Cladribine tablets for highly active relapsing-remitting multiple sclerosis in Poland: a real-world, multi-centre, retrospective, cohort study during the COVID-19 pandemic.

Treatment with cladribine tablets is indicated in highly active relapsing-remitting multiple sclerosis (RRMS). Cladribine tablets proved safe and effective in the pivotal CLARITY trial, but that trial included primarily treatment-naïve patients. In clinical practice however, cladribine tablets are often given to patients who have failed other treatments. Therefore, this study investigated the real-world safety and efficacy of cladribine tablets. We gathered data from nine MS clinical centres across Poland for patients with RRMS who started treatment with cladribine tablets from December 2019 to June 2022. We enrolled 140 patients, with follow-up data available for 136 in year 1 and for 66 in year 2. At baseline, the mean age was 35.6 years, mean disease duration was 7.3 years, median EDSS score was 2.5, and 94% of patients were treatment- -experienced. Thirty-nine patients (27.9%) had undergone COVID-19, and 94 (67.1%) were vaccinated against COVID-19. The annualised relapse rate (ARR) decreased from 1.49 at baseline to 0.33 in year 1 (p < 0.001) and to 0.25 in year 2 (p < 0.001). The percentage of relapse-free patients increased from 11.5% at baseline to 70.2% in year 1 and 82.1% in year 2. The percentage of patients with active lesions decreased from 91.4% at baseline to 36.2% in year 1 and 18.2% in year 2. EDSS score remained stable or improved in 83.7% of patients in year 1 and 89.6% in year 2. No evidence of disease activity (NEDA-3) was achieved in 42.7% of patients in year 1 and 66.7% in year 2. Only one patient (0.72%) had grade 4 lymphopenia and 21 (15.1%) had grade 3 lymphopenia. Varicella zoster virus infections occurred in three patients. Eight patients discontinued treatment with cladribine: five due to inefficacy, one due to lymphopenia, and two due to a personal decision. Cladribine tablets proved safe and effective in a real-world cohort of treatment-experienced patients. However, the efficacy measures improved to a lesser extent in our cohort than in the pivotal clinical trial, which is probably due to a higher proportion of treatment-experienced patients in our cohort.