A Safety and Tolerability Study of CC- 97540 (BMS-086353) in Anti-Aquaporin 4 Antibody Positive Neuromyelitis Optica Patients

The goal of this clinical trial is to find out if the investigational medicine BMS-986353 is safe and well tolerated in adults with anti-aquaporin-4 (AQP4) antibody-positive neuromyelitis optica spectrum disorder (NMOSD). NMOSD is a long-term autoimmune condition that affects the optic nerves and spinal cord and can lead to relapses. Most people with NMOSD have antibodies against AQP4, which are linked to future disease activity. The main questions this study aims to answer are: "-" Is CC-97540 (BMS-986353) safe and well tolerated, based on how many participants experience serious side effects that limit dosing (called dose-limiting toxicities)? "-" Does CC-97540 (BMS-986353) show early signs of benefit, based on how many participants no longer have detectable AQP4 antibodies in their blood (called sero-reversion)? Participants are adults aged 18 to 60 years with AQP4 antibody-positive NMOSD who are currently clinically stable on ravulizumab or satralizumab. Approved NMOSD treatments reduce relapses by changing how the immune system works, but they do not remove the cells that make AQP4 antibodies. This study is designed to see whether BMS-986353 can target these cells without the need for long-term immune suppression. Participants will: "-" Receive CC-97540 (BMS-986353) as part of the study "-" Continue their current NMOSD therapy "-" Attend study visits for safety checks, exams, and lab tests