FG-B901 is a recombinant humanized IgG2 bispecific antibody targeting PD-L1 and CD40. It is designed to provide PD-L1-dependent CD40 agonism, thereby enhancing selectivity for the tumor microenvironment and reducing systemic toxicity compared with conventional CD40 agonists. Preclinically, FG-B901 promotes antigen-presenting cell activation and synergizes with PD-L1/PD-1 blockade to potentiate T-cell anti-tumor immunity. This is an open-label, multicenter phase I/II trial in subjects with unresectable locally advanced or metastatic solid tumors. The primary objectives are to evaluate the safety, tolerability, and pharmacokinetics of FG-B901 as monotherapy and in combination with chemotherapy. Secondary objectives include preliminary anti-tumor efficacy (e.g., objective response rate, disease control rate, progression-free survival, and overall survival).