Pegvisomant: a new treatment modality for acromegaly

Acromegaly, a multisystemic disease resulting from excessive growth hormone (GH) and insulin-like growth factor-I (IGF-I) levels in adults, is associated with a two-to-threefold increase in mortality. The available treatment options (surgery, radiotherapy and medical treatment with somatostatin analogues or dopamine agonists) fail to achieve the currently accepted goals of therapy in a substantial number of patients. Pegvisomant, a newly developed GH receptor antagonist, represents a novel treatment modality for this disease. It binds with the GH receptor and induces internalization, but blocks receptor signaling events, thereby reducing IGF-I production. The two main published studies suggest that it is the most potent medical therapy with greater specificity, without being dependent on the tumour characteristics. However, apart from its high cost and the dilemmas raised concerning the appropriateness of using serum IGF-I concentrations as a marker of disease activity, it may also occasionally be associated with elevations in liver enzyme levels. Further studies are required to confirm its high success rates as well as to investigate the possibility of inducing an increase in the pituitary tumour size. Currently, pegvisomant is a second line treatment for acromegaly with an adjuvant role and possibly of greater value in cases of resistance to other therapeutic options.