The approval comes as the company plans to seek conditional approval for its antibody drug, CT-P59, for emergency use by the end of this year.
The treatment, the most advanced antibody drug in terms of research in South Korea, is directed against the surface of the virus and designed to block it from locking on to human cells.
The third stage trials will be conducted on some 1,000 asymptomatic coronavirus patients and those who have come into close contact with COVID-19 patients in Korea, Celltrion said in a statement.
The Ministry of Food and Drug Safety recently approved a Phase 2/3 study on patients with mild and moderate cases of COVID-19, Lee Sang-joon, Celltrion's senior executive vice president, told Reuters.
Celltrion began commercial production of the drug in September - likely to amount to around 1 million doses - in anticipation of demand in both domestic and overseas markets.
In July, Celltrion separately launched overseas human trials of its treatment in Britain.
(Reporting by Sangmi Cha; Editing by Kenneth Maxwell)
By Sangmi Cha