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Trade names | Avigan (アビガン, Abigan), Avifavir, [1] Areplivir, [2] others |
Other names | T-705, favipira, favilavir |
Routes of administration | By mouth |
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Formula | C5H4FN3O2 |
Molar mass | 157.104 g·mol−1 |
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Favipiravir, sold under the brand name Avigan among others, [3] is an antiviral medication used to treat influenza in Japan. [4] It is also being studied to treat a number of other viral infections, including SARS-CoV-2. [4] Like the experimental antiviral drugs T-1105 and T-1106, it is a pyrazinecarboxamide derivative. [5]
It is being developed and manufactured by Toyama Chemical (a subsidiary of Fujifilm) and was approved for medical use in Japan in 2014. [6] In 2016, Fujifilm licensed it to Zhejiang Hisun Pharmaceutical Co. [7] It became a generic drug in 2019.[ citation needed ]
Favipiravir has been approved to treat influenza in Japan. [6] It is, however, only indicated for novel influenza (strains that cause more severe disease) rather than seasonal influenza. [6] [8] As of 2020, the probability of resistance developing appears low. [6]
There is evidence that use during pregnancy may result in harm to the baby. [6] Teratogenic and embryotoxic effects were shown on four animal species. [6] [9] In one case report, a 6-month old infant developed benign bright blue discolouration of the cornea after treatment with favipiravir which resolved after treatment cessation. [10]
The mechanism of its actions is thought to be related to the selective inhibition of viral RNA-dependent RNA polymerase. [11] [ medical citation needed ] Favipiravir is a prodrug that is metabolized to its active form, favipiravir-ribofuranosyl-5'-triphosphate (favipiravir-RTP), available in both oral and intravenous formulations. [12] [13] In 2014, favipiravir was approved in Japan for stockpiling against influenza pandemics. [14] However, favipiravir has not been shown to be effective in primary human airway cells, casting doubt on its efficacy in influenza treatment. [15]
Favipiravir-RTP is a nucleoside analogue. It mimics both guanosine and adenosine for the viral RdRP. Incorporating two such bases in a row stops primer extension, although it is unclear how as of 2013. [11]
There are multiple pathways to synthesize favipiravir. [16] [17] One synthesis starts with 3-Hydroxypicolinic acid, [18] which is first reacted with thionyl chloride and then aqueous ammonia to produce 3-Hydroxypyrazine-2-carboxamide. The resulting material is nitrated with potassium nitrate and sulfuric acid to add a nitro group in the 6 position, which is then reduced using hydrazine hydrate to the corresponding amine. Finally, the amine is turned into a diazonium group using sodium nitrite and replaced with a fluorine group using hydrofluoric acid.
The US Department of Defense developed favipiravir in partnership with MediVector, Inc. as a broad-spectrum antiviral and sponsored it through FDA Phase II and Phase III clinical trials, where it demonstrated safety in humans and efficacy against the influenza virus. [19] favipiravir remains unapproved in the UK and the USA. [20] In 2014, Japan approved favipiravir for treating influenza strains unresponsive to current antivirals. [21] Toyama Chemical initially hoped that favipiravir would become a new influenza medication that could replace oseltamivir (brand name Tamiflu). However, 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. [22]
Despite limited data on efficacy, as of March 2021 favipiravir is widely prescribed for outpatient treatment of mild to moderate COVID-19 in Egypt, [23] Hungary [24] and Serbia. [25] Patients are required to sign a consent form before obtaining the drug.[ citation needed ]
Favipiravir is sold under the brand names Avigan (アビガン, Abigan), Avifavir, [1] Avipiravir, [26] Areplivir, [2] FabiFlu, [27] Favipira, [28] Reeqonus, [29] [30] and Qifenda.
