EGFR/HER2 Dual-Target CAR-NK Cells for Recurrent or Metastatic HNSCC

Inclusion Criteria: * Age 18 to 75 years at the time of consent. * Histologically or cytologically confirmed squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx that is recurrent or metastatic and not amenable to curative surgery or radiotherapy. * Tumor meets protocol-defined central biomarker criteria for both EGFR and HER2 / ERBB2. Suggested example thresholds: EGFR membranous IHC 2+ / 3+ in at least 50% of viable tumor cells and HER2 IHC 2+ / 3+ in at least 10% of viable tumor cells and / or protocol-defined genomic amplification / activating alteration. * Disease progression on or after at least one prior systemic regimen for recurrent / metastatic disease, including platinum therapy and PD-1 / PD-L1 inhibitor unless contraindicated or not appropriate. Prior cetuximab is allowed. * At least one measurable lesion by RECIST 1.1. * ECOG performance status 0 to 1. * Adequate marrow, renal, hepatic, cardiac, and pulmonary function per protocol-defined laboratory thresholds. * Life expectancy of at least 12 weeks. * Availability of archival tissue or willingness to provide fresh tumor tissue for central biomarker testing; willingness to undergo serial blood sampling and optional research biopsy if medically feasible. * Negative pregnancy test for participants of childbearing potential and agreement to use highly effective contraception during protocol-defined treatment and follow-up windows. * Ability to understand and sign informed consent. Exclusion Criteria: * Nasopharyngeal carcinoma, salivary gland malignancy, cutaneous squamous cell carcinoma, non-squamous histology, or carcinoma of unknown primary. * Untreated, unstable, or symptomatic central nervous system metastases or leptomeningeal disease. * Prior gene-modified adoptive cell therapy (for example CAR-T, CAR-NK, or TCR-T) within a protocol-defined washout period, or prior allogeneic stem-cell transplant with active graft-versus-host disease. * Active uncontrolled infection, including uncontrolled bacterial, fungal, or viral infection; active hepatitis B or C with detectable viral load; or uncontrolled HIV infection. * Active autoimmune disease requiring systemic immunosuppression, or chronic corticosteroid use above the protocoldefined threshold before lymphodepletion. * Clinically significant interstitial lung disease, oxygen dependence, or another serious pulmonary condition that would materially increase cell-therapy risk. * Clinically significant cardiovascular disease including recent myocardial infarction, unstable angina, uncontrolled arrhythmia, uncontrolled hypertension, or symptomatic heart failure. * Major surgery within 28 days before lymphodepletion, or anticancer therapy / investigational therapy within the protocol-defined washout window. * Pregnancy or breastfeeding. * Known severe hypersensitivity to fludarabine, cyclophosphamide, or cell-product excipients. * Any medical, psychiatric, or social condition that, in the investigator's judgment, would compromise safety, protocol compliance, or informed consent.