Everything you need to know about Favipiravir, the potential drug for COVID-19 treatment
Favipiravir is a broad-spectrum antiviral drug that was originally made to treat the flu in Japan.
Favipiravir is quickly emerging as the top choice among 25 drug candidates that the Council of Scientific and Industrial Research (CSIR) is considering for COVID-19 treatment, the Ministry of Science and Technology said in a press release yesterday (April 30). Favipiravir is an antiviral drug that was originally made to treat the flu in Japan. It is also marketed in Russia and China.
CSIR is one of the government bodies leading India’s fight against COVID-19. In the absence of definitive treatment, this research organisation has been putting a lot of emphasis on repurposing existing drugs for treating coronavirus patients. This is because developing a new drug would take years.
On the other hand, the existing drug candidates can be quickly tested in clinical trials to check their efficiency against SARS-CoV-2, the virus that causes COVID-19.
CSIR has already developed a cost-effective way to make favipiravir in the lab and has shared the formula with Cipla, an Indian-origin multinational pharmaceutical and biotech company that is a consistent partner of CSIR for developing affordable drugs both for India and the world. The company has already asked for permission from the Drug Controller General of India to launch this drug in India.
What is favipiravir used for normally?
As per the World Health Organization (WHO), favipiravir is an experimental antiviral drug that was licensed in Japan in 2014 to treat influenza virus infections. For influenza treatment, patients are given a 1600 mg dose of this drug on Day 1 and about 600 mg dose from Day 2 to 5.
Why is favipiravir being considered for COVID-19 trials?
Favipiravir is a broad-spectrum antiviral drug (this is important, as most antivirals are effective against a specific virus only). Apart from the influenza virus, favipiravir has shown significant activity against several RNA viruses for which we don’t yet have a treatment. This includes the genus Flavivirus which includes the dengue virus and Zika virus and the genus Norovirus, which causes gastroenteritis (inflammation of the gut) and diarrhoea. Favipiravir has already been used to treat Ebola patients (off-label use) and studies indicate that it is hard for a virus to develop resistance against this drug.
There has been enough evidence in favour of favipiravir for treating COVID-19. The Chinese ministry of science and technology said in March that this drug is effective in treating mild to moderate cases of COVID-19, as seen in more than 300 patients. The drug was seen to reduce viral load and improve lung health.
After this, various clinical trials began all over the world to study the drug.
Researchers are saying favipiravir is a viral RNA polymerase inhibitor. What does that mean?
RNA polymerase is the enzyme that helps SARS-CoV-2 virus make new RNA, so it is essential for the virus to make more copies of itself in the body. Favipiravir selectively targets this enzyme, to inhibit the replication of the COVID-19 causing virus in the body.
Here’s how it works: Studies suggest that favipiravir gets activated inside the cells and then gets incorporated into the viral RNA, inducing mutations in the RNA and causing a massive reduction in viral load. It is also suggested that this drug binds to certain conserved areas in the viral RNA polymerase and stops the enzyme from performing its function.
What is the latest news on these trials in India?
In India, Glenmark Pharmaceuticals, a Mumbai-based pharmaceutical company has already received the green signal from the Drug Controller General of India (DCGI) to conduct clinical trials with favipiravir. Cipla has also applied for approval to conduct favipiravir investigations.
For their study, Glenmark will administer favipiravir to 150 COVID-19 patients with mild to moderate illness and compare the treatment with an equal and similar group of patients who got standard treatment at the same time. The treatment may go on for 14 days though the study may be done for a whole month (28 days).
Strides Pharma Science Ltd, another pharmaceutical company in India, has said that it has prepared favipiravir in their lab and has asked for permission to conduct trials.
Do antivirals weaken the immune system? Does favipiravir have this effect also?
Many antiviral drugs have immunosuppressive action, meaning they suppress the immune function. This is why these drugs are mostly given in combination with immunomodulatory drugs to maintain the host immune response. Antiviral therapy is usually given to those who have an intact immune system.
There is no evidence so far to say that favipiravir has an immunosuppressive effect.
Does India make favipiravir?
Strides Pharma Science Ltd, a Bangalore-based company, has already developed a generic version of favipiravir tablets in 400mg and 200 mg strengths. The company is reportedly approved by various organizations in the world, including the WHO and the US Food & Drug Administration and has the capacity to produce up to six billion tablets per year. As per media reports Strides Pharma has also teamed up with a leading Active Pharmaceutical Ingredient (API) company to make sure that it can make the drug constantly and the supply chain is maintained.
Is India exporting favipiravir?
Strides Pharma Science Ltd has recently begun exporting favipiravir to various Gulf Cooperation Council Countries for the treatment of COVID-19 patients there.
Are there significant differences in how favipiravir works compared with hydroxychloroquine and Gilead’s remdesivir?
Just like favipiravir, remdesivir targets the viral RNA polymerase and gets inserted into the RNA of the virus. However, unlike favipiravir that causes mutations in the viral RNA, insertion of remdesivir completely stops the formation of new RNA. No new RNA means no new virus.
The action of hydroxychloroquine is quite different from both these drugs. Hydroxychloroquine and chloroquine are immunomodulatory drugs that suppress inflammation in the body. Inflammation and excess cytokines are two of the major causes of lung damage and death in COVID-19 patients.
There’s more: favipiravir and remdesivir inhibit RNA polymerase in two different ways. RNA, as you know, is an abbreviation of ribonucleic acid. Both favipiravir and remdesivir are nucleoside analogues, meaning they contain a nitrogenous base and a sugar.
But while remdesivir competes with the ATP in the viral RNA, favipiravir is a purine analogue: it competes with both A and G base. What this means is that while remdesivir replaces the ATP in the viral RNA, to change the virus enough that it can no longer make copies of itself, favipiravir tries to achieve the same effect by trying to take the place of A and G nitrogenous bases in the viral RNA.
ATP, or adenosine triphosphate, is one of the four organic compounds that make an RNA chain. The other three are GTP, CTP and UTP. A and G are called purines while C and U are called pyrimidines. Studies with flu virus have shown that favipiravir causes shifts from G to A and C to U changes in the RNA sequence of the virus.
Does Favipiravir have any side effects? Is it safe for people with other conditions and pregnant women as well?
Favipiravir is contraindicated in pregnant women as animal studies have shown that this drug can have adverse effects on the fetus.
Those who have a history of allergy to any of the ingredients of favipiravir are not given this drug.
Have the trials of Favipiravir started on COVID-19 patients?
A study done in China found that favipiravir is more effective and safer than the combination of lopinavir-ritonavir. The latter is a drug combination which is originally used to treat and prevent HIV and is another repurposed drug candidate for COVID-19.
Another study found that favipiravir works more quickly than arbidol (another broad-spectrum antiviral drug used to treat influenza in some countries). However, there was no significant difference between the number of people who recovered from the disease.
More studies are currently underway to check the effectiveness of favipiravir on COVID-19 patients.
For more information, read our article on Scientists are trying these drugs for COVID-19 treatment
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