RiMO-HNC-NEO1: Phase 2 Study of RiMO-301 and Hypofractionated Radiotherapy With Pembrolizumab for the Neoadjuvant Treatment of Resectable, Locally Advanced Head-Neck Cancer

Inclusion Criteria: * Diagnosis of head and neck cancer that requires surgical resection * Must have at least one lesion that is clinically accessible to RiMO-301 injection and amenable to receiving hypofractionated radiotherapy * The selected target lesions must be measurable on cross-sectional imaging, and repeated measurements at the same location should be achievable * Target tumor not in the previously irradiated field or in the field irradiated at least six months prior to RiMO-301 injection, and with no complications from the prior radiation course * Patients must have recovered from acute toxic effects (≤ grade 1 CTCAEv6) of previous cancer treatments prior to enrollment * Patients with locally advanced, resectable head and neck cancer: * suitable to receive a PD-1 inhibitor (pembrolizumab) as a standard of care in the discretion of the treating physician or Principal Investigator * suitable to receive hypofractionated radiotherapy as a standard of care in the discretion of the treating physician or Principal Investigator * Have adequate bone marrow reserve: * Absolute neutrophil count ≥1.5x109 cell/L * Platelet count ≥100x109 cell/L * Hemoglobin at least ≥9.0 g/dL unless confirmed by treating physician as not posing any increased harm to patient and approved by Sponsor (transfusion is allowed to achieve hemoglobin of ≥9.0 g/dL 14-days prior to dosing) * Have adequate liver function: * Total serum bilirubin no more than 1.5x upper limit of normal (ULN) * Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5x ULN or ≤5.0x ULN in case of documented hepatic metastasis * Alkaline phosphatase ≤5x ULN * Have a life expectancy of at least 12 weeks (in the opinion of the investigator) * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Females with childbearing potential should be using adequate contraceptive measures from the time of screening until 6 months after study discontinuation, should not be breastfeeding, and must have a negative pregnancy test prior to start of dosing * Patients must sign a study-specific informed consent form prior to study entry. Exclusion Criteria: Diagnosis other than resectable, locally advanced head and neck cancers * HPV associated head and neck cancer * Nasopharynx head and neck cancer * Have signs or symptoms of end-stage failure, major chronic illnesses other than cancer, or any severe concomitant conditions * Symptomatic central nervous system metastases and/or carcinomatous meningitis * Has received any approved or investigational anti-neoplastic agent or immunotherapy other than PD-1 inhibitors, pembrolizumab, within 4 weeks prior to RiMO-301 injection. * Patients who are intolerant to pembrolizumab * Active autoimmune disease that has required systemic treatment in the past 2 years * Ongoing clinically significant infection at or near the incident lesion * Major surgery over the target area (excluding placement of vascular access) ≤21 days from the beginning of the study drug or minor surgical procedures ≤7 days. No waiting is required following implantable port, enteral feeding tube, and catheter placement * Other severe acute or chronic medical or psychiatric conditions or laboratory abnormality that would make the patient inappropriate for enrollment in this study * Has any mental or medical condition that prevents the patient from giving informed consent or participating in the trial * Pregnant and nursing women are excluded because of the potential teratogenic effects and potential unknown effects on nursing newborns * Patients with a target lesion in the field that had complications from prior radiotherapy that are not amenable to repeat irradiation in the discretion of the treating physician or Principal Investigator * Patients with lesions that have significant blood vessel involvement (such as carotid artery encasement) or other major structures