Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Antiviral drugs are one class of antimicrobials, a larger group which also includes antibiotic, antifungal and antiparasitic drugs, or antiviral drugs based on monoclonal antibodies. Most antivirals are considered relatively harmless to the host, and therefore can be used to treat infections. They should be distinguished from viricides, which are not medication but deactivate or destroy virus particles, either inside or outside the body. Natural viricides are produced by some plants such as eucalyptus and Australian tea trees.
Zanamivir is a medication used to treat and prevent influenza caused by influenza A and influenza B viruses. It is a neuraminidase inhibitor and was developed by the Australian biotech firm Biota Holdings. It was licensed to Glaxo in 1990 and approved in the US in 1999, only for use as a treatment for influenza. In 2006, it was approved for prevention of influenza A and B. Zanamivir was the first neuraminidase inhibitor commercially developed. It is marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation.
Oseltamivir, sold under the brand name Tamiflu, 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 due to widespread drug resistance. It acts as a nicotinic antagonist, dopamine agonist, and noncompetitive NMDA antagonist. The antiviral mechanism of action is antagonism of the influenzavirus A M2 proton channel, which prevents endosomal escape.
Neuraminidase inhibitors (NAIs) are a class of drugs which block the neuraminidase enzyme. They are a commonly used antiviral drug type against influenza. Viral neuraminidases are essential for influenza reproduction, facilitating viral budding from the host cell. Oseltamivir (Tamiflu), zanamivir (Relenza), laninamivir (Inavir), and peramivir belong to this class. Unlike the M2 inhibitors, which work only against the influenza A virus, NAIs act against both influenza A and influenza B.
Peramivir is an antiviral drug developed by BioCryst Pharmaceuticals for the treatment of influenza. Peramivir is a neuraminidase inhibitor, acting as a transition-state analogue inhibitor of influenza neuraminidase and thereby preventing new viruses from emerging from infected cells. It is approved for intravenous administration.
Treatments for influenza include a range of medications and therapies that are used in response to disease influenza. Treatments may either directly target the influenza virus itself; or instead they may just offer relief to symptoms of the disease, while the body's own immune system works to recover from infection.
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.
An antiviral stockpile is a reserve supply of essential antiviral medications in case of shortage. Many countries have chosen to stockpile antiviral medications against pandemic influenza. Because of the time required to prepare and distribute an influenza vaccine, these stockpiles are the only medical defense against widespread infection for the first six months. The stockpiles may be in the form of capsules or simply as the active pharmaceutical ingredient, which is stored in sealed drums and, when needed, dissolved in water to make a bitter-tasting, clear liquid.
JNJ-26990990 is a broad-spectrum anticonvulsant drug currently under development by Janssen Pharmaceutica as a second-generation follow-up to the marketed drug topiramate. It was designed to have the same anticonvulsant effects as topiramate, but without the side effects associated with topiramate's carbonic anhydrase inhibition. It also has potential use in the treatment of inflammatory pain, neuropathic pain, and depression.
Quisinostat is an experimental drug candidate for the treatment of cancer. It is a "second generation" histone deacetylase inhibitor with antineoplastic activity. It is highly potent against class I and II HDACs.
Favipiravir, sold under the brand name Avigan among others, is an antiviral medication used to treat influenza in Japan. It is also being studied to treat a number of other viral infections, including SARS-CoV-2. Like the experimental antiviral drugs T-1105 and T-1106, it is a pyrazinecarboxamide derivative.
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.
Neuraminidase inhibitors inhibit enzymatic activity of the enzyme neuraminidase (sialidase). These type of inhibitors have been introduced as anti-influenza drugs as they prevent the virus from exiting infected cells and thus stop further spreading of the virus. Neuraminidase inhibitors for human neuraminidase (hNEU) have the potential to be useful drugs as the enzyme plays a role in several signaling pathways in cells and is implicated in diseases such as diabetes and cancer.
Riamilovir 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.
ADX-71149, also known as JNJ-40411813 and JNJ-mGluR2-PAM, is a selective positive allosteric modulator of the mGlu2 receptor. It is being studied by Addex Therapeutics and Janssen Pharmaceuticals for the treatment of schizophrenia. It was also researched by these companies for the treatment of anxious depression, but although some efficacy was observed in clinical trials, it was not enough to warrant further development for this indication. As of 2015, ADX-71149 is in phase II clinical trials for schizophrenia.
JNJ-42165279 is a drug developed by Janssen Pharmaceutica which acts as a potent and selective inhibitor of the enzyme fatty acid amide hydrolase (FAAH), with an IC50 of 70 nM. It is described as a covalently binding but slowly reversible selective inhibitor of FAAH. JNJ-42165279 is being developed for the treatment of anxiety disorders and major depressive disorder. Clinical development has progressed as far as Phase II human trials with two studies in patients with mood disorders registered in ClinicalTrials.gov.
Baloxavir marboxil, sold under the brand name Xofluza, is an antiviral medication for treatment of influenza A and influenza B flu. It was approved for medical use both in Japan and in the United States in 2018, and is taken as a single dose by mouth. It may reduce the duration of flu symptoms by about a day, but is prone to selection of resistant mutants that render it ineffectual.
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.
Merimepodib (VX-497) is a drug which acts as an inhibitor of the enzyme inosine monophosphate dehydrogenase, which is required for the synthesis of nucleotide bases containing guanine. This consequently inhibits synthesis of DNA and RNA, and results in antiviral and immunosuppressive effects. It progressed as far as Phase 2b human clinical trials against Hepatitis C but showed only modest benefits in comparison to existing treatments, however it continues to be researched, and also shows activity against other viral diseases such as Zika virus and foot and mouth disease virus.
