Clinical and Histological Characterization of Toxic Keratopathy From Depatuxizumab Mafodotin (ABT-414), an Antibody-Drug Conjugate

To report the histological findings and clinical course of 2 patients with microcyst-like epithelial keratopathy (MEK) associated with antibody-drug conjugate, depatuxizumab mafodotin.Case series.Two patients with glioblastoma multiforme participating in a phase 3 clinical trial of the antibody-drug conjugate, depatuxizumab mafodotin, presented with bilateral MEK. Confocal imaging showed multiple large, round, hyperreflective lesions in the epithelium. Epithelial debridement was performed for symptomatic relief in both patients. Along with aggressive lubrication, bandage contact lenses, and reduction in the chemotherapeutic dose to maintenance levels, both patients experienced symptomatic improvement. However, MEK lesions recurred after re-epithelialization. Immunohistochemistry of the diseased epithelium showed immunoglobulin (Ig)G-positive granular cytoplasmic inclusions and increased cell apoptosis.Depatuxizumab mafodotin accumulates in the basal corneal epithelium resulting in MEK because of increased apoptosis. Frequent lubrication and bandage contact lenses can provide symptom relief.