Antiviral Drug Behavior Varies Widely Across Rare Bird Species

High pathogenicity avian influenza virus poses a serious threat to captive rare birds, yet effective countermeasures remain limited. One option under consideration is the use of human antiviral drugs to treat infections in these animals. Baloxavir marboxil, a human antiviral not approved for treating influenza virus infection in birds, has previously shown antiviral efficacy in experimental avian models. However, pharmacokinetic studies have revealed substantial differences between species in how the drug behaves after administration, suggesting that each species may require its own dosing regimen.

In a new study, researchers administered baloxavir marboxil to 14 avian species with the aim of optimizing dosing regimens for each one. The work focused on measuring how the drug and its active metabolite, baloxavir acid, behave in the body across this taxonomically diverse group of birds.

The team tested different oral administration methods and found that drug–food interactions had only a limited impact on systemic drug exposure. This suggests that how the drug is given orally is less critical to overall exposure than other factors, simplifying practical administration in captive settings.

Pharmacokinetic analysis of baloxavir marboxil and baloxavir acid demonstrated marked interspecies variability in drug exposure. In other words, the same dose can produce very different systemic drug levels depending on the species, reinforcing the need for species-specific dosing rather than a one-size-fits-all approach.

The analysis also showed that systemic exposure to baloxavir acid was strongly associated with indicators of drug absorption. This points to species-specific differences in absorption efficiency as a major determinant of how much active metabolite reaches the systemic circulation among avian species.

By characterizing these pharmacokinetic patterns, the study provides a basis for the rational use of baloxavir marboxil in diverse avian species. The findings contribute to the development of practical antiviral strategies aimed at protecting captive rare birds against high pathogenicity avian influenza viruses, where effective countermeasures are otherwise scarce.

Subject of Research: Pharmacokinetics of the antiviral baloxavir marboxil across rare avian species for avian influenza treatment

Article Title: Pharmacokinetic diversity of baloxavir marboxil across rare avian species

Article References: Shimazu, Y., Obara, R. D., Miki, M., Osaki, H., Yoshimoto, Y., Hayashi, M., Toyoda, K., Ozaki, M., Hanada, I., Matsumoto, R., Ota, K., Yamaguchi, A., Toda, K., Ishii, J., Kizaki, T., Hirano, Y., Sugimoto, Y., Watanabe, Y., Saito, K., … Sakoda, Y. (2026). Pharmacokinetic diversity of baloxavir marboxil across rare avian species. PLOS One, 21(10), e0361119. https://doi.org/10.1371/journal.pone.0361119

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0361119

Keywords: baloxavir marboxil, avian influenza, pharmacokinetics, rare birds, antiviral drugs, high pathogenicity avian influenza virus, baloxavir acid, drug dosing, captive birds, interspecies variability, Pharmacokinetic, diversity