Global landscape of neuromyelitis optica spectrum disorder clinical trials: trends in therapies, geography, and outcomes

Background: Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disease for which several targeted therapies have emerged in recent years. A systematic overview of registered clinical trials can clarify development trends and research priorities. Methods: We searched the Trialtrove database for interventional NMOSD trials registered up to August 15, 2025. Eligible studies were analyzed for trial phase, status, geography, therapeutic agents, and primary endpoints. Results: A total of 141 trials met inclusion criteria. Phase I studies were most common (35.8%), while phase III trials (14.2%) exceeded standalone phase II designs (13.3%). Nearly half were completed, though 31.9% lacked public results. China (64.5%) and the United States (24.8%) led global activity. Therapeutic programs focused on B-cell depletion (34.0%), complement C5 inhibition (17.6%), and IL-6 receptor blockade (10.9%), with BTK inhibitors and other novel approaches emerging. Primary endpoints emphasized safety and relapse prevention, while visual outcomes, patient-reported measures, and biomarkers were rarely included. Conclusion: Taken together, these findings illustrate the rapid expansion of NMOSD clinical research, alongside persistent gaps in transparency and trial design. NMOSD research has expanded rapidly, driven by biologics and regulatory momentum. Future trials should strengthen transparency, address recruitment challenges, and broaden outcome measures to better reflect patient needs.