Coronavir is the brand name of favipiravir used in Russia, where it is approved for the treatment of COVID-19. It is produced and sold by R-Pharm. [31] [32] Coronavir was approved for use in Russia in hospitals in July 2020, and in September 2020 it received approval for prescription sales for outpatient use. [33]
Favipiravir, as an antiviral drug, has been authorized for treating COVID-19 in several countries including Japan, Russia, Serbia, Turkey, India, and Thailand, under emergency provisions. [34] [35] [36] [37] A rapid meta-review in September 2020 (analyzing four studies) noted that the drug led to clinical and radiological improvements; however, no reduction in mortality or differences in oxygen-support requirement were observed and more rigorous studies were sought. [38] [39] A Cochrane Systematic review published in Feb 2024, noted that there is actually no real benefit with Favipiravir in treating Covid-19 in terms of mortality benefits, or admission to mechanical ventillation, or hospitalisation, and it may not make any difference in adverse effects or serious adverse effects. [40]
As of May 2021 [update] , large-cohort clinical trials are underway. [41]
Research in 2014, suggested that favipiravir may have efficacy against Ebola based on studies in mouse models; efficacy in humans was unaddressed. [42] [43] [44]
During the 2014 West Africa Ebola virus outbreak, a French nurse who contracted Ebola while volunteering for Médecins Sans Frontières (MSF) in Liberia reportedly recovered after receiving a course of favipiravir. [45] A clinical trial investigating the use of favipiravir against Ebola virus disease began in Guéckédou, Guinea, in December 2014. [46] Preliminary results presented in 2016 at the Conference on Retroviruses and Opportunistic Infections (CROI), later published, showed a decrease in mortality in patients with low-to-moderate levels of virus in blood, but no effect on patients with high levels (the group at a higher risk of death). [47] [48] [49] The trial design was concomitantly criticised for using only historical controls. [50]
Nipah virus is a causative agent of outbreaks of encephalitis with pneumonia and has a high case fatality rate. The first outbreak occurred in Malaysia-Singapore, related to contact with pigs in slaughterhouses and an outbreak in Philippines related to slaughter of horses, most other outbreaks have affected India and Bangladesh. in Bangladesh outbreaks are often associated with consumption of raw date palm sap contaminated by saliva and urine of fruit bats. [51] In a study published in the Scientific Reports, Syrian hamster model for Nipah virus infection was used, which closely mirrors most aspects of human disease, such as widespread vasculitis, pneumonia, and encephalitis. The hamsters were infected with a lethal dose of 104 PFU NiV-M via the intraperitoneal (i.p.) route similar to previous studies and treatment was initiated immediately after infection. Favipiravir was administered twice daily via the peroral (p.o.) route for 14 days. The treated hamsters displayed 100% survival and no obvious morbidity after lethal NiV challenge, whereas all the control cases died of severe disease. [52]
In experiments in animals favipiravir has shown activity against West Nile virus, yellow fever virus, foot-and-mouth disease virus as well as other flaviviruses, arenaviruses, bunyaviruses and alphaviruses. [53] Activity against enteroviruses [54] and Rift Valley fever virus has also been demonstrated. [55] Favipiravir has showed limited efficacy against Zika virus in animal studies, but was less effective than other antivirals such as MK-608. [56] The agent has also shown some efficacy against rabies, [57] and has been used experimentally in some humans infected with the virus. [58]
The possible tautomerism of favipiravir has been investigated computationally [59] and experimentally. [60] It was found that the enol-like form was substantially more stable in organic solvents than the keto-like form, meaning that Favipiravir likely exists almost exclusively in the enol-like form. In aqueous solution the keto-like tautomer is substantially stabilized due to the specific interaction with the water molecules. Upon protonation the keto form is switched on.[ citation needed ]
Ribavirin, also known as tribavirin, is an antiviral medication used to treat RSV infection, hepatitis C and some viral hemorrhagic fevers. For hepatitis C, it is used in combination with other medications such as simeprevir, sofosbuvir, peginterferon alfa-2b or peginterferon alfa-2a. It can also be used for viral hemorrhagic fevers, specifically for Lassa fever, Crimean–Congo hemorrhagic fever, and Hantavirus infection with exceptions for Ebola or Marburg infections. Ribavirin is usually taken orally or inhaled. Despite widespread usage, it has faced scrutiny in 2010 because of lack of efficacy in treating viral infections as it has historically been prescribed for.
Oseltamivir, sold under the brand name Tamiflu among others, is an antiviral medication used to treat and prevent influenza A and influenza B, viruses that cause the flu. Many medical organizations recommend it in people who have complications or are at high risk of complications within 48 hours of first symptoms of infection. They recommend it to prevent infection in those at high risk, but not the general population. The Centers for Disease Control and Prevention (CDC) recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. It is taken by mouth, either as a pill or liquid.
