Favipiravir

History Favipiravir is a broad-spectrum antiviral drug that was cleared by the Drugs Controller General of India (DCGI) last week for “emergency restricted” use among Covid-19 patients. Glenmark will sell the generic favipiravir under the brand name FabiFlu.
Favipiravir was originally developed in the late 1990s by a company that was later purchased by the Japanese firm Fujifilm as part of its transition from the photo business to healthcare. After being tested against a range of viruses, the drug was approved in Japan in 2014 for emergency use against flu epidemics or to treat new strains of influenza.
Mode of Action Favipiravir inhibits the RNA-dependent RNA polymerase (RdRp) — an enzyme that allows the coronavirus to replicate inside host cells.Inside the cells, favipiravir is converted to favipiravir ribofuranosyl-5′-triphosphate (favipiravir-RTP) by host cells. This molecule then blocks the RdRp enzyme of SARS-CoV-2, the virus that causes Covid-19.According to a statement by Glenmark, favipiravir works only during the earlier stages of the disease, when the viral replication is higher, but the body's immune response has not gone into overdrive.
Metabolism of favipiravir to its triphosphate form occurs in an extracellular environment in a concentration-dependent manner. The vRNA polymerase mistakenly recognizes favipiravir-RTP as a purine nucleotide. This favipiravir-RTP is misincorporated in nascent vRNA, or it may act by binding to conserved polymerase domains, preventing incorporation of nucleotides for vRNA replication and transcription (Jin et al., 2013).