Sequential Treatment With Romosozumab Followed by Denosumab vs. Zoledronic Acid for Gains in HIP BMD

Osteoporosis is associated with a high risk of fractures, disability, loss of independence, and excess mortality. Zoledronic acid is an established first-line treatment in Sweden, but many patients at high fracture risk remain at substantial residual fracture risk. Short-course treatment with romosozumab followed by denosumab produces large increases in bone mineral density, but has not been directly compared with zoledronic acid. STRONG-HIP is a multicentre, randomized, active-controlled phase 4 trial in 216 postmenopausal women aged 60 years or older with osteoporosis and high fracture risk. Participants are randomized 1:1 to receive romosozumab 210 mg monthly for 3 months followed by denosumab 60 mg every 6 months, or zoledronic acid 5 mg intravenously at baseline and Month 12. The primary objective is to determine whether the romosozumab-denosumab sequence produces a greater percentage increase in total hip bone mineral density from baseline to Month 24 than zoledronic acid. Secondary outcomes include total hip and lumbar spine BMD at earlier time points, vertebral and clinical fractures, bone turnover markers, safety, health-related quality of life, and health-economic outcomes. A mechanistic substudy will assess bone microarchitecture and estimated strength using HR-pQCT. Participants are followed for 24 months in the main study and may enter an optional extension with follow-up to Month 48 to assess the durability of treatment effects.

Inclusion Criteria: 1. The subject is a postmenopausal woman aged 60 years or older at screening. 2. The subject has provided written informed consent before any trial-specific procedure is performed. 3. The subject has osteoporosis at screening defined as a T-score of -2.5 or lower at the total hip or lumbar spine (L1-L4) on central reader confirmed bone densitometry by DXA. 4. The subject is at high fracture risk, defined by at least one of the following: a previous low-trauma fracture after age 50 years (excluding skull, face, fingers and toes); FRAX probability at or above the age-specific Swedish intervention threshold (using Nordic and Nordic borne calculations, as appropriate) in use at screening. 5. Corrected plasma calcium or ionized calcium is within the local reference range before randomization. 6. Serum 25-hydroxyvitamin D concentration ≥50 nmol/L before randomization. 7. Adequate renal function for zoledronic acid treatment, defined as creatinine clearance ≥35 mL/min calculated using the clinical trial center specified calculation procedure (e.g. the Cockcroft-Gault equation) before randomization. 8. The subject is able and willing, in the investigator's judgment, to comply with the trial procedures and attend scheduled visits. 9. For participants entering the extension, separate written extension consent is obtained before any extension-specific procedure is performed. Exclusion Criteria: 1. Severe osteoporosis, defined as total hip or lumbar spine T-score \< -3.5 and/or prevalent grade 2 or grade 3 vertebral fracture. 2. Previous myocardial infarction or stroke at any time before screening. 3. Transient ischemic attack, unstable angina, coronary or major peripheral revascularization within 12 months before screening, decompensated heart failure, uncontrolled clinically relevant arrhythmia, or any cardiovascular condition that in the investigator's judgment confers unacceptably high risk of a major adverse cardiovascular event during study participation. 4. Use of intravenous bisphosphonate therapy or teriparatide within 3 years before randomization. 5. Use of oral bisphosphonate or denosumab within 12 months before randomization. 6. Any previous use of romosozumab. 7. Use of systemic estrogen, selective estrogen receptor modulator within 3 months. 8. Use of oral glucocorticoids for more than 14 consecutive days during the 6 months before screening. 9. Known metabolic bone disease other than postmenopausal osteoporosis, including but not limited to Pagets disease, osteomalacia, untreated hyperparathyroidism, osteogenesis imperfecta, or active renal osteodystrophy. 10. Creatinine clearance below 35 mL/min, rapidly deteriorating renal function, or another renal condition that makes zoledronic acid unsafe. 11. Hypocalcaemia (ionized calcium \