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Grant Abstract: A phased clinical trial of a dietary supplement kava: biomarker changes and anxiolytic effects

Grant Number: 1R61AT00988-01A1
PI Name: Xing
Project Title: A phased clinical trial of a dietary supplement kava: biomarker changes and anxiolytic effects

Abstract: Generalized anxiety disorder (GAD) affects more than 16 million American adults annually, and is primarily treated with antidepressants or benzodiazepines (BZDs). Unfortunately, many GAD patients report only a partial response or cannot tolerate the side effects of these medications. BZD-based anxiolytics are of particular concern because of the risk for chemical dependence, addiction, cognitive impairment, and even death. There is thus an unmet clinical need for new anxiolytics free of BZD adverse effects. However, our limited understanding of the neurobiology of anxiety has impeded the discovery of novel pharmacotherapies for GAD. Kava, prepared from the root of Piper methysticum, is consumed in many parts of the world as a daily beverage to help people relax, socialize and improve sleep. Clinical trials in Europe and elsewhere also indicate that it is an effective anxiolytic. In these studies, kava usage showed no signs of addiction or withdrawal, indicating that its mechanism of action differs from that of BZD, which is mediated through GABAA. Although the mechanisms behind kava's anxiolytic activity are not yet established, in vivo studies indicate that it is not mediated through GABAA. Kava thus is a promising source to search for novel anxiolytics with unique mechanism(s) of action to help manage GAD. In a pilot study of daily dietary kava use among general smokers, we found that a one-week kava ingestion reduced smoking dependence, supporting kava's anxiolytic activity. More interestingly, this treatment regimen significantly and consistently reduced the plasma levels of protein kinase A catalytic subunit alpha (PRKACA) and plasma cortisol among the general smokers. Given the well-established role of PRKACA and cortisol in anxiety and stress, kava may induce its anxiolytic activity via a novel PRKACA-dependent mechanism. Thus, plasma levels of PRKACA, and potentially plasma cortisol and cyclic AMP and urinary N-acetyl serotonin may serve as biomarkers to monitor kava's anxiolytic efficacy. Thus, the R61 phase of this phased clinical trial aims 1) to validate the changes of plasma PRKACA, cortisol, c-AMP and urinary NA-5HT in GAD patients upon kava ingestion and 2) to characterize the safety, compliance, bioavailability and pharmacokinetics of kava. The R33 phase will build on the R61 to 1) explore the potential of the identified biomarkers in predicting kava's anxiolytic efficacy and 2) identify the specific subgroup of GAD patients that are most likely to benefit from kava treatment. Safety Measures: Built upon our understanding of kava's hepatotoxic risk, a flavokavain A/B-free kava dietary supplement will be used in this trial, which is expected to reduce/eliminate kava's potential hepatotoxic risk. We will exclude individuals with elevated risk for hepatotoxicity, and will closely monitor liver function and other potential adverse events during and for 12 weeks following treatment. PUBLIC HEALTH RELEVANCE: Generalized anxiety disorder (GAD) affects more than 16 million American adults annually, and there is an urgent need for novel anxiolytics. This phased clinical trial will 1) identify potential surrogate biomarkers for the anxiolytic effect of the dietary supplement kava in participants with GAD; and 2) evaluate kava's anxiolytic efficacy and the relationship of biomarker changes to reductions in anxiety scores to explore kava's novel mechanisms with the long-term goal of developing new anxiolytic agents that can address this unmet clinical need.

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