Pegvisomant

PEGylated, genetically modified version of human growth hormone that acts as a growth hormone receptor antagonist. FDA-approved for acromegaly patients who do not respond well to surgery or other drugs. Works by binding growth hormone receptors with high affinity at one site but blocking productive binding at the second site, preventing the receptor pair from forming the working complex. This stops the liver and other tissues from producing IGF-1, the hormone responsible for most acromegaly symptoms. Does not shrink the pituitary tumor or lower circulating growth hormone levels.