Statins are the most-effective
therapy currently available for lowering the
LDL-cholesterol (
LDL-C) level and preventing cardiovascular events. Additional
therapies are necessary for patients who cannot reach the target
LDL-C level when taking the maximum-tolerated dose of a
statin.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an
enzyme with an important role in
lipoprotein metabolism. Rare gain-of-function mutations in PCSK9 lead to a high
LDL-C level and premature
coronary heart disease, whereas loss-of-function variants lead to a low
LDL-C level and a reduced incidence of
coronary heart disease. Furthermore, the PCSK9 level is increased with
statin therapy through negative feedback, which promotes
LDL-receptor degradation and decreases the efficacy of
LDL-C lowering with
statins. PCSK9 inhibition is, therefore, a rational therapeutic target, and several approaches are being pursued. In phase I, II, and III trials, inhibition of PCSK9 with
monoclonal antibodies has produced an additional 50-60% decrease in the
LDL-C level when used in combination with
statin therapy, compared with
statin monotherapy. In short-term trials,
PCSK9 inhibitors were well tolerated and had a low incidence of adverse effects. Ongoing phase III trials will provide information about the long-term safety of these drugs, and their efficacy in preventing cardiovascular events.