Figure 4.

Mutations of HERG that affect potency for block of HERG channels by MK-499, cisapride, and terfenadine. (a) Structures of the three compounds. (b) -Fold increase in IC₅₀ determined for each mutant channel plotted on a logarithmic scale. The IC₅₀ was 0.134 ± 0.019 μM for terfenadine (n = 5) and 0.133 ± 0.011 μM for cisapride (n = 4).