Secukinumab in Moderate-to-Severe Graves Orbitopathy: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Study

CONTEXT: Interleukin (IL)-17, a key proinflammatory cytokine, drives inflammation and fibrosis in Graves orbitopathy (GO), and elevated IL-17 and Th17 cells correlate with disease activity and severity. OBJECTIVE: The ORBIT study aimed to evaluate the efficacy and safety of secukinumab, an IL-17A inhibitor, in individuals with active, moderate-to-severe GO. METHODS: A randomized, double-blind, placebo-controlled, parallel-group, multicenter trial was conducted. Adults with active, moderate-to-severe, non-sight-threatening GO randomly (1:1) received secukinumab 300 mg or placebo subcutaneously over a 16-week double-blind treatment period, followed by an additional 16-week open-label treatment phase for proptosis nonresponders. Safety parameters, thyroid-related hormones, and autoantibodies were also assessed. The primary end point was overall response of reduced Clinical Activity Score (CAS) of 2 or more points and a reduction of 2 mm or greater in proptosis from baseline without worsening in the fellow eye at week 16. RESULTS: Twenty-eight adult GO patients with a CAS of 4 or greater were enrolled (secukinumab, n = 14; placebo, n = 14). None in either the secukinumab or placebo group achieved an overall response at weeks 16 and 32, respectively, when all patients received open-label secukinumab. No clinically meaningful changes were observed in ophthalmic symptoms and signs, proptosis, lid aperture, eye muscle motility, CAS, and health-related quality of life either at week 16 or week 32. No meaningful effect on serum levels of thyroid-related hormones and antibodies was observed. Secukinumab was well tolerated, with mostly mild adverse events. Neither treatment-induced study discontinuation nor new safety signals were registered. CONCLUSION: Secukinumab did not show clinical efficacy vs placebo when treating patients with active, moderate-to-severe GO.