Repurposing Radiopharmaceutical Carriers for Targeted Drug Delivery and Theranostics: A Translational Framework

Radiopharmaceuticals have long demonstrated precise, organ- and receptor-specific targeting in humans, supported by well-characterized pharmacokinetics, standardized formulation, and regulatory validation; however, the carrier systems underlying these agents remain largely underexplored as platforms for therapeutic delivery. This review introduces a translational framework that repositions clinically validated radiopharmaceutical carriers, including peptides, nanocolloids, lipophilic complexes, and antibody fragments, as ready-to-deploy scaffolds for targeted drug delivery and theranostic applications. Focusing on advances from 2018 to 2025, this work examines how established systems based on technetium-99m ( 99 ᵐTc), gallium, lutetium, rhenium, copper, iodine, and actinium can be systematically re-engineered through linker design, bifunctional chelation, and payload integration. Unlike conventional nanocarriers that rely heavily on preclinical optimization and passive targeting mechanisms, these platforms offer pre-validated human biodistribution, reproducible pharmacokinetics, and compatibility with good manufacturing practice (GMP), providing a distinct advantage for clinical translation. Emerging clinical evidence, including peptide–drug conjugates and antibody-based systems, highlights both the feasibility and current limitations of this approach, particularly the gap between diagnostic success and therapeutic adaptation. By integrating mechanistic insights, design strategies, and translational considerations, this review proposes a shift from de novo carrier design toward the strategic repurposing of clinically proven systems, with the potential to reduce translational attrition and accelerate the development of precision therapeutics and next generation theranostic platforms.