Background: Corticosteroid therapy is often employed in thyroid eye disease (TED), but its efficacy is variable. Teprotumumab and tocilizumab have been considered as effective alternatives. This study aims to evaluate their clinical outcomes and safety in patients with steroid-resistant TED. Methods: A retrospective case-control study was conducted between 2018 and 2022 within a national multicenter health system. Thirty-seven patients with moderate to severe steroid-resistant TED treated with teprotumumab or tocilizumab (cases) were compared with steroid-naïve patients treated with similar therapy (controls). Due to lack of steroid-naïve patients treated with tocilizumab, a control subgroup for tocilizumab was not included in the analysis. Demographic and clinical characteristics were described. Proptosis, diplopia, clinical activity score (CAS), and disease severity (European Group on Graves' orbitopathy classification) were evaluated at weeks 0, 12, 24, and 52 after therapy initiation. Results: Thirty-one patients received teprotumumab (13 cases and 18 controls) and 6 received tocilizumab (cases). The mean age was 57 years (standard deviation ±14.3), median duration of TED was 11.5 months (interquartile range [IQR]: 7.2-17.7), and median excess proptosis was 4 mm (IQR: 2-8) above the upper limit of normal for sex and race. At week 24, in the teprotumumab cases, 81% had proptosis response (reduction of ≥2 mm), 45.5% resolution of diplopia, 85.7% disease inactivation (CAS <3), and 58.3% reverted to mild disease severity. There were comparable results in teprotumumab controls, with no significant differences between subgroups. In the tocilizumab cases, 50% had a proptosis response, 16.7% resolution of diplopia, 100% disease inactivation, and 75% returned to mild disease. In the teprotumumab cases, there was a trend toward worsening proptosis and diplopia between weeks 24 and 52. In the same time frame, the tocilizumab cases had a trend toward worsening diplopia, disease activity, and severity. In the teprotumumab subgroup, 46.2% experienced otic changes and 23.1% hyperglycemia. In the tocilizumab subgroup, there were no reported adverse events. Conclusions: Teprotumumab and tocilizumab improved inflammation in patients with moderate to severe TED who had failed previous steroid therapy. Additionally, the teprotumumab cases demonstrated similar improvement in proptosis and diplopia to the teprotumumab controls. Further evaluation, particularly regarding the long-term response and side effect profile, of these medications in steroid-resistant TED is needed.

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