A Study of RT023 in Patients With Advanced Solid Tumors

Inclusion Criteria: 1. Male or female participants aged 18 years or older at the time of signing the informed consent form (ICF); 2. Participants with histologically or cytologically confirmed advanced malignant solid tumors; 3. Participants with an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1; 4. Participants with an expected survival ≥ 12 weeks; 5. Participants must have at least one measurable lesion based on RECIST v1.1; In dose escalation phase, participants without measurable lesions are permitted. Exclusion Criteria: 1. Participants with active central nervous system (CNS) metastases are excluded. However, participants are eligible if they have previously received radiotherapy or surgery, and imaging within 4 weeks prior to the first dose shows stable brain metastases without progression or new neurological symptoms, and corticosteroids have been withheld for at least 2 weeks prior to first dose. Participants with leptomeningeal or brainstem metastasis are not eligible regardless of treatment status; 2. Participants with clinically symptomatic pleural effusion, ascites, or pericardial effusion requiring repeated intervention; 3. Participants with poorly controlled hypertension, or with a history of hypertensive crisis or hypertensive encephalopathy; 4. Participants with a history of (non-infectious) interstitial lung disease (ILD)/pneumonitis that requiring corticosteroid therapy (e.g., idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, radiation pneumonitis, idiopathic pneumonitis, etc.), or participants with current ILD/non-infectious pneumonitis; 5. Participants with clinically significant intercurrent lung-specific illnesses, including but not limited to any underlying pulmonary diseases diagnosed within 3 months prior to the first dose (e.g., pulmonary embolism, severe asthma, severe chronic obstructive pulmonary disease \[COPD\], restrictive lung disease, etc.), any autoimmune, connective tissue, inflammatory disorders with pulmonary involvement (e.g., rheumatoid arthritis, Sjögren's syndrome, sarcoidosis, etc.), or prior pneumonectomy; 6. Participants with a history of immunodeficiency, including a positive test for human immunodeficiency virus (HIV), or a known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation; 7. Participants with any other conditions that may lead to premature discontinuation from the study, such as severe physical or psychiatric illness or laboratory abnormalities, which may increase the risk of study participation, affect treatment compliance, or interfere with the interpretation of study results, and who are deemed unsuitable for enrollment by the investigator.