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 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