Drug repurposing runs into the same obstacles long before a new indication reaches patients
Repurposing has become an appealing shortcut in drug development, especially after the Food and Drug Administration issued emergency use authorizations for several existing drugs during Covid-19. The attraction is obvious: a shelved or approved compound already has human safety data, manufacturing pathways, and at least some regulatory history. Yet the path from a promising molecule to a second life in a new disease remains crowded with friction. A systematic review in BMC Health Services Research examined why so many candidates are abandoned, what keeps repurposing from scaling, and which conditions seem to help the strategy succeed.
The review pulled together evidence from a broad search across ABI/Informa, Academic Search Premier, Business Source Complete, Cochrane Library, EconLit, Google Scholar, Ovid Embase, Ovid Medline, PubMed, Scopus, and Web of Science Core Collection. Investigators identified 11,814 records, screened 5,976 for relevance, reviewed 437 full texts, and included 115 studies in the final analysis. The design was not a clinical trial and did not measure patient outcomes directly. Its value lies elsewhere: it maps the structural reasons repurposing stalls and the conditions that make it more feasible.
Promising drugs are often abandoned for the simplest reason of all: they do not work well enough. In the review, lack of efficacy or failure to outperform another therapy was the most common explanation for deprioritization, appearing 59 times among the included studies. Strategic business decisions followed closely, with 35 mentions, while safety problems accounted for 28. Research design decisions appeared 12 times, the complexity of the disease or the compound itself appeared 7 times, and regulatory demands for more information appeared 2 times. Those reasons matter because repurposing does not erase the original development risk. A compound that looked biologically plausible in one indication can still fail when the disease mechanism, dosing window, or target population changes.
A drug can be shelved for reasons that have little to do with biology and everything to do with commercial viability.
Why abandoned compounds rarely re-enter development on their own
Most of the included articles, 76 of 115 or 66%, focused on the reasons drugs are abandoned rather than on repurposing success stories. That skew itself is revealing. The literature is still wrestling with the upstream problem: a large pool of compounds exists, but many are trapped behind incomplete records, corporate restructuring, or decisions made years earlier in a different market environment. Industry consolidation further narrows the pathway, since ownership changes can scatter data, limit continuity, and blur responsibility for pursuing a new indication.
Several barriers emerged repeatedly. Inadequate resources was the most frequent, appearing 42 times. Intellectual property challenges followed with 26 mentions. Trial data access and transparency around abandoned compounds appeared 20 times, and uncertainty about the value of repurposing appeared 13 times. Expertise was mentioned 11 times, while liability risks appeared 5 times. These are not abstract obstacles. A repurposing program needs regulatory knowledge, statistical and clinical expertise, funding for preclinical or translational work, and access to legacy data that may sit inside company archives or proprietary systems. Without those inputs, even a biologically attractive compound can remain stranded.
IP disputes also shape what can be done with a repurposed drug. When ownership, patent scope, data rights, or licensing terms are unclear, companies and academic groups face delays before a trial can even begin. The review points to a familiar problem in drug development: scientific opportunity often outruns the legal and financial infrastructure needed to test it.
Data access, collaborations and database tools make the difference
The facilitators listed in the review were concrete and operational. Multi-partner collaborations appeared 38 times, and access to compound databases and database screening tools appeared 32 times. Regulatory modifications were mentioned 5 times, and tax incentives 2 times. Those findings suggest that repurposing is less a singular scientific act than a coordination problem. Researchers need repositories that can surface candidate compounds quickly, and they need partnerships that connect academia, industry, funders, and legal expertise.
Compound databases matter because they reduce the search cost of finding an overlooked drug with plausible pharmacology. Screening tools can help match chemistry, target biology, and disease mechanism, especially when old data are scattered across discontinued programs. Multi-partner collaborations matter for a different reason: they distribute risk. A repurposing program may require one group to provide compound access, another to run translational work, another to manage regulatory filings, and another to support clinical evaluation. When those roles align, a shelved asset can be reintroduced into development with less duplication and less delay.
There is a practical bedside consequence in all of this. If repurposing is blocked by missing data, opaque ownership, or legal uncertainty, patients lose access to potentially useful treatments that already exist in some form. The bottleneck is not always discovery; often it is retrieval, permission, and execution.
What the review says about the next phase of repurposing research
The review makes a clear argument for more work on the current value of repurposing in drug development and on the support systems needed to make it viable. That includes financial backing for out-licensing shelved products, staffing to manage the transfer of abandoned compounds, and legal expertise for negotiating IP agreements in multi-partner settings. Those needs are especially important because repurposing has been widely promoted as a faster, cheaper route to innovation, but the actual process still depends on scarce human and institutional resources.
The protocol for the review was registered on the Open Science Framework because it was not eligible for PROSPERO registration; the review did not focus on a health-related outcome. That detail fits the broader theme of the paper. Repurposing is often discussed as a scientific or clinical shortcut, yet its success turns on infrastructure, governance, and access to information as much as on pharmacology.
The most actionable message is plain: repurposing will not fulfill its promise unless the research ecosystem can move abandoned compounds through data-sharing, collaboration, and licensing with far less friction than exists now.