The information in this section provides an overview of what drug repurposing is, its benefits and how it differs from other drug development techniques.

The above short video introduces the concept of drug repurposing and its benefits. For a more indepth explanation, watch part one of Rick Thompson’s presentation from Findacure’s “Diving into drug repurposing” workshop.

In this topic we will cover: 

• What is drug repurposing? 
• Types of drugs that can be repurposed 
• Variations of drug repurposing 

What is drug repurposing? 

The information in this section provides an overview of what drug repurposing is, its benefits and how it differs from other drug development techniques.

Drug repurposing, at its simplest, can be considered as a type of recycling. It involves taking an existing drug already approved for human use in one disease and investigating whether it can be used to treat another condition. This idea can then be tested through a clinical trial to confirm its efficacy (effect) in the new patient population, with the ultimate aim of achieving approval of the drug for the new condition (indication).

De novo drug development is often described as the ‘traditional’ route used to produce treatments and involves generating a completely new drug for a particular condition, from scratch. The process of de novo drug discovery begins with the identification of a target biological process, synthesis of a novel compound with desirable biological activity and compound screening. A candidate drug is identified through this process and taken to preclinical development, followed by clinical trial testing. Drug repurposing differs from de novo drug development in that the medication in question already exists, thereby removing the need for synthesis of a new compound. The advantages of this strategy are discussed in the ‘benefits of drug repurposing’ section later in the course.

Types of drugs that can be repurposed

In general, there are three types of drugs that can be targeted for repurposing:

1. Existing generic drugs: A drug is said to be generic when it is no longer affected by patents (i.e. market exclusivity or intellectual property). This means that different companies can make the drug, which normally makes it more widely available and lowers its price.

2. Current branded compounds: These are sold under a licence to treat a specific condition and are protected by intellectual property. These means that they are only produced by a single company.

3. Shelved compounds: These are drugs that have been proved to be safe in humans but did not prove efficacious for a particular disease during their initial development or were deemed not to be worth pursuing. This means that the drugs are shelved e.g. they are retained by the developing company, and never reach market.

Variations of drug repurposing

• The term ‘drug repurposing’ is often used interchangeably with ‘drug repositioning’. Here, we use drug repurposing to refer to a generic drug being used for a new condition, whereas drug repositioning involves re-developing a patented drug (that may be available on the market for a different condition or that might have been shelved by the developing company).   
• Drug reprofiling is an additional variation of drug repurposing that involves slightly altering an approved drug for a new indication, by creating an isomer (a version with tiny variations), a pro-drug (a compound that breaks down in the body to release a known drug), or a metabolite (the piece of a drug that the body uses to tackle a disease)
• Drug reformulation involves taking an existing approved drug and creating a new delivery form (e.g. taking a medication applied to the skin and making it into an oral drug), or a new dosage (e.g. original formulation is provided as 100 mg tablets and the new drug is provided as 1 mg tablets). Reformulating a drug can generate novel intellectual property, potentially opening up new business opportunities.