Favipiravir: A light of hope for COVID-19

The antiviral drug Favipiravir, better known as Avigan, is being trialed as a treatment for the novel coronavirus disease (COVID-19). Avigan is the brand name of the drug Favipiravir, it was developed by the Japanese Fujifilm Toyama Chemical Company, has emerged as a potential drug to treat patients infected with the deadly novel coronavirus.

Two renowned pharmaceutical industries of Bangladesh have manufactured this drug in their plant for the trial of COVID-19 patients in Bangladesh. Other pharmaceutical industries are also in the process of getting permission to produce the drug from the Directorate General of Drug Administration (DGDA), Bangladesh.

In Japan, Favipiravir was approved in 2014 for sale domestically under the brand name Avigan for stockpiling against influenza pandemics. Testing in the development stages, however, revealed that the drug can result in elevated blood uric acid levels and cause deformities in the unborn young of animals.

This anti-influenza drug has shown some promise in the fight against COVID-19, but experts warn that it has known side effects and that there is insufficient clinical data for its use. Favipiravir works by blocking the ability of a virus to replicate inside a cell. It induces lethal RNA transversion mutations, producing a nonviable viral phenotype.

Favipiravir is a prodrug that is metabolised to its active form, favipiravir-ribofuranosyl-5-triphosphate, available in both oral and intravenous formulations. It does not inhibit RNA or DNA synthesis in mammalian cells and is not toxic to them.

However, Favipiravir has not proven effective in primary human airway cells, casting doubt on its efficacy in influenza treatment. Japan approved favipiravir for treating influenza strains unresponsive to current antivirals. The Japanese Fujifilm Toyama Chemical Company initially hoped that favipiravir would become a new influenza medication that could replace oseltamivir (brand name Tamiflu).

On the other hand, animal experiments show the potential for teratogenic effects, and the approval of production by the Ministry of Health, Labor and Welfare was greatly delayed and the production condition is limited only in an emergency in Japan.

The Italian Pharmaceutical Agency, however, has reminded the public that the existing evidence in support of this drug is scant and preliminary Favipiravir has shown limited efficacy against the Zika virus in animal studies, but was less effective than other antivirals such as MK-608. The agent has also shown some efficacy against rabies and has been used experimentally in some humans infected with the virus.

A study of 80 people in comparison to ritonavir found that it reduced viral clearance time and that 91% of people had improved Computed Tomography (CT) scans with few side effects. The limitation of this study was that it was not randomised, double-blinded and placebo-controlled.

The drug has been approved for use in clinical trials of the novel coronavirus disease 2019 in China and at the same time, in March 2020, Italy also has approved the drug for experimental use against COVID-19 and has begun conducting trails in three regions most affected by the disease. Though this drug is on the trial process and in some cases on phase II or III, this drug could be a light of hope for the treatment of COVID-19 until we get a better option.

The author is an undergraduate student at the Department of Pharmacy, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh.