Fanastomig (also known as EMB-02) is a bispecific antibody targeting programmed cell death protein-1(PD-1) and lymphocyte activation gene-3 (LAG-3), developed for the treatment of advanced solid tumors. A first-in-human (FIH) Phase I study (NCT04618393) evaluated safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and clinical efficacy of Fanastomig in patients with advanced solid tumors. To determine the recommended Phase II dose (RP2D), population pharmacokinetics (PopPK), and exposure and response analysis (E-R) were conducted. The PopPK model, demonstrating good performance, showed no clinically meaningful relationship between areas under the concentration-time curve (AUC) or maximum concentration (C