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Promising New Candidate to Treat Influenza Infections

A Better Drug Candidate to Treat Influenza Infections

Influenza viruses are responsible for over 600,000 deaths globally and have a huge impact on human health and productivity. However, the moderate efficacy of influenza vaccines means that many individuals, particularly the elderly, still develop influenza infections even with vaccination. Current drug treatments for influenza infections include the adamantanes (amantadine and rimantadine) and a newer class of neuraminidase inhibitors (zanamivir [Relenza] and oseltamivir [Tamiflu]), but the development of viral resistance to these compounds has diminished their effectiveness, leading researchers to develop other therapeutic options.

Toots and Colleagues published a recent study to explore the efficacy and pharmacokinetics of a new clinical candidate, EIDD-2801 against influenza virus infection. The authors created EIDD-2801, an isopropylester prodrug of the ribonucleoside analog N4-hydroxycytidine (NHC, EIDD-1931) that has shown broad anti-influenza virus activity in previous studies using in vivo and in vitro animal models (i.e., canine, mice, ferrets). Here, the goal was to confirm these findings using a physiologically relevant in vitro 3D human airway epithelium model to determine the mechanism of action and identify efficacy and safety thresholds to facilitate future clinical evaluation.

To create their 3D human airway epithelia model, Lifeline’s normal primary human bronchial tracheal epithelial cells (HBTECs) were cultured in the companion Lifeline BronchiaLife cell culture medium in a Transwell plate system (pore size 0.4 μm). Once the cells reached confluence, the media in the apical (top) chamber was removed and the media in the basal chamber was changed to Lifeline’s HBTEC Air-Liquid Interface Differentiation Medium to induce HBTEC differentiation at the air-liquid interface to create the fully developed 3D airway model for testing.

Data obtained from previous animal models was used to establish relevant drug concentrations to assess EIDD-2801 efficacy in the disease-relevant human tissues. Genetic sequencing analysis after influenza virus challenge of the 3D airway system led the authors to conclude that EIDD-2801’s mechanism of action is through specific C-to-U and G-to-A transition mutations in the viral genome that causes lethal replication errors. Pharmacokinetic studies define an efficacy and cytotoxicity range of approximately 0.2 μM and 50 μM, respectively, in human airway epithelia.  Additionally, EIDD-2801 appears to have higher antiviral activity with an ED50 concentration of 0.06-0.08 μM compared to 0.19 μM for the current standard influenza treatment Tamiflu. The development of viral resistance to the compound was also evaluated using dose escalation and prolonged exposure of EIDD-2801 to compound-experienced influenza populations. Whole genome deep-sequencing of compound- or vehicle-experienced virus populations after ten passages revealed only dose-dependent accumulation of random low-frequency mutations indicating a high genetic barrier to influenza virus resistance to the compound.

Next steps will be formal two-species multi-day toxicity and adverse event testing to determine first-in-human dose concentrations. Treatment simulation models developed in this study reveal high SI values against influenza viruses (high SI values translate to better drug safety profiles), no significant lung toxicity, and a high barrier to the development of viral resistance, making it a promising new candidate to treat influenza infections that warrant further investigation in clinical trials.

The Lifeline® catalog offers a wide range of high-quality cell culture media kits optimized to culture many different cell types including the HBTECs used in the study reviewed here. Our media products do not contain antimicrobials and are phenol red-free to mitigate any undesirable, off-target effects they may cause to ensure the accuracy of your results.

Let us know how you are using Lifeline products to find the answers to your research questions. Contact us with your published study and it could be featured in our next blog!

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