Orbital Inflammatory Syndrome Associated with Bispecific T-Cell Engager Therapy: Case and Literature Review

Bispecific T-cell engager (BiTE) immunotherapy is a growing treatment option for various oncologic disorders and is associated with inflammatory side effects. We report a unique case of orbital inflammation following BiTE therapy. Two days after xaluritamig administration, a 70-year-old man developed right-sided periorbital swelling with significantly reduced vision, proptosis, and restricted extraocular motility. MRI revealed right optic nerve sheath enhancement with retrobulbar fat edema. Symptoms resolved with intravenous methylprednisolone followed by an oral taper. BiTE therapy was resumed, and 5 months later, the patient re-presented with similar symptoms developing in the left orbit, which again resolved with corticosteroids. This is the first reported case of BiTE-associated orbital inflammation. BiTE therapies may elicit off-target orbital inflammation via immune activation pathways similar to those described with immune checkpoint inhibitors, despite their distinct mechanisms of T-cell engagement. This case underscores the need for vigilant ocular monitoring and judicious steroid management during BiTE therapy.