Effect of a Monoclonal Antibody to PCSK9 on Low-Density Lipoprotein Cholesterol Levels in Statin-Intolerant Patients

Abstract

An estimated 10% to 20% of patients cannot tolerate statins or adequate doses to achieve treatment goals. Plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low-density lipoprotein (LDL) receptors, promoting their degradation and increasing LDL cholesterol levels. In phase 1 studies, a human monoclonal antibody to PCSK9, AMG145, was well tolerated and reduced LDL cholesterol levels. To assess the efficacy and tolerability of AMG145 in patients with statin intolerance due to muscle-related side effects. A 12-week, randomized, double-blind, placebo- and ezetimibe-controlled, dose-ranging study conducted between July 2011 and May 2012 in statin-intolerant adult patients at 33 international sites. Patients were randomized equally to 1 of 5 groups: AMG145 alone at doses of 280 mg, 350 mg, or 420 mg; AMG145 at 420 mg plus 10 mg of ezetimibe; or 10 mg of ezetimibe plus placebo. AMG145 or placebo was administered subcutaneously every 4 weeks. The primary end point was percentage change from baseline to week 12 in ultracentrifugation-measured LDL cholesterol. Other end points included measures of safety and tolerability of different doses of AMG145 and AMG145 plus ezetimibe. Of 236 patients screened, 160 were randomized (mean age, 62 years; 64% female; mean baseline LDL cholesterol, 193 mg/dL); all patients had intolerance to 1 or more statins because of muscle-related events. At week 12, mean changes in LDL cholesterol levels were -67 mg/dL (-41%; 95% CI, -49% to -33%) for the AMG145, 280-mg, group; -70 mg/dL (-43%; 95% CI, -51% to -35%) for the 350-mg group; -91 mg/dL (-51%; 95% CI, -59% to -43%) for the 420-mg group; and -110 mg/dL (-63%; 95% CI, -71% to -55%) for the 420-mg/ezetimibe group compared with -14 mg/dL (-15%; 95% CI, -23% to -7.0%) for the placebo/ezetimibe group (P < .001). Four serious adverse events were reported with AMG145 (coronary artery disease, acute pancreatitis, hip fracture, syncope). Myalgia was the most common treatment-emergent adverse event during the study, occurring in 5 patients (15.6%) in the 280-mg group (n = 32); 1 patient (3.2%) in the 350-mg group (n = 31), 1 patient (3.1%) in the 420-mg group (n = 32), 6 patients (20.0%) receiving 420-mg AMG145/ezetimibe, and 1 patient (3.1%) receiving placebo/ezetimibe. In this phase 2 study in statin-intolerant patients, subcutaneous administration of a monoclonal antibody to PCSK9 significantly reduced LDL cholesterol levels and was associated with short-term tolerability. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01375764.