Reduction in extraocular muscle and orbital fat volumes after teprotumumab treatment in Japanese patients with thyroid eye disease: an exploratory magnetic resonance imaging analysis from the OPTIC-J trial.

PURPOSE: This substudy of the OPTIC-J trial analyzed magnetic resonance imaging (MRI) scans from a subset of Japanese patients to examine changes in orbital tissues after teprotumumab treatment vs placebo for active thyroid eye disease (TED). STUDY DESIGN: Post hoc exploratory. METHODS: Volumes and inflammation/edema of extraocular muscles (EOMs) and orbital fat were measured before and after 24 weeks of teprotumumab treatment or placebo using MRI in patients enrolled at four of the 16 trial sites. Inflammation/edema in EOM and orbital fat were evaluated using the signal intensity ratio, based on T2 intensity in the cerebral white matter, and an ordinal grading scale (0-3), respectively. Key clinical outcomes included proptosis, diplopia, and clinical activity score (CAS). RESULTS: Mean (%) changes in total EOM and orbital fat volumes in study eyes treated with teprotumumab (n = 6) and placebo (n = 8) were -1,022 mm3 (-31%; P = 0.007) and -348 mm3 (-11%; P = 0.039), and -771 mm3 (-6%; P = 0.120) and 418 mm3 (4%; P = 0.084), respectively. Reductions were significantly greater with teprotumumab vs placebo (EOM, P = 0.021; fat, P = 0.016). Mean (%) changes in total EOM and orbital fat inflammation/edema grading of study eyes treated with teprotumumab were -1.82 (-31%; P = 0.005) and -1 (P = 0.031), respectively. Patients administered teprotumumab exhibited improvements in proptosis (83%), diplopia (67%), and resolution of activity determined by CAS (50%). CONCLUSION: In this OPTIC-J trial substudy, reductions in orbital soft tissue volumes and inflammation/edema were observed with MRI after teprotumumab treatment vs placebo; corresponding improvements in TED clinical outcomes were also observed.