WNK-IN-B is an inhibitor of Wnk signalling. WNK-IN-B is a cell-permeable diaminoacridine derivative that targets the CCT domain of SPAK and OSR1 via reversible binding. WNK-IN-B selectively suppress hypotonic shock-induced WNK signaling pathway activation in mpkDCT and MOVAS (100 µM) cultures without affecting p38 MAPK phosphorylation.