Key Inclusion Criteria:
* ≥18 years old
* Eastern Cooperative Oncology Group (ECOG) Performance status 0 to 1
* Confirmed as malignant solid tumor by histopathology
* Have measurable lesions based on RECIST 1.1
* Have failed standard treatment (disease progression or intolerance) or lack of standard treatment
* Positive FAP expression confirmed by FAP PET/CT
* Sufficient bone marrow capacity and organ function
Key Exclusion Criteria:
* High intensity and large amounts of off-target uptake detected by FAP molecular imaging, and were assessed as inappropriate for \[177Lu\]Lu-XT117 therapy by the investigators
* Previous systemic antitumor therapy (including prior chemotherapy, radiotherapy, immunotherapy, and other investigational drugs) ≤28 days before receiving study therapy; previous treatment with Chinese medicine with anti-tumor indications within 2 weeks before receiving study therapy
* Uncontrolled diabetes, with baseline fasting blood glucose \> 2×ULN
* Clinically significant serious cardiovascular disease, including but not limited to: a. \>Grade II congestive heart failure as per New York Heart Association (NYHA) ; b. Unstable angina pectoris or myocardial infarction within 6 months before the first administration of the study drug; c. Severe arrhythmia within 6 months prior to the first administration; d. Poorly controlled hypertension (patients who keep the blood pressure to ≤ Grade 2 hypertension \[CTCAE5.0\] with hypotensors are acceptable for enrollment); e. QTc\>450 ms (male) or 470 ms (female), congenital prolonged QT syndrome, and use of medications that prolong QT
* Clinically serious thromboembolic disease within 6 months prior to the first administration of the study drug
* Major surgery within 4 weeks prior to the first administration
* History of severe gastrointestinal ulcers or perforations or history of intestinal obstruction within 6 months prior to the first administration
* Active infection requiring systemic treatment (oral or intravenous administration) within 2 weeks prior to the first administration, except for topical treatment
* History of non-infectious interstitial lung disease (ILD), such as idiopathic pulmonary fibrosis, idiopathic interstitial pneumonia, pneumoconiosis, and drug-related interstitial pneumonia, or severe impairment of lung function
* Had other malignancies within 5 years prior to screening (except clinically cured early stage malignancies)
* Primary central nervous system (CNS) tumor or symptomatic CNS metastasis, expect:
* Subjects with asymptomatic brain metastases;
* Subjects whose CNS lesions were stable for ≥4 weeks after local treatment and who stopped glucocorticoid or anticonvulsant therapy at least 2 weeks prior to study drug administration could be enrolled;
* Uncontrolled pleural effusion, pericardial effusion, or ascites requiring repeated drainage
