Antitumor B (ATB), also known as Zeng Sheng Ping, is a tablet made according to modern GMP standards. It contains the extracts of following six Chinese medicinal herbs: Sophora tonkinensis, Polygonum bistorta, Prunella vulgaris, Sonchus brachyotus, Dictamnus dasycarpus, and Dioscorea bulbifera. Previously, clinical studies have shown significant chemopreventive efficacy of ATB against human esophageal squamous cell carcinomas and oral cancers. In a randomized clinical trial in patients with oral leukoplakia, treatment with ATB (4 tablets, 3 times per day for 8–12 months) reduced the size of oral lesions in 68% of the patients versus 17% of the patients in the placebo control group (P < 0.01), indicating that ATB may be a potent preventive agent against the development of oral cancer in humans. We found that ATB inhibited chemically induced oral squamous cell carcinomas (by ~60%) in mice and identified several key active compounds that are capable of inhibiting oral cancer cell proliferation. Our published study also showed that several key active compounds were found in the oral tissues and likely contributed to the chemoprevention effects of ATB. However, it is unknown if a key active component (KAC), called ATB-KACα which is enriched with 50% or more of three active compounds (i.e., dictamine, fraxinellone and maackiain) and therefore better chemically defined for QA/QC purposes, will have a stronger efficacy against oral carcinogenesis than ATB. We will use both the 4NQO-induced oral carcinogenesis mouse model and a “window of opportunity (WOO)” trial approach to determine the efficacy of ATB-KACα along with its pharmacodynamic (PD) responses and pharmacokinetic (PK) properties and biomarkers of efficacy. We hypothesize that oral administration of a better chemically defined ATB-KACα can significantly increase efficacy in preventing oral carcinogenesis in mouse models and will have the desirable PK properties and biomarker responses in both mice and humans. Aim 1 will perform phytochemical and pharmacokinetic characterizations of ATB-KACα and develop a PD/PK model to describe their efficacy and biomarker responses. Aim 2 will conduct mouse oral cancer chemoprevention studies to determine the efficacy of ATB-KACα on oral carcinogenesis and to identify novel biomarkers. Aim 3 will perform a WOO trial of ATB, ATB-KACα, or placebo in patients with newly diagnosed oral cancer. This proposal is timely and significant because the proposed WOO trial is important step for the development of ATB-KACα for future human phase II studies by filling the knowledge gap between biomarkers in humans and those in the matched mouse models. In addition, we will measure the PD and PK responses of ATB-KACα in the WOO trial and develop a PK/PD model to further enhance our understanding the necessary dose needed for future phase II human studies.