Umifenovir

Umifenovir, sold under the brand name Arbidol, is an antiviral medication for the treatment of influenza infection used in Russia and China. The drug is manufactured by Pharmstandard (). Russian and China studies have shown it to be effective and it is approved in both countries while, it is not approved by the US FDA for the treatment or prevention of influenza because it was never applied for FDA approval since the drug company is in Russia not the US. 
Chemically, umifenovir features an indole core, functionalized at all but one positions with different substituents. The drug has been shown in studies to inhibit viral entry into target cells and stimulate the immune response. 
Umifenovir is manufactured and made available as tablets, capsules and syrup.
Status.
Testing of umifenovir's efficacy has mainly occurred in China and Russia, and it is well known in these two countries. Some of the Russian tests showed the drug to be effective and a direct comparison with oseltamivir showed similar efficiency "in vitro" and in a clinical setting. In 2010 Arbidol was the drug brand with the highest sales volume in Russia. In the first quarter of 2020 it had a 16 percent share in the Russian antiviral market.
Mode of action.
Biochemistry.
Umifenovir inhibits membrane fusion of influenza virus. Umifenovir prevents contact between the virus and target host cells. Fusion between the viral envelope (surrounding the viral capsid) and the cell membrane of the target cell is inhibited. This prevents viral entry to the target cell, and therefore protects it from infection.
Some evidence suggests that the drug's actions are more effective at preventing infections from RNA viruses than infections from DNA viruses.
As well as specific antiviral action against both influenza A and influenza B viruses, umifenovir exhibits modulatory effects on the immune system. The drug stimulates a humoral immune response, induces interferon-production, and stimulates the phagocytic function of macrophages.
Clinical application.
Umifenovir is used primarily as an antiviral treatment for influenza. The drug has also been investigated as a candidate drug for treatment of hepatitis C.
More recent studies indicate that umifenovir also has "in vitro" effectiveness at preventing entry of Zaire ebolavirus (Kikwit strain), Tacaribe arenavirus and Kaposi's sarcoma-associated herpesvirus in mammalian cell cultures, while confirming umifenovir's suppressive effect "in vitro" on Hepatitis B and poliovirus infection of mammalian cells when introduced either in advance of viral infection or during infection.
Research.
, umifenovir and darunavir were being studied as a potential combination treatment for COVID-19 in China.
Side effects.
Side effects in children include sensitization to the drug. No known overdose cases have been reported and allergic reactions are limited to people with hypersensitivity. The is more than 4 g/kg.
Criticism.
In 2007, the Russian Academy of Medical Sciences stated that the effects of Arbidol (umifenovir) are not scientifically proven.
Russian media criticized lobbying attempts by Tatyana Golikova (then-Minister of Healthcare) to promote umifenovir, and the unproven claim that Arbidol can speed up recovery from flu or cold by 1.3-2.3 days. They also made claims that the efficacy of umifenovir is supported by peer-reviewed studies.
Names.
Arbidol is the INN. 
The brand name Arbidol is known as and .