A Study to Evaluate the Efficacy, Pharmacodynamics, Safety, and Immunogenicity of FKS518 in Postmenopausal Women With Osteoporosis

Inclusion criteria

• Female ≥55 to ≤85 years of age, inclusive, at screening.
• Have a body mass index (BMI) ≥18 to ≤32 kg/m^2.
• Participant should have confirmed postmenopausal status, defined as age-related or early/premature amenorrhea ≥12 consecutive months and increased follicle-stimulating hormone (FSH) >40 mIU/mL at screening; or surgical menopause (bilateral oophorectomy with or without hysterectomy) ≥12 months prior to screening.
• Absolute bone mineral density (BMD) consistent with T-score ≤-2.5 and ≥-4.0 at the lumbar spine as measured by dual energy x-ray absorptiometry (DXA) as per central assessment.
• At least 2 vertebrae in the lumbar vertebrae 1 to lumbar vertebrae 4 (L1-L4) region and at least 1 hip joint are evaluable by DXA.
• Clinically acceptable physical examinations and laboratory tests and no history or evidence of any clinically significant concomitant medical disorder that, in the opinion of the Investigator, would pose a risk to participant safety or interfere with study evaluations or procedures.
• Written informed consent including accepting a separate Information Sheet containing important information about COVID-19 and its general risks for participants participating in the clinical trial.

Exclusion criteria

Disease-related

• History and/or presence of 1 severe or >2 moderate vertebral fractures or hip fracture confirmed by x-ray.
• Presence of active healing fracture at screening.
• History and/or presence of bone-related disorders, such as but not limited to Paget's disease, osteomalacia, hyperparathyroidism (or parathyroid disorders), or renal osteodystrophy.
• Osteonecrosis of the jaw (ONJ) or risk factors for ONJ such as invasive dental procedures (eg, tooth extraction, dental implants, or oral surgery in the past 6 months), poor oral hygiene, periodontal, and/or pre-existing dental disease as assessed by the Investigator.
• Evidence of hypocalcemia (albumin-adjusted serum calcium <2.13 mmol/L or <8.5 mg/dL) or hypercalcemia (albumin-adjusted serum calcium >2.6 mmol/L or >10.5 mg/dL) as assessed by the central laboratory at screening.
• Vitamin D deficiency (25-hydroxy vitamin D levels <12 ng/mL) as assessed by central laboratory at screening (retest is allowed once).
• Known intolerance to calcium or vitamin D supplements.

Other Medical Conditions

• Known or suspected clinically relevant drug hypersensitivity to any components of the study drug, comparable drugs, or to latex.
• Renal impairment: creatinine clearance <30 mL/min at screening or receiving dialysis.
• Medical evidence of current or history of primary or secondary immunodeficiency.
• Infection-related exclusions as further defined in the protocol.
• Major surgical procedure within 8 weeks prior to the screening or scheduled during the study.
• Current or history of any malignancy, or myeloproliferative, or lymphoproliferative disease within 5 years before screening.
• History of clinically significant drug or alcohol abuse within the last year prior to randomization.
• Prior denosumab (Prolia, Xgeva, or proposed denosumab biosimilar) exposure.
• Prior use of fluoride within the 5 years before inclusion in the study.
• Any current or prior use of strontium ranelate.
• Any current or prior use of intravenous bisphosphonates.
• Current or prior use of teriparatide and other parathormone (PTH) analogues within 12 months before screening.
• Current or prior use of systemic oral or transdermal estrogen or selective estrogen receptor modulators or tibolone within 6 months before screening.
• Current or prior use of calcitonin or cinacalcet within 3 months before screening or any cathepsin K inhibitor (eg, odanacatib) within 18 months before screening.
• Current or prior use of romosozumab or antisclerostin antibody.
• Current or prior use of other osteoporotic agents used for the prevention or treatment of osteoporosis.
• Current use within 3 months before screening of any medication with known influence on the skeletal system (eg, systemic corticosteroids, heparin, lithium, etc) with exceptions described in the protocol.
• Concomitant treatment with another biologic drug.
• Have received a COVID-19 vaccine within 4 weeks before randomization or COVID-19 vaccination is ongoing at the time of screening.