Study of TST002 Injection in Postmenopausal Women With Osteoporosis or Low Bone Mass

Inclusion Criteria: 1. Voluntary signed informed consent; able to walk freely; willing/able to complete all study procedures. 2. BMI 18.0-30.0 kg/m² (inclusive); body weight ≥45 kg. 3. Postmenopausal women aged 45-80 years (inclusive) at screening, postmenopausal ≥2 years (≥12 consecutive months without spontaneous vaginal bleeding/spotting). 4. BMD T-score \<-2.00 at lumbar spine (L1-L4 total), total hip, or femoral neck at screening; OR history of fragility fracture with T-score \<-1.00 at one of these sites (central imaging read). 5. At least 2 contiguous evaluable vertebrae (L1-L4) and at least one evaluable hip for DXA assessment. 6. No disease, per investigator history/exam/workup, likely to significantly affect the study or increase health risk (documented exceptions permitted with justification). Exclusion Criteria: 1. BMD T-score ≤-3.50 at lumbar spine, total hip, or femoral neck at screening. 2. Prior hip fracture. 3. ≥2 vertebral fractures on screening lateral spine X-ray (investigator-assessed). 4. Known skeletal, endocrine, or rheumatic disease that could confound results (e.g., Paget's disease, osteomalacia, osteopetrosis, osteogenesis imperfecta, sclerosteosis, rheumatoid arthritis, ankylosing spondylitis, Cushing's disease, hyperprolactinemia, uncontrolled thyroid disease, hyper-/hypoparathyroidism, or CN VIII compression hearing loss). 5. Prior osteoporosis therapy (incl. trial participation) within protocol-specified washout windows (IV bisphosphonates, oral bisphosphonates, denosumab/cathepsin K inhibitors, tibolone/cinacalcet/calcitonin, teriparatide/PTH analogs, systemic estrogen/SERMs, strontium ranelate/fluoride, hormonal castration therapy, systemic glucocorticoids ≥5 mg/day prednisone-equivalent for \>14 days) - see protocol for exact windows per agent. 6. History of TMJ disorder, TMJ osteonecrosis, or atypical fracture. 7. Hypercalcemia or hypocalcemia (albumin-corrected) at screening. 8. Serum 25(OH)D \<20 ng/mL at screening. 9. History of MI, or serious cardiac disease (CAD, NYHA class II-IV heart failure) within 6 months before screening. 10. History of stroke (cerebral infarction, ischemic or hemorrhagic). 11. ALT/AST \>3× ULN; ALP \>2.5× ULN; total bilirubin or creatinine \>1.5× ULN at screening. 12. Multiple myeloma, primary/metastatic bone malignancy, or history of skeletal radiotherapy. 13. Malignancy within 5 years before screening (except cured skin squamous/basal cell carcinoma or documented cured in situ cervical cancer, no recurrence ≥3 months before dosing). 14. Known hypersensitivity to study drug. 15. History of solid organ or bone marrow transplant. 16. Positive HIV, syphilis, HCV antibody, or HBsAg at screening; or HBcAb-positive with detectable HBV DNA. 17. Active tuberculosis within 6 months before screening. 18. Participation in another clinical trial within 30 days or 5 half-lives of the investigational product (whichever longer) before screening. 19. Any other condition the investigator judges unsuitable for participation, a safety risk, or interfering with study assessments/completion.