**5. Drug repurposing database**

Physical collection of approved drugs to carry out experimental repositioning screens is challenging task. Smaller digital libraries containing information of approved drugs or drugs with expired patents are available to serve drug repurposing like Enzi Life Sciences, Prestwick, Spectrum and many other like National Institute of Health's Chemical Genomics Center (NCGC) [49]. It may happen that drug get failed in clinical trials because of lack of effectiveness (efficacy) but not due to toxicity represent good candidate for drug repositioning. There is some web

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world.

**7. Future perspective**

*Drug Repurposing in Oncotherapeutics DOI: http://dx.doi.org/10.5772/intechopen.92302*

• http://drugrepurposingportal.com

• CLUE: The Drug Repurposing Hub

• http://apps.chiragjpgroup.org/repoDB/

can be used for repurposing.

**6. Conclusion**

portal available that store large drug screening database based on clinical trials and

Current status of drug repurposing based on drug and disease search option is available at repoDB site. This drug repositioning database contains information of

The process of drug repurposing or repositioning help the Pharmaceutical companies in terms saving capital expenditure and decrease efforts of scientific community from long drug discovery and development process that pass through much experimental and regulatory task. Drug repositioning works well for those drug molecules for which disease targets are not get altered over a period of time. All the drug repositioning hypothesis will not transferred to successful outcome. It was happened with bevacizumab (Avastin), a kinase inhibitor drug that failed to prove its efficacy during phase- III of clinical trial in gastric cancer therapy although it has good efficacy against colon, rectal, brain, lung and kidney cancer by targeting vascular endothelial growth factor (VEGF) and decreasing the blood supply to the tumor that required for tumor growth and metastasis [51, 52]. Similar thing happened for sunitinib, a kinase inhibitor where it has proven its efficacy in certain cancers while unable to show same in other cancers [53]. It is significant to consider the unique drug indication during repositioning with proper justification for risk and benefits ratio. Any cytotoxic anti-cancer drug may not be an ideal drug for cardiovascular disorder in same dose, as it may kill many normal cells with high proliferation index. But it can be utilized at low doses for drug repurposing with less side effects as in the case of methotrexate at 10–20 mg per week for rheumatoid arthritis due to its anti-inflammatory property. Although, there are many obstacles present on the path of drug repurposing now, but future will bring more advancement in the technologies with the help of combinatorial chemistry, virtual screening, data mining and artificial intelligence that raise the success rates. At the last, we hope that all these scientific advancements translated into clinical setting to improve oncotherapy and reduce the burden of cancer related mortality in the

Tumor is heterogeneous mutated cell mass with genomic instability that acquired new forms over period of time. As time goes on, tumor heterogeneity environment become less vulnerable to chemotherapeutic and radiation agent with development of tumor resistance in multiple ways. So, every tumor shows different pathological picture in every cancer patient and even different pattern of intratumoural mutation in same patient at different time interval. Based of therapeutic modality, specific subpopulation of drug tolerant cancer cells come out as resistant cells within tumor. So, it seems personalized medicine will be future of Cancer medicines. In these regards, single cell analysis, multiple omics, research autopsy,

about 2051 diseases, all mapped to UMLS terms for easier integration [50].

portal available that store large drug screening database based on clinical trials and can be used for repurposing.


Current status of drug repurposing based on drug and disease search option is available at repoDB site. This drug repositioning database contains information of about 2051 diseases, all mapped to UMLS terms for easier integration [50].

• http://apps.chiragjpgroup.org/repoDB/
