Current Status of Novel Pyridine Fused Derivatives as Anticancer Agents: An Insight into Future Perspectives and Structure Activity Relationship (SAR).

Cancer is a heterogeneous disease characterized by an abnormal and uncontrolled division of the cells leading to tumors that invade the adjacent normal tissues. After cardiovascular diseases, it is the second most prevalent disease accounting for one in every six deaths worldwide. This alarming rate thus, demands an urgent need to investigate more effective drugs to combat the said disease. Oxygen and nitrogen-based heterocyclic compounds have shown remarkable therapeutic activity towards several diseases, including cancer. In this review, we have attempted to summarize the work done in the last decade (2009-2019), highlighting the anticancer activity of pyrido fused fivemembered heterocyclic ring derivatives. Additionally, we have focused on seven heterocyclic pyridine fused rings: Imidazopyridine, Triazolopyridine, Pyrrolopyridine, Pyrazolopyridines, Thienopyridine, and Isoxazolopyridine. A total of forty-nine compounds have been studied based on their invitro cytotoxic activity and their structure-activity relationship, underlining the anticancer activity of their various pharmacophores and substituents. This review, therefore, aims to draw the attention of the researchers worldwide towards the enormous scope of development of heterocyclic drug compounds, focussing mainly on pyrido fused five-membered heterocyclic rings as anticancer drugs.