Oral AHR Antagonist in Combination With Nivolumab in Patients With PD-1 Resistant Metastatic or Recurrent Head and Neck Cancer

Key Inclusion Criteria: * Subject has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2. * Subject has a histologically confirmed metastatic or locally incurable, recurrent HNSCC that has progressed within 12 weeks of initiation of PD-1 inhibitor agent, whether it was administered alone or in combination with chemotherapy. * Tumors must express PD-L1 with a minimum CPS ≥ 1. * Subjects can be enrolled regardless of their tumor's expression of human papillomavirus (HPV). * Subjects are required to have received prior treatment with a platinum-based chemotherapy in the recurrent or metastatic disease setting, unless medically contraindicated. * Subject has at least 1 measurable lesion per RECIST v1.1. Key Exclusion Criteria: * Subject has untreated or symptomatic central nervous system (CNS) tumors or brain metastases. * Subject must have recovered to ≤ Grade 1 from clinically significant AEs related to prior therapy (eg, myelosuppression or renal or hepatic dysfunction.) * Subject has received prior treatment with an AHR inhibitor. * Subject has a medical condition that limits oral administration or impairment of gastrointestinal function that is expected to significantly reduce the absorption of IK-175. * Uncontrolled or life-threatening symptomatic concomitant disease. * Clinically significant cardiovascular disease as defined in the protocol. * Subject is on a medication that is a sensitive substrate of CYP2C8, 2C9, 2C19, or 3A4 that cannot be subs…