A Study of FG-B901 Monotherapy or Combination With Chemotherapy in Advanced or Metastatic Solid Tumors

Inclusion Criteria: * Voluntarily sign the informed consent form, understand the study, are willing to comply with and have the ability to complete all trial procedures; * Age 18-75 years (inclusive), any gender; * Have histologically or cytologically confirmed locally advanced or metastatic solid tumors, and have failed standard therapy, or are intolerant to standard therapy, or for whom standard therapy is not available; * Able to provide tumor tissue specimens and peripheral blood samples that meet testing requirements, or provide prior test reports that meet the requirements; * ECOG performance status of 0 or 1; * Expected survival ≥3 months; * Have at least one measurable tumor lesion according to RECIST 1.1 criteria; * Adequate cardiac, bone marrow, liver, renal function; Exclusion Criteria: * Have received a live vaccine within 3 months prior to randomization; * Have received radiotherapy within 4 weeks prior to randomization; * Have received other anti-tumor drug therapy within 4 weeks or within 5 half-lives of the anti-tumor drug prior to randomization; * Have undergone major surgery within 4 weeks prior to randomization; * Have received any clinical study drug treatment within 4 weeks prior to randomization; * Have undergone major surgery within 4 weeks prior to randomization; * Have a history of other (non-study tumor) malignancies within 3 years prior to randomization; * Have received any organ transplant or bone marrow transplant; * Have previously received any tumor necrosis factor receptor (TNFR) agonist antibody therapy, such as anti-CD40, anti-OX40, anti-CD137, anti-CD27, anti-CD357 antibodies, etc; * Have experienced Grade ≥3 immune-related adverse events (irAEs) from prior immunotherapy; * Have a history of severe allergic reactions or are allergic to the investigational drug (FG-B901); * Have a history of central nervous system metastases and/or carcinomatous meningitis; * Have adverse reactions from prior treatments that have not recovered to CTCAE v5.0 Grade ≤1 (excluding alopecia and anemia) prior to randomization; * Have a history of severe respiratory disease; * Have experienced a clinically significant cardiac disease within 6 months before the first dose of study drug; * Have uncontrolled systemic diseases assessed by the investigator, including diabetes, hypertension, pulmonary fibrosis, interstitial lung disease, etc.; * The investigator judges the subject to have obvious active gastrointestinal bleeding; * Known history of Hepatitis C or chronic active Hepatitis B; * Have experienced systemic treatment with corticosteroids within ≤2 weeks prior to randomization; * Any other condition of the subject (e.g., psychological, geographical, or medical condition) that does not permit compliance with the study and follow-up procedures; * Are pregnant or breastfeeding;