Observational Characterization of the Retreatment Course of Patients With Thyroid Eye Disease

BACKGROUND: To characterize the retreatment course of patients with thyroid eye disease (TED), who had reactivation after initial therapy with teprotumumab. METHODS: This was a single-center longitudinal cohort study of patients who received an initial course of teprotumumab for active TED and were followed for at least 6 months. Reactivation was defined as the increase of proptosis of 2 mm or more or an increase in Clinical Activity Score (CAS) of two points or more, as adapted from the Optic-X study. Data collection included patient age, sex, smoking status, history of thyroidectomy or radioactive iodine, proptosis measurements, clinical activity score (CAS) before initial infusion of teprotumumab, time interval to reactivation, diplopia assessment by the Bahn-Gorman scale, CAS at the time of reactivation, and CAS and proptosis measurements after completion of retreatment and retreatment modalities, including clinical monitoring, corticosteroids, teprotumumab, and/or surgery. Among the reactivated cohort, the treatment response of patients who received a second course of teprotumumab was compared with patients who were treated with intravenous (IV) steroids. RESULTS: Twenty-six percent (11/42) of patients experienced reactivation of TED with an average time to reactivation of 9 (SD:5) months (range: 2-20 months), average CAS at reactivation of 4 (SD:1) (range: 3-7), and average increase in proptosis of 3 (SD:1) mm (range: 2-6 mm). Of the 11 patients who reactivated, 4 received a second course of teprotumumab, while 6 received IV steroids. One patient elected to monitor. The patients who received a second course of teprotumumab had a mean (SD) posttreatment CAS score of 0 reduction in proptosis of 4 (2) mm (range: 3-6). The patients who received IV steroids had a mean (SD) posttreatment CAS of 2 (1) (range: 1-4) and a reduction in proptosis of 0 (1) mm (range: [-1] to [2]). Univariate analyses to look at predictors of reactivation found no correlation between factors such as age, sex, duration of TED, smoking status, presence of diplopia, previous treatment with radioactive iodine, history of periorbital surgery, and/or thyroidectomy after initial completion of teprotumumab between the 2 cohorts. We found a significant correlation between the CAS scores before initial treatment ( P = 0.036) and thyroid hormone dysregulation ( P = 0.006) in those who experienced reactivation. CONCLUSIONS: Patients with TED may experience reactivation of the disease after initial therapy with teprotumumab. Reactivated disease responds to repeat therapy with teprotumumab with higher previous CAS and thyroid hormonal dysregulation being the variables that were significantly associated with reactivation. These data underscore the importance of long-term monitoring and exploring underlying triggers for disease reactivation. Understanding these factors could help predict which patients may require retreatment or chronic dosing with teprotumumab. Further studies are essential to advance our understanding of the immunomodulatory effects of teprotumumab, duration of its therapeutic benefit, and potential retreatment strategies to improve long-term patient outcomes.