Background: The COVID-19 pandemic has become a significant concern for patients with multiple sclerosis (MS) and their healthcare providers, prompting various guidelines on the appropriate use of disease-modifying therapies (DMT) such as cladribine tablets (CladT). Objectives: We report on clinical outcomes in patients who developed COVID-19 infection during two ongoing Phase IV studies of CladT (CLARIFY-MS [NCT03369665] and MAGNIFY-MS [NCT03364036]). Post-approval cases of COVID-19 infection are reported elsewhere. Methods: CLARIFY-MS is investigating the impact of CladT on health-related quality of life in patients with highly active relapsing MS, while MAGNIFY-MS aims to determine the onset of action of CladT in such patients. Both studies utilize an open-label, single-arm, multicenter design, in which patients are treated with CladT 10 mg (3.5 mg/kg cumulative dose over 2 years). Some 680 patients are continuing in both studies. Cases of suspected COVID-19 infection were identified from adverse event reports and reviewed in terms of patient baseline characteristics, comorbidity, disease/treatment history (including most recent Extended Disability Status Scale [EDSS] score before COVID-19), and timing of CladT dosing/lymphocyte counts in relation to COVID-19 severity and outcomes. Results: Three cases of suspected COVID-19 infection were identified (CLARIFY-MS, n=2; MAGNIFY-MS, n=1). Patient #1 (21-year history of MS; most recent EDSS score, 4.5; concomitant cardiovascular disease/asthma; prior DMT use) developed severe COVID-19 infection (confirmed) necessitating hospitalization but recovered and was discharged with residual cough/fatigue. Patient #2 (2-year history of MS; most recent EDSS score, 2; previous deep vein thrombosis during pregnancy; no prior DMTs) was also hospitalized for severe COVID-19 symptoms (not confirmed) but self-discharged and was recovering with chest tightness, fatigue, and neuropathic pain under self-isolation. The remaining patient (7-year history of MS; most recent EDSS score, 1; prior use of interferon ?-1a) experienced mild symptoms of COVID-19 infection (confirmed); hospitalization was not required and the patient recovered under self-isolation. None of the patients required mechanical ventilation or died. Conclusions: All 3 patients who developed COVID-19 infection during two ongoing Phase IV studies of CladT recovered or were recovering, and none required mechanical ventilation.