ABSTRACT
The inward rectifier potassium (Kir) channel Kir7.1 (KCNJ13) has recently emerged as a key regulator of melanocortin signaling in the brain, electrolyte homeostasis in the eye, and uterine muscle contractility during pregnancy. The pharmacological tools available for exploring the physiology and therapeutic potential of Kir7.1 have been limited to relatively weak and nonselective small-molecule inhibitors. Here, we report the discovery in a fluorescence-based high-throughput screen of a novel Kir7.1 channel inhibitor, VU714. Site-directed mutagenesis of pore-lining amino acid residues identified glutamate 149 and alanine 150 as essential determinants of VU714 activity. Lead optimization with medicinal chemistry generated ML418, which exhibits sub-micromolar activity (IC50 = 310 nM) and superior selectivity over other Kir channels (at least 17-fold selective over Kir1.1, Kir2.1, Kir2.2, Kir2.3, Kir3.1/3.2, and Kir4.1) except for Kir6.2/SUR1 (equally potent). Evaluation in the EuroFins Lead Profiling panel of 64 GPCRs, ion-channels, and transporters for off-target activity of ML418 revealed a relatively clean ancillary pharmacology. While ML418 exhibited low CLHEP in human microsomes which could be modulated with lipophilicity adjustments, it showed high CLHEP in rat microsomes regardless of lipophilicity. A subsequent in vivo PK study of ML418 by intraperitoneal (IP) administration (30 mg/kg dosage) revealed a suitable PK profile (Cmax = 0.20 µM and Tmax = 3 h) and favorable CNS distribution (mouse brain/plasma Kp of 10.9 to support in vivo studies. ML418, which represents the current state-of-the-art in Kir7.1 inhibitors, should be useful for exploring the physiology of Kir7.1 in vitro and in vivo.
Subject(s)
Models, Molecular , Potassium Channel Blockers/chemistry , Potassium Channel Blockers/pharmacology , Potassium Channels, Inwardly Rectifying/antagonists & inhibitors , Potassium Channels, Inwardly Rectifying/metabolism , Animals , Dose-Response Relationship, Drug , HEK293 Cells , Humans , Membrane Potentials/drug effects , Membrane Potentials/genetics , Mutagenesis, Site-Directed , Mutation/genetics , Patch-Clamp Techniques , Potassium/metabolism , Potassium Channels, Inwardly Rectifying/chemistry , Potassium Channels, Inwardly Rectifying/genetics , Structure-Activity Relationship , Time Factors , TransfectionABSTRACT
Unexpected losses in stereochemistry from Stille reactions involving Z-alkenyl halides have been shown to be ligand dependent. A new set of reaction conditions has been developed that, in most cases, leads to highly stereoselective cross-couplings under mild conditions, along with improved yields.
ABSTRACT
The ligands associated with various Pd catalysts play a crucial role in determining the stereochemistry of cross-couplings between boronic acids and Z-alkenyl halides. A ligand on palladium has been found that leads to the desired products under mild conditions and in high yields that, in most cases, retain their Z-olefin geometry.
ABSTRACT
New technology for palladium-catalyzed cross-couplings between B2pin2 and aryl bromides leading to arylboronates is described. Micellar catalysis serves to enable borylations to take place in water as the only medium at ambient temperatures.
