What is Drug Repurposing? Advantages and Drawbacks

Drug repurposing (also known as drug reprofiling, repositioning, or re-tasking) is a technique for discovering new applications for authorized or experimental medications that go beyond the original medical indication.

In academics, there is a common belief that drug repurposing is just about finding new targets for existing therapies (Cha, Y., et al., 2018). When evaluating medication repurposing potential, several factors should be examined, including illness relevance, side effect tolerability for the new use, and intellectual property position.

Drug repurposing has the potential to make drugs with well-established safety profiles available to new patient groups (Oprea & Mestres, 2012). The need for innovative methods for pharmacological R&D, as well as the emergence of big-data repositories and accompanying analytics, has sparked interest in creating systematic ways for drug repurposing in recent years.

Advantages

This approach has several advantages over designing a whole new medication for a specific indication. Because the repurposed medicine has previously been demonstrated to be adequately safe in preclinical animals and people if early-stage trials have been completed, the chance of failure is minimal.

It has a number of benefits in major fields of medicine and has shown promising results against well-known diseases. For example, it has been very useful in the prevention of cancer as the repurposed drugs such as Aspirin, Statins, Metformin and Selective Estrogen Receptor Modulators (SERMs) are being used by major countries for the prevention of a number of cancers (Sleire, et al., 2017).

In recent years, drug reposing strategies have also been utilized for Covid-19. As stated by (Senanayake, 2020):

“Drug repurposing will have to compete with the structure-based design of preventative/therapeutic vaccines and small molecules on efficacy and off-target toxicity turfs”

This research has also found that, Following the COVID-19 outbreak in December 2019, a few existing BSAAs have been rapidly introduced into clinical trials, spanning Phases II through IV.

Through drug repurposing, drugs like Zidovudine, Minoxidil, Sildenafil, Duloxetine, and Rituximab which were originally used for the indications of cancer, hypertension, Angina, and Depression, are now being used for new indications of HIV, hair loss, erectile dysfunction, SUI, and rheumatoid arthritis respectively.

Researches done by (Fischl, et al., 1989), (Randolph & Tosti, 2021), (Goldstein, et al., 1998), (Millard, Moore, Rencken, Yalcin, & Bump, 2004), (Cipriani A, et al., 2012) and (Edwards, et al., 2004), prove their effectiveness in the treatment of such diseases.

Drawbacks

While the National Institutes of Health is paying more attention to drug rescue and repurposing, this policy is not without hazards, particularly for the industrial sector. Indeed, when all relevant aspects are taken into account, medication repurposing may end up being quite expensive, further depleting the pharmaceutical industry’s already limited resources.

On the one hand, most medications are the outcome of a lengthy optimization process aimed at improving affinity and selectivity (among other things) for a certain main target. As a result, the efficacy of novel targets discovered for old medications will almost certainly be lower than the potency of the main target (Pushpakom, et al., 2019).

If alternative medications for that indication have previously been licensed, establishing superiority in terms of effectiveness and safety may be unachievable.

Conclusion

To conclude, there are several examples of new indications for existing compounds being discovered, the majority of which arise from fortuitous discoveries or targeted recent efforts especially confined to the mode of action of a certain medicine. Research is being done towards analyzing whether the advantages of drug repurposing outweigh its drawbacks.

It is indisputable that drug repurposing has saved many lives and has lowered the time of the drug-making process drastically. In the future, the use of drug repurposing in medicine and pharmaceutical can prove to be extremely crucial in case another global pandemic strikes, and further research is already underway focused on improving and assessing the process of drug repurposing and finding the medicine for new indications.

References

Cha, Y., Erez, T., Reynolds, I. J., Kumar, D., Ross, J., Koytiger, G., . . . Laifenfeld, D. (2018). Drug repurposing from the perspective of pharmaceutical companies. British Journal of Pharmacology, 175(2), 168–180. doi:10.1111/bph.13798

Cipriani A, Koesters M, Furukawa TA, Nosè M, Purgato M, Omori IM, . . . Barbui C. (2012). Duloxetine versus other anti‐depressive agents for depression. doi:10.1002/14651858.CD006533.pub2

Edwards, J. C., Szczepański, L., Szechiński, J., Filipowicz-Sosnowska, A., Emery, P., Close, D. R., . . . Shaw, T. (2004). Efficacy of B-Cell–Targeted Therapy with Rituximab in Patients with Rheumatoid Arthritis. The New England Journal of Medicine, 350, 2572–2581. doi:10.1056/NEJMoa032534

Fischl, M. A., Richman, D. D., Causey, D. M., Grieco, M. H., Bryson,, Y., & Mildvan, D. (1989, November). Prolonged Zidovudine Therapy in Patients With AIDS and Advanced AIDS-Related Complex. JAMA, 262(17), 2405–2410. doi:10.1001/jama.1989.03430170067030

Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral Sildenafil in the Treatment of Erectile Dysfunction. The New England Journal of Medicine, 338, 1397–1404. doi:10.1056/NEJM199805143382001

Millard, R., Moore, K., Rencken, R., Yalcin, I., & Bump, R. (2004). Duloxetine vs placebo in the treatment of stress urinary incontinence: a four-continent randomized clinical trial. BJU International, 93(3), 311–318. doi:10.1111/j.1464–410X.2004.04607.x

Oprea, T., & Mestres, J. (2012, July). Drug Repurposing: Far Beyond New Targets for Old Drugs. The AAPS Journal, 14(4), 759–763. doi:10.1208/s12248–012–9390–1

Pushpakom, S., Iorio, F., Eyers, P. A., Escott, K., Hopper, S., Wells, A., . . . Guilliams, T. (2019). Drug repurposing: progress, challenges and recommendations. Nature Reviews Drug Discovery, 18(1), 41–58. doi:10.1038/nrd.2018.168

Randolph, M., & Tosti, A. (2021, March). Oral minoxidil treatment for hair loss: A review of efficacy and safety. Journal of the American Academy of Dermatology, 84(3), 737–746. doi:10.1016/j.jaad.2020.06.1009

Senanayake, S. L. (2020). Drug repurposing strategies for COVID-19. Future Drug Discovery, 2(2). doi:10.4155/fdd-2020–0010

Sleire, L., Førde, H. E., Netland, I. A., Leiss, L., Skeie, B. S., & Enger, P. Ø. (2017). Drug repurposing in cancer. Pharmacol Res., 124, 74–91. doi:10.1016/j.phrs.2017.07.013