4-1BBL x 5T4

Primary objective: To evaluate the safety, tolerability, maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE) and recommended dose for phase II study (RP2D) of FTL008.16 in patients with advanced solid tumors. Secondary objectives: 1) To preliminarily evaluate the anti-tumor activity of FTL008.16 in patients with advanced solid tumors. According to RECIST version 1.1 and iRECIST criteria, ORR, DOR, DCR and PFS were used to describe the preliminary anti-tumor activity. 2) To evaluate the pharmacokinetic (PK) characteristics of FTL008.16 in patients with advanced solid tumors. 3) To evaluate the immunogenicity of FTL008.16 in patients with advanced solid tumors. Exploration objectives: 1) To explore the pharmacodynamic characteristics of FTL008.16. 2) To explore the relationship between relevant biomarkers and anti-tumor efficacy. 3) Explore the drug exposure-effect (safety and/or efficacy) relationship of FTL008.16 (if data permit).