The Phase II Clinical Trial Award FOA is intended to build upon work that has identified and replicated a biological signature of the a given natural product and complete collections of the necessary preliminary data needed to inform the design of a fully powered multi-site efficacy trial. Investigators should only apply for the U01 Natural Product Phase II Clinical Trial Cooperative Agreement after they have strong evidence that the proposed biological signature of the natural product can be reliably assessed for a condition of interest in the designated clinical population. It is recognized that for certain conditions (. pain), a direct biological effect or biological signature may not be measurable in human participants for a variety of reasons. In such instances, a strong justification for why including a biological signature is not possible or impractical with human participants is required. In these cases, investigators should consider including other objective measures that may be a marker of the mechanism of action and provide evidence of a biological or behavioral effect of the natural product in human participants. The U01 clinical trial FOA will support natural product clinical trials (phase II) such as dosing and formulation optimization of the natural product to be used in a future multi-site randomized clinical trial; collecting additional data documenting ability to recruit/accrue participants, achieve adherence to the study protocol, retain participants during study, and complete collection of follow-up data; or determining which patient phenotypes will be likely responders versus non-responders to the natural product to inform inclusion/exclusion criteria of a future multi-site efficacy trial.