**7. Future perspective**

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,

and sampling from multiple regions can help. Based on tumor heterogeneity and evolution of drug resistance point of view, the drug repurposing might be not evolved as unjustifiable tool with time consuming approach, if not utilized for early stages of Cancer patients.

Drug repurposing involves many challenges like proper utilization of database, demand of expected repurposing drug, issues associated with intellectual property rights and patents. Although to accomplish efficient drug repurposing, there is a need to work from multiple paradigms. Many drugs get failed in third phase of clinical trials and Drug repurposing trials due to lack of efficacy, so it should be realized in well advance by combining multiple techniques. Literature belongs to applied sciences and medical fields containing important information for complementary relationship in between repositioning of drugs and its proposed targets. The vital information can be extracted with "text mining" tools like Biovista, BioWisdom, TextFlow, DrugQuest, Polysearch, etc. Based on semantic integration network approach, diverse information can be interrelated. Later, many algorithms in machine learning techniques can be developed to promote the efficacy and speed of drug repurposing. At present, multiple-omics discipline emerge out like genomics, proteomics, transcriptomics, bioinformatics, metabolomics and interactomics that consist of vast data related to biological sciences. Analyzing these multiple-omics disciplines with computational methods by integrative approach can be utilized to identify the best drug molecule that work at more than single target in different diseases. This approach may suit well with personalized medicine concept that will become inadvertent reality and demand in the case of oncotherapeutics. With these diverse but harmonizing computational with multiomics incorporation, scientist and researcher achieve meaningful understanding of cellular physiology, Drug -receptor interaction, pathogenesis and prognosis of diseases, stages and types of same disease with acquired changes at molecular level, possible drug reactions, on-target and off-target interactions, diagnostic and prognostic biomarkers.

According to WHO, Cancer is a leading cause of death worldwide, accounting for an estimated 9.6 million deaths in 2018. The most common causes of cancer death are cancers of lung (1.76 million deaths), colorectal (862,000 deaths), stomach (783,000 deaths), liver (782,000 deaths), and breast (627,000 deaths). Definitely at present scenario priority should be given for these cancers. There are many diseases are coming under the category of orphan disease. According to U. S. FDA, an orphan disease defined as a condition that affects fewer than 200,000 people nationwide. There is good opportunity for repurposing to orphan drugs. According to Genetic and rare diseases (GARD) information center, many cancers comes under orphan diseases category like CDK4 linked melanoma (orphan drug Aldesleukin), carcinoid tumor (orphan drug Everolimus, Lutetium Lu 177 dotatate), chronic myeloid leukemia (orphan drug Bosutinib, Omacetaxine mepesuccinate), clear cell renal cell carcinoma (orphan drug Sorafenib, Temsirolimus). These all orphan drugs that utilized for rare cancers are good candidates for Drug repurposing in other common types of cancer. Also, the drugs like thalidomide which was once withdraw from the market due to its dangerous teratogenic effects in one class of human population but later approved by FDA for myeloma and other disease treatment. The negative and positive sides of this drug are contributed by anti-angiogenesis property. But this one off-target property was proved to defame its efficacy in one situation while with Drug repurposing in other condition it has proved its anti-cancer effects. Future will become where more robust and sound techniques will be utilized to create successful Drug repurposing candidate and making drug discovery and development process beneficial to Human kind.

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**Author details**

Alkeshkumar Patel

Anand, Gujarat, India

Department of Pharmacology, Ramanbhai Patel College of Pharmacy, CHARUSAT,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

I personally thank CHARUSAT (Charotar University of Science and Technology, India) for providing me access to various resources to write this manuscript and encouraging me indirectly to write about this wonderful topic of Cancer Biology science. I appreciate this organization for the priority given to the research and

The authors declare that they have no competing interests.

\*Address all correspondence to: alkeshpatel.ph@charusat.ac.in

provided the original work is properly cited.

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

innovation with proper nurturing.

**Acknowledgements**

**Conflict of interest**
