Therapeutic Exosomes: From Molecular Biology to Clinical Translation

Exosomes, extracellular vesicles of 30-150 nm generated via fusion of multivesicular bodies with the plasma membrane, have evolved from poorly characterized cellular byproducts into a promising platform for translational medicine. Their intrinsic biological properties, including low immunogenicity, biocompatibility, capacity to cross the blood-brain barrier, and natural tissue tropism, confer fundamental advantages over synthetic nanocarriers.

This review systematically covers biogenesis (ESCRT-dependent and ceramide-mediated pathways), molecular cargo composition, cellular sources and GMP-- compliant manufacturing, pharmacokinetics and biodistribution, clinical experience across major disease areas, engineering strategies for cargo loading and surface modification, and the current regulatory landscape.

Exosome biogenesis is orchestrated by ESCRT-0-III complexes and the neutral sphingomyelinase pathway, yielding vesicles enriched in tetraspanins (CD63, CD9, CD81), heat-shock proteins, and functional nucleic acids including miRNA and circRNA. Mesenchymal stromal cell-derived exosomes dominate clinical pipelines, with scalable 3D hollow-fiber bioreactor production enabling GMP-grade manufacturing. Circulating half-lives vary markedly by source: most cell line-derived exosomes are cleared within 2-30 minutes, whereas platelet-derived EVs persist in circulation for 5.3-5.8 hours. These values are substantially prolonged by CD47-mediated phagocytosis evasion and PEGylation. Engineering approaches, LAMP-2B-mediated genetic display of targeting ligands, click chemistry conjugation, and hybrid Exosome-Liposome Nanoparticles (HELN)markedly enhance tissue selectivity and therapeutic potency. Completed Phase I-IIb trials in oncology and pulmonology demonstrate favourable safety profiles without severe systemic adverse events. As of 2025-2026, no extracellular vesicle therapeutic has received regulatory approval by the FDA, EMA, or equivalent agencies.

Engineered exosomes combine multicomponent cargo, context-dependent uptake, and tissue tropism in a single platform. Validated potency assays, batch consistency, and regulatory harmonisation remain the principal unresolved barriers to clinical approval.

Convergence of AI-driven manufacturing optimisation, multimodal engineering platforms, and international regulatory harmonisation defines the translational roadmap for exosome-based medicines over the coming decade.