**Conflict of interest**

*Drug Repurposing - Hypothesis, Molecular Aspects and Therapeutic Applications*

Traditional drug development strategies are costly, failure prone and expensive ventures. Therefore, drug repositioning has recently drawn considerable attention to discover drugs with new therapeutic uses with the goal to bring drugs out at comparatively faster rate for clinical use. Some regulatory issues that are commonly encountered in drug repositioning are described as follows [37, 38]. As per regulatory guidelines, new preclinical and/or clinical trials may be required to be carried out if the available data are not satisfactory and do not comply with the requirements of regulatory agencies such as FDA or EMA. Another important issue is related to patent application and intellectual property rights (IPR). There are no provisions of IP protection of drug discovery by repositioning approach as per the IP and patent laws. For repositioned drugs, IP protection is limited. For repositioning drugs, IP protection is limited. For example, some novel drugtarget disease associations found by repositioning researchers were confirmed by publications or online databases; however, it is difficult to seek IP protection for such associations because of the law. The IP issue prevents some repositioned drugs from entering even into the market [39, 40]. Moreover, some repositioning projects are forced to be abandoned, which is a waste of time, money and lot of efforts. Although many omics data and medical databases have been established, selecting the appropriate approach for repositioning is still a challenge due to the regulatory issues because massive amounts of data may not be valid if not obtained from reliable sources. It is, therefore, necessary that researchers or manufacturers must strictly adhere with standard regulatory guidelines for drug discovery by

Traditionally, the dug repurposing has a long recorded history discovery of drug molecules particularly through serendipitous observations. In recent years, it has embarked a new avenue in the development of new therapies based upon existing/ approved medicines. The strategic drug repositioning in a more systematic and rational way has brought innovation with the discovery of drug molecules with unknown therapeutic indications. As drug repositioning approach offers significant reduction in R&D costs, greater chances of success, shorter research time and lower investment risk, it has gained increasing market demands. Because these advantages are beneficial for discovery scientists, drug researchers, consumers and pharmaceutical companies, enabling the application of novel approaches of repositioning strategy in the drug discovery program for almost all human diseases. Moreover, the use of *in silico* techniques along with the application of structure-based drug design (SBDD) and pharmacophore modeling strategies and artificial intelligence (AI) technology can further accelerate the process of drug purposing in the drug discovery program. In the era of precision medicine, the drug repositioning strategy has become very much useful to establish the unknown mechanism of action of drugs through exploration of novel disease/metabolic/signaling pathways, or off-targets and target-specific mechanisms/ genetic expression profile for even genetic disorders. Advancement in genomics have provided us with genomic and transcriptomic data in huge quantities using technologies like next generation sequencing, microarray data and transcriptomics, etc. Network biology and systems biology approaches may add additional benefits to unveil such novel mechanisms of actions with through insights into drug-target interaction profile at molecular/genetic level. For better drug repositioning, more in-depth understanding are required to be executed

**8. Regulatory and intellectual property issues**

repositioning approaches [2, 41–43].

**9. Conclusion**

**18**

Authors declare that there is no conflict of interest.
