BETHESDA, MD. -- A protease inhibitor derived from soybeans reduced the size of oral leukoplakia lesions by 24% in a 1-month phase II clinical trial, Dr. Frank L. Meyskens Jr. reported at the annual meeting of the American Society of Preventive Oncology.
The agent, a concentrate of the soybean extract known as Bowman-Birk inhibitor (BBI) will now be tested in a 6-month, randomized, blinded trial of 90 patients, said Dr. Meyskens, director of the Chao Family Comprehensive Cancer Center at the University of California, Irvine.
BBI has been found to prevent cancers in many animal systems and causes little or no toxicity. Its safety and clinical effectiveness were assessed in this dose-escalation trial involving 32 patients who had oral leukoplakia.
The patients swished in their mouths a solution containing BBI concentrate and then swallowed it. There were no signs of toxicity even at the highest doses tested, he reported.
Overall, lesion size decreased by 24% at 1-month follow-up, as judged by non-blinded clinical assessment and by blinded analysis of lesion photographs. The treatment response was dose related, Dr. Meyskens said.
In addition, samples of the subjects' buccal mucosal cells and serum were analyzed for expression of neu protein, which is known to be overexpressed in oral dysplastic lesions. A dose-dependent decrease in neu protein expression was observed and correlated with clinical improvement, he said.
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