Context: 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.
Objective: To assess the efficacy and tolerability of AMG145 in patients with statin intolerance due to muscle-related side effects.
Design, setting, and patients: 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.
Intervention: 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.
Main outcome measures: 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.
Results: 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.
Conclusion: 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.