Drug repurposing, sometimes called drug repositioning, is the process of identifying new therapeutic uses for already marketed drugs beyond their original approved indication. This approach is especially valuable in rare diseases or in therapeutic areas where few treatment options exist, and can lower development costs while increasing the likelihood of approval.
A recent and clinically important example is efgartigimod. The drug was originally approved by FDA in December 2021 for the treatment of generalized myasthenia gravis1. Then, in June 2024, it gained further approval for the treatment of adult patients with chronic inflammatory demyelinating polyneuropathy2 (a rare neurological condition that causes progressive muscle weakness, numbness and other symptoms).
In many cases, drug repurposing is faster and cheaper than developing new drugs from scratch, given established safety profiles. Repurposing can save 50-70% in cost alone, with the average program running at about $300M vs. $2-3B for a new drug. Acceleration is a significant part of those cost-saving measures, given repurposed drugs, on average, complete in 6-7 years compared to 10-17.
Not only is drug repurposing more cost effective, but the success rate averages about 25-30% for approval, compared to 10% for novel drugs. For patients awaiting new treatments, that time is precious.
Efficacy evaluations can often proceed more quickly when the new use for a drug is in a therapeutic area similar to its original indication. For example, sildenafil was first developed for hypertension and angina, then repurposed for erectile dysfunction based on observed side effects, and later for pulmonary arterial hypertension.
Drug repurposing requires a thorough understanding of disease etiology. Natural history studies, also called observational and non-interventional studies (ONIS), play an important role in gaining important insights into disease etiology, especially for rare or orphan diseases where it can be complex. Because these diseases are so rare, enrollment can be a significant challenge for large studies. ONIS that assess natural history and disease prognosis of rare diseases, conducted in real-world healthcare settings, can also help in identifying best practices and existing standards of care.
Importantly, ONIS in real-world settings can be beneficial for finding therapies that are candidates for drug repurposing by identifying off-label prescribing patterns. For example, in type 1 interferonopathies (a group of ultra-rare diseases characterized by overactivity of specific pathways in the immune system due to genetic mutations), real-world studies have shown that anti-retroviral medications, originally approved to treat human immunodeficiency virus (HIV) infection, can improve patient response and positively affect the disease pathway, possibly through increased cerebral blood flow and reduced interferon activity in the cerebrospinal fluid3,4.
Reflecting the growing importance of natural history studies, the FDA has encouraged the use of these studies to support approval applications for novel drug molecules or new indications for existing products,5 and has established a grants program to help fund natural history studies6.
Drug repurposing offers a pathway to leverage existing drugs and available safety and efficacy data to speed up the drug discovery process and reduce the cost of bringing effective therapies to market to supplement already marketed treatments. Natural history studies are instrumental in supporting these efforts, especially for rare disease indications.
Our sponsors know that UBC is an industry leader in the conception, design, and execution of natural history studies, with a dedicated team of epidemiologists, clinicians, and biostatisticians providing expert guidance every step of the way.
For additional information and/or guidance on the conduct of natural history studies, read our white paper,7 or get in touch with us here.
REFERENCES
1. Heo YA. Efgartigimod Alfa in Generalised Myasthenia Gravis: A Profile of Its Use. CNS Drugs. 2023;37(5):467-473. doi:10.1007/s40263-023-01000-z
2. U.S. Food & Drug Administration. FDA approves treatment for chronic inflammatory demyelinating polyneuropathy (CIDP) in adults. June 24, 2024. Accessed October 27, 2025. https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-treatment-chronic-inflammatory-demyelinating-polyneuropathy-cidp-adults#xd_co_f=Y2NjZDc3ZTMtMGMwZi00MmE3LWE3NjktZjhhM2I0NmI4M2Iz~
3. Crow YJ, Stetson DB. The type I interferonopathies: 10 years on. Nat Rev Immunol. 2022;22(8):471-483. doi:10.1038/s41577-021-00633-9
4. d’Angelo DM, Di Filippo P, Breda L, Chiarelli F. Type I Interferonopathies in Children: An Overview. Front Pediatr. 2021;9:631329. Published 2021 Mar 31. doi:10.3389/fped.2021.631329
5. Food and Drug Law Institute. FDA’s Historical Use of “Real World Evidence”. August 10, 2018. Accessed October 27, 2025. https://www.fdli.org/2018/08/update-fdas-historical-use-of-real-world-evidence/#:~:text=Brineura%E2%80%94In%202017%2C%20FDA%20approved,in%20the%20natural%20history%20cohort
6. U.S. Food & Drug Administration. Natural History Studies Grants Program. October 1, 2024. Accessed October 27, 2025. https://www.fda.gov/industry/orphan-products-grants-program/natural-history-studies-grants-program#:~:text=About%20the%20Natural%20History%20Studies,biomarkers%20for%20a%20given%20disease
7. Stemhagen A, Moran E, Lytle J. White Paper: Understanding the Natural History of Disease. 2024. https://ubc.com/resources/understanding-the-natural-history-of-disease/
About UBC
United BioSource LLC (UBC) is the leading provider of evidence development solutions with expertise in uniting evidence and access. UBC helps biopharma mitigate risk, address product hurdles, and demonstrate safety, efficacy, and value under real-world conditions. UBC leads the market in providing integrated, comprehensive clinical, safety, and commercialization services and is uniquely positioned to seamlessly integrate best-in-class services throughout the lifecycle of a product.
About the Author
Samuel Igweokpala, Associate Epidemiologist.
Samuel Igweokpala is an Associate Epidemiologist at UBC. He contributes to UBC’s cross-functional expertise, including the design, conduct, and interpretation of real-world studies using data from various sources such as databases, registries, and patient medical charts. He also has a pharmacy degree and combines his pharmaceutical knowledge and epidemiology skills to support public health research.
