Inhibition of Fibrotic Contraction by Sirolimus (Rapamycin) in an Ex Vivo Model of Thyroid Eye Disease

Graves disease: latest understanding of pathogenesis and treatment options

Graves disease is the most common cause of hyperthyroidism in iodine-sufficient areas. The main responsible mechanism is related to autoantibodies that bind and activate the thyrotropin receptor (TSHR). Although Graves hyperthyroidism is relatively common, no causal treatment options are available. Established treatment modalities are antithyroid drugs, which reduce thyroid hormone synthesis, radioactive iodine and surgery. However, emerging drugs that target the main autoantigen (monoclonal antibodies, small molecules, peptides) or block the immune pathway have been recently tested in clinical trials. Graves disease can involve the thyroid exclusively or it can be associated with extrathyroidal manifestations, among which Graves orbitopathy is the most common. The presence of Graves orbitopathy can change the management of the disease. An established treatment for moderate-to-severe Graves orbitopathy is intravenous glucocorticoids. However, recent advances in understanding the pathogenesis of Graves orbitopathy have allowed the development of new target-based therapies by blocking pro-inflammatory cytokine receptors, lymphocytic infiltration or the insulin-like growth factor 1 receptor (IGF1R), with several clinical trials providing promising results. This article reviews the new discoveries in the pathogenesis of Graves hyperthyroidism and Graves orbitopathy that offer several important tools in disease management.

Long-term outcome of Graves' orbitopathy following treatment with sirolimus

OBJECTIVES

Sirolimus was found to be associated with a better outcome of Graves' orbitopathy (GO) at 24 weeks compared to methylprednisolone. We conducted a retrospective study to investigate its efficacy and safety over a longer period.

METHODS

Data from 40 consecutive patients with moderate-to-severe, active GO, 20 treated with sirolimus and 20 with methylprednisolone, were collected.

PRIMARY OUTCOME

overall outcome (composite evaluation) of GO at 48 weeks.

SECONDARY OUTCOMES

(1) GO outcome at 24 weeks, and, at 24 and 48 weeks: (2) outcome of single eye features; (3) quality of life (GO-QoL); (4) TSH-receptor antibodies; (5) GO relapse at 48 weeks; (6) adverse events.

RESULTS

The overall GO outcome at 48 weeks did not differ between the two groups (responders: 55% vs 55%). At 24 weeks, prevalence of responders was greater in sirolimus group (65% vs 25%; P = 0.01). A reduction ≥ 1 point in clinical activity score (CAS) was more frequent in sirolimus patients at 24 (85% vs 40%; P = 0.005) and 48 weeks (75% vs 60%; P = 0.03). The proportion of GO-QoL responders (appearance subscale) at 24 weeks was greater in sirolimus group (62.5% vs 26.3%; P = 0.03). No difference was observed for the remaining outcome measures.

CONCLUSIONS

Treatment with sirolimus is followed by a greater overall response of GO compared with methylprednisolone at 24 weeks, but not at 48 weeks, when only CAS is affected. A more prolonged period of treatment may be required for a better outcome to be observed over a longer period.

Current Therapeutic Approaches for Graves' Orbitopathy - are Targeted Therapies the Future?

Graves' orbitopathy is an autoimmune disease of the orbit that most frequently occurs with Graves' hyperthyroidism. The occurrence of autoantibodies directed against the TSH receptor (TRAb) is of central importance for the diagnosis and pathogenesis. These autoantibodies are mostly stimulating, and induce uncontrolled hyperthyroidism and tissue remodelling in the orbit and more or less pronounced inflammation. Consequently, patients suffer to a variable extent from periocular swelling, exophthalmos, and fibrosis of the eye muscles and thus restrictive motility impairment with double vision. In recent decades, therapeutic approaches have mainly comprised immunosuppressive treatments and antithyroid drug therapy for hyperthyroidism to inhibit thyroid hormone production. With the recognition that TRAb also activates an important growth factor receptor, IGF1R (insulin-like growth factor 1 receptor), biological agents have been developed. Teprotumumab (an inhibitory IGF1R antibody) has already been approved in the USA and the therapeutic effects are enormous, especially with regard to the reduction of exophthalmos. Side effects are to be considered, especially hyperglycaemia and hearing loss. It is not yet clear whether the autoimmune reaction (development of the TRAb/attraction of immunocompetent cells) is also influenced by anti-IGF1R inhibiting agents. Recurrences after therapy show that the inhibition of antibody development must be included in the therapeutic concept, especially in severe cases.