MicroRNAs (miRNAs) have emerged as promising therapeutic agents in cancer because of their ability to simultaneously regulate multiple oncogenic pathways and gene networks. Early preclinical studies demonstrated substantial anti-tumor activity, generating considerable enthusiasm for the rapid clinical translation of miRNA-based therapeutics. However, despite strong mechanistic rationale and encouraging experimental results, the successful clinical application of miRNA therapeutics has remained limited. To date, only a small number of miRNA-based candidates have entered clinical trials, and none have achieved regulatory approval for cancer treatment. This review summarizes advances in miRNA-based cancer therapeutics and discusses the major factors limiting their translation into clinical practice. We discuss current strategies for miRNA restoration and miRNA inhibition, together with advances in delivery technologies, including lipid nanoparticles, polymer-based carriers, viral vectors, exosomes, and ligand-conjugated systems. Furthermore, evidence from preclinical and clinical studies to assess the efficacy, safety, and translational potential of these approaches have been summarized. Special emphasis was placed on the biological and technical barriers which continue to restrict the clinical success, including inefficient and nonspecific delivery, off-target effects, immune-related toxicities, tumor heterogeneity, and the contextdependent nature of miRNA function within complex tumor microenvironments. Overall, the available evidence suggests that miRNA-based therapeutics continues to hold a significant promise in oncology. Although substantial biological and technical challenges still remains to be addressed to achieve their widespread clinical implementation.
