Rethinking Phase I units in the era of immuno-oncology: a three-layer framework.

The rapid expansion of immuno-oncology (I-O) and other advanced therapies is reshaping the complexity of early-phase clinical development. While core Phase I principles remain fundamental across oncology, emerging modalities introduce additional requirements for translational integration, specialized safety management, and therapeutic-specific infrastructure. However, the organizational functions of Phase I units have not evolved at the same pace and remain largely centered on conventional operational responsibilities. Drawing on the practices of leading Phase I units across the USA, Europe, and China, and comparing evolving regulatory frameworks of the US Food and Drug Administration, European Medicines Agency/Medicines and Healthcare products Regulatory Agency, and China's National Medical Products Administration, we propose a global perspective on the future development of Phase I units. We present a three-layer framework encompassing core Phase I foundations applicable across oncology, advanced translational capabilities, and ecosystem-level functions supporting emerging therapeutic development. Beyond ensuring patient safety and high-quality trial conduct, modern Phase I units should integrate translational research, artificial intelligence-enabled and model-informed drug development, regulatory science, and public engagement, while specialized centers may additionally support advanced therapy infrastructure, such as point-of-care manufacturing. Recognizing the diversity of institutional resources, we further propose a collaborative network model to facilitate scalable implementation and international harmonization. This framework positions Phase I units as integrated platforms connecting clinical investigation, translational science, regulatory innovation, and emerging therapy development, providing practical guidance for building future-ready early-phase clinical research infrastructure worldwide.