Lonidamine is a derivative of the indazole-3-carboxylic acid, with limited antineoplastic activity as a single agent but with exceptional potential in modulating the activities of conventional chemotherapeutic agents such as N-mustard alkylating agents and anthracyclines as well as hyperthermia, radiation therapy and photodynamic therapy. The most critical property of Lonidamine is its selective activity against a broad range of tumors with little to no effect on normal tissues provided that doses are below a threshold level of ~400 mg/m^2 (oral or i.v. doses). Selective effects of Lonidamine on tumors compared to other potential targets probably result from the dependence of most tumors on glycolytic metabolism, but the exact mechanism of specificity is still not fully known. Current evidence indicates that Lonidamine inhibits lactate export by the proton-linked monocarboxylate transporter(s) (MCT) and pyruvate uptake into mitochondria via the mitochondrial pyruvate carrier (MPC), whereas inhibition of respiration involves both diminished mitochondrial uptake of pyruvate via the MPC as well as inhibition of the mitochondrial electron-transport chain at Complex II and perhaps also Complex I, in both instances at the ubiquinone reduction step. There is also evidence that the drug may indirectly inhibit hexokinase as well as possibly other glycolytic and pentose shunt enzymes as a result of cytosolic acidification. Key problems that remain to be addressed are the production of Lonidamine under GMP conditions since Angelini Pharmaceuticals in Rome, Italy, the sole commercial source of this drug, stopped producing it in 2006. In addition, utilization of Lonidamine in the US requires IND approval by the FDA, which has previously been granted for a number of clinical trials. Finally, even though LND is a potent enhancer of the activity of a number of potent anti-cancer agents, potentially less toxic (and patentable) “targeted-tumor agents” are replacing traditional chemotherapy. Another problem remaining to be addressed is the limited solubility of Lonidamine at neutral pH. Oral delivery has led to variable results; more soluble derivatives that can be administered by the intravenous administration are needed to accurately control the dosing schedules.