This is a single-center, single-arm clinical study to evaluate the safety, tolerability and preliminary efficacy of [225Ac]Ac-FAPI-XT injection in patients with FAP-positive advanced solid tumors.

A Clinical Study to Evaluate the Safety, Tolerability, Dosimetry and Preliminary Efficacy of [225Ac]Ac-FAPI-XT Injection in FAP-positive Patients With Advanced Solid Tumors

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 standard treatment Positive FAP expression confirmed by FAP PET/CT Sufficient bone marrow capacity and organ function

Exclusion Criteria:

• High intensity and large amounts of off-target uptake by FAP molecular imaging 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 hypotensor are allowed 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 initial administration of the study drug 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