Mechanism of action of pegvisomant
- Pegvisomant is a human GH receptor antagonist that competes with endogenous GH for binding to its receptor and blocks production of IGF-1.
- This improves the clinical effects and metabolic defects in acromegaly. Pegvisomant controls IGF-1 levels in about two thirds of patients.
- It does not appear to affect tumor size in the great majority of patients, but tumor size should be monitored, given the drug’s mechanism of action.
- It is usually used in patients who are resistant to or do not tolerate somatostatin analogues, or in combination with somatostatin analogues to improve biochemical control.
- The main side effect of pegvisomant is liver function abnormalities, which are usually transient.
- Note that IGF-1 remains an accurate biomarker for acromegaly control in pegvisomant-treated patients, but GH levels cannot be monitored because of the persistence of GH hypersecretion.