Longitudinal Data on Lymphopenia in Multiple Sclerosis Patients Treated with Dimethyl Fumarate (P2.101)

Objective: To assess the prevalence of lymphopenia in patients treated with DMF in a real world setting and to assess the effect of DMF dose reduction on lymphopenia. Background: Oral dimethyl fumarate (DMF) was approved for the treatment of relapsing-remitting multiple sclerosis (MS) in the United States in March 2013. In pivotal trials grade 3 lymphopenia (absolute lymphocyte count ALC <500) developed in about 6 [percnt] of patients during the study. Lymphopenia has been associated with rare cases of progressive multifocal leukoencephalopathy (PML), an opportunistic infection of the central nervous system caused by reactivation of JC virus. Methods: A retrospective chart review of 250 patients prescribed DMF in our center was performed and patients with low lymphocyte counts were identified. Correlations of lymphopenia with demographic factors were assessed. Longitudinal data following dose reduction or cessation of DMF were analyzed. Results: In our cohort 13[percnt] of patients had grade 3 lymphopenia (ALC <500) and a total of 45[percnt] of patients had lymphopenia (ALC <1000). Lower ALC was correlated with higher EDSS, higher age, and lower ALC before starting DMF. Recovery of ALC typically required several months. The rate of infections was not significantly higher in patients with lymphopenia. Conclusions: The rates of lymphopenia in our cohort were higher than those reported in clinical trials. Blood counts should be monitored throughout treatment as lymphopenia can occur early and late in the treatment with DMF. Older patients with higher EDSS or lower lymphocyte counts prior to starting DMF may be at higher risk of developing lymphopenia. Improvement of lymphocytes following dose reduction or discontinuation may take several months. Disclosure: Dr. Romba has nothing to disclose. Dr. Wundes has nothing to disclose. Dr. Von Geldern has nothing to disclose.