Claudin 18.2

This open-label, multicenter Phase I/II trial evaluates the combination of FG-M108 and FG-B901 in patients with unresectable locally advanced or metastatic solid tumors that are positive for Claudin 18.2 and have progressed on, are intolerant to, or lack standard therapy. The Phase I dose-escalation part (using a BF-BOIN design) assesses safety, tolerability, and pharmacokinetics, and determines the recommended Phase II dose (RP2D) of FG-B901 when given with fixed-dose FG-M108. The Phase IIa expansion cohorts, grouped by tumor type, further evaluate safety and preliminary efficacy, with antitumor activity measured by RECIST 1.1 and iRECIST, while also exploring biomarker correlates. Key eligibility requires CLDN18.2 positivity (≥10% tumor cells with ≥1+ membrane staining by IHC), ECOG performance status 0-1, and measurable disease. Up to approximately 30 participants will be enrolled per cohort in Phase IIa. The study aims to provide initial evidence on the combination's safety, tolerability, PK, immunogenicity, and clinical activity in this hard-to-treat population.