Drug repurposing approach to fight COVID-19

Abstract

Currently, there are no treatment options available for the deadly contagious disease, coronavirus disease 2019 (COVID-19). Drug repurposing is a process of identifying new uses for approved or investigational drugs and it is considered as a very effective strategy for drug discovery as it involves less time and cost to find a therapeutic agent in comparison to the de novo drug discovery process. The present review will focus on the repurposing efficacy of the currently used drugs against COVID-19 and their mechanisms of action, pharmacokinetics, dosing, safety, and their future perspective. Relevant articles with experimental studies conducted in-silico, in-vitro, in-vivo, clinical trials in humans, case reports, and news archives were selected for the review. Number of drugs such as remdesivir, favipiravir, ribavirin, lopinavir, ritonavir, darunavir, arbidol, chloroquine, hydroxychloroquine, tocilizumab and interferons have shown inhibitory effects against the SARS-CoV2 in-vitro as well as in clinical conditions. These drugs either act through virus-related targets such as RNA genome, polypeptide packing and uptake pathways or target host-related pathways involving angiotensin-converting enzyme-2 (ACE2) receptors and inflammatory pathways. Using the basic knowledge of viral pathogenesis and pharmacodynamics of drugs as well as using computational tools, many drugs are currently in pipeline to be repurposed. In the current scenario, repositioning of the drugs could be considered the new avenue for the treatment of COVID-19.

Keywords: COVID-19; Coronavirus; Repurposing; SARS-CoV2.

Fig. 1

Therapeutic targets of the currently considered drugs for repurposing against COVID-19. 1. Coronaviruses suppress the antiviral immunity, hence maintaining an antiviral state with interferons. 2. Virus enters the cell by fusion of the viral spike proteins with cellular ACE2 receptor, followed by ACE2 downregulation. Angiotensin receptor blockers (ARBs), Angiotensin-converting enzyme inhibitors (ACEIs) and statins increase ACE2 expression, hence may have efficacy in this condition. 3. Fusion is followed by endocytosis of the virus, where low endosomal pH helps in lysis of the viral structural proteins. Disruption of this acidic environment by diprotic bases like chloroquine and hydroxychloroquine may produce an antiviral effect. 4, 5. Release of nucleic acid (NA) into the cytoplasm and translation of the viral proteins using host ribosomes, 6. Proteolysis by viral main protease enzyme makes functional proteins e.g. RNA dependent RNA polymerase (RDRP). Thus, inhibition of the main protease enzyme by inhibitors like lopinavir, ritonavir and darunavir, may have efficacy against the virus. 7. RDRP is essential for replication and transcription of the virus. RDRP inhibitors, remdesivir, favipiravir, ribavirin and arbidol may be effective against coronaviruses. 7, 8. Subsequent translation and proteolysis into structural proteins followed by packaging makes intact virions, which get exocytosed (9) from the cell

Fig. 2

Overview of the drugs with potential for repurposing against COVID-19. The drugs being considered for primary therapy of COVID either acts on targets of the virus or on the targets of the host