A 24-month prospective, open-label, randomized, multicenter, multinational, non-inferiority pragmatic clinical trial evaluating zoledronate single or double infusion versus oral alendronate following denosumab

125 postmenopausal women treated with Dmab for 3 or more years who will reach osteopenia with denosumab will be randomized into three groups: i) zoledronate infusion (5mg) at 6 months after last Dmab dose (single Zol group) ii) zoledronate infusion (5mg) at 6 and 12 months after last Dmab dose (double Zol group) iii) alendronate 70mg orally weekly for 12 months (ALN group) All women will receive no further treatment during the 2nd year of the study.

Participating centers: ECTS affiliated bone centers

Endpoints: Primary: BMD changes at the lumbar spine at 12 months. Secondary: i) BMD changes at the lumbar spine at 24 months; ii) BMD changes at the non-dominant femoral neck and total hip at 12 and 24 months; iii) changes at levels of bone turnover markers throughout the study; iv) incident fractures: vertebral (clinical and morphometric identified on VFA scans) and non-vertebral; v) clinical parameters: height change, VAS for back pain, and use of analgesics

Inclusion Criteria:

• Postmenopausal women treated with denosumab for 3 or more years who will reach osteopenia

Exclusion Criteria:

• a bone disease other than postmenopausal osteoporosis
• use of medications other than bisphosphonates or SERMS affecting bone metabolism during the last 12 months before entering the study
• creatinine clearance <60 mL/min/1.73 m2
• liver failure
• any type of cancer
• uncontrolled endocrine diseases
• serum 25-hydroxy vitamin D (25-OHD) concentrations lower than 20 ng/mL (50 nmol/L)

postmenopausal women

Postmenopausal women treated with denosumab