NS1643 is ether-a-go-go (ERG) channel activator with EC₅₀ = 10.5 μM in Xenopus oocytes and hERG channels expressed in HEK293 cells.

The new diphenylurea compound 1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea (NS1643) was tested in hERG channel. In Xenopus laevis oocytes, NS1643 increased both steady-state and tail current at all voltages tested. The EC₅₀ value for hERG channel activation was 10.5 μM. The effect could be reverted by application of the specific hERG channel inhibitor 4′-[[1-[2-(6-methyl-2-pyridyl)ethyl]-4-piperidinyl]carbonyl]-methanesulfonanilide (E-4031) at 100 nM. Application of NS1643 also resulted in a prolonged postrepolarization refractory time. hERG channel activation by small molecules such as NS1643 increases the repolarization reserve and presents a new antiarrhythmic approach.

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