TABLE 8.
Summary of susceptibility data in vitro and coding changesa
| Study/treatment group | Subject | Sample day | Plaque reduction assay IC50 (μg/ml) | NA assay IC50 (ng/ml) | HA coding changesb | NA coding changesb |
|---|---|---|---|---|---|---|
| NAIB2005/IH | 2871 | 1 | 0.003 ± 0.001 | 2.25 ± 0.49 | ||
| 2 | 5.75 ± 6.63 | 2.1 ± 1.48 | None | None | ||
| NAIB2008/QID | 7228 | 1 | 0.04 ± 0.05 | 0.75 ± 0.35 | ||
| 3 | 0.09 ± 0.05 | 0.95 ± 0.78 | G275D* | None | ||
| NAIB2008/QID | 7241 | 1 | >100 | C | ||
| 2 | >100 | C | None | L29P† | ||
| NAIB2008/QID | 7249 | 1 | >100 | 0.9 ± 0.14 | ||
| 4 | >100 | 0.75 ± 0.21 | G275D* | None | ||
| NAIB2008/BID | 7230 | 1 | 0.22 ± 0.12 | C | ||
| 2 | 50.3 ± 49.72 | C | R135K*‡ | Y22F* |
a
All isolates with coding changes were influenza A (H3N2) isolates. Changes were observed in influenza virus clinical isolates during treatment with zanamivir in studies NAIB2005 and NAIB2008.
b
Results indicate a comparison between pre- and intratreatment samples. *, natural variation; †, transmembrane region; ‡, close to the primary sialic acid binding site.