A small molecule activator of KCNQ2 and KCNQ4 channels

ML213 was identified following a high throughput fluorescent screen of the Molecular Libraries Small Molecule Repository (MLSMR) library and structure activity relationship (SAR) studies using fluorescent and electrophysiological assays to determine potency and selectivity of test compounds. ML213 is a potent activator of potassium voltage-gated channel, KQT-like subfamily, member 2 (KCNQ2) (Kv7.2, EC50 = 230 nM) and KCNQ4 (Kv7.4, EC50 = 510 nM) and selective against the other members of the KCNQ family of ion channels (KCNQ1, KCNQ3 and KCNQ5). ML213 shifts the voltage-dependence of KCNQ2 opening in a concentration dependent manner with a comparable half maximal effective concentration (EC50) value and produces a maximal hyperpolarizing shift of 37 mV. In addition, ML213 has been tested in 247 assays performed within the MLPCN network and was active in only one assay that was not dependent on KCNQ channels. ML213 was also tested at Ricerca’s Lead Profiling Screen (binding assay panel of 68 G protein coupled receptors [GPCRs], ion channels and transporters screened at 10 μM), and was found to not significantly bind with any of the 68 assays conducted. This is consistent with its high selectivity. ML213 was stable in aqueous media (>24 hour half life). However, it exhibited poor metabolic stability when incubated with rat or human liver microsomes, predicting rapid clearance after systemic exposure. Although there are several reported KCNQ2/3 activators in the primary literature, ML213 (CID 3111211) has several unique features, especially being the first KCNQ2 and KCNQ4 selective probe compound and, as such, ML213 will be an important tool for understanding the roles of these channels in regulating neuronal excitability. The probe may be used for investigations of the roles of KCNQ2 and KCNQ4 channels in epileptogenesis in mechanistic cellular studies and tissue slice experiments. Its metabolic properties may be improved with a more extensive and systemic SAR campaign.