Plain Language Summary: What is this summary about? This article summarises the findings from the CLARIFY-MS study. Cladribine tablets are an oral medication for the treatment of relapsing multiple sclerosis (MS). The exact number of tablets and number of days depends on the person's body weight. In the CLARIFY-MS study, researchers investigated whether treatment with cladribine tablets improved the health-related quality of life of people with highly active relapsing MS over a 2-year period. Most of the participants(348/482, 72%) were previously treated with other MS diseasemodifying treatments(DMTs) before starting treatment with cladribine tablets in this study. What were the results? Treatment with cladribine tablets significantly improved the health-related quality of life of the participants over the 2-year study period. Similar level of improvement in health-related quality of life was seen in participants who had previously been treated with other MS DMTs and in those who had not. Safety findings were also similar to previously reported data for cladribine tablets. No cases of the most severe grade of reduction in lymphocyte counts (grade 4; severely compromised immune system) were recorded. What do the results mean? Treatment with cladribine tablets improves the health-related quality of life of people with highly active relapsing MS regardless of whether they received or did not receive DMTs for MS before cladribine tablets treatment.Read less <