• Safety and Tolerability of Rituximab in NMO (monitor for any AE during two years of follow up) [ Time Frame: 96 weeks ] [ Designated as safety issue: Yes ]
  

• Time from treatment to recurrence of either optic neuritis or myelitis [ Time Frame: 96 weeks ] [ Designated as safety issue: Yes ]
  
• Change in Kurtzke expanded disability status scale (EDSS) at weeks 4, 12, 24, 48, 72, 96 [ Time Frame: 96 weeks ] [ Designated as safety issue: Yes ]
  

Drug: Rituximab
Rituximab is a highly purified, 1328-amino acid antibody with an approximate molecular mass of 145 kD. Rituximab is a sterile, clear, colorless, preservative-free liquid concentrate for intravenous (IV) administration. Rituximab is supplied at a concentration of 10 mg/mL in either 100 mg (10 mL) or 500 mg (50 mL) single-use vials.

Rituximab is a genetically engineered, chimeric, murine/human monoclonal antibody directed against the CD20 antigen found on the surface of normal and malignant pre-B and mature B cells. The antibody is an IgG1 immunoglobulin containing murine light- and heavy chain variable region sequences and human constant region sequences. Rituximab is composed of two heavy chains of 451 amino acids and two light chains of 213 amino acids (based on cDNA analysis) and has an approximate molecular mass of 145 kD. Rituximab has a binding affinity for the CD20 antigen of ~8.0 nM.

Rituximab was developed by Biogen Idec and Genentech, Inc. It was approved by the FDA in 1997 for the treatment of relapsed or refractory low grade or follicular, CD20+, B-cell non-Hodgkin's lymphoma (NHL).

Rituximab has also been studied in a variety of non-malignant autoimmune disorders where B cells and auto antibodies appear to play a role in pathophysiology. Rituximab has been reported to relieve signs and symptoms of rheumatoid arthritis , lupus , immune thrombocytopenia , autoimmune anemia , autoimmune neuropathy , and paraneoplastic opsoclonus/myoclonus .

A Phase II study (WA16291) has been completed in patients with rheumatoid arthritis (RA) . A total of 161 patients were randomized to 4 treatment arms: Methotrexate, Rituximab alone, Rituximab and Methotrexate, Rituximab and Cyclophosphamide. Two doses of Rituximab, 1 gm each, were administered IV two weeks apart. Infusion reactions were observed in 36% of patients during their first infusion of Rituximab compared to 30% for placebo . Four Rituximab-treated patients developed serious infections, for a rate of 4.6 per 100 patient years. For context, the rate of infections requiring hospital admission was 9.57 per 100 patient years in a community based epidemiologic study in RA. (Doran et al. 2002).

We treated 8 patients with NMO with Rituximab and observed that Rituximab appears to be well tolerated with 0/8 of the patients suffering serious adverse reactions that could be directly related to Rituximab administration. Moreover, 7/8 patients experienced decrease in neurological disability following treatment, suggesting that B-cell depletion may enhance neurological recovery from attacks. 7/8 of the patients remained attack-free within a period of 18 months of follow-up on average (range 3 to 12 months) following treatment. We observed one attack following treatment in a single patient, whereas 14 attacks would have been predicted by the pre-treatment attack rate (p=0.012, paired t test comparing pre- and post-treatment attack rates). Nevertheless, the observed impact of treatment on recovery is more than what would be expected from spontaneous recovery and deserves further investigation. If B cells are essential for pathogenesis of recurrent attacks in NMO, B cell depletion may induce sustained remission. We also observed in one case, a dramatic recovery of electrophysiological conduction in the optic nerves (visual evoked potentials), which implies that in this case, rituxan did not impair repair mechanisms, for example, demyelination following the acute attack.