Sirolimus in Graves' Orbitopathy

Graves\' Orbitopathy (GO) is a disabling and disfiguring condition associated with Graves\' Disease, due to autoimmunity against antigens expressed by the thyroid and orbital tissues, and resulting in orbital fibroblast proliferation and release of glycosaminoglycans. The current treatments available, especially glucocorticoids, are not effective in all patients. Two cases of patients with GO treated with Sirolimus have been reported with an excellent response to the drug. The rationale for the use of Sirolimus lies in its mechanisms of action. Sirolimus is able to inhibit T-cell activation as well as fibroblast proliferation. In addition, acts indirectly on the Insulin-Like Growth Factor-1 (IGF-1) pathway, and recent clinical trials have shown that a monoclonal antibody against the IGF-1 receptor (Teprotumumab) is effective in patients with GO. Thus, Sirolimus could be used in GO as monotherapy in patients with GO. The aim of the present drug vs standard treatment, observational study is to evaluate the efficacy of Sirolimus as a second-line treatment in patients with moderately severe, active GO.