G-quadruplex interacting small molecules and drugs: from bench toward bedside

G-quadruplexes are non-Watson-Crick four-stranded nucleic acid structures. Recent evidence points toward their existence in vivo and their implication in various biological processes. Over the past two decades, small molecules have been developed to specifically and selectively target these structures in order to dissect mechanisms they have been linked to. This has led to the development of potential therapeutic agents, particularly for anti-carcinogenic activity. Here, we first present how major biological roles of G-quadruplexes have been uncovered by the use of specifically designed small molecule probes. We use this to highlight how fundamental research has contributed to identifying biological functions of G-quadruplexes and their potential as therapeutic targets. We then discuss the development of G-quadruplex interacting small molecules as potential drug candidates.