Learning Objective:

By the end of this section, learners should be able to explain the role of PCSK9 in LDL receptor regulation, describe how PCSK9 inhibitors lower plasma LDL cholesterol, and understand their clinical use in combination with statin therapy.

Drugs

• Alirocumab,
• Evolocumab

Mechanism of Action

• PCSK9 (Proprotein Convertase Subtilisin/Kexin 9) is a hepatic protease that binds LDL receptors (LDLR) on hepatocytes, targeting them for lysosomal degradation.
• Result: Fewer LDL receptors on the liver surface → reduced clearance of LDL cholesterol from the blood.
• PCSK9 inhibitors (e.g., alirocumab, evolocumab) are monoclonal antibodies that block PCSK9, preventing LDL receptor degradation.
• Effect: Increased LDL receptor density → enhanced clearance of LDL cholesterol → substantial LDL-C reduction.

Clinical Effects

• LDL cholesterol reduction: 50–60% additional decrease beyond what is achieved with statin therapy alone.
• Can be used in
  • heterozygous familial hypercholesterolemia,
  • atherosclerotic cardiovascular disease, or
  • patients intolerant to high-intensity statins.

Administration

• Subcutaneous injection every 2–4 weeks, depending on the agent and dose.
• Often combined with statins or other lipid-lowering therapies for maximal LDL reduction.

Advantages

• Highly effective for patients with persistent hypercholesterolemia despite statins.
• Can achieve LDL levels not possible with statins alone.

Safety

• Generally well tolerated.
• Most common adverse effects: injection site reactions, nasopharyngitis, flu-like symptoms.

Activity