Change in the clinical activity of multiple sclerosis after treatment switch for suboptimal response

Background: Therapy for multiple sclerosis (MS) has a partial efficacy, and a significant proportion of treated patients will develop a suboptimal response with first-line disease-modifying drugs (DMD). Therapy switch in patients with MS can be a strategy after a treatment failure. We studied the change in clinical activity after switching of first-line DMD because of a treatment failure. Methods: Relapsing-remitting multiple sclerosis (RRMS) patients treated with interferon-beta (IFNB) or glatiramer acetate (GA) were divided into (i) patients without change in DMD, (ii) patients with a change in DMD because of a poor response, and (iii) those with a change in DMD without relation with response. Annualized relapse rate (ARR) and relapse-free proportions were analyzed. Results: We identified 923 patients with RRMS. Of the 180 who experienced a change because of suboptimal response, 90 switched to another first-line DMT, 38 to mitoxantrone, and 52 to natalizumab. Median ARR in the pre-DMD period on first DMD and second DMD was the following: 1, 1, and 0 for switchers from IFNB to another IFNB (P=0.0001); 0.67, 1, and 0 for switchers from GA to IFNB (P=0.01); 1, 1, and 0 for switchers from an IFNB to GA (P=0.02); 1.1, 1.5, 0.2 for switchers from IFNB or GA to mitoxantrone (P=0.0001); 0.9, 1, 0 for switchers from IFNB or GA to natalizumab (P=0.0001). Conclusions: In patients with RRMS who have a poor response, switch to another DMD may reduce the clinical activity of the disease.