Cancer is a global concern leading to millions of deaths every year. A declining trend in new drug discovery and development is becoming one of the major issues among the pharmaceutical, biotechnology industries and regulatory agencies. New drug development is proven to be a very lengthy and a costly process. Launch of a new drug takes 8-12 years and huge investments. Success rate in oncology therapeutics is also low due to toxicities at the pre-clinical and clinical trials level. Many oncological drugs get rejected at very promising stage showing adverse reactions on healthy cells. Thus, exploring new therapeutic benefits of the existing, shelved drugs for their anti-cancerous action could result in a therapeutic approach preventing the toxicities which occurs during clinical trials. Drug repurposing has the potential to overcome the challenges faced via conventional way of drug discovery and is becoming an area of interest for researchers and scientists. Although very few in vivo studies are conducted to prove the anti-cancerous activity of the drugs. Insufficient in vivo animal studies and lack of human clinical trials are the lacuna in the field of drug repurposing. This review focuses on the aspect of drug repurposing for cancer therapeutics. There are various studies which show that drugs approved for clinical indications other than cancer have shown promising anti-cancer activities. Some of the commonly used drugs like Benzodiazepines (Diazepam, Midzolam), Antidepressants (Imipramine, Clomipramine, and Citalopram), Antiepileptic (Valporic acid, Phenytoin), Anti diabetics (metformin) etc., have been reported to show potential activity against the cancerous cells.

癌症是一个全球性的问题，每年导致数百万人死亡。新药发现和开发的下降趋势正在成为制药、生物技术行业和监管机构之间的主要问题之一。新药开发被证明是一个非常漫长和昂贵的过程。推出一种新药需要 8-12 年和巨额投资。由于临床前和临床试验水平的毒性，肿瘤治疗的成功率也很低。许多肿瘤药物在非常有希望的阶段被拒绝，显示出对健康细胞的不良反应。因此，探索现有的、被搁置的药物的抗癌作用的新治疗益处可能会导致一种治疗方法，防止临床试验期间发生的毒性。药物再利用有可能克服传统药物发现方式面临的挑战，并正在成为研究人员和科学家感兴趣的领域。尽管很少进行体内研究来证明药物的抗癌活性。体内动物研究不足和缺乏人体临床试验是药物再利用领域的空白。本综述侧重于癌症治疗药物再利用方面。有各种研究表明，批准用于癌症以外的临床适应症的药物已显示出有希望的抗癌活性。一些常用的药物如苯二氮卓类（地西泮、咪唑仑）、抗抑郁药（丙咪嗪、氯米帕明和西酞普兰）、抗癫痫药（丙戊酸、苯妥英）、抗糖尿病药（二甲双胍）等，