VU0134992 hydrochloride is the first subtype-preferring, orally active and selective blocker of the Kir4.1 potassium channel pore (IC50: 0.97 μM).

In whole-cell patch-clamp electrophysiology experiments, VU0134992 inhibits Kir4.1 with an IC50 value of 0.97 M and is 9-fold selective for homomeric Kir4.1 over Kir4.1/5.1 concatemeric channels (IC50 = 9 M) at -120 mV. In thallium (Tl+) flux assays, VU0134992 is greater than 30-fold selective for Kir4.1 over Kir1.1, Kir2.1, and Kir2.2; is weakly active toward Kir2.3, Kir6.2/SUR1, and Kir7.1; and is equally active toward Kir3.1/3.2, Kir3.1/3.4, and Kir4.2. This potency and selectivity profile is superior to Kir4.1 inhibitors amitriptyline, nortriptyline, and fluoxetine. Medicinal chemistry identified components of VU0134992 that are critical for inhibiting Kir4.1. Patch-clamp electrophysiology, molecular modeling, and site-directed mutagenesis identified pore-lining glutamate 158 and isoleucine 159 as critical residues for block of the channel.

VU0134992 displayed a large free unbound fraction (fu) in rat plasma (fu = 0.213).Consistent with the known role of Kir4.1 in renal function, oral dosing of VU0134992 led to a dose-dependent diuresis, natriuresis, and kaliuresis in rats.Thus, VU0134992 represents the first in vivo active tool compound for probing the therapeutic potential of Kir4.1 as a novel diuretic target for the treatment of hypertension.

VU0134992 hydrochloride (250-300 g Male Sprague-Dawley rats;50 and 100 mg/kg) Oral gavage