A Clinical Study of PD-L1 Antibody ZKAB001(Drug Code) in Limited Stage of High-grade Osteosarcoma

Inclusion Criteria:

1. The patient voluntarily gives written informed consent to participate in the study.

2. Patients aged between 18 and 55 (inclusive).

3. To diagnosed with limited stage of high-grade osteosarcoma (AJCC stage I-III) byhistologically, the patients must have received neoadjuvant chemotherapy and adjuvantchemotherapy and primary tumor radical surgery (R0). The end of adjuvant chemotherapyshould less than 12 weeks. Chemotherapy regimens must contain doxorubicin (ADM)/epirubicin (EPI)/pirarubicin (THP)/doxorubicin liposome (PLD) and cisplatin (DDP), the minimum cumulative doses are ADM 360 mg/m2, EPI 450mg/m2, THP 300mg/m2, PLD 240 mg/m2 and DDP 480 mg/m2.

4. Eastern Cooperative Oncology Group（ECOG）performance status of 0 or 1, with estimatedlife expectancy of at least 3 months.

5. Adequate blood routine, hepatic and renal function:

1)neutrophil count (ANC) absolutely acuity≥1.5 x 109 / L; 2)platelet count≥80 x 109 / L; 3)hemoglobin≥90 g/L; 4)serum albumin≥28 g/L; 5)bilirubin≤1.5 x ULN（upper limit of normal）; 6)Alanine transaminase （ALT）and AST≤1.5 x ULN, serum Cr≤1.25 x ULN; 7) endogenouscreatinine clearance≥50 ml/min (according Gault Cockcroft formula).

7.Female reproductive subjects should take effective contraception during the study periodand within 3 months after the study treatment period. The serum or urine human chorionicgonadotropin（HCG） examination must be negative within 7 days before the subject isenrolled.

Exclusion Criteria:

1. Local recurrence or metastasis.

2. Any active autoimmune disease or history of autoimmune disease (such as, but notlimited to, interstitial pneumonia, uveitis, enteritis, hepatitis, arthritis,nephritis, pituitary inflammation, hyperthyroidism, hypothyroidism, etc.); Patientswith vitiligo or asthma in childhood, adult still need medical intervention; Patientsneed bronchodilators for medical intervention of asthma.

3. Patients are using immunosuppressive agents, or systemic, or absorbable topicalcorticosteroid medications to achieve immunosuppressive purposes (doses >10mg/dayprednisone or equivalent), which is ongoing 2 weeks before enrollment.

4. Have received any form of organ transplantation, including allogeneic stem celltransplantation.

5. Known allergy to macromolecular protein inhibitors or any of the components ofZKAB001.

6. Suffering from other malignant tumors other than this diseases in 5 years except forskin basal cell and squamous cell carcinoma.

7. Central nervous system metastases with clinical symptoms (such as cerebral edema andbrain metastases requiring corticosteroid intervention). Previous treatment with brainor meningeal metastasis, such as clinical stabilization (MRI) less than 2 months, orsystemic corticosteroid (dose >10mg/day prednisone or equivalent) less than 2 weeks.

8. Patients with clinical symptoms or diseases of the heart that cannot be wellcontrolled, such as heart failure above New York Heart Association（NYHA ）2 grade,unstable angina pectoris, myocardial infarction in 1 year, and clinically significantsupraventricular or ventricular arrhythmia requiring treatment or intervention, haveleft ventricular ejection fraction < 50% at rest in the ultrasound cardiogram.

9. Previous radiotherapy, chemotherapy, surgery or molecular targeted therapy, less than 3 weeks after treatment and before study drug; Patients whose adverse events caused byprevious treatment did not recover to level 1 of CTCAE, except for hair loss.

10. Active infection, or unexplained fever> 38.5 degrees during screening period or beforethe first dose of ZKAB001 (subjects with fever from the tumor could be enrolled uponinvestigator's decision).

11. Human immunodeficiency virus (HIV) positive, syphilis spirochete positive, untreatedactive hepatitis.

12. The patient is participating in other clinical studies or is less than 1 month awayfrom the end of the previous clinical study.

13. To receive other anti-tumor treatment during the study.

14. To treated with other PD-1 and/or PD-1, or CTLA-4（Cytotoxic T LymphocyteAntigen-4）antibodies, or other drugs for immunomodulatory receptor preparationspreviously.

15. Recent history of prophylactic non-cancer vaccination (such as seasonal influenzavaccine and human papillomavirus（HPV）vaccine) within 28 days before screening.

16. History of mental drug abuse, alcohol abuse or drug abuse.

17. Pregnant or lactating women.

18. Any mental condition that prevents the understanding or provision of the informedconsent.

19. It is determined by the investigator that the patient has other factors that may leadto the termination of the study, such as other serious diseases or serious laboratorytest abnormalities or other factors that may affect the safety of the patients ,family or social factors that may affect the study data and sample collection.