A Phase 3 Study to Evaluate Petosemtamab Compared With Investigator's Choice Monotherapy in Previously Treated Head and Neck Squamous Cell Carcinoma Patients (LiGeR-HN2)

Inclusion Criteria: * Signed ICF before initiation of any study procedures. * Age ≥ 18 years at signing of ICF. * Histologically previously confirmed HNSCC with evidence of metastatic or locally advanced disease not amenable to standard therapy with curative intent. * HNSCC participants progressed on or after anti-PD-1 therapy and platinum-containing therapy. * The eligible HNSCC primary tumor locations are oropharynx, oral cavity, hypopharynx, and larynx. * Documentation of p16 status (positive or negative) by local laboratory IHC for participants with primary oropharyngeal cancer. * A baseline new tumor sample unless the participant has an available tumor sample as an FFPE block with sufficient material. * Measurable disease as defined by RECIST v1.1 by radiologic methods. * ECOG PS of 0 or 1 * Life expectancy ≥ 12 weeks, as per investigator * Adequate organ function (as per protocol) Exclusion Criteria: * Central nervous system metastases that are untreated or symptomatic, or require radiation, surgery, or continued steroid therapy to control symptoms within 14 days prior to randomization. * Known leptomeningeal involvement * Any systemic anticancer therapy within 4 weeks prior to randomization. * Major surgery within 3 weeks or palliative radiotherapy within 2 weeks prior to randomization. * Persistent Grade \>1 clinically significant toxicities related to prior antineoplastic therapies * History of hypersensitivity reaction to any of the excipients of treatment requir…