**4. Future prospective**

To tackle all the challenges associated with the drug development process for breast cancer, scientists need to shift their interest to the alternative drug development, that is, drug repurposing. All the BC repurposed drugs discussed in the book chapter show impressive results that suggest exploring more new non-cancerous drugs for cancerous use [92]. Using the drugs repurposing approaches alone and in combination with other drugs will also reduce the side effects associated with high doses. It will also reduce the cost of the drug development process, ultimately patient compliances and burden. Patients who could not afford the treatment due to the high cost can take treatment and improve survival. As the safety is already studied of drugs that seem a novel interest in the repurposing for BC, the chances of failure at the clinical level will also be less. With the advancement in drug repurposing, there is still a need to develop a valuable model of different types of cancers that mimic cancer. The development of such a model provides the actual clue for drug repurposing. So far, the advantages we discussed, there are some challenges associated with the drugs repurposing such as patent issue, regulatory consideration, inequitable prescription that need to be overcome so, more and more pharma companies show their interest in drug repurposing. It is expected that drug repurposing will achieve the milestone that is currently not possible with the conventional available treatment for cancers in the future. Furthermore, new nanoformulations need to be developed for the targeted and specific delivery of repurposed anticancer drug to avoid the off-target side effects.

*Breast Cancer Drug Repurposing a Tool for a Challenging Disease DOI: http://dx.doi.org/10.5772/intechopen.101378*