Amantadine, sold under the brand name Gocovri among others, is a medication used to treat dyskinesia associated with parkinsonism and influenza caused by type A influenzavirus, though its use for the latter is no longer recommended because of widespread drug resistance. It is also used for a variety of other uses. The drug is taken by mouth.
Umifenovir, sold under the brand name Arbidol, is sold and used as an antiviral medication for influenza in Russia and China. The drug is manufactured by Pharmstandard. It is not approved by the U.S. Food and Drug Administration (FDA) for the treatment or prevention of influenza.
Nitazoxanide, sold under the brand name Alinia among others, is a broad-spectrum antiparasitic and broad-spectrum antiviral medication that is used in medicine for the treatment of various helminthic, protozoal, and viral infections. It is indicated for the treatment of infection by Cryptosporidium parvum and Giardia lamblia in immunocompetent individuals and has been repurposed for the treatment of influenza. Nitazoxanide has also been shown to have in vitro antiparasitic activity and clinical treatment efficacy for infections caused by other protozoa and helminths; evidence as of 2014 suggested that it possesses efficacy in treating a number of viral infections as well.
Inosine pranobex is an antiviral drug that is a combination of inosine and dimepranol acedoben in a ratio of 1 to 3. It is used primarily in European countries, especially as a treatment for acute viral infections, such as the common cold.
Brincidofovir, sold under the brand name Tembexa, is an antiviral drug used to treat smallpox. Brincidofovir is a prodrug of cidofovir. Conjugated to a lipid, the compound is designed to release cidofovir intracellularly, allowing for higher intracellular and lower plasma concentrations of cidofovir, effectively increasing its activity against dsDNA viruses, as well as oral bioavailability.
ZMapp is an experimental biopharmaceutical medication comprising three chimeric monoclonal antibodies under development as a treatment for Ebola virus disease. Two of the three components were originally developed at the Public Health Agency of Canada's National Microbiology Laboratory (NML), and the third at the U.S. Army Medical Research Institute of Infectious Diseases; the cocktail was optimized by Gary Kobinger, a research scientist at the NML and underwent further development under license by Mapp Biopharmaceutical. ZMapp was first used on humans during the Western African Ebola virus epidemic, having only been previously tested on animals and not yet subjected to a randomized controlled trial. The National Institutes of Health (NIH) ran a clinical trial starting in January 2015 with subjects from Sierra Leone, Guinea, and Liberia aiming to enroll 200 people, but the epidemic waned and the trial closed early, leaving it too statistically underpowered to give a meaningful result about whether ZMapp worked.
Galidesivir is an antiviral drug, an adenosine analog. It was developed by BioCryst Pharmaceuticals with funding from NIAID, originally intended as a treatment for hepatitis C, but subsequently developed as a potential treatment for deadly filovirus infections such as Ebola virus disease and Marburg virus disease, as well as Zika virus. Currently, galidesivir is under phase 1 human trial in Brazil for coronavirus.
JK-05 is a broad-spectrum antiviral drug developed by the Chinese company Sihuan Pharmaceutical along with the Chinese Academy of Military Medical Sciences. It is reported to act as an inhibitor of the viral enzyme RNA polymerase, which is essential for viral replication. In tests on mice, JK-05 was claimed to show efficacy against a range of RNA viruses, including influenza, Ebola virus, and yellow fever, as well as several arenaviruses and bunyaviruses. The chemical structure of JK-05 has not been disclosed as of October 2014, but it is claimed to be a small molecule drug with a comparatively simple structure, which should be readily amenable to synthesis scale-up for mass production if testing is successful. The drug is, however, admitted to be similar to the Japanese anti-influenza drug favipiravir, developed by Fujifilm Holdings Corp, which has been used effectively to treat patients with Ebola. In addition, WHO committee members mentioned that the drug is a copy product of favipiravir, because patents of favipiravir were already registered in 2006 in China. The drug has been given preliminary approval by the Chinese authorities to be available for Chinese health workers involved in combating the 2014 West African Ebola outbreak, or if Ebola were to spread into mainland China. Several other Chinese developed antiviral drugs with anti-Ebola activity have also been disclosed, but have not progressed so far through development as JK-05.
