Study design
The present study was an open-label, multicenter, parallel-group, randomized controlled clinical trial involving patients diagnosed with mild-to-moderate COVID-19. Participants with mild-to-moderate COVID-19 were planned to be randomly assigned in a 1:1:1 ratio to one of three groups: a control group (normal treatment), a group receiving 150 mg of demeclocycline once daily, and a group receiving 300 mg of demeclocycline (150 mg twice daily). Individuals allocated to the demeclocycline groups received a daily dose of 150 mg once daily or 150 mg twice daily for a period of 14 days.This clinical trial was conducted in accordance with the guidelines set forth in the Declaration of Helsinki. The study protocol received approval from the Certified Review Board of Osaka University (CRB5180007) and each individual participating institution. Written informed consent was obtained from patients prior to their inclusion in the study. This study was registered with the Japan Registry of Clinical Trials as jRCTs051200049 (