Kristoffer Hellstrand, MD, PhD, of Sahlgrenska Cancer Center, University of Gothenburg, Gothenburg, Sweden, speaks at the International Symposium on Acute Leukemias (ISAL) 2019, held in Munich, Germany. Prof. Hellstrand takes us through the development of the NOX2 inhibitor histamine dihydrochloride for the prevention of relapse in acute myeloid leukemia (AML), leading to its approval in 2009, before discussing ongoing work investigating the underlying effects of this therapy.