Drug Repurposing Identifies Inhibitors of Oseltamivir‐Resistant Influenza Viruses

Abstract

The inhibitor of neuraminidase (NA), oseltamivir, is a widely used anti-influenza drug. However, oseltamivir-resistant H1N1 influenza viruses carrying the H275Y NA mutation spontaneously emerged as a result of natural genetic drift and drug treatment. Because this and other potential mutations may generate a future pandemic influenza strain that is oseltamivir-resistant, alternative therapy options are needed. Here show that a structure-based computational method can be used to identify existing drugs that inhibit resistant viruses, thereby providing a first line of pharmaceutical defense against this very possible scenario. We identified two drugs, nalidixic acid and dorzolamide, that potently inhibit the NA activity of oseltamivir-resistant H1N1 viruses with the H275Y NA mutation at very low concentrations, but have no effect on wild-type H1N1 NA even at a much higher concentration, suggesting that the oseltamivir-resistance mutation itself caused susceptibility to these drugs. Keywords drug discovery; influenza viruses; neuraminidase; computational chemistry; drug repurposing During the early stages of any influenza pandemic, specific vaccines are unavailable; therefore, effective drugs are the only means of preventing the spread of infection. [1] The 2009 H1N1 pandemic, for example, reached its peak well before a vaccine became available in the United States. [2] The potent neuraminidases (NA) inhibitor oseltamivir (Tamiflu) is the most widely used anti-influenza drug. However, oseltamivir-resistant H1N1 influenza viruses carrying the H275Y NA mutation spontaneously emerged worldwide as a result of natural genetic drift and drug treatment. [3] NA catalyzes the hydrolysis of sialic acid residues between newly formed virions and host glycoproteins to allow virion release. Oseltamivir was designed to fit perfectly into the NA enzyme active site of influenza virus. This site is altered in oseltamivir-resistant viruses, inhibiting binding of the drug. Most oseltamivir-resistant strains of seasonal and pandemic H1N1 influenza virus to date have carried the H275Y NA mutation. [4] This mutant has a bulky hydrophobic side chain at Y275 * jzheng@jsei.ucla.edu. HHS Public Access Author ManuscriptAuthor Manuscript Author ManuscriptAuthor Manuscript that forces the E277 side chain to rotate, disrupting the intramolecular E277-R225 electrostatic interactions normally formed upon binding to oseltamivir. The E277 side chain is also forced toward the center of the NA sialic acid binding site by the side chain of Y275. These changes reduce the binding affinity of the site for the large aliphatic side chain of oseltamivir. [5] Had oseltamivir-resistant viruses dominated during the 2009 H1N1 pandemic mortality would have been much greater.We reasoned that available drugs that are structurally similar to oseltamivir may bind to the mutant NA active site and that sensitivity to these drugs may be enhanced by the structural changes in the mutant NA binding site. To search for such drugs, we used hierarchical computational...

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