Why is finding new indications for existing drugs so important?

The primary reasons is that it is much faster and less expensive to repurpose an existing drug for a new disease than trying to identify a new therapeutic agent. A paper by Islam et al. (2021) explains why:

Available information. A repurposed drug has an extensive portfolio of knowledge relating to human pharmacokinetics, bioavailability and toxicology, which helps to mitigate risk of drug failure. (Ashburn et al. 2004, Pantziarka et al. 2015)Drug development times are shorter. A new drug typically takes up to 17 years to develop, whereas a drug repurposed for a new indication takes only 3–12 years (McCabe et al. 2015, Pantziarka et al. 2014) Drug development cost is much less. Whereas the cost of development for a new drug range from $1.8 to $3.0 billion, the development cost for a repurposed drug is only $300, assuming the repurposed drug only needs to undergo Phase II and Phase III trials. (Pushpakom et al. 2018, Naylor 2015). This could result in up to an 85% savings in drug development cost.

In fact, many governments are partnering with industry to examine whether existing drugs can be used to treat new diseases:

…the “Discovering new therapeutic uses of existing molecules” initiative by the NIH-National Centre for Advancing Translational Sciences (NIH-NCATS) in partnerships with eight pharmaceutical companies (Abbie Vie, AstraZeneca, Bristol Myers Squibb, Lilly, GlaxoSmithKline, Janssen, Sanofi-Aventis and Pfizer) in the USA, the AstraZeneca and Medical Research Council (MRC) partnerships in the UK, the AstraZeneca and the National Research Program for Biopharmaceuticals (NRPB) in Taiwan are all examples of large public-private partnerships to maximize repurposing research and development.

While some may claim that new indications represent obvious extensions of existing products, oftentimes trials for new indications do fail. Thus policymakers must either incentivize drug manufacturers with financial reward to conduct studies for additional application of existing drugs or risk using existing drugs off-label for diseases in which a treatment’s efficacy and safety are unknown.