NPPB is a blocker of the outwardly rectifying chloride channel (ORCC). IC50 & Target: ORCC^[1] In Vitro: 0.1 mM NPPB in the bath solution reduces channel open probability from 0.89±0.06 to 0.11±0.04 (n=5, P<0.01)^[1]. Dose-dependent inhibition of chloride currents is observed with a 50% inhibitory concentration (IC₅₀) of 125 μM NPPB. NPPB itself also shows cytotoxicity against glioma cells with a GI₅₀ of approximately 500 μM^[2].