Enisamium Reduces Influenza Virus Shedding and Improves Patient Recovery by Inhibiting Viral RNA Polymerase Activity

Abstract

Infections with respiratory viruses constitute a huge burden on our health and economy. Antivirals against some respiratory viruses are available, but further options are urgently needed. Enisamium iodide (laboratory code FAV00A, trade name Amizon®) is an antiviral marketed in countries of the Commonwealth of Independent States for the treatment of viral respiratory infections, but its clinical efficacy and mode of action are not well understood. Here, we investigated the efficacy of enisamium in patients aged between 18-60 years with confirmed influenza and other viral respiratory infections. Enisamium treatment resulted in reduced influenza virus shedding (at day 3, 71.2% in enisamium group tested negative versus 25.0% in placebo group, p < 0.0001), faster patient recovery (at day 14, 93.9% in enisamium group had recovered versus 32.5% in placebo group, p < 0.0001), and reduced disease symptoms compared to placebo (from 9.6 ± 0.7 to 4.6 ± 0.9 score points in enisamium group versus 9.7 ± 1.1 to 5.6 ± 1.1 score points in placebo group, p < 0.0001). Using mass-spectrometry, and cell-based and cell-free viral RNA synthesis assays, we identified a hydroxylated metabolite of enisamium, VR17-04. VR17-04 is capable of inhibiting influenza virus RNA synthesis and present in plasma of patients treated with enisamium. VR17-04 inhibits the activity of the influenza virus RNA polymerase more potently than its parent compound. Overall, these results suggest that enisamium is metabolized in humans to an inhibitor of the influenza virus RNA polymerase that reduces viral shedding and improves patient recovery in influenza patients.

Enisamium Inhibits SARS-CoV-2 RNA Synthesis

“…Previous experiments showed that enisamium ( Figure 1 A) can efficiently inhibit influenza virus replication in normal human bronchial epithelial (NHBE) cultures and A549 cells, and to a lesser extent in Caco-2 cells [ 13 ]. Previous experiments have also demonstrated that enisamium is not cytotoxic to these cells [ 13 ].…”

“…The cells were infected with SARS-CoV-2 at multiplicity of infection 0.01 for 1 h, and compound reapplied following virus removal. At 48 h post infection, the cytopathic effect was recorded by examination of the infected cultures by light microscopy and supernatant collected to quantify virus RNA by RT-qPCR as described previously, using nsp12-specific primers 5′-GTGARATGGTCATGTGTGGCGG-3′ and 5′-CARATGTTAAASACACTATTAGCATA-3′ [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Cells were fixed with acetone/methanol (40:60) and immunostained using a SARS-CoV-2 nucleoprotein monoclonal antibody (1:500, Sinobiological, Cat #40143-R019-100 µL).…”

“…One of the drugs highlighted by the World Health Organization as a candidate therapeutic against SARS-CoV-2 is enisamium (4-(benzylcarbamoyl)-1-methylpyridinium); Figure 1 A). Enisamium is licensed for use against influenza in 11 countries and it was shown to reduce virus shedding and improve influenza patient recovery [ 13 ]. A recent study found that enisamium is hydroxylated in humans and human lung cells to a compound called VR17-04 ( Figure 1 A) [ 13 ].…”

“…Enisamium is licensed for use against influenza in 11 countries and it was shown to reduce virus shedding and improve influenza patient recovery [ 13 ]. A recent study found that enisamium is hydroxylated in humans and human lung cells to a compound called VR17-04 ( Figure 1 A) [ 13 ]. VR17-04 inhibits the activity of the influenza virus RNA polymerase [ 13 ].…”

“…A recent study found that enisamium is hydroxylated in humans and human lung cells to a compound called VR17-04 ( Figure 1 A) [ 13 ]. VR17-04 inhibits the activity of the influenza virus RNA polymerase [ 13 ].…”