Antivirals

Nucleoside analog
Ribavirin, a nucleoside analog, shows antiviral activity against some animal CoVs, and in the SARS-CoV epidemic, many patients were treated with ribavirin along with corticosteroids and became a standard regimen for the treatment of SARS-CoV. However, lack of control group hindered the estimation of true effect size. Again, in vitro testing did not show efficacy of ribavirin against SARS-CoV. Ribavirin is known for its side effects (hemolytic anemia, hypocalcemia, and hypomagnesemia). Many subsequent studies questioned the efficacy of ribavirin. Many patients on ribavirin and corticosteroid combination even showed an increase in viral load following the treatment. Thus, its use declined over a period.[8] Other important nucleoside analogs are favipiravir and galidesivir, but these are not evaluated till now in 2019-nCoV.

Neuraminidase inhibitors
Neuraminidase inhibitors are indicated in the management of influenza.[9] In a study on possible MERS-CoV cases in Paris from 2013 to 2016, a total of 35 patients received oseltamivir (37.6%). In patients positive for influenza virus (n = 25), 52% (n = 13) received oseltamivir and it was concluded that empirical oseltamivir can be started in suspected MERS-CoV cases.[10] Many other studies also evaluated oseltamivir in MERS-CoV.[11] Oseltamivir was also used in the management of 2019-nCoV; however, definite evidence of efficacy is inconclusive because of lack of suitable control group in the studies.[12]

Protease inhibitor
There are two types of protease present in SARS-CoV, the CL-like protease and the papain-like protease, which is important for cleaving the polyproteins and releasing the nonstructural proteins (NSP1–16), which carry out important functions in the CoV life cycle. Among protease inhibitors, lopinavir was the most inhibitor and saquinavir was the least powerful inhibitor of CoV protease.[13] In molecular dynamic studies, flap closing was observed when these inhibitors bound to the SARS-CoV 3CL (pro).[14] Hong Kong University researchers demonstrated anti-SARS-CoV action of lopinavir at concentration of 4 μg/ml in vitro against the HKU-39849 isolate.[15] Ritonavir boosting along with lopinavir is used in the management of HIV.[16] A clinical study at the same Hong Kong University suggests that even after adjustment for LDH level (possible confounder), a significant association was seen between lopinavir/ritonavir use and better outcome.[15] As per the current guidelines, lopinavir + ritonavir is the recommended protease inhibitor for the treatment of 2019-nCoV (weak recommendation).[17]