Aquaporin-4 antibody titration in NMO patients treated with Rituximab: a retrospective study. (S20.007)

Objective: We undertook an observational retrospective study to investigate the usefulness of Aquaporin (AQP)-4 antibodies (Ab) titration in the management of Neuromyelitis Optica (NMO) patients treated with Rituximab (RTX) by studying 1) the correlation between AQP4-Ab titre and disease activity, 2) the influence of RTX on antibody levels, 3) the association between AQP4-Ab levels and responsiveness to RTX. Background: The detection of AQP4-Abs is crucial in the diagnosis of NMO. RTX is widely used to prevent relapses. The usefulness of AQP4-Ab titration in the management of NMO patients treated with RTX has not yet been defined. Design/Methods: A cell-based assay was used for AQP4-Ab titration in 322 serum samples from 7 NMO patients treated with RTX (median follow-up 65 months), according to a treatment-to target approach. Serum samples were collected every month following standardized procedures. Results: 1) In group analysis, AQP4-Ab titres correlated with the disease activity showing higher titres during and preceding relapses than during remission. However, in individual analysis, an increase in AQP4 Ab titres and CD19+ B cells did not always precede a relapse. 2) A reduction of AQP4-Ab titers in short-term and long-term period was observed during RTX treatment. 3) Reduction of AQP4-Ab titres was observed in responder patients both 3 months after RTX infusion, and in the long-term follow up. In one non-responder patient AQP4-Ab levels never decreased during the treatment period. Conclusions: Titration of AQP4-Abs could be useful in the clinical management of NMO patients treated with RTX: titration before each re-infusion and 3 months after each re-infusion may provide information about responsiveness to RTX. Although, a relationship between AQP4-Ab levels, disease activity and response to RTX was observed, the usefulness of AQP4-Ab titration to predict relapses is limited. Study Supported by: Euroimmun Italia. Fondazione Italiana Sclerosi Multipla, grant 2014/PMS/1. Fondazione per la Ricerca Biomedica ONLUS. Disclosure: Dr. Bertolotto received personal compensation for activities with Almirall, Biogen, Merck, Novartis, Sanofi Genzye, and TEVA as a speaker and/or consultant. Dr. Bertolotto has received research support from Biogen, Merck, Novartis, and TEVA. Dr. Capobianco has received personal compensation for activities with TEVA, Almirall, Biogen, Sanofi Genzyme, Merck Serono, Bayer Schering, Novartis, and Roche as a speaker and advisory board member. Dr. Granieri received compensation for activities with Biogen, EMD Serono, and Euroimmun as a speaker. Dr. Marnetto has received personal compensation for activities with Biogen, Euroimmun, and Merck Serono. Dr. Valentino received has received personal compensation for activities with Biogen Idec, Merck Serono and Euroimmun