Abstract
Introduction: The outcomes of cladribine tablets treatment (CladT) dosing in year one and two, and its longer-term treatment persistence and effectiveness in real-world MS treatment need to be better understood. Objectives/Aims: This study aimed to describe the baseline characteristics, treatment persistence, relapse rate and 24-week confirmed disability progression (CDP) or improvement (CDI) of people with MS (PwMS) treated with CladT in the MSBase registry. Methods: All PwMS recorded in MSBase on 1st February 2025 with a confirmed diagnosis of relapsing-remitting MS (RRMS) initiating CladT were included. Descriptive statistics were used to summarise demographic, clinical and treatment characteristics. Cox proportional hazard regression was used to compare clinical outcomes between treatment naive and experienced groups. Results: A total of 3834 PwMS with a confirmed diagnosis of RRMS initiated CladT since 2017. Mean (standard deviation [SD]) age at CladT initiation was 40.95 years (11.53) and 74.6% were female. Mean (SD) time from diagnosis to first CladT exposure was 7.94 years (7.21). 16.7% were treatment-naive. Mean (SD) observation time from first CladT dose was 2.19 years (1.69). Treatment switching from CladT occurred at a mean rate of 4.82% per year (95% confidence interval [CI] 4.36, 5.31). In switchers, the median (interquartile range) time to switch was 2.74 years (1.78, 3.69). The annualised relapse rate (ARR) was 0.135 (95% CI 0.13, 0.14). The rate of 24-week CDP was 0.038 per year (95% CI 0.03, 0.04) and the rate of 24-week CDI was 0.052 per year (95% CI 0.05, 0.06). In PwMS with a minimum follow-up duration of 3, 4, 5, or 6 years, annual rates for additional CladT treatment courses were 4.6, 4.8, 10.3, and 4.9%, respectively. Comparison of treatment-naive and previously treated PwMS showed no difference in time to CladT discontinuation (hazard ratio [HR] 0.99; 95% CI 0.77, 1.28), 24-week CDP (HR 0.92; 95% CI 0.67, 1.27) or 24-week CDI (HR 1.13; 95% CI 0.79, 1.61), but treatment naive PwMS had a significantly longer time to first relapse (HR 0.72; 95% CI 0.58, 0.89, p = .003). Conclusion: In the MSBase cohort of 3834 CladT-treated PwMS, treatment persistence was very high, with 4.82% of PwMS per year switching to other treatments. ARR was 0.135, and a small proportion of PwMS continued CladT treatment beyond year 4. Rates of annualised CDP were low (3.8%). CDI events were slightly more frequent (5.2%). In this real-world cohort, CladT treatment is highly effective and has very high treatment persistence.