The Expendables: Overlooked Medications with Anti-Cancer Properties

Cancer is a leading cause of death worldwide. The process to develop new anti-cancer drugs is long and arduous. Therefore, additional strategies for drug development could involve drug repositioning, i.e., identifying new uses for already approved medications that have been deemed expendable in the oncologic treatment realm. Indeed, there are already drugs that have proven that they are extendable into oncology and are now Food and Drug Administration (FDA) approved for malignancies, though they were initially developed for other conditions.

These drugs include: all-trans retinoic acid, first approved as a topical agent for photo-aging, with dramatic activity in acute promyelocytic leukemia (APL); arsenic, a compound known for its use as a homicidal poison with remarkable activity in APL; thalidomide, a drug with a scandalous past as it was given to pregnant women and resulted in severe fetal limb deformities, which is now approved for multiple myeloma; and the antibiotics amoxicillin, clarithromycin, and metronidazole, which can result in total regression of MALT lymphomas (triggered by Helicobacter pylori infections). There is also a wealth of compounds that could be repositioned including, but not limited to anti-inflammatory drugs, anti-infectious compounds (anti-bacterial, anti-viral, anti-fungal, anti-parasitic agents), autonomic system regulators, and commonly used drugs such as statins or metformin, which have anti-cancer properties, demonstrated in both preclinical and clinical studies. With improvement in molecular technologies as well as in our understanding of cancer biology, drug repositioning may be exploitable for target-defined anti-neoplastic compounds that are already in use for non-malignant disease.