Drug Repurposing: Recent Advancements, Challenges, and Future Therapeutics for Cancer Treatment

1. Abstract
Cancer is a prime public health burden that accounts for approximately 9.9 million deaths worldwide. Despite recent advances in treatment regimen and huge capital investment in the pharmaceutical sector, there has been little success in improving the chances of survival of cancer patients. Drug repurposing sometimes-termed drug repositioning is a strategy of discovery and redeveloping existing drugs for new therapeutic purposes. This novel approach is highly efficient, considerably cuts research and development costs, reduces the drug development timeline, maximizes therapeutic value and consequently increases success rate with minimum risk of failure. In this review, prioritizing drug repurposing to activate immune and inflammatory responses to target tumor cells through immune surveillance mechanism is a promising strategy for cancer immunotherapy. Cancer immunotherapy cover myriad of therapeutic approaches as cytokine therapy, immune checkpoint blockade therapy, cancer vaccines, natural killer cells, adoptive T cell therapies, monoclonal antibodies, oncolytic viruses, computational approach and host of others. In the current pipeline, drug repurposing is devoid of adequate funding and the necessary legal support for research and development by stakeholders. At the moment, immunotherapy strategies combine with computational biology could be considered the new milestone in drug re-profiling for cancer treatment.