**4. Drug repurposing**

Drug repurposing is an old weapon in the arsenal for new drug development strategies. This approach identifies new therapeutic indications for available marketed drugs making it time-efficient in a cost-effective manner [27, 28]. It has been assumed that about 75% of existing drugs could be repurposed for various diseases [29]. Global pandemic like novel coronavirus disease 2019 (COVID-19) has an urgent need to select appropriate therapeutic options with limited time to discover the new drug candidates [30]. It takes 10–15 years to develop a new drug, and the actual cost would be more than a billion dollars, with only 2.01% of its success rate

#### *Coronavirus Disease 2019 (COVID-19): Origin, Impact, and Drug Development DOI: http://dx.doi.org/10.5772/intechopen.98358*

[31, 32]. Existing drug compounds, including Raltegravir, Paritaprevir, Bictegravir, and Dolutegravir, identify promising inhibitors against 3C-like protease 2′-O-ribose methyltransferase from COVID-19 is cost-effective and a drug repurposing approach [33, 34]. A recent in-silico study suggested that natural compounds like guggulsterone and drug rifampicin can be repurposed for COVID-19, insights from the molecular docking analysis [35, 36]. Thus, the concept of drug repurposing could be utilized as a novel drug discovery process to discover an effective therapeutic option against COVID-19. Recent examples of drug repurposing against COVID-19 are given in **Table 1**.

Based on previous experiences in the treatment of previous coronavirus diseases like SARS-CoV and MERS-CoV, drugs currently being implemented in the management of this disease are entry or inhibitors of SARS-CoV-2, RNA mutagens that stop replication, host inflammatory response inhibitors, viral protease inhibitors, monoclonal antibodies (mAbs), and convalescent plasma-based immunogenicity, blockers of the release of mature virion and glucocorticoids based cell tissue and organ injury management apart from necessary ventilation for support [54]. It is an urgent need to perform more prospective, rigorous population studies and further preclinical and clinical trials to gain a perspective on the safety and therapeutic effect of new and potential therapeutic agents that may help contain the spread and enhance recovery from SARS-CoV-2 infection.


#### **Table 1.**

*Recent examples of drug repurposing against COVID-19.*
