Combination treatment with GW788388 and IL-23 slows the progression of premalignant oral lesions to cancer. Starting from Week 6 of 4NQO administration, when premalignant oral lesions were detectable on the tongue, mice were initiated on treatment with diluent, GW788388, IL-23 or both GW788388 and IL-23. At weekly intervals, their oral cavity was examined and photographed in a blinded manner by endoscopy. The number of visible lesions was counted, and lesions were given a gross pathologic score based on their horizontal and vertical size (1: flat macule, 2: raised papule, 3: raised plaque, 4: grossly exophytic). Differences in clinical score between mice receiving the combination GW788388 plus IL-23 treatments and the other three groups of mice are indicated as follows: * = p <0.05, ** = p <0.01.