From Laboratory to Patient Access: A Scoping Review of the Multi-Dimensional Challenges in Drug Repurposing.

Drug repurposing is often promoted as a faster, lower-risk alternative to de novo discovery, yet substantial barriers continue to limit successful implementation. We performed a scoping review of articles included in PubMed and ScienceDirect with the aim to identify and categorize challenges and analyze the intersections between them. Our review included 73 articles which revealed scientific, clinical, regulatory, economic, and implementation barriers, with the principal being the clinical translation of generated candidates. Scientific challenges include the necessity for new Phase II/III trials to validate efficacy, safety, and optimal dosing in new therapeutic contexts. Across disease areas, domain-specific barriers include subgroup-dependent responses in oncology, resistance and penetration challenges in anti-infectives, and data scarcity in rare diseases. Computational and AI-assisted approaches face fragmented data, model robustness, and insufficient validation. In addition, off-patent drugs face evidence requirements as rigorous as those for de novo entities, yet lack the market exclusivity incentives required to attract private investment. Additionally, an "institutional bottleneck" hinders academic researchers from bringing findings "on-label" due to a lack of regulatory infrastructure and collaborative frameworks. We conclude that drug repurposing requires a distinct translational paradigm involving multi-stakeholder collaboration and early regulatory engagement to bridge the gap between laboratory discovery and patient access.