Repurposing Metformin for Cancer Treatment: A Great Challenge of a Promising Drug.

The safety windows and toxicity of clinically available known drugs allow drug repurposing to be a popular treatment strategy for several diseases, including cancers. Several common drugs, e.g., metformin, statin, and aspirin are on clinical trials for repurposing in oncology treatment. Most of repurposed drugs, however, cannot be used as single agents and some do not exert any clinically significant effects. The limitations and possible biases from observational studies and preclinical models to repurpose these drugs are debatable. In this article, the limitations and probability of using metformin, one of the most repurposed drugs for cancer treatment and in oncological practice, are discussed.