A real-world single-centre analysis of alemtuzumab and cladribine for multiple sclerosis

Background: Highly active MS may warrant higher efficacy treatments for disease control. However, these often confer more risk and have not been compared in head-to-head clinical trials, making relative efficacy and safety difficult to interpret. Alemtuzumab and cladribine are two high-efficacy treatments given as discrete courses separated by one year, followed by a durable response that potentially does not require ongoing treatment. Before the approval of oral cladribine, our centre had been treating patients with a bioequivalent intravenous (IV) regimen since 2010. The objective of this study is to report the safety and efficacy data of alemtuzumab and cladribine in a real-world, single centre setting. Methods: We retrospectively reviewed all patients treated with alemtuzumab or cladribine at the Ottawa Hospital MS Clinic with 2 or more years of follow-up. Information on baseline demographic variables, previous treatment, and prior disease activity was collected. Outcomes investigated were "no evidence of disease activity" (NEDA) and its constituents: new clinical relapse, new MRI activity, and Expanded Disability Status Scale (EDSS) progression; as well as any adverse events or treatment discontinuation. We performed univariate and multiple logistic regression to determine differences in 2-year NEDA and time-to-event analyses with Cox regression models to determine factors associated with each outcome through the study period. Results: Forty-six patients were treated with alemtuzumab and 65 with cladribine of whom 51 (78%) received the intravenous regimen, followed for a total of 420.1 person-years. The cladribine group was older (p=.0002), with higher baseline EDSS (p=.0015), and more likely secondary progressive (p<.0001). Alemtuzumab had a higher rate of 2-year NEDA than cladribine (OR 4.78, 95%CI: 1.57-14.50, p=.006), but beyond 2 years the difference was not statistically significant (HR 0.50, 95%CI: 0.25-1. 30, p=.061). More prior treatments were associated with lower likelihood of retaining NEDA (HR 1.26, 95%CI: 1.03-1.54, p=.027). Alemtuzumab had more infusion reactions (80% vs. 17%, p<.0001), shingles (22% vs. 2%, p=.005), and secondary autoimmunity (52% vs. 3%, p<.0001) than cladribine, but there was no difference in grade 3 or higher adverse events (21.7% vs. 18.5%, p=1.0). Conclusion: In our cohort alemtuzumab and cladribine achieved similar rates of NEDA in long-term follow-up, with overall less adverse events with cladribine. Patient registries would allow more robust comparisons, detection of adverse events, and assessment of a durable response.