A Randomized Placebo-Controlled Trial of Two Schedules of RRx-001 for the Attenuation of Severe Oral Mucositis in Patients Receiving Concomitant Chemoradiation for the Treatment of Locally Advanced Squamous Cell Carcinoma of the Oral Cavity or Oropharynx

Inclusion Criteria: 1. Pathologically confirmed diagnosis of squamous cell carcinoma (SCC) of the oral cavity or oropharynx Note: Patients with primary cancers that are presumed to be of oropharyngeal origin may be included if they meet radiation field dosing criteria as specified in Inclusion Criterion #2 below. Unknown primaries which are HPV+ are acceptable. HPV determination must be made for all patients. 2. Radiation Treatment planned to receive standard IMRT with daily fractions of 2.0 to 2.2 Gy for a total cumulative dose of 60-72 Gy in conjunction with definitive or adjuvant chemotherapy. Planned radiation treatment fields must include at least two oral sites (soft palate, floor of mouth, buccal mucosa, tongue) that are each planned to receive a total of \> 55 Gy. Patients who have had prior surgery are eligible, provided they have fully recovered from surgery, and patients who may have surgery in the future are eligible. 3. ECOG performance status ≤ 2. 4. Participants must have adequate organ and marrow function as defined below: • Absolute neutrophil count (ANC) ≥ 1,500 / mm3 2. Platelets ≥ 75,000 / mm3 3. Hemoglobin ≥ 9.0 g/dL 5. Adequate renal and liver function as indicated by: • Serum creatinine acceptable for treatment with cisplatin per institutional guidelines) 2. Total bilirubin ≤ 1.5 x upper-normal limit (ULN) 3. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3.0 x ULN 4. Alkaline phosphatase ≤ 2.5 x ULN 6. Human papilloma virus (HPV) status in tumor must be documented using tumor immunohistochemistry for HPV-p16 or other accepted test (such as such as in situ hybridization) for patients with cancers of the oropharynx (Rooper et al, 2016, Martens 2017). HPV status at baseline optional for oral cavity tumors. 7. Age 18 years or older 8. Patient must consent to the access, review, and analysis of previous medical and cancer history, including imaging data, by the sponsor or a third party nominated by the sponsor. 9. Ability and willingness to understand and sign a written informed consent document. 10. Women of childbearing potential and men with partners of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control) prior to study entry, for the duration of study participation, and for 90 days following completion of therapy. Note: A woman of child-bearing potential is any female (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria: * Has not undergone a hysterectomy or bilateral oophorectomy; or * Has not been postmenopausal for at least 12 consecutive months 11. Adequate visual access to permit examination of the following oral cavity sites: lips, buccal mucosa, floor of mouth, ventral and lateral tongue, and soft palate. Exclusion Criteria: 1. Prior radiotherapy to the head and neck region. 2. Prior induction chemotherapy. 3. Tumors of the lips, salivary gland, nasopharynx, hypopharynx, or larynx. 4. Patients with simultaneous primaries 5. Stage IV, M1 (distant metastasis) 6. Prior or current use of approved or investigational anticancer agent other than those provided in this study. 7. Grade 3 or 4 dysphagia or odynophagia (National Cancer Institute Common Toxicity Criteria, version 5.0) or inability to eat a normal (solid) diet 8. Requirement at baseline for parenteral or gastrointestinal tube-delivered nutrition for any reason or prophylactic insertion of gastrostomy tube with dependency on tube feeding at baseline. 9. Malignant tumors other than squamous cell carcinoma of the head and neck within last 5 years, unless treated definitively and with low risk of recurrence in the judgment of the treating investigator. 10. Active infectious disease excluding oral candidiasis. 11. Presence of oral mucositis (WHO Score ≥ Grade 1) or other oral mucosal ulceration at baseline. 12. Untreated active oral or dental infection 13. Known history of human immunodeficiency virus or active hepatitis B or C. 14. Any significant medical diseases or conditions, as assessed by the investigators and sponsor that would substantially increase the medical risks of participating in this study (e.g, immunosuppression, uncontrolled diabetes, NYHA II-IV congestive heart failure, myocardial infarction within 6 months of study, severe chronic pulmonary disease or active uncontrolled infection, uncontrolled or clinically relevant pulmonary edema) 15. Use of the following within 48 hours of enrollment and duration of Oral Mucositis follow up: vitamin B12 (cobalamin) or synthetic vitamin B12, cyanocobalamin, or the vitamin B12 precursor, cobinamide, or any supplement or multivitamin with vitamin B12 or vitamin E in it since both vitamin B12 and vitamin E interact negatively with RRx-001. 16. Use of prebiotics and probiotics 17. Pregnant or nursing. 18. Known allergies or intolerance to cisplatin or other platinum-containing compounds. 19. Sjogren syndrome