This study is a single-arm, open-label, multi-cohort, single-center phase II clinical trial designed to observe and evaluate the efficacy and safety of MRG003 (a EGFR-ADC) in combination with pucotenlimab (a PD-1 inhibitor) for the treatment of EGFR-positive unresectable recurrent or metastatic ATC/PDTC. All patients will receive the combination therapy every three weeks until disease progression or other event as defined in the protocol occurs.