A Phase I Study to Assess the Safety and Efficacy of [225Ac]Ac-DOTATATE in Patients With SSTR+ GEP-Nens

Inclusion Criteria:

1. Patients must have the ability to understand and sign an approved informed consentform (ICF).

2. Patients must be >= 18 and <＝80 years of age.

3. Histopathologically confirmed G1 or G2 or G3 GEP-NET or GEP-NEC；

4. Unresectable locally advanced or metastatic GEP-NET which confirmed by imagingexamination.

5. G1 or G2 NET patients: previously received fixed-dose Octreotide LAR (20-30 mg/3-4weeks) for at least 12 weeks of continuous treatment with disease progression;G3 NETorNEC patients: previously received at least 1 line therapy with diseaseprogression.

6. Presence of at least 1 measurable site of disease (based on RECIST 1.1).

7. SSTR-PET positive.

8. ECOG score of 0 or 1.

9. Life expectancy of at least 12 weeks.

10. Sufficient bone marrow capacity and organ function: Serum creatinine ≤1.5×ULN or creatinine clearance ≥50 ml/min (Cockcroft Gaultformula). Hemoglobin≥90g/L, neutrophil count ≥1.5×10^9/L, platelets≥100×10^9/L. Serum totalbilirubin ≤1.5×ULN. Serum albumin ≥30g/L. Alanine aminotransferase (ALT) oraspartate aminotransferase (AST) ≤ 2.5×ULN，or ALT/AST≤5×ULN with liver metastases. Partially activated prothrombin time (APTT) ≤1.5 x ULN.

11. Subjects of childbearing potential voluntarily use an effective method ofcontraception, such as condoms, oral or injectable contraceptives, IUDs, etc.,during treatment and within 6 months of the last use of the trial drug.

Exclusion Criteria:

1. Pregnant or lactating females.

2. Received the following treatments within 4 weeks prior to initiation of studytreatment, including but not limited to surgery (except biopsy), radicalradiotherapy, hepatic artery interventional embolization, cryoablation of livermetastases, or radiofrequency ablation.

3. Received systemic antitumor therapy such as targeted therapy, immunotherapy,antitumor herbal therapy, chemotherapy within 4 weeks prior to initiation of studytreatment.

4. Rapid progression with previous PRRT therapy.

5. Any patient receiving treatment with short-acting Octreotide, which cannot beinterrupted for 24 h before and 24 h after the administration of initiation of studytreatment, or any patient receiving treatment with Octreotide LAR, which cannot beinterrupted for at least 6 weeks before the administration of initiation of studytreatment.

6. Toxicity of prior antitumor therapy has not returned to ≤ grade 1 levels (except foralopecia).

7. Received external beam radiation therapy for bone metastases within 2 weeks prior toinitiation of study treatment.

8. Known brain metastases, unless these metastases have been treated and stabilized forat least 24 weeks, prior to enrollment in the study.

9. Uncontrolled congestive heart failure.

10. uncontrolled diabetes mellitus, including baseline fasting glucose > 2 x ULN.

11. Known other malignancies (except for those without recurrence within 5 years afteradequate treatment).

12. Known hypersensitivity to Lutetium[177Lu] Oxodotreotide Injection or [225Ac]Ac-DOTATATE Injection and their excipients.

13. Known to be unsuitable for enhanced CT or MRI contrast imaging due to allergicreaction or renal insufficiency.

14. Any clinically significant active infection.

15. Participated in other drug clinical trials within 4 weeks prior to initiation ofstudy treatment and received treatment with the corresponding trial drug.

16. Any other disease, mental status or surgical condition that is uncontrolled, mayinterfere with study completion (including poor compliance) or is inappropriate forthe use of the investigational drug.

17. Other treatment options (e.g., chemotherapy, targeted therapy) that, in the opinionof the investigator, are more appropriate for the patient than the treatmentprovided in the study based on the patient's disease characteristics.

18. Unsuitable for the study for any reason, in the opinion of the investigator.