Background: Despite the compelling evidence indicating that early initiation of high-efficacy disease modifying therapies (DMTs) is more effective in controlling disease activity and preventing long-term disability in relapsing-remitting multiple sclerosis (RRMS), there is a scarcity of data regarding the implementation of such treatments in Korea. This study aimed to investigate the actual proportion of patients requiring high-efficacy DMT when disease activity is closely monitored.Methods: We conducted a retrospective analysis of medical records of 104 patients with RRMS who developed their disease after 2015 at the National Cancer Center in Korea. The status of no evidence of disease activity-3 (NEDA-3) was defined as no relapse, disability progression, or active lesions in annual magnetic resonance imaging evaluations.Results: Among 104 RRMS patients, 95 started with moderate-efficacy DMT, and nine with high-efficacy DMT. Of patients, 51% showed disease activity despite moderate-efficacy DMT, and prompting 41% to escalate high-efficacy DMT with a median time to switch of 20 months. Following the switch to a high-efficacy DMT, NEDA-3 was maintained in 82% of patients for a median of 27 months (interquartile range: 22, 45). Among the nine patients initially on high-efficacy DMT, no patient exhibited any signs of disease activity after median 34 months of treatment. The majority of patients experienced no significant side effects of high-efficacy DMT.Conclusion: The study showed a significant number of patients requiring escalation to high-efficacy DMT within a few years of treatment initiation with moderate-efficacy DMT, emphasizing the importance of early intervention strategies in managing the patients.