Osteogenesis Imperfecta Trial of AGA2115 for ADUlts With COL1A1 and/or COL1A2 GeNetic Variations (IDUN)

This study will determine the effect of treatment of AGA2115 in adults with Type I, III, or IV osteogenesis imperfecta versus placebo.

Inclusion Criteria: * Male or female adults (aged 18 to 75 years inclusive) with a clinical diagnosis of osteogenesis imperfecta Type I, III, or IV with documented genetic testing confirmation of genetic variations in the COL1A1 or COL1A2 genes * Capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in the protocol * BMD T-score of ≤ -1.0 at the lumbar spine, total hip, or femoral neck Exclusion Criteria: * Vitamin D deficiency * Concomitant uncontrolled diseases or conditions that could affect bone metabolism such as hypo-/hyperparathyroidism, hypo-/hyperthyroidism, abnormal thyroid function or thyroid disease, or other endocrine disorders * Current hyper- or hypocalcemia * History of rickets or osteomalacia or any skeletal condition (other than OI) leading to long-bone deformities and/or increased risk of fractures * Treatment with bisphosphonates within the past 6 months * Treatment with teriparatide, abaloparatide, strontium ranelate, or hormone replacement therapy within the past 12 months * Treatment with denosumab (or denosumab biosimilars) within the past 2 years * Treatment with anti-sclerostin antibody medications (romosozumab, setrusumab, blosozumab) at any time * History of myocardial infarction or stroke (or other cardiovascular associated event deemed significant) within the past 12 months * Malignancy within the last 5 years * Pregnant or breastfeeding women, or women planning to become pregnant during the study * Participation in any clinical study within the past 12 months during which the participant was administered any IP (participant must also agree not to enroll in any other clinical study concurrently in which IP is administered)