Perspectives of new potential therapeutic applications of somatostatin analogs

At the present time only two long-acting somatostatin (SS) analogs, octreotide and lanreotide, are commonly used in the routine therapy. Both analogs have a high affinity mainly to a somatostatin receptor subtype 2 (SSTR2). The established indications for SS analogs treatment include acromegaly, neuroendocrine tumors of the pancreas and gastrointestinal tract, and some gastro-enterologic diseases (pancreatitis, gastrointestinal bleedings, refractory diarrheas, pancreatic and intestinal fistulas). The recent investigations allow to predict the enlargement of therapeutic applications of SS analogs. It concerns pituitary tumors other than somatotropinoma, tumors of other endocrine glands like thyroid and adrenal gland, as well as some non-endocrine tumors. The progress depends on the introduction of new SS analogs with high affinity for SS receptor subtypes other than SSTR2, because some tumors present the high expression of SSTR1 (e.g. prostatic cancers) or SSTR5 (e.g. colonic cancers). Great hopes are connected with the coupling of SS analogs with the radioactive isotopes or non-radioactive cytotoxic agents to destruct the neoplastic cells highly expressing the specific subtypes of SS receptors. The pre- or postoperative in vivo imaging of SS receptors by means of the receptor scintigraphy, as well as the post-operative identification of SS receptor subtypes in the excised tumor tissues using immunohistochemistry, should play an important role in the prediction of the effects of SS analog treatment. Beside oncology, new therapeutic applications of SS analogs could be presumed among others in ophthalmology; it concerns the treatment of progressive Graves-Basedow ophtalmopathy, diabetic retinopathy, glaucoma and corneal diseases connected with corneal vascularization.