Apoptosis signal-regulating kinase 1 (ASK1) is the ubiquitously expressed mitogen-activated protein kinase kinase kinase 5 involved in a wide range of biological functions that are dependent on cell survival or death. NQDI-1 is a specific inhibitor of ASK1 (IC50 = 3 μM; Ki = 500 nM) that demonstrates potent selectivity against various serine/threonine and tyrosine protein kinases. It has been used to promote survival of induced pluripotent stem cell populations and to protect neurons from reactive oxygen species-induced apoptosis in a model of ischemia.