Evaluating the Safety and Efficacy of Transitioning Multiple Sclerosis Patients from Natalizumab to Rituximab (P6.187)

Objective: To evaluate the safety and efficacy of transitioning multiple sclerosis patients from natalizumab to rituximab. Background: There is a significant risk of Progressive Multifocal Leukoencephalopathy (PML) in patients who continue natalizumab treatment beyond two years, if they are JC virus antibody positive. At our center, we frequently transition these patients to rituximab as it is also highly efficacious. Methods: This is a retrospective chart review of all patients at a single MS center who have received at least six treatments of natalizumab and then infused rituximab within twenty-six weeks. Results: Ninety-two patients (63 female, average age 50.6 +/- 11.9 years) received at least six natalizumab treatments (mean number of treatments = 30 +/- 17.6) before rituximab administration. MS subtypes included RRMS (56), SPMS (28), PRMS (6), and PPMS (1). The mean time between natalizumab and rituximab was 15.7 +/- 4.4 weeks. The reason for treatment change was risk of PML in 77.2[percnt] of patients, 12[percnt] due to disease progression, and 7.6[percnt] due to relapse or MRI activity, and 3.2[percnt] due to side effects. 81.5[percnt] of patients were JC antibody positive (unknown in 16.3[percnt], negative in 2.2[percnt]). Average duration of rituximab use was 3.1 +/- 2.0 years. There were no cases of PML in this cohort and no serious adverse events. The most frequent adverse events were infusion reactions though not serious in any patient. Minor urine and respiratory infections were noted, though at an expected rate in this population. 8.7[percnt] of patients demonstrated disease activity (by relapse or MRI changes) on rituximab and 6.5[percnt] had progression of their disease. There were no cases of immune reconstitution inflammatory syndrome (IRIS). Conclusion: 91.3[percnt] of MS patients maintained no evidence of inflammatory activity during the transition from natalizumab to rituximab and no cases of IRIS or PML were observed.