Efficacy, Safety and Tolerability of AG013 in Oral Mucositis Compared to Placebo When Administered Three Times Per Day

Inclusion Criteria: 1. Willing and able to understand and sign the study specific Informed Consent Form 2. Pathologically-confirmed squamous cell carcinoma of the oral cavity, oropharynx, nasopharynx or hypopharynx or HPV-positive unknown primaries presumed to be of oropharyngeal, nasopharyngeal or hypopharyngeal origin 3. Tumor HPV status established 4. Planned to receive either primary or post-operative CRT 5. Planned IMRT (Intensity-Modulated Radiotherapy) 6. Planned administration of cisplatin administered weekly or tri-weekly during RT 7. Males or females 21 years or older 8. Karnofsky performance score (KPS) ≥ 70% 9. Screening laboratory assessments: * Hemoglobin ≥ 10g/dl * White blood count ≥ 3500 cells/mm3 * Absolute neutrophil counts ≥ 1500 cells/ mm3 * Serum AST (aspartate aminotransferase) and ALT (alanine aminotransferase) ≤ 3 x ULN * Calculated Creatinine Clearance ≥ 50 ml/min * Negative pregnancy test (serum or urine) for females of childbearing potential performed 7 days before IMP (Investigational Medicinal Product) administration. 10. Subjects of childbearing potential must confirm to use an effective method of birth control during study participation and for 30 days following the last treatment with IMP. Male subjects, when having hetero-sexual intercourse with a female of childbearing potential must use a condom during study participation and 90 days following the last treatment with IMP and their partner should use an effective method of birth control during that period as well. Exclusion Criteria: 1. Prior radiation to the head and neck 2. Increased risk of developing infectious endocarditis 3. Prior gene therapy 4. Presence of active infectious oral disease 5. Presence of any oral lesions that may confound the ability to assess oral mucositis grade 6. Current use of antibiotic rinses or troches 7. Herbal, alternative remedies, and alcohol containing over-the-counter mouthwashes are excluded during the course of the study 8. Current alcohol abuse syndrome 9. Chronic immunosuppression 10. Known seropositive for HIV 11. Use of investigational agent within 30 days of signing informed consent 12. Tooth extraction prior to radiation in which the extraction site is not epithelialized 13. Signs and symptoms of active dental disease 14. Female subjects who are pregnant or nursing 15. Known allergy to excipients of the IMP 16. Inability to give informed consent or comply with study requirements 17. Unwilling or unable to complete subject diary 18. Any other clinical condition, psychiatric condition or prior therapy that, in the opinion of the Investigator, would make the subject unsuitable for the study or unable or to comply with follow-up visits