Phase I/II Clinical Study of SYS6043 in the Treatment of Advanced/Metastatic Solid Tumors This study is a first-in-human phase I/II, multicenter, open-label, dose-escalation trial with PK expansion and cohort expansion, designed to evaluate the safety, tolerability, pharmacokinetic (PK) profile and preliminary anti-tumor efficacy of SYS6043 (a B7-H3-targeted antibody-drug conjugate) in patients with advanced/metastatic solid tumors. It consists of three parts: dose escalation, PK expansion and cohort expansion.