Posted: July 30, 2019

Letter of Intent due October 1, 2019; Full proposal due November 1, 2019

Americans consume natural products (NP) every day either through their diet or via dietary supplements. The 2012 National Health Interview Study estimates that 18% of adults in the U.S. use non-vitamin, non-mineral natural products as supplements. An estimated 20-30% of patients on prescription medication indicate they are also taking dietary supplements concomitantly. In the late 1990s reports emerged regarding severe and life-threatening interactions involving both St. John's Wort and grapefruit juice and a variety of medications (Rx). This led to widespread concerns about potential interactions with other natural products. Subsequently, numerous reports emerged describing possible interactions between large numbers of NP/Rx pairings. However, the evidence for many of these purported interactions came from case studies or was based on models without clear relevance to humans.

While studies in human subjects are the only way to establish definitive evidence of a clinically relevant drug interaction, the justification for the investment in such a trial is often built on in vitro data. The FDA has published guidance for industry regarding metabolism mediated drug interaction studies that recommends using carefully designed in vitro studies to determine the mechanisms and magnitude of pharmacokinetics interactions ( If those studies indicate a strong interaction the guidance recommends additional studies in humans. Yet, much of the existing published preclinical research does not follow that guidance and therefore does not provide much meaningful data to predict NP/Rx interactions in humans.

NCCIH is supporting a Center of Excellence for Natural Product Drug Interaction Research that is focused, in part, on conducting rigorous human subjects studies to establish the clinical relevance of interactions for selected natural products. Therefore, this companion initiative will support rigorous screening of natural product libraries in assays with clear relevance to human metabolism for evidence of pharmacokinetic interactions. The data generated will provide additional information on potential NP/Rx interactions and will help inform prioritization strategies regarding which natural products may warrant future investments in clinical studies.

Read full solicitation here.

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