SAT-500 Response to Tocilizumab Retreatment in Refractory Thyroid Eye Disease

Background: The current standard of care for moderate to severe thyroid eye disease (TED) is intravenous methylprednisolone (IVMP), though alternative immunosuppressive options are emerging. In a recent randomized trial, Tocilizumab (TCZ), an anti-IL-6 receptor antibody, demonstrated improved efficacy for corticosteroid-resistant TED compared to placebo. Clinical response to TCZ retreatment, however, has not been previously reported. Clinical case: A 64-year old man presented with progressive diplopia, eyelid retraction and edema and retrobulbar pain. Initial labs revealed TSH 0.221 uIU/mL, free thyroxine (FT4) 1.11 ng/dL, total T3 172 ng/dL and a thyroid stimulating immunoglobulin (TSI) index of 329 (normal < 140). The patient was a former cigarette smoker who had recently transitioned to e-cigarettes. He was treated with 12 weeks of IVMP with improvement in ocular redness and swelling. Three months following completion of treatment, he presented with worsening left sided proptosis, restrictive strabismus, and compressive optic neuropathy (CON) evidenced by deteriorating central acuity and color vision. He underwent urgent surgical decompression for CON with full restoration of visual acuity. He then received a second 12-week course of IVMP with concomitant orbital radiation. Of note, his hyperthyroidism was well controlled with methimazole. Two months after his second IVMP course, he had a third flare of ophthalmic symptoms. He was then treated with TCZ 8 mg/kg (800mg) IV monthly for six months. The patient’s Clinical Activity Score (CAS) improved from 4 to 2 and TSI index decreased from 610 to 92 (normal). He had significant improvement in periorbital edema, caruncle/plica swelling, and conjunctival injection. However, ten months following completion of the TCZ course he again complained of worsening diplopia and left proptosis. Of note, relapse of his TED symptoms was preceded by an increase in TSI from 92 to 300 two months prior. Orbital CT demonstrated progression of left orbitopathy and increased orbital apex crowding. Following these CT findings he was restarted on TCZ, of which he has now completed 5 additional infusions. His CAS has improved from 3 to 2 and TSI index has decreased from 284 to 100. Conclusion: This is the first reported case of response to successive courses of TCZ in relapsing, severe, corticosteroid-resistant TED. TCZ can be an effective option for refractory TED though retreatment may be necessary for recurrent inflammation. Further study of TCZ is required to determine its role in relapsing TED and the optimal duration of therapy needed. References: Perez-Moreiras et al., 2018. Efficacy of Tocilizumab in patients with moderate to severe corticosteroid resistant Graves’ orbitopathy: a randomized controlled trial. Am J Ophthalmol 195:181