A Phase I Study of RGT-264 in Subjects With Advanced Solid Tumors

Inclusion Criteria: * Able to sign the ICF and agree to comply with the requirements of the study; * Subjects with pathologically confirmed advanced solid tumors who have failed standard-of-care therapy, or have no standard-of-care therapy available, or are currently not eligible for standard-of-care therapy; * ECOG performance status score of 0 to 1; * Expected survival ≥ 3 months; * With at least one measurable lesion per RECIST v1.1; * Subjects should discontinue all anti-tumor therapies prior to receiving study treatment, and the toxicity caused by prior anti-tumor therapy has recovered to ≤ Grade 1 per CTCAE v5.0; * The specific requirements of washout period should be met before first dose; * Adequate organ function * Female subjects of childbearing potential must have a negative pregnancy test prior to the first dose and are required to use effective contraception from signing the ICF until 6 months after the last dose of study treatment Exclusion Criteria: * Presence of risks that may significantly affect the absorption of the investigational product (e.g. inability to swallow, intestinal obstruction, chronic diarrhea, etc.); * Having received immunotherapy and experienced ≥ Grade 3 immune-related adverse events (irAEs) or ≥ Grade 2 immune-related myocarditis; * Having received systemic glucocorticoids (\> 10 mg/day of prednisone or equivalent) or other immunosuppressants within 14 days prior to the first dose of investigational product; * Presence of symptomatic parenchymal brain metastasis or leptomeningeal metastasis; * Active, or previous autoimmune disease with the potential for relapse (excluding well-controlled type 1 diabetes mellitus; manageable hypothyroidism with hormone replacement therapy only).; * Any other malignancy (except cured basal cell carcinoma of skin and in-situ carcinoma of the cervix) within 3 years prior to the first dose; * History of serious cardiovascular and cerebrovascular diseases; * Presence of active interstitial lung disease or history of interstitial lung disease requiring glucocorticoid treatment; * Presence of severe chronic or active infections (including tuberculosis infection, etc.) requiring intravenous antimicrobial, antifungal or antiviral therapy; * Active HBV or HCV infection; * History of immunodeficiency or organ transplantation; * Presence of uncontrolled third spacing fluid; * Concomitant diseases or any other conditions that may seriously jeopardize the subject's safety or affect the subject's completion of the study, at the discretion of the investigator.