AbstractGP‐2250, a novel anticancer agent, severely limits the energy metabolism, as demonstrated by the inhibition of hexokinase 2 and glyceraldehyde‐3‐phosphate dehydrogenase and a decrease of ATP. Rescue experiments with supplementary pyruvate or oxaloacetate demonstrated that a TCA cycle deficit largely contributed to cytotoxicity. Activation of the energy‐deficit sensor, AMP‐dependent protein kinase, was associated with increased phosphorylation of acetyl‐CoA carboxylase and Raptor, pointing to a possible deficit in the synthesis of fatty acids and proteins as essential cell components. Binding of p65 to DNA was dose‐dependently reduced in nuclear lysates. A transcriptional deficit of NF‐κB (nuclear factor kappa‐light‐chain‐enhancer of activated B cells) was substantiated by the downregulation of cyclin D1 and of the anti‐apoptotic Bcl2, in line with reduction in tumour cell proliferation and induction of apoptosis, respectively. The upregulation of p53 concomitant with an excess of ROS supported apoptosis. Thus, the anticancer activity of GP‐2250 is a result of disruption of energy metabolism and inhibition of tumour promotion by NF‐κB.