pegvisomant

Pegvisomant is a pegylated recombinant protein that acts as a growth hormone receptor antagonist. It is used in adults with acromegaly who are not adequately controlled by surgery, radiotherapy, or other medical therapies, or who cannot tolerate alternative treatments. By blocking growth hormone signaling, it lowers circulating IGF-1 levels and can improve associated symptoms.

The drug binds to the growth hormone receptor without activating it, preventing endogenous growth hormone from signaling. The attached polyethylene glycol (PEG) increases its size and half-life, allowing less frequent clearance and reducing immunogenicity. Because it blocks receptor activity rather than replacing hormone, pegvisomant does not directly suppress pituitary GH secretion.

Pegvisomant is given by subcutaneous injections, typically daily, with dose adjustments guided by measurements of serum IGF-1 to maintain levels within the normal range for age. Because the mechanism does not suppress GH production, serum growth hormone levels can rise during treatment, which is not indicative of worsening disease when IGF-1 is controlled.

Common adverse effects include injection-site reactions, flu-like symptoms, diarrhea, and nausea. Liver function test abnormalities have been reported and monitoring of hepatic enzymes is recommended due to a potential risk of hepatic dysfunction. Rare immune reactions or development of anti-drug antibodies have been described in some patients.

Pegvisomant is often used as part of a broader treatment plan for acromegaly and may be combined with somatostatin analogs or other therapies as clinically indicated. Regular monitoring of IGF-1, liver function, and clinical response guides ongoing management.