# Preclinical validation of Kir4.1/5.1 inhibitors for overcoming diuretic resistance

> **NIH NIH R01** · VANDERBILT UNIVERSITY MEDICAL CENTER · 2024 · $458,819

## Abstract

SUMMARY
Edema is a common, life-threatening consequence of congestive heart failure (HF), chronic kidney disease
(CKD), and chronic liver disease. Loop diuretics are often used as a first-line therapy to quickly reduce the fluid
volume burden in HF, CKD, and liver failure patients. This class of diuretic works by inhibiting NaCl reabsorption
in the thick ascending limb (TAL) of Henle’s loop and increasing the delivery of NaCl to the distal convoluted
tubule (DCT) and cortical collecting duct (CCD) comprising the distal nephron. In response to the increased NaCl
load, the DCT and CCD increase their NaCl reabsorption capacity through distal tubule remodeling involving
cell/tissue hypertrophy and by upregulating the expression of ion transporters and channels involved in NaCl
reabsorption. This compensatory mechanism diminishes the effectiveness of loop diuretics and gives rise to loop
diuretic resistance, which is a common clinical problem in the treatment of HF, CKD, and liver failure. A growing
consensus is that distally acting diuretics that inhibit sodium (Na+) reabsorption in the DCT (i.e., thiazide diuretics)
or CCD (i.e., amiloride) downstream of the TAL should be administered to overcome loop diuretic resistance.
However, both diuretic classes have serious liabilities that highlight the need for more effective, safer, and novel-
mechanism distal nephron-targeted diuretics. Heteromeric Kir4.1/5.1 inward rectifier potassium (Kir) channels
have emerged over the last decade as potential distal nephron diuretic targets for two main reasons. First, these
basolateral membrane channels are expressed in the DCT and CCD and are essential for Na+ reabsorption in
both nephron segments. Secondly, and importantly, the loss of Kir4.1/5.1 function in patients with
SeSAME/EAST syndrome leads to renal salt wasting and low blood pressure, providing strong genetic
validation for Kir4.1/5.1 as a diuretic target in humans. We recently performed an NIH-funded
(R01DK120821; Denton PI) high-throughput screen (HTS) of 80,475 compounds from the Vanderbilt Institute of
Chemical Biology Discovery Collection and identified hundreds of structurally diverse small-molecule inhibitors
of Kir4.1/5.1. We employed iterative medicinal chemistry and functional analysis to drive the development of the
first-in-class, moderately potent (IC50 = 0.24 µM), highly selective (>30 fold over 9 related Kir channels), in vitro
inhibitor of Kir4.1/5.1, named VU6036720 (PMID 35246480). Unfortunately, however, VU6036720 failed to
induce a diuretic response in mice due to high plasma protein binding and rapid metabolic clearance. In Aim 1
of this follow-up application, we propose to employ medicinal chemistry and established functional assays to
further optimize the potency, selectivity, and drug metabolism and pharmacokinetic (DMPK) properties of
VU6036720 and other backup scaffolds identified in our HTS campaign. In Aim 2, we will evaluate the in vivo
activity of optimized inhibitors in mous...

## Key facts

- **NIH application ID:** 10904756
- **Project number:** 5R01DK137302-02
- **Recipient organization:** VANDERBILT UNIVERSITY MEDICAL CENTER
- **Principal Investigator:** Jerod S. Denton
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $458,819
- **Award type:** 5
- **Project period:** 2023-08-15 → 2028-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10904756

## Citation

> US National Institutes of Health, RePORTER application 10904756, Preclinical validation of Kir4.1/5.1 inhibitors for overcoming diuretic resistance (5R01DK137302-02). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10904756. Licensed CC0.

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