trials with background statins, and it would not preclude the use of alirocumab every 4 weeks in patients taking these nonstatin lipid-lowering therapies concomitantly.