Study to Evaluate Efficacy and Safety of Romosozumab Compared With Bisphosphonates in Children and Adolescents With Osteogenesis Imperfecta

Inclusion Criteria: Participant has provided informed consent/assent prior to initiation of any study specific activities/procedures. OR Participant's legally authorized representative has provided informed consent when the participant is legally too young to provide informed consent and the participant has provided written assent based on local regulations and/or guidelines prior to any study-specific activities/procedures being initiated. Ambulatory male and female children and adolescents, age 5 to <18 years, including ambulatory with assistance as defined in the pediatric osteogenesis imperfecta (OI) population. Clinical diagnosis of OI, defined as clinical history consistent with type I, III, or IV OI as determined by presence of expected phenotype (examples include: facial shape, voice, blue sclera, dentinogenesis imperfecta, typical radiographic features, fracture pattern) and lack of additional features unrelated to type I, III, or IV OI (eg, blindness, mental retardation, neuropathy, and craniosynostosis). o If familial, also must be autosomal dominant. Meets at least one of the following: 3 or more fractures within the previous 2 years, or 1 or more nonvertebral fracture(s) within the previous 2 years and at least 1 prevalent vertebral fracture, or 2 or more prevalent vertebral fractures. Lumbar spine Z-score of ≤-1.0. Exclusion Criteria: Disease Related History of an electrophoresis pattern inconsistent with type I, III or IV OI. History of known mutation in a gene other than collagen type I alpha 1/collagen type I alpha 2 (COL1A1/COL1A2) causing OI or other metabolic bone disease. History of congenital dislocation of the radial head, interosseous membrane calcification, or exuberant callus formation. Other Medical Conditions History of osteomalacia or rickets. Body weight less than 10 kg or greater than 90 kg. History of other bone diseases that affect bone metabolism (e.g., osteoporosis pseudoglioma syndrome, idiopathic juvenile osteoporosis, osteopetrosis, hypophosphatasia). History of Kawasaki disease, rheumatic myocarditis, ischemic cardiomyopathy, inherited cardiomyopathies, nephrotic syndrome, familial hypercholesterolemia, stroke, or any thromboembolic disorder. Evidence of untreated or unhealed oral infections. Unhealed or planned invasive dental or tooth procedure as determined by treating dentist; removal of baby teeth is acceptable and not considered an invasive dental procedure. Unhealed fracture as defined by orthopedic opinion. Osteotomy, rodding surgery or spinal fusion surgery within 5-months prior to screening, or not yet healed per orthopedic surgeon. History of clinically significant valvular heart disease previously documented with local echocardiogram results. Evidence of any of the following: Current hyper- or hypoparathyroidism (parathyroid hormone outside the normal range). Renal disease: Estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m^2 (calculated by the bedside Schwartz equation at screening) eGFR (mL/min/1.73 m^2) = 0.413 X (height/serum creatinine) 1. (Height is in centimeters, and serum creatinine is in mg/dL). Current hypocalcemia (albumin-adjusted serum calcium <lower limit of normal [LLN]) or hypercalcemia (albumin-adjusted serum calcium > upper limit of normal [ULN] of the laboratory's reference range). Serum vitamin D <20 ng/mL; rescreening for Vitamin D level < 20 ng/mL will be allowed, after adequate supplementation. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) > 1.5 x ULN. Total bilirubin (TBL) >1.5 x ULN (participants with Gilbert syndrome are eligible). Serum phosphorus < LLN for age. Symptoms associated with skull abnormalities such as basilar invagination, basilar impression or Chiari malformation (e.g., headache induced by coughing or straining for stool, visual disturbances, paresthesias or weakness). History of malabsorption (in children with serum albumin <LLN, malabsorption should be clinically ruled out by the investigator to confirm eligibility). History of long QT syndrome. History of malignancy. History of any solid organ or bone marrow transplant. History of hyper- or hypothyroidism, unless participant is on stable therapy > 6-months and has supporting laboratory documentation within 6-months prior to or at screening indicating normal serum thyroid-stimulating hormone (TSH) value. Known intolerance to calcium or vitamin D supplements. Prior/Concomitant Therapy Prior treatment with: Romosozumab or other anti-sclerostin antibody within 12-months prior to screening. Fluoride or strontium for bone disease. Parathyroid hormone (PTH) or PTH derivatives within 12-months prior to screening. Denosumab within 12-months after the last injection prior to first dose of romosozumab. Administration of any of the following treatments within 3-months prior to screening: Systemic glucocorticoids (≥ 5.0 mg prednisone equivalent/day for more than 10 days) within 3-months prior to screening. Topical and inhaled glucocorticoids will be allowed. Growth hormone (participants on stable dose of growth hormone for at least 3-months prior to screening will be allowed). Calcitonin. Other bone active drugs including anticonvulsants (except gabapentin and benzodiazepines) and heparin (unless low molecular weight heparin). Chronic systemic ketoconazole, androgens (except participants who have received testosterone therapy for physiologic replacement in the setting of documented hormonal deficiency), adrenocorticotropic hormone (ACTH), cinacalcet, aluminum, lithium, protease inhibitors, gonadotropin-releasing hormone agonists. Prior/Concurrent Clinical Study Experience - Currently receiving treatment in another investigational device or drug study, or less than 2 years since ending treatment on another investigational device or drug study(ies). Other investigational procedures while participating in this study are excluded. Other Exclusions Positive blood screen for hepatitis B surface antigen (HbsAg), hepatitis B core antibody (HBcAb), or hepatitis C antibody (HepCAb), human immunodeficiency virus (HIV) -1 or -2 antibody. HIV testing to be performed if required by local health authorities, ethics boards, or based on investigator's judgement. Less than 2 evaluable vertebrae by dual-energy x-ray absorptiometry evaluation in the region of interest, L1-L4, as confirmed by the central imaging laboratory. Any planned major surgery, including skeletal surgery (eg, rodding surgery, spinal surgery) within the next 12-months from Day 1 that would interfere with study procedures or would require missing of any investigational product Female participants of childbearing potential unwilling to use protocol specified method of contraception during treatment and for an additional 3-months after the last dose of investigational product or non-investigational product. Female participants who are breastfeeding or who plan to breastfeed while on study through 3-months after the last dose of investigational product or non-investigational product. Female participants planning to become pregnant or donate eggs while on study through 3-months after the last dose of investigational product or non-investigational product. Female participants of childbearing potential with a positive pregnancy test assessed at Screening and/or Day 1 by a highly sensitive urine or serum pregnancy test. Male participants with a female partner of childbearing potential who are unwilling to practice sexual abstinence (refrain from heterosexual intercourse) or use contraception during treatment and for an additional 3-months after the last dose of investigational product or non-investigational product. Male participants unwilling to abstain from donating sperm during treatment and for an additional 3-months after the last dose of investigational product or non-investigational product. Participant has known sensitivity to any of the products to be administered during dosing. Participant likely to not be available to complete all protocol-required study visits or procedures, and/or to comply with all required study procedures (eg, Clinical Outcome Assessments) to the best of the participant and investigator's knowledge. History or evidence of any other clinically significant disorder, condition or disease (with the exception of those outlined above) that, in the opinion of the investigator or Amgen physician, if consulted, would pose a risk to participant safety or interfere with the study evaluation, procedures or completion