Objectives: To evaluate the efficacy and safety of alemtuzumab over 7 y in pooled CARE-MS patients who initiated alemtuzumab after discontinuing SC IFNB-1a.

Methods: In the 4-y extension, patients could receive additional alemtuzumab (12 mg/day; 3 days; ⩾12 months apart) as needed for disease activity or receive another disease-modifying therapy (DMT) per investigator discretion. Patients completing the 4-y extension could enroll in a subsequent 5-y extension (TOPAZ [NCT02255656]) and receive additional alemtuzumab (⩾12 months apart) at the investigator’s discretion (no criteria) or other DMTs at any time.

Results: Of 282 pooled CARE-MS patients from the SC IFNB-1a arm who entered the CAMMS03409 extension, 230 (82%) completed Y3 of TOPAZ (Y7 after initiating alemtuzumab); 163/282 (58%) received neither additional alemtuzumab nor another DMT through Y7. Annualized relapse rate at Y7 post alemtuzumab was 0.11. At Y7, 68% of patients had stable/improved EDSS scores, and mean change in EDSS score was +0.29 from core study baseline. Through Y7, 61% were free of 6-month confirmed disability worsening, and 37% achieved 6-month confirmed disability improvement. At Y7, 74% were free of MRI disease activity (no new gadolinium-enhancing or new/enlarging T2 hyperintense lesions). Median cumulative brain volume loss (BVL) from core study baseline through Y7 post alemtuzumab was 1.84%; BVL was 0.18% or less annually in Y2-7 after initiating alemtuzumab. Over 7 y after alemtuzumab, safety was consistent with the alemtuzumab arm of the core and extension studies. Incidence of overall adverse events (AEs), infections, and thyroid AEs (peaked in Y3 post alemtuzumab) declined through Y7 post alemtuzumab. No cases of nephropathy were reported over the core and extension studies in this cohort.

Conclusions: Patients who initiated alemtuzumab after first receiving SC IFNB-1a in the CARE-MS trials demonstrated favorable outcomes over 7 y. Safety was consistent with alemtuzumab-treated patients from the core and extension studies.