Comparative Efficacy and Safety Study of RGB-14-P and Prolia® in Women With Postmenopausal Osteoporosis

Inclusion Criteria: * Participant is an ambulatory postmenopausal woman, diagnosed with osteoporosis, able to walk, and not bedridden * Participant has an absolute BMD consistent with T score ≤ 2.5 and ≥ 4.0 at the lumbar spine as measured by dual-energy X-ray absorptiometry (DXA) during the Screening Period and at least 2 lumbar vertebrae (from L1 to L4) must be evaluable by DXA * Participant has body weight ≥ 50 and ≤ 90 kg at the Screening Period Participants must meet the following criteria to be enrolled in the Transition Period: \- Have been enrolled, received both doses of the test drug, and completed the scheduled Main Period (up to Week 52) of the RGB-14-101 study Exclusion Criteria: * Participant has a history and/or presence of a severe or more than two moderate vertebral fractures as determined by central reading of lateral spine X-ray during the Screening Period * Participant has a history and/or presence of hip fracture * Participant has a history and/or presence of atypical femur fracture * Participant presents with an active healing fracture * Participant has a bilateral hip replacement (unilateral is allowed if the other hip is evaluable with DXA) * Participant has a vitamin D deficiency * Participant has hypocalcaemia or hypercalcemia at the Screening Period * Participant has a history and/or presence of bone metastases, renal osteodystrophy, osteomyelitis, any metabolic, endocrine or traumatic bone disease * Participant has a current uncontrolled status of hypothyroidism or hyperthyroidism * Participant has a history (within 5 years prior to Screening) and/or current hypoparathyroidism or hyperparathyroidism * Participant has malignancy within 5 years before Screening * Participant has a history and/or presence of significant cardiac disease * Participant has a known intolerance or malabsorption of calcium or vitamin D supplements * Participant shows contraindications to denosumab therapy (e.g., hypocalcaemia), or calcium or vitamin D supplementation before starting test drug administration * Participant has a latex allergy * Participant has a history and/or presence of osteonecrosis of the jaw (ONJ) or risk factors for ONJ such as invasive dental procedures * Participant has history and/or presence of osteonecrosis of the external auditory canal * Participant requiring ongoing use of any osteoporosis treatment * Participant has previously received denosumab or biosimilar denosumab * Participant has weight or girth measurements which may preclude accurate DXA measurements * Participant has an active infection, including, but not limited to severe acute respiratory syndrome coronavirus-2, hepatis B, hepatitis C and human immunodeficiency virus infections during the Screening Period