A Critical Review of Chloroquine and Hydroxychloroquine as Potential Adjuvant Agents for Treating People with Cancer

Chloroquine (CQ) and hydroxychloroquine (HCQ) have been used to treat malaria and autoimmune diseases for more than 70 years; they also have immunomodulatory and anticancer effects, which are linked to autophagy and autophagy-independent mechanisms. Herein, we review the pharmacokinetics, preclinical studies and clinical trials investigating the use of CQ and HCQ as adjuvant agents in cancer therapy. We also discuss their safety profile, drug–drug and drug–disease interactions. Systematic studies are required to define the use of CQ/HCQ and/or their analogues in cancer treatment and to identify predictive biomarkers of responder subpopulations.