The purpose of this clinical trial is to assess the safety and efficacy of Clevudine 150 mg versus placebo once daily administration with standard of care therapy for 10 days in patients with mild and moderate COVID-19.

Key Inclusion Criteria:

1. Over 19 years of age
2. COVID-19 confirmed by a real-time RT-PCR tests, and hospitalized
3. Patients who experienced first symptom related to COVID-19 within 7days prior to enrollment and confirmed 2 or more relative symptoms at the time of randomization.
4. Patients with peripheral capillary oxygen saturation(SpO2) greater than 94% at the time of screening, who do not need supplemental oxygen therapy.

Key Exclusion Criteria:

1. Patients who participated in other clinical trials related to COVID-19
2. Patients who were administered drugs directly to COVID-19 24hours prior to the start of the study.
3. Patients who need oxygen supply or breathing device (non-invasive mechanical ventilation(via mask)), mechanical ventilator requirement (via endotracheal tube or tracheostomy tube, ECMO requirement) at the time of screening or baseline
4. Patients whose AST or ALT has increased by more than 5 times the normal lab value.