An antiviral drug called favipiravir (Avigan) was unintentionally found at Toyama Chemical Co., Ltd.'s research labs. It effectively inhibits the RNA polymerase of the influenza virus. It has a wide range of activity against numerous viral infections while being primarily researched for the treatment of viral influenza illness. The recent outbreak of the deadly virus COVID-19 has compelled scientists to come up with a solution. While the role of Remdesivir, chloroquine, and Lopinavir/ritonavir in the treatment of the COVID-19 is being evaluated, Favirpiravir is thought to be another potential drug for the treatment and prevention of the outbreak. In fact, Favipiravir is the first approved drug in the fight against COVID-19 and China has already started manufacturing it on a larger scale. Recently, the Massachusett General Hospital published guidelines for the treatment of Coronavirus. However, Favipiravir has not been mentioned in these guidelines.
What is Favipiravir?
Favipiravir is a novel broad-spectrum antiviral drug that has potent antiviral activity. It inhibits the viral RNA polymerase. It is effective against all the subtypes of influenza strains including those sensitive and resistant to the neuraminidase and M2 inhibitors. It is a prodrug that is activated intracellularly to Favipiravir-RTP.
The spectrum of antiviral activity of Favipiravir:
It is active against the following viral pathogens [Ref]:
| Orthomyxoviridae | Pandemic A (seasonal) Pandemic A (H5N1) H1N1 influenza A pdm09 Pandemic A (H7N9) B influenza Chlamydia C |
| Togaviridae | Western equine encephalitis Venezuelan equine encephalitis Eastern equine encephalitis Barmah forest Ross river Mayaro Chikungunya |
| Bunyaviridae | La Crosse Punta Toro Rift Valley fever Sandfly fever Dobrava Maporal Crimean-Congo hemorrhagic fever Prospect Hill Severe fever thrombocytopenia syndrome |
| Caliciviridae | Noro |
| Paramyxoviridae | Human metapneumovirus Respiratory syncytial virus |
| Arenaviridae | Junin Pichinde Tacaribe Guanarito Machupo Lassa |
| Filoviridae | Ebola |
| Rhabdoviridae | Rabies |
| Picornaviridae | Polio Rhino Enterovirus 71 |
| Flaviviridae | West Nile Yellow fever Zika virus |
It showed activity against influenza viruses that were resistant to both oseltamivir and zanamivir. In investigations on animals, mice who received the medicine at a dose of 30 mg/kg/day divided into two or four doses showed a substantial improvement compared to mice who did not get the treatment. None of the mice in the control group survived [Ref]. Compared to ribavirin, it was also found to be more potent in the treatment of viruses from the Bunyaviridae group. This group includes the deadly Lassa virus and Crimean Congo Hemorrhagic fever. Another serious emerging viral infection is the "Severe fever with thrombocytopenia syndrome" (SFTS) which infects individuals residing primarily in Japan, Korea, and China. Cases are seen throughout the year, however, most cases occur in the winters. Favipiravir was studied and found to be effective against the SFTS virus in vitro. It has also been found to be effective in infections caused by the Zika virus and Ebola viruses. Lastly, if given at a dose of 30 mg/kg/day in divided doses during the presymptomatic phase of rabies virus infection, it was found to inhibit the viral activity and disease progression.
In conclusion:
Favipiravir is an attractive antiviral drug for the treatment of the COVID-19 infection that is associated with a high mortality rate. It may also be used in the treatment of other deadly viral infections such as Ebola, Zika, and Rabies virus infections.
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