The study will be conducted in 2 stages. In Stage 1 of the study, 11 patients will receive daily treatment with PTC299 administered at 100 mg/dose twice per day for up to 1 year or until tumor progression. If no subject responds with tumor shrinkage or an improvement in hearing, then the study will be stopped. If ≥1 out of 11 subjects respond, then the study will proceed to Stage 2 to enroll an additional 14 subjects for a total of 25 subjects.