Safety and persistence of dimethyl fumarate as a treatment for relapsing-remitting multiple-sclerosis

Abstract

ObjectiveDimethyl fumarate is a medication approved for the treatment of relapsing-remitting multiple sclerosis. The purpose of the study was to evaluate the safety and persistence of dimethyl fumarate in clinical practice and analyze the occurrence of lymphopenia is patients treated with dimethyl fumarate over a period of at least 6 months. MethodThis is a retrospective longitudinal observational study carried out between August 2015 and March 2019. The study cohort was made up of patients who had been treated with dimethyl fumarate for at least 6 months. Lymphocyte counts were recorded at different points of time (pre-treatment, at 3, 6, 12 months, and at the end of the study period). The evolution of lymphopenia was evaluated by means of a logistic regression statistical model. An analysis was performed of the relationship between a decreased lymphocyte count over the first 6 months of treatment and the development, by the end of the study, of grade II-III lymphopenia necessitating discontinuation of dimethyl fumarate. Other safety indicators were also evaluated including adverse events and interruptions or discontinuations of treatment. Persistence was determined by measuring the time to discontinuation of treatment. ResultsThe study included a total of 55 patients, of whom 80% were female. The most common adverse events were lymphopenia (27), rubefaction (16), digestive symptoms (11), fatigue (9), headache (3) and sleep disturbances (2). Eleven subjects interrupted/discontinued their treatment during the study period; reasons were as follows: pregnancy (2), personal decision (2), John Cunningham virus infection (1), allergy to the drug (2), and lymphopenia (4). Median duration of treatment was 23 months (4-43 months). A statistically significant association was found between a lower lymphocyte count over the first 6 months of treatment and the development of severe lymphopenia by the end of the study [OR = 1.34 (1.27-11.41); 95% CI (p = 0.001)]. ConclusionsThe adverse events observed in the present study are in line with those reported in previous analyses. Lymphopenia was the most common adverse event. The persistence of the medication was similar to that found in pivotal trials. The significant association found between a decreased lymphocyte count over the first 6 months of treatment and the development of severe lymphopenia by the end of the study suggests a connection between both variables, which could be instrumental in being able to predict and even prevent the occurrence of such lymphopenias.