1. To conduct short-term Phase Il clinical trials of chemopreventive agents to be named (CATBN) in oral leukoplakia. 2. To apply native cellular fluorescence (NCF) (tissue autofluorescence) in the clinical evaluation of regression of oral leukoplakic lesions induced by CATBN. 3. To use a variety of surrogate endpoint biomarkers (SEB) in the histologic evaluation of regression of oral leukoplakic lesions induced by CATBN. 4. To document the degree of recurrence of oral dysplastic leukoplakia after the administration of CATBN is terminated, both at the same site and at new sites.