RecruitingPhase 3Drug trialQLC5508 vs. Chemotherapy in Pretreated Advanced or Metastatic Esophageal Squamous Cell CarcinomaThis study is designed to assess the efficacy and safety of QLC5508 in patients with unresectable advanced or metastatic esophageal squamous cell carcinoma (ESCC) who have experienced disease progression following treatment with a platinum-based systemic therapy and an immune checkpoint inhibitor (ICI) compared with investigator's choice of chemotherapy (ICC).