Navigating the translational Valley of death in oncology nanotheranostics: manufacturing, biological, clinical, and regulatory barriers to implementation

Nanotheranostics integrate diagnostic and therapeutic functions within nanoscale platforms and have emerged as promising tools for precision oncology by enabling image-guided drug delivery, real-time biodistribution tracking, treatment monitoring, and improved patient stratification. Despite substantial preclinical advances, few integrated nanotheranostic systems have achieved routine clinical implementation. This narrative review critically examines the translational barriers limiting the clinical adoption of oncology nanotheranostics, emphasizing manufacturing reproducibility, biological delivery, safety, clinical validation, and regulatory uncertainty. A structured literature search was conducted across PubMed, Scopus, Web of Science, ClinicalTrials.gov, U.S. Food and Drug Administration resources, European Medicines Agency resources, and relevant regulatory websites for evidence published between 2015 and 2026. Peer-reviewed studies, regulatory guidance documents, and authoritative institutional reports were prioritized, with evidence synthesized according to SANRA principles and PRISMA transparency guidelines. The review shows that clinical translation is constrained more by misalignment between technology development and clinical and regulatory requirements than by lack of innovation. Major challenges include batch-to-batch variability, limited Good Manufacturing Practice scalability, instability of multifunctional nanoparticle constructs, inconsistent tumor delivery, poor predictability of animal models, immunogenicity, protein corona formation, long-term safety concerns, and complex combination-product regulatory pathways. The review proposes a decision-oriented translational framework that prioritizes clinically actionable diagnostics, quality-by-design manufacturing, standardized characterization, human-relevant preclinical models, validated imaging endpoints, and early regulatory engagement. Aligning nanotheranostic development with clinical needs, manufacturing feasibility, and regulatory expectations is essential to accelerate successful translation into routine oncology practice.