This is a single-center, open-label, dose-escalating study to evaluate the safety, pharmacokinetics, immunogenicity, and preliminary efficacy of single dose subcutaneous injection of a fully human monoclonal antibody of receptor activator for nuclear factor-κ B ligand (RNAKL) (code name: TK006) in postmenopausal women.

This is a phase I, open-label, single-dose, dose escalation study in postmenopausal women conducted at single center.

The objectives are to assess the safety and tolerability, effects on bone turnover measured by biochemical markers and bone density, and the pharmacokinetics and immunogenicity of a fully human monoclonal antibody of receptor activator for nuclear factor-κ B ligand (RNAKL), (code name: TK006).

Subjects would sequentially enroll in one of three cohorts. Subjects in the first cohort would receive a single 30-mg subcutaneous injection of TK006. If no safety signals are observed in the first cohort after 28 days, subjects would enroll in the second cohort and receive a single 60-mg subcutaneous injection of TK006. After an 28-day period for observation of safety of the second dose, subjects would enroll in the third cohort and receive a single 120-mg subcutaneous injection of TK006.

Inclusion Criteria:

1. Subjects who provide informed consent voluntarily;
2. Women who are postmenopausal defined as being amenorrheic for at least 24-month, and follicule-stimulating hormone (FSH)>40 U/L, estradiol (E2)<110pmol/L (or <30pg/mL) as well;
3. ≤65 years old, with no restricted activity.

Exclusion Criteria:

1. Known hypersensitivity to similar medicines or other products derived from mammalian cells, or medical history of severe allergic to foods or medicines;

2. Treatment with diphosphonate or fluoride, oestrogen, selective estrogen receptor modulators, calcitonin, parathyroid hormone, high dose Vitamin D (≥1000 IU/day), anabolic steroids, systemic glucocorticoids within 12-month before dosing, or administered with calcitriol within 6 months before dosing;

3. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) >2.0 times the upper limit of normal (ULN), or alkaline phosphatase (ALP)>1.5×ULN, or Total bilirubin (TBIL) >1.5×ULN, creatinine clearance rate<60 mL/min;

4. Disorders that could affect the study outcomes, such as osteomalacia, dysostosis, Paget's disease, Cushing syndrome, hyperprolactinemia, rheumatoid arthritis, hyperparathyroidism, hypoparathyroidism, or other diseases that could affect bone metabolism;

5. Hyperthyroidism or hypothyroidism, unless hypothyroidism patients are receiving regular treatment with thyroid hormone and:

   • Thyroid stimulating hormone (TSH) is normal, or
   • TSH>4.78μIU/Ml, ≤10.0μIU/mL and thyroxine (T4) is normal.

6. Malabsorption syndrome or other disorders that could affect intestinal absorption function, such as Crohn's disease, chronic pancreatitis, etc;

7. Hepatocirrhosis or severe liver disease (defined as ascites, hepatic encepalopathy, coagulation disorder, hypoalbuminemia, Esophagus and fundus gastricus varication, persistent jaundice), known diseases of biliary tract (excluding Gilbert syndrome and Asymptomatic gallstone);

8. Past or currently suffering from mandibular osteomyelitis or osteonecrosis, or any fracture within 6 months prior to first dosing; or suffering from acute tooth or mandibular disease that require tooth extracting, dental implanting or other invasive surgery; or had the above operation within 1-month before first dosing; or unhealing wound of oral surgery;

9. HBsAg positive, or anti-HCV antibody positive, or anti-HIV antibody positive, or anti-Syphilis antibody positive;

10. Prior malignancies (excluding the targeted breast cancer, basal cell carcinoma, or cervical cancer in situ) within 5 years (excluding completely resected Basal cell or squamous-cell carcinoma in situ, cervical carcinoma and Breast ductal carcinoma；

11. A variety of diseases that affect the ability of the subject to sign informed consent or follow the steps of the study; or suffer from various physical or mental illnesses that the investigators consider to affect the subject's successful completion of the study or may interfere with the interpretation of the findings;

12. Albumin-adjusted calcium≥2.0mmol/L, ≤2.9mmol/ L(Calcium supplements are not allowed within 8 hours before examination);

13. Subjects with fracture high risk and requiring treatment;

14. Has been selected for the study of other test devices or test drugs, or the duration of the clinical studies that have taken less than 30 days or 5 half-lives or biological effects, whichever is longer.

15. Other situations which are not suitable for participation judged by the principal investigator (PI).