The isocitrate dehydrogenase IDH2 interconverting isocitrate and α-ketoglutarate (αKG) is involved in various essential pathways, such as the production of mitochondrial NADPH, a crucial cofactor, e.g. for iron-sulfur cluster biogenesis, cholesterol biosynthesis and the regeneration of the glutathione reactive-oxygen (ROS) scavenging system. Additionally, IDH2 downregulation has been associated with increased matrix metalloproteinase (MMP) activity via increased NF-KB signaling. Importantly, hypoxic conditions as well as mitochondrial ETC dysfunction trigger the reverse reductive carboxylation of αKG to isocitrate under NADPH consumption (Figure ). Interestingly, the in vitro forward oxidative decarboxylation activity of isocitrate to αKG of IDH2 was significantly inhibited upon Ciprofloxacin and Levofloxacin treatment by 25 -30% reduction at 100 µM (Figure , Figure ). The extent of inhibition was similar in presence of Enadisenib, a known inhibitor for IDH2 with point mutations involved in various cancers, that exhibits a weaker potency for the wild-type enzyme (Figure ). To check if impaired IDH2 activity correlates with altered mitochondrial NADPH synthesis we determined its levels after short and long Ciprofloxacin treatments. As expected, exposure for 6 h in PDL-hTERT cells revealed a NADPH decrease of approximately 25% at low ciprofloxacin concentrations (only 7.5 µM tested to prevent the early onset of ETC dysregulation at high concentrations), which is in line with inhibition of IDH2´s forward oxidative decarboxylation activity. However, prolonged incubation for 3 days especially at Ciprofloxacin concentration (75 µM) induced the above described ETC dysfunction (as determined by FQ whole proteome experiments) and thus, resulted in an increase of NADPH levels likely based on IDH2´s metabolic rewiring and switching to the reverse reductive carboxylation reaction (Figure ). Thus, the FQ induced ETC dysfunction via AIFM1 and the impaired formation of isocitrate in the reverse carboxylation pathway of IDH2 simultaneously contribute to mitochondrial dysfunction.