Inclusion Criteria:  Age ≥18 years, Patients with onset of symptoms >15 days, Laboratory (RT-PCR) confirmed infection with 2019-nCoV.  Exclusion Criteria:  Pregnant or breast feeding, On specific monoclonal antibodies, or other drug trial treatment for COVID-19 within one week prior to study enrolment, Liver function tests >2 fold of upper limits of normal (ULN) reference levels of the respective testing assay, Patients with known hypersensitivity to leflunomide, Patients with severe immunodeficiency syndrome and hypoalbuminaemia.