Remdesivir and chloroquine[33]
Using clinical isolates of 2019-nCoV, Wang et al., 2020 evaluated the efficacy of seven agents (ribavirin, penciclovir, nitazoxanide, nafamostat, chloroquine, remdesivir [GS5734], and favipiravir [T-705]) in in vitro conditions. Cytotoxicity was evaluated in vero E6 cells, which was followed by infection of the cells with 2019-nCoV clinical isolates, and the test drug was evaluated at different doses. Reverse transcription polymerase chain reaction-based quantification was done to get the viral yield, which was later confirmed by immunofluorescence microscopy (nucleocapsid protein visualization). Both chloroquine and remdesivir inhibited virus infection at micromolar level (0.77–1.13 μM) and with high selectivity.[33]
Being an adenosine analog, remdesivir gets incorporated into viral RNA and causes premature chain termination.[34] The importance of chloroquine as an antiviral agent is coming up. Chloroquine even showed efficacy as a potent antiviral against SARS-CoV infection and spread.[35] Pretreatment with chloroquine renders vero E6 cells refractory to SARS CoV infection. Moreover, in the postinfection period, treatment with chloroquine prevents the spread of SARS-CoV infection.[35] Chloroquine increases endosomal pH and thus makes the environment unfavorable for the virus/cell fusion. Chloroquine also affects the glycosylation process of angiotensin-converting enzyme 2 (ACE-2, receptor for binding of viral spike protein, which is essential for interaction with the host).[35] Being nonexpensive and easily available agent, chloroquine may prove as a promising candidate.