Indole: A privileged scaffold for the design of anti-cancer agents

In general, heterocyclic compounds are a significant source of pharmacologically active compounds. Among them, the indole scaffold widely distributes in natural products and bioactive molecules including anti-cancer agents. In view of its unique physic-chemical and biological properties, it has been used as a privileged scaffold in the anti-cancer agents design. So far, many natural and synthetic indole derivatives have been discovered as promising anti-cancer agents used in clinic or clinical evaluations, suggesting its prominent place in anti-cancer drugs development. This review aimed to provide a clear knowledge on the recent development of indoles as anti-cancer agents, such as myeloid cell leukemia-1 (Mcl-1) inhibitors, proviral insertion site in moloney murine leukemia virus (Pim) inhibitors, histone deacetylase (HDAC) inhibitors, silent mating type information regulation 2 homolog (SIRT) inhibitors and tubulin inhibitors, and made an insight into the corresponding structure-activity relationships (SARs). We hope the review could give a guide to develop new anti-cancer agents with greater potency against drug-sensitive and drug-resistant cancers in the future.