Background and Importance Treatment for multiple sclerosis (MS) has changed in the last few years. The introduction of new therapies has led to improved tolerance and new options in the progression of disease.

Aim and Objectives To evaluate the reasons for changing treatment in patients diagnosed with MS and its economic impact.

Material and Methods Descriptive, retrospective and observational study of patients with MS, who changed treatment during 2022.

The variables collected from the clinical history were: age, sex, type of MS, EDSS scale, previous and new treatment and reason for the change. The economic impact associated with treatment changes was also evaluated.

Results During 2022 there was a 12% change in treatments (n=63/535 patients, 67 changes).

68% (n=43) were women with a mean age of 45 years. At the moment of change, mean EDSS was 2.9 (0.0–7.0) and 86% (n=54) had a diagnosis of relapsing-remitting MS and 14% (n=9) of secondary progressive multiple sclerosis (SPMS).

Treatment changes were due to: 46% (n=31) adverse events (AEs), 46% (n=31) progression, 5% (n=3) AEs/progression and 3% (n=2) pregnancy desire.

The AEs were: 50% injection site disorders and/or flu-like symptoms (100% IM/SC drugs), 17% gastrointestinal disorders ± flushing or uncontrolled blood pressure (100% oral drugs), 15% infusion-related reactions, 12% lymphopenia and 3% hepatotoxicity and increased anti-JC titre. 100% SC/IM treatments switched to oral drugs and 100% natalizumab_IV was changed to natalizumab_sc.

Changes for progression (n=34) were: 74% highly effective drugs (12 ocrelizumab, 7 cladribine and 6 natalizumab), 21% progression to SPMS (5 siponimod and 2 rituximab), and 5% dimethyl fumarate.

Previous treatments were 19% dimethyl fumarate, 16% teriflunomide, 15% natalizumab_IV, 9% glatiramer, 9% fingolimod, 7% interferon beta-1a_IM, 7% peginterferon_SC, 6% interferon beta-1b_SC, 4% interferon beta-1a_SC, 3% rituximab, 1% siponimod and cladribine.

New treatments were 19% ocrelizumab, 18% teriflunomide, 15% cladribine, 10% dimethyl fumarate, 9% natalizumab_SC, 7% natalizumab_IV, 7% siponimod, 6% rituximab, 3% glatiramer, 1% ozanimod, ponesimod and diroximel fumarate.

The mean monthly cost before the changes was 833€ and 1,543€ with the new treatments.

Conclusion and Relevance The introduction of new therapies has led to having more therapeutic alternatives and they are well tolerated in those patients with AEs or progressive MS, but the economic impact is higher.

Conflict of Interest No conflict of interest.