. 2025 Mar 24;86(2):e70080. doi: 10.1002/ddr.70080

Table 2.

Inhibitory effect on polykaryon formation induced by WT or mutant forms of H3 HA ^a .

Compound	EC₅₀ ^b (µM)
	HA‐WT	HA‐E57₂K	HA‐D112₂N
	pH: 5.2^c	pH: 5.2^c	pH: 5.6^c
2c	7.6	≥ 28	> 50
4c	1.4	12	> 50

^{^a}

The two mutations in the HA2 subunit (E57₂K and D112₂N) were previously identified in influenza A/H3N2 viruses selected for resistance to imidazo[2,1‐b]thiazole analogue 4c (Vanderlinden et al. 2010). The mutations were introduced in an expression plasmid encoding the X‐31 H3 HA, to perform the polykaryon assay.

^{^b}

EC₅₀: compound concentration at which the number of polykaryons was 50% relative to the number observed in the no compound control. The EC₅₀ values for compound 4c were reported earlier (Vanderlinden et al. 2010),

^{^c}

Fusion pH: pH at which the number of polykaryons was 50% relative to the number seen at pH 4.9. Values reported in (Vanderlinden et al. 2010).