Pegvisomant

Pegvisomant (trade name Somavert) is a growth hormone receptor antagonist used in the treatment of acromegaly. It is used if the tumor of the pituitary gland causing the acromegaly cannot be controlled with surgery or radiation, and the use of somatostatin analogues is unsuccessful. It is delivered as a powder that is mixed with water and injected under the skin.

Structure
Pegvisomant is a protein containing 191 amino acid residues to which several polyethylene glycol polymers have been covalently bound in order to slow clearance from the blood. The protein is a modified version of human growth hormone designed to bind to and block the growth hormone receptor. It is manufactured using genetically modified E. coli bacteria. The polyethylene glycol polymers are subsequently added chemically.

Mechanism of action
Pegvisomant blocks the action of growth hormone at the growth hormone receptor to reduce the production of IGF-1. IGF-1 is responsible for most of the symptoms of acromegaly thus normalising its levels is effective to control the symptoms.

Side effects
Side effects of Pegvisomant include reactions at the injection site, swelling of the limbs, chest pain, hypoglycemia, nausea and hepatitis.

Blocking of the growth hormone's receptor reduces feedback control of the growth hormone regulation leading to approximately doubled GH levels.