Anti-Drug Antibody-Associated Biologic Switch in Bilateral Aggressive Mooren’s Ulcer

PURPOSE: To report a case of bilateral aggressive Mooren's ulcer (MU) requiring hospitalization, multimodal immunosuppression, and anti-tumor necrosis factor (TNF)-α biologic switching guided by therapeutic drug monitoring due to anti-adalimumab antibody (AAA) formation. METHODS: Observational case report prepared in accordance with the CARE guidelines. A 47-year-old man presented to the emergency department with bilateral corneal ulceration and high perforation risk. Comprehensive infectious and autoimmune evaluation was performed. Treatment included topical and systemic corticosteroids, methotrexate, amniotic membrane grafting, tarsorrhaphy, and sequential biologic therapy. RESULTS: Bilateral aggressive MU was diagnosed after exclusion of infectious and systemic autoimmune etiologies, including the absence of scleritis. The patient required escalation from adalimumab to infliximab following AAA formation associated with secondary loss of response. Serum adalimumab trough concentration and AAA were measured by enzyme-linked immunosorbent assay (ELISA) at the time of suspected treatment failure. At two-year follow-up on continuous infliximab therapy, the right eye had dense corneal scarring with hand motion vision, while the left eye achieved 20/20 best-corrected visual acuity following cataract extraction during sustained disease quiescence, with no recurrence observed. CONCLUSION: This case illustrates AAA-associated biologic switching in MU-a phenomenon well described in uveitis but not previously reported in peripheral ulcerative keratitis. Therapeutic drug monitoring may have a role in optimizing biologic therapy for severe corneal autoimmune disease.