developed for identification of new candidates for drug repurposing (Mercorelli

et al., 2016, 2018). The success of drug repositioning in providing benefits in certain

diseases brought the global attention on the potential off-target effects of some of the

drugs (Yan et al., 2014; Yeo et al., 2018). In view of the fact that these existing drugs

have been used previously in humans, their dose regimen with favorable pharmaco-

kinetics and pharmacodynamics properties, including any side effects, is already in

public domain, making these old drugs useful in new drug discovery.

3.2

Benefits Associated with Drug Repositioning

Drug repositioning has various advantages that are interrelated in nature. The

simplification associated with the regulatory procedures involved in introduction

of a previously approved drug is the most essential part of it. As the data on the safety

and toxicity of the drug is available, this makes the initial development phase of drug

repositioning considerably faster (Nosengo, 2016) and therefore cheaper with

increase in chances of it being introduced on the market. Although the level of

safety required for a particular drug is heavily dependent upon its indication, hence,

the acceptance of the adverse effects of a drug when repurposed for a less severe

disease than its original indication will be proportionately less acceptable (Cavalla,

2017).

3.3

Challenges Associated with Drug Repositioning

The major challenge faced by the companies working on drug repositioning is the

relatively weak intellectual property protection on these products, which can lead to

reduction in return on their investment, further discouraging these companies from

developing these drugs (Rastegar-Mojarad et al., 2015; Talevi and Bellera, 2020).

The drug that is being repositioned had already been patented as a new chemical

entity, making the task of protecting it even more difficult involving a new applica-

tion patent based on a new formulation process. The scope of application patents is

narrower in comparison to a new chemical entity in terms of coverage of their

therapeutic uses. These patents are also tough to defend from a legal perspective

as it can be challenged that the new indication proposed for the drug was predictable

from the already available data in the scientific literature. However, there are certain

advantages for the companies working on repositioning of drugs for the treatment of

orphan diseases (defined in Europe as those with prevalence no higher than 5 in

10,000), such as reduction in fees and guaranteed market exclusivity for a period of

time (Xu and Coté, 2011).

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A. Sharma and J. Kaur