Effectiveness of Natalizumab in Extended Dosing Interval (P3.078)

Objective: To analyze clinical and radiological evolution of relapsing remitting multiple sclerosis patients (RRMS) treated with natalizumab at Expanded dose (ED) of 300 mg/6 weeks and their VLA-4 saturation levels of lymphocytes. Background: Natalizumab is an effective treatment for RRMS when utilized a standard natalizumab dose of 300mg/4 weeks (SD). The administration of natalizumab in ED can maintain the same effectiveness. VLA-4 saturation levels could be a good indicator to predict clinical and radiological activity. Methods: Descriptive and prospective study of patients treated with at least 13 doses of natalizumab SD who were proposed to receive treatment at ED. Clinical course was analyzed by the annual relapse rate and EDSS.Radiological activity was studied by measuring Gadolinium enhancing (Gd+) and new T2 lesions on brain MRI performed every 6 months. VLA-4 saturation levels from peripheral blood lymphocytes were assessed by flow cytometry. Results: We included 16 patients who received natalizumab ED (Mean age 43 years; women 69[percnt] (11/16), mean duration of natalizumab treatment 60.4 months, mean duration of natalizumab ED 18.1 months). 69[percnt] (11/16) of patients were JC virus seropositive (44[percnt] index value ≥1.5). 8 patients (50[percnt]) received natalizumab for more than 5 years. No patient had a relapse under ED. Mean EDSS with natalizumab SD was 3.7 and with natalizumab ED 3.6(p=0.4). Before natalizumab treatment 63[percnt] of patients had Gd+ lesions and under SD or ED 6[percnt] and 0[percnt], respectively. Any patient presented new T2 lesions in both regimen doses. NEDA-3 was achieved in 75[percnt] in SD and 94[percnt] in ED. VLA-4 saturation levels of CD4 T lymphocytes were between 70-90[percnt] in SD and 50-70[percnt] in ED. Conclusions: In this sample, it has not been observed clinical or radiological worsening disease under ED of natalizumab/6 weeks.VLA-4 saturation levels decreased about the 20[percnt] with ED without compromising the disease activity. Disclosure: Dr. Hervas has nothing to disclose. Dr. Punet-Ortiz has nothing to disclose. Dr. Teniente-Serra has nothing to disclose. Dr. Mansilla has nothing to disclose. Dr. Quirant-Sanchez has nothing to disclose. Dr. Navarro has nothing to disclose. Dr. Presas has nothing to disclose. Dr. Martinez-Caceres has nothing to disclose. Dr. Ramo received research support from Biogen Idec Iberia.