Urea transporters (UTs) have been identified as new targets for diuretics. Functional deletion of UTs led to urea-selective urinary concentrating defects with relative salt sparing. In our previous study, a UT inhibitor with a diarylamide scaffold, which is denoted as 11a, was demonstrated as the first orally available UT inhibitor. However, the oral bioavailability of 11a was only 4.38%, which obstructed its clinical application. In this work, by replacing the nitro group of 11a with an acetyl group, 25a was obtained. Compared with 11a, 25a showed a 10 times stronger inhibitory effect on UT-B (0.14 μM vs. 1.41 μM in rats, and 0.48 μM vs. 5.82 μM in mice) and a much higher inhibition rate on UT-A1. Moreover, the metabolic stability both in vitro and in vivo and the drug-like properties (permeability and solubility) of 25a were obviously improved compared with those of 11a. Moreover, the bioavailability of 25a was 15.18%, which was 3 times higher than that of 11a, thereby resulting in significant enhancement of the diuretic activities in rats and mice. 25a showed excellent potential for development as a promising clinical diuretic candidate for targeting UTs to treat diseases that require long-term usage of diuretics, such as hyponatremia.
Keywords: Diarylamides; Diuretics; Oral administration; Structure optimization; Urea transporter inhibitors.
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