Effectiveness of Rituximab in Pediatric OMS Patients.

Opsoclonus-myoclonus syndrome (OMS) is a rare but pervasive, paraneoplastic neurological disorder, purported to be autoantibody-mediated. We demonstrated expansion of B-cells in cerebrospinal fluid (CSF) despite tumor resection, chemotherapy, or conventional immunotherapy. Whether B-cells can be purged from the CSF compartment with benefit to the patient is unknown. Targeting of CSF B lymphocytes represents a novel and valuable paradigm shift in the therapy of centrally-mediated paraneoplastic disorders. The objective of this preliminary study is to determine if rituximab, a monoclonal antibody against CD20+ B-cells, reduces or eliminates CSF B-cells in OMS and whether the reduction results in clinical improvement. B lymphocyte subsets and relevant T-cell subsets will be immunophenotyped in the CSF and peripheral blood of children with OMS by four-color dual-laser flow cytometry. Sixteen children with an increased percentage of CSF B-cells will be treated with rituximab 375 mg/m2 IV once weekly for four consecutive weeks and CSF testing will be repeated at six months with more frequent clinical evaluations and blood testing out to 12 months. Clinical outcome will be rated blindly from videotapes by an experienced observer using a validated 12-item motor evaluation scale and quantifiable parameters of sleep, behavior and motor function. Immunological outcome variables will include percentages of B-cell subsets and quantitative immunoglobulins. Post-treatment results will be compared to pre-treatment values statistically. If rituximab proves to be an efficacious and safe method of treating CSF B-cell expansion and the neurological syndrome, this study will lead to a phase II trial with the eventual aim of gaining FDA approval of rituximab for this indication.