Targeting IL-6 Receptor Signaling with Satralizumab in Thyroid Eye Disease: Design of the Phase 3 SatraGO-1 and SatraGO-2 Trials

Abstract

Introduction: Thyroid eye disease (TED) is a rare, autoimmune, orbital inflammatory disorder that is disfiguring, debilitating, and potentially sight-threatening. There is an unmet need for a fast-acting, durable, systemic disease-modifying therapy in active TED, for which current options are associated with relapses and side effects, and for chronic inactive TED, which is largely managed with surgery. Satralizumab is a recombinant humanized anti–interleukin-6 receptor (IL-6R) monoclonal antibody that prevents IL-6 from binding to its receptor, thereby reducing proinflammatory and profibrotic signaling. The SatraGO-1 and SatraGO-2 trials evaluated the efficacy, safety, pharmacokinetics, and pharmacodynamics of satralizumab in participants with active, moderate-to-severe, and chronic inactive TED. Methods: SatraGO-1 and SatraGO-2 were two identically designed, 72-week, double-masked, placebo-controlled, multicenter, two-stage randomization, phase 3 trials in adults with active, moderate‑to‑severe TED or chronic inactive TED. Participants were randomized 1:1 to receive satralizumab or matching placebo. Based on the proptosis response assessed at week 24, nonresponders received satralizumab every 4 weeks (Q4W), while responders were rerandomized in a 1:1 ratio to receive satralizumab or placebo Q4W through week 44. The primary end point was the proportion of participants with active, moderate-to-severe TED who achieved ≥ 2-mm reduction in proptosis in the study eye from baseline at week 24. Results: SatraGO-1 and SatraGO-2 enrolled 131 and 127 participants, respectively. Conclusions: The SatraGO-1 and SatraGO-2 trials investigated IL-6R inhibition via satralizumab in TED. Satralizumab offers a potential disease-modifying treatment option for TED while minimizing safety risks associated with current treatments. Trial registration: SatraGO-1 (NCT05987423) and SatraGO-2 (NCT06106828).