There is a cure for the Ebola virus disease that is currently approved for market the US government has inventory in the Strategic National Stockpile. For past and current Ebola epidemics, treatment has been primarily supportive in nature.
Riamilovir, sold under the brand name Triazavirin, is a broad-spectrum antiviral drug developed in Russia through a joint effort of Ural Federal University, Russian Academy of Sciences, Ural Center for Biopharma Technologies and Medsintez Pharmaceutical. It has a novel triazolotriazine core, which represents a new structural class of non-nucleoside antiviral drugs.
MK-608 is an antiviral drug, an adenosine analog. It was originally developed by Merck & Co. as a treatment for hepatitis C, but despite promising results in animal studies, it was ultimately unsuccessful in clinical trials. Subsequently it has been widely used in antiviral research and has shown activity against a range of viruses, including Dengue fever, tick-borne encephalitis virus, poliovirus, and most recently Zika virus, in both in vitro and animal models. Since it has already failed in human clinical trials previously, it is unlikely MK-608 itself will be developed as an antiviral medication, but the continuing lack of treatment options for these emerging viral diseases means that much research continues using MK-608 and related antiviral drugs.
NITD008 is an antiviral drug classified as an adenosine analog. It was developed as a potential treatment for flavivirus infections and shows broad spectrum antiviral activity against many related viruses such as dengue virus, West Nile virus, yellow fever virus, Powassan virus, hepatitis C virus, Kyasanur Forest disease virus, Omsk hemorrhagic fever virus, and Zika virus. However, NITD008 proved too toxic in pre-clinical animal testing to be suitable for human trials, but it continues to be used in research to find improved treatments for emerging viral diseases.
Remdesivir, sold under the brand name Veklury, is a broad-spectrum antiviral medication developed by the biopharmaceutical company Gilead Sciences. It is administered via injection into a vein. During the COVID‑19 pandemic, remdesivir was approved or authorized for emergency use to treat COVID‑19 in numerous countries.
Nipah virus infection is an infection caused by the Nipah virus. Symptoms from infection vary from none to fever, cough, headache, shortness of breath, and confusion. This may worsen into a coma over a day or two, and 50% to 75% of those infected die. Complications can include inflammation of the brain and seizures following recovery.
Drug repositioning is the repurposing of an approved drug for the treatment of a different disease or medical condition than that for which it was originally developed. This is one line of scientific research which is being pursued to develop safe and effective COVID-19 treatments. Other research directions include the development of a COVID-19 vaccine and convalescent plasma transfusion.
COVID-19 drug development is the research process to develop preventative therapeutic prescription drugs that would alleviate the severity of coronavirus disease 2019 (COVID-19). From early 2020 through 2021, several hundred drug companies, biotechnology firms, university research groups, and health organizations were developing therapeutic candidates for COVID-19 disease in various stages of preclinical or clinical research, with 419 potential COVID-19 drugs in clinical trials, as of April 2021.
Convalescent plasma is the blood plasma collected from a survivor of an infectious disease. This plasma contains antibodies specific to a pathogen and can be used therapeutically by providing passive immunity when transfusing it to a newly infected patient with the same condition. Convalescent plasma can be transfused as it has been collected or become the source material for hyperimmune serum or anti-pathogen monoclonal antibodies; the latter consists exclusively of IgG, while convalescent plasma also includes IgA and IgM. Collection is typically achieved by apheresis, but in low-to-middle income countries, the treatment can be administered as convalescent whole blood.
A viral vector vaccine is a vaccine that uses a viral vector to deliver genetic material (DNA) that can be transcribed by the recipient's host cells as mRNA coding for a desired protein, or antigen, to elicit an immune response. As of April 2021, six viral vector vaccines, four COVID-19 vaccines and two Ebola vaccines, have been authorized for use in humans.
Led by University of Oxford researchers, PRINCIPLE is one of the UK Government's national priority platform trials for COVID-19 treatments and was set-up with the intention that drugs shown to have a clinical benefit could be rapidly introduced into routine NHS care.