The main purpose of this study is to compare the effects of one of two different dose levels of an investigational drug called GC4419 when given with the standard radiation therapy and chemotherapy for the treatment of head and neck cancers. This study drug is not yet approved by the FDA. The study will be looking at the effect that the drug GC4419 will have on mucositis, which is a side effect of the chemotherapy and radiation therapy for the treatment of head and neck cancers.