Regulatory Science of Extracellular Vesicles: From ISEV Standards to Translational Implementation (Insights From Japan).

Extracellular vesicles (EVs) offer compelling opportunities for diagnostics and therapeutics, yet translation toward routine clinical use and commercial readiness remains limited. In diagnostics, EV-based assays may reach practice as laboratory-developed tests, while in therapeutics unproven "exosome" offerings have prompted safety communications, together underscoring the need for fit-for-purpose regulatory science. Here, we organize implementation challenges into six recurring bottlenecks: Identity; Purity; Potency; Measurement comparability; Manufacturing control; and Safety. We summarize how international standardization efforts led by the International Society for Extracellular Vesicles (ISEV), including MISEV2023 and task-force outputs, strengthen reproducibility and comparability, while highlighting remaining gaps that arise when descriptive guidance must be converted into operational specifications and submission-ready evidence packages. Using Japan as a case example, we illustrate how regulatory-authority discussions, professional-society statements, and emerging implementation-oriented guidance can clarify review questions, distinguish therapeutic EV products from conditioned medium, and support trust-preserving translation. Finally, we propose a non-binding, deliverables-based roadmap across near-, mid-, and long-term horizons to enable clinical and commercial readiness. The roadmap should be adapted to product context, risk profile, and jurisdiction, and it emphasizes precompetitive collaboration across academia, industry, and government to build shared infrastructure for measurement, standardization, reproducibility, and quality evaluation, thereby translating scientific consensus into operational development and review frameworks.