clinical trial phase clinical trial early phase 1 A clinical trial phase that is designed to use an investigational agent that is available only in very limited quantities and which has never previously given to humans or for which there is extremely limited human experience. Phase 0 clinical trials are intended to enable researchers to understand the path of the drug in the body and its efficacy. Adverse event reporting in Phase 0 trials is expedited. [def-source: NCI] https://en.wikipedia.org/wiki/Clinical_trial http://purl.obolibrary.org/obo/NCIT_C54721 C54721 Leon Li, Asiyah Lin, Oliver He Early Phase 1 C1882358 Pre-Clinical Phase clinical trial phase 0