The PCSK9 Inhibitors: A Novel Therapeutic Target Enters Clinical Practice

There is a critical need for alternative, potent agents that can reduce low-density lipoprotein cholesterol (LDL-C) levels in patients with heterozygous familial hyperlipidemia and statin intolerance and those not reaching lipid-lowering treatment goals who are at high risk for cardiovascular (CV) events. The first proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor was approved in July 2015 by the US Food and Drug Administration as an adjunct to diet and maximally tolerated statin therapy for treatment of adults with heterozygous familial hyperlipidemia or clinical atherosclerotic CV disease, who require additional lowering of LDL-C levels. In clinical trials, PCSK9 inhibitors have been shown to reduce LDL-C levels by as much as 60% to 70% when administered as monotherapy or as an add-on treatment to statins and other lipid-lowering therapies. In studies of PCSK9 genetic mutations, loss of function in the PCSK9 allele was associated with a relative decrease of 88% in the risk for atherosclerotic CV events during 15 years of patient follow-up. The use of PCSK9 inhibitors may eventually support the LDL-C hypothesis that the lower the LDL-C level, the lower the CV risk. Although some recent clinical practice guidelines have deemphasized the importance of numeric LDL-C targets, many clinicians are reluctant to discard them, and this position is supported by recent clinical evidence. We eagerly await the results of the ODYSSEY, FOURIER, and SPIRE clinical outcome trials, which we anticipate will provide further validation that "lower is better" with respect to reducing LDL-C levels and improving clinical outcomes.