Transitioning to a C5 inhibitor for aquaporin-4 antibody–positive neuromyelitis optica spectrum disorder intolerant of anti-CD19 therapy: a case report

• Hypogammaglobulinemia and infections may complicate anti-CD19 therapy • Timing, vaccination, and antibiotic prophylaxis inform treatment switch decisions • C5 inhibitor treatment demonstrates effective control of AQP4-IgG+ NMOSD • Transition to ravulizumab from eculizumab allows for less frequent treatment dosing : Neuromyelitis optica spectrum disorder (NMOSD) is a rare inflammatory disease of the central nervous system associated with pathogenic aquaporin-4 (AQP4) immunoglobulin G (IgG) antibodies. Without treatment, patients experience recurrent attacks, which can lead to significant disability from accumulated neurological damage. Agents targeting CD19, interleukin-6 receptor, and complement C5 have been approved for treatment of patients with AQP4-IgG+ NMOSD. Real-world data on patients transitioning from an anti-CD19 therapy to a C5 inhibitor are limited, and there are no published data on transitioning between C5 inhibitors, eculizumab and ravulizumab. : We describe a patient with AQP4-IgG+ NMOSD who transitioned from inebilizumab to eculizumab after developing hypogammaglobulinemia and infections; the patient later transitioned to ravulizumab for less frequent dosing. : Throughout treatment with inebilizumab, eculizumab, and ravulizumab, the patient remained clinically and radiographically stable. : This complex case highlights the importance of monitoring and managing treatment-related complications associated with anti-CD19 therapy and key factors to consider when transitioning from B-cell–depleting therapy to complement inhibition therapy.