**5. Drug repurposing in DNA viruses (HIV, CMV, HSV, and HCV)**

According to WHO, 26 million people have died due to HIV/AIDS in year 1981, and from 2018 till more than 1.10 million people were affected, this was the worst outbreak managed by hydroxy-chloroquine [9]. HCMV was the best example of host adaptation and the ability of virous to subvert, completely, cellular physiological processes in infected cells (**Table 3**).

#### Drugs:


## **6. Concluding remarks and future perspectives**

Viral infectious diseases remain a major challenge due to the lack of specific medical regimen, to counteract the viral replication and pathogenesis required knowledge to understand the virus-host interaction and mutagenesis, which is now a days remain a puzzle for several known viral pathogens emerging as time and eternity. The development of a drug molecule which is able to target the exact replication is still remain challenging, to encounter the emerging new viral pathogenesis, in this context, DR or positioning approach on FDA-approved drug evaluation, reduce the risk for pipeline new drug discovery, with economic advantages and remarkable generation up to \$25 billion annual sales.

The potentiality of the DR approach will target the host function as time and costeffective route to develop the broad-spectrum antiviral, which already gave a positive outcome successfully by opening-up new pathways for viral infection. The drug repurposing approach feasibly worked on anticancer, antiviral, and antibacterial FDAapproved medicines, to counteract EBOV, MERS-CoV, SARS-CoV, COVID-19, and now a day to control newly emerging OMICRON. Moreover, the successful repurposing is based upon the concentrating required for antiviral activity, which is often higher than approved regimens. Reconsideration on regimen the combined dosage form will be more effective and feasible to reach the new target mentioned in (**Table 3**) [11]. The synergistic therapy will be the milestone formulation to combat EBOVA influenza and could also be the regimen to target other viral infections [12].

On the other hand, the combined formulation will be less toxic and the dose of the drug can also be minimized as compared to the approved formulation with less chances of drug resistance due to synergistic effect, [7, 13].

There is still to be vigilant: synergistic effect at low dose, medication required to interfere with each other to have different mechanism of action. The viral replication pathway or host needs to be targeted early, to inhibit the mutation with antiviral combination, finding the new approach might be the only possible way to encounter such kind of viral outbreak with different therapeutic intervention, it remains mandatory and can be addressed by DR (Drug Repurposing) or reprofiling camping. To overcome the drug discovery bottleneck for emerging and re-emerging viral infectious disease, even the more concerned one is death associated with COVID-19 and HIV, DR will be the major interest due to reduced failure rate and decreased time as well as resource consumptions, to be put forward the first HIV medicine innovated by DR which was initially used to treat cancer patient, this will be the millstone to turn the entire scenario tempted the researcher, during the global pandemic outbreak to design novel molecules by the re-tasking look on FDA-approved drugs.

*Reprofiling of Octogenarian Antiviral Agent: A New Avenue Venture to Discover Viral Infection DOI: http://dx.doi.org/10.5772/intechopen.102825*

Before reprofiling, it requires to be vigilant towards the challenges associated with the copyrights. This chapter represents the importance of research that need to be conducted by closing the leftover loops on FDA-approved drugs. The author was overwhelmed to represent the glimpse associated with reprofiling by putting it down, and look forward to work practically at YPCRC for fruitful future.

### **Acknowledgements**

The author gratefully acknowledges the principle and management of Yenepoya Pharmacy College & Research Centre, Yenepoya University, Mangaluru, to carry out the work in the area of drug repurposing we look forward to do research on antiviral and antidiabetic domine.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Acronyms and abbreviations**


#### **Reference tables**


*Antiviral Drugs - Intervention Strategies*
