SPEARHEAD 2 Study in Subjects With Recurrent or Metastatic Head and Neck Cancer

Key Inclusion Criteria * Age ≥18 and \<75 years * Diagnosis of head and neck squamous cell carcinoma with metastatic or unresectable, recurrent disease. confirmed by histology cytology. * Checkpoint inhibitor naïve and indicated for pembrolizumab or currently receiving pembrolizumab (monotherapy). May have received prior platinum containing chemotherapy regimen or checkpoint inhibitor therapy. * Subjects that have already received pembrolizumab (alone or in combination) and are progressing or have completed immune checkpoint inhibitor therapy for recurrent/metastatic disease, may still be enrolled and will skip Part A of the study. These subjects will enroll into Part B when manufactured T cells are available. * Measurable disease according to RECIST v1.1. * HLA-A\*02 positive by central laboratory. * Tumor shows MAGE-A4 expression confirmed by central laboratory. * ECOG Performance Status of 0 or 1. * Left ventricular ejection fraction (LVEF) ≥50%. Note: other protocol defined Inclusion criteria may apply Key Exclusion Criteria: * Positive for any HLA-A\*02 allele other than: one of the inclusion alleles, HLA- A\*02:07P or HLA-A\*02 null alleles * History of allergic reactions attributed to compounds of similar chemical or biologic composition to fludarabine, cyclophosphamide or other agents used in the study or history of severe hypersensitivity to another monoclonal antibody. * History of autoimmune or immune mediated disease * Leptomeningeal disease, carcinomatous meningitis or CNS metastases. * Other prior malignancy that is not considered by the Investigator to be in complete remission * Clinically significant cardiovascular disease * Uncontrolled intercurrent illness * Active infection with human immunodeficiency virus, hepatitis B virus, hepatitis C virus, or human T cell leukemia virus * Pregnant or breastfeeding Note: other protocol defined Exclusion criteria may apply.