Glycolytic intermediaries are affected by the PK activator mitapivat in ways that improve hemolysis in SCD. Mature RBCs lack mitochondria; glycolysis is the anaerobic furnace for ATP production in these cells. Metabolic bypasses from the glycolytic pathway include the Rapoport-Luebering shunt, which generates 2,3-DPG, and the pentose phosphate shunt, which is a primary source of antioxidants (reduced glutathione) in RBCs. 2,3-DPG is a major allosteric effector of oxygen affinity in Hb; less 2,3-DPG results in slower oxygen release from Hb and delayed formation of deoxyhemoglobin, which is the major substrate for polymer formation in SCD. Activated PK (mitapivat, blue chevron) depletes 2,3-DPG, presumably through effective competition for 1,3-DPG. Theoretically, by decreasing 2,3-DPG and increasing oxygen affinity, less deoxyhemoglobin is produced. Xu et al have shown that in SCD, 2,3-DPG and ATP levels measurably changed (red chevrons) and that Hb levels increased after PK activation. NADPH, nicotinamide adenine dinucleotide phosphate hydrogen.