Development of WNK signaling inhibitors as a new class of antihypertensive drugs. 
Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia and hypertension despite a normal glomerular filtration rate.  Abnormal activation of the signal cascade of with-no-lysine kinase (WNK) with OSR1 (oxidative stress-responsive kinase 1)/SPAK (STE20/SPS1-related proline/alanine-rich kinase) and NCC (NaCl cotransporter) results in characteristic salt-sensitive hypertension.  Thus, inhibitors of the WNK-OSR1/SPAK-NCC cascade are candidates for a new class of antihypertensive drugs.  In this study, we developed novel inhibitors of this signal cascade from the 9-aminoacridine lead compound 1, one of the hit compounds obtained by screening our chemical library for WNK-SPAK binding inhibitors.  Among the synthesized acridine derivatives, several acridine-3-amide and 3-urea derivatives, such as 10 (IC50: 6.9μM), 13 (IC50: 2.6μM), and 20 (IC50: 4.8μM), showed more potent inhibitory activity than the lead compound 1 (IC50: 15.4μM).  Compounds 10 and 20 were confirmed to inhibit phosphorylation of NCC in vivo.