Background: In CARE-MS II (NCT00548405), 2 alemtuzumab courses (12 mg/day; baseline: 5 days; 12 months [M] later: 3 days) significantly improved clinical/MRI outcomes versus SC IFNB-1a over 2 years (y) in RRMS patients with inadequate response to prior therapy. Efficacy was maintained in a 4-y extension (NCT00930553), wherein patients could receive additional alemtuzumab (12 mg/day; 3 days; ⩾12M apart) as needed for disease activity or other disease-modifying therapy (DMT). Patients could continue in an additional 5-y extension (TOPAZ; NCT02255656).

Aims: To evaluate 8-y efficacy/safety of alemtuzumab in CARE-MS II patients.

Methods: At investigator’s discretion, patients in TOPAZ can receive as-needed additional alemtuzumab (⩾12M apart; no criteria) or other DMT (any time).

Results: 300/435 (69%) patients completed TOPAZ Y2 (Y8 after initiating alemtuzumab); 44% received neither additional alemtuzumab nor another DMT. At Y8, annualised relapse rate was 0.18, 85% were relapse-free, 70% had stable/improved EDSS versus baseline, and mean EDSS change was 0.17. Through Y8, 64% were free of 6-month confirmed disability worsening, and 47% achieved 6-month confirmed disability improvement. In Y8, 58% achieved no evidence of disease activity, and 70% were free of MRI disease activity. Median percent brain volume loss (BVL) from baseline through Y8 was –1.06%; BVL was –0.19% or less annually in Y3–8. Safety remained consistent through Y8, with no new immune thrombocytopenia or nephropathy cases.

Conclusion: Efficacy of alemtuzumab on clinical, MRI, and BVL outcomes was maintained through Y8 in absence of continuous treatment in CARE-MS II patients, with a consistent and manageable safety profile.