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. Author manuscript; available in PMC: 2025 Nov 18.
Published in final edited form as: Antiviral Res. 2025 Oct 11;244:106299. doi: 10.1016/j.antiviral.2025.106299

Table 2.

Baseline susceptibility of influenza viruses to NA inhibitors determined in NA inhibition assay.a.

Test viruses IC50 nM Oseltamivir Zanamivir Peramivir Laninamivir
Mean ± SD Range Median Mean ± SD Range Median Mean ± SD Range Median Mean ± SD Range Median
A (H1N1)pdm09 n = 224 0.23 ± 0.14 0.10–1.16 0.21 0.18 ± 0.06 0.11–0.75 0.17 0.07 ± 0.03 0.03–0.28 0.07 0.21 ± 0.07 0.10–0.56 0.20
A (H3N2) n = 204 0.16 ± 0.08 0.08–0.90 0.14 0.33 ± 0.18 0.14–2.23 0.29 0.09 ± 0.02 0.05–0.25 0.08 0.35 ± 0.09 0.22–0.98 0.34
B/Victoria n = 168 24.80 ± 5.33 9.47–44.10 24.91 0.99 ± 0.35 0.49–2.96 0.90 0.35 ± 0.11 0.14–0.88 0.33 0.80 ± 0.13 0.50–1.29 0.80
Reference virusesb Mean ± SD Range Fold Mean ± SD Range Fold Mean ± SD Range Fold Mean ± SD Range Fold
A/Illinois/45/2019 0.16 ± 0.02 0.14–0.20 – 0.15 ± 0.03 0.12–0.21 – 0.05 ± 0.01 0.05–0.06 – 0.18 ± 0.02 0.16–0.23 –
A/Alabama/03/2020 NA-H275Y 225.31 ± 47.66 154.37–302.27 1408 0.21 ± 0.04 0.16–0.31 1 16.13 ± 2.77 12.94–20.56 301 0.39 ± 0.05 0.32–0.46 2

IC50, 50 % inhibitory concentration; NA, neuraminidase; SD, standard deviation.

a

Indicated numbers of influenza viruses were tested in presence of NA inhibitors using fluorescence-based NA inhibition assay to determine the subtype- or lineage-specific baseline susceptibility. The test viruses did not contain any known NA substitutions of concern.

b

NA-H275Y virus and its NA sequence-matched counterpart lacking this substitution are from the CDC NA inhibitor susceptibility reference virus panel. Mean ± SD of IC50s and fold change conferred by NA-H275Y were calculated based on results from 11 independent tests.