Wang M, Zhao Y, Hu W, et al. - This study was undertaken to assess the efficacy and safety of leflunomide, an approved dihydroorotate dehydrogenase inhibitor, to treat COVID-19 patients with prolonged post-symptomatic viral shedding. Researchers carried out a prospective, randomized, controlled, open-label trial involving hospitalized adult COVID-19 patients with prolonged PCR positivity. Individuals were allocated randomly to receive either leflunomide (50 mg, q12h, three consecutive times, orally; then 20 mg, once daily for 8 days), in addition to nebulized interferon alpha 2a (IFN α-2a, 3 million IU each time, twice daily for 10 days), or nebulized IFN α-2a alone for 10 days. The primary outcome included the duration of viral shedding. They randomized a sum of 50 COVID-19 patients with prolonged PCR positivity into 2 groups; 26 were assigned to the leflunomide group, and 24 were assigned to the interferon alone group. There was no advantage in terms of the duration of viral shedding with the combined treatment of leflunomide and IFN α-2a beyond IFN α-2a alone in COVID-19 patients with prolonged PCR positivity.