New perspectives in the medical treatment of acromegaly.
Currently available medical treatment of acromegaly includes dopamine agonists, slow release formulation of somatostatin analogues and pegvisomant, a GH-receptor antagonist. Dopamine agonists are well tolerated, not expensive but poorly effective. Somatostatin analogues are highly effective in 60-70% of patients based on the receptor profile of individual tumors. Pegvisomant is reported to normalize IGF-I levels in nearly the totality of the patients, but is devoted of tumor shrinking effect. In a preliminary study in patients with acromegaly, a new somatostatin analogue with affinity to four of the five somatostatin receptors (SOM230) was shown to be similarly effective as octreotide in some patients and more effective than octreotide in other patients. Moreover, new molecules with selective activity on the somatostatin receptor type 2, or 5, or 1 have been reported in vitro to strongly suppress GH secretion. Other new promising alternatives are the chimeric compounds with both somatostatin receptor and dopamine receptor binding. These drugs have been also shown to possess strong GH-inhibitory activity in primary cultures from GH-secreting adenomas. These drugs are the future perspectives in the treatment of patients with GH-secreting or GH/PRL-secreting tumors.