Circulating Mature PCSK9 Level Predicts Diminished Response to Statin Therapy

BACKGROUND: Statin‐mediated efficacy of lowering low‐density lipoprotein (LDL) cholesterol varies in each individual, and its diminished response is associated with worse outcomes. However, there is no established approach to predict hyporesponse to statins. PCSK9 (proprotein convertase subxilisin/kexin type 9) is a serine‐protease associated with LDL metabolism, which circulates as mature and furin‐cleaved PCSK9. Since mature PCSK9 more potently degrades the LDL receptor, its evaluation may enable the identification of statin hyporesponders. METHODS AND RESULTS: We analyzed 101 statin‐naive patients with coronary artery disease who commenced a statin. PCSK9 subtypes at baseline and 1 month after statin use were measured by ELISA. Hyporesponse to statins was defined as a percent reduction in LDL cholesterol <15%. The relationship between each PCSK9 subtype level and hyporesponse to statins was investigated. Statins significantly lowered LDL cholesterol level (percent reduction, 40%±21%), whereas 11% of study participants exhibited a hyporeseponse to statins. Multivariable logistic regression analysis demonstrated that baseline mature PCSK9 level was an independent predictor for hyporesponse to statins even after adjusting clinical characteristics (mature PCSK9 per 10‐ng/mL increase: odds ratio [OR], 1.12; 95% CI, 1.01–1.24 [P=0.03]), whereas furin‐cleaved level was not (per 10‐ng/mL increase: OR, 1.37; 95% CI, 0.73–2.58 [P=0.33]). Receiver operating characteristic curve analysis identified mature PCSK9 level of 228 ng/mL as an optimal cutoff to predict hyporesponse to statins (area under the curve, 0.73 [sensitivity, 0.91; specificity, 0.56]). CONCLUSIONS: Baseline mature PCSK9 level >228 ng/mL is associated with hyporesponse to statins. This finding suggests that mature PCSK9 might be a potential determinant of hyporesponse to statins.