Real-World Efficacy and Safety of Mycophenolate Mofetil in Active Moderate-to-Sight-Threatening Thyroid Eye Disease

PURPOSE: There is no universal consensus on second-line agents for the treatment of moderate/severe to sight-threatening thyroid eye disease (TED) to maintain remission after first-line intravenous methylprednisolone (IVMP). This study investigates the efficacy and safety of mycophenolate mofetil (MMF) in TED patients in a real-world setting and over a longer period than previous randomized controlled trials. METHODS: A retrospective cohort study of TED patients with active moderate/severe to sight-threatening TED seen over a 4-year period. Data collected were visual acuity (VA), Clinical Activity Score (CAS), Gorman Diplopia scores, MMF dosing and side effects at 24, 52 and 78 weeks. Clinical efficacy was defined as an absence of relapse: no decline in best corrected LogMAR VA, no need for further steroids, no increase in CAS of ≥2. RESULTS: Out of 23 patients, 20 patients were included in this study. 10% (2/20) stopped MMF before 24 weeks. Median duration of MMF treatment was 76 weeks (1–140 weeks). 55% (11/20) had dysthyroid optic neuropathy (DON). In those with active moderate-severe TED without DON, clinical efficacy was seen in 100% (8/8) at 24 weeks, 87.5% (7/8) at 52 weeks, and 83.3% (5/6) at 78 weeks, with CAS decreasing from a baseline of 2.78±1.99 to 0.50±0.58 at 24 weeks, 0.50±0.82 at 52 weeks and 1.00±1.30 at 78 weeks. In DON, improvements were seen in 90% (9/10) at 24 weeks, 100% (7/7) at 52 weeks and 100% (4/4) at 78 weeks, with significantly reduced CAS scores from 2.55±1.54 to 0.83±1.27, 1.00±1.17 and 0.63±0.95 at 24, 52 and 78 weeks, respectively. Gorman score, VA and soft tissue inflammation parameters also improved throughout. There were two significant side effects over the treatment period. CONCLUSION: MMF appears to be an effective and safe second-line immunosuppressive agent. Further studies aimed at elucidating optimal dosing regimens and ideal treatment duration will prove helpful.