The expression of human pyruvate kinase M2 (hPK-M2) in cancer cells appears to be critical for tumor cell growth and proliferation in vivo. Because the PK-M2 isoform is expressed in all cancer cells studied, it represents a target for drug development that could potentially enable tumor cells to return to a normal state of metabolism. If this novel strategy for targeting malignancy were successful, it would be applicable to diverse types of cancer. The probes ML083 (CID-650361) and ML082 (CID-654376) are members of a series of highly specific allosteric activators for the tumor-specific isoform of human pyruvate kinase (M2 isoform). Both probes affect the cooperativity of phosphoenolpyruvate (PEP) binding with little effect on adenosine diphosphate (ADP) binding in a manner similar to FBP.