XBORSO

What it is

XBORSO is a biosimilar medicine to Prolia containing denosumab . Each 1 mL single-use pre-filled syringe contains 60 mg denosumab . Denosumab is a human monoclonal IgG2 antibody with high affinity and specificity for RANK ligand (RANKL) . Denosumab has an approximate molecular weight of 145 kDa and is produced in genetically engineered mammalian (Chinese Hamster Ovary, CHO) cells .

Approved indications

— The treatment of osteoporosis in postmenopausal women, in which XBORSO significantly reduces the risk of vertebral, non-vertebral and hip fractures . — Treatment to increase bone mass in men with osteopaenia receiving androgen deprivation therapy for non-metastatic prostate cancer . — Treatment to increase bone mass in men with osteoporosis at increased risk of fracture . — Treatment to increase bone mass in women and men at increased risk of fracture due to long-term systemic glucocorticoid therapy .

Dosing overview

The recommended dose of XBORSO is a single subcutaneous injection of 60 mg, once every 6 months . To reduce the risk of hypocalcaemia, patients must be adequately supplemented with calcium and vitamin D; in the major clinical trials of denosumab, daily supplementation with 1,000 mg of calcium and at least 400 IU vitamin D was recommended .

Key safety warnings

Hypocalcaemia must be corrected prior to initiating therapy with XBORSO. In the post-marketing setting, severe symptomatic hypocalcaemia (resulting in hospitalisation, life-threatening events and fatal cases) has been reported, particularly in patients with severe renal impairment, receiving dialysis or treatment with other calcium lowering drugs . Clinical monitoring of calcium levels is recommended before each dose . Patients receiving XBORSO may develop skin infections (predominantly cellulitis) leading to hospitalisation, and patients should be advised to seek prompt medical attention if they develop signs or symptoms of cellulitis . Osteonecrosis of the jaw (ONJ) has been reported in patients treated with denosumab or bisphosphonates. Most cases have been in cancer patients; however some have occurred in patients with osteoporosis. ONJ has been reported rarely in clinical studies in patients receiving denosumab at a dose of 60 mg every 6 months for osteoporosis . It is important to evaluate patients for risk factors for ONJ before starting treatment. If risk factors are identified, a dental examination with appropriate preventive dentistry is recommended prior to treatment with XBORSO . Atypical femoral fractures have been reported in patients receiving denosumab. Atypical femoral fractures may occur with little or no trauma in the subtrochanteric and diaphyseal regions of the femur and may be bilateral . During XBORSO treatment, patients should be advised to report new or unusual thigh, hip, or groin pain . Multiple vertebral fractures (MVF) may occur following discontinuation of treatment with XBORSO, particularly in patients with a history of vertebral fracture. New vertebral fractures occurred as early as 7 months after the last dose of denosumab . If XBORSO treatment is discontinued, consideration should be given to transitioning to an alternative antiresorptive therapy .

Contraindications

Hypocalcaemia . Hypersensitivity to the active substance, to CHO-derived proteins or to any of the excipients . Pregnancy and in women trying to get pregnant .

Regulatory history

XBORSO received approval on 2025-06-13 . XBORSO was approved by the TGA as a biosimilar medicine to Xgeva. The approval was based on demonstrated comparability across quality, nonclinical, and clinical aspects, supporting its use for the specified indications . XBORSO denosumab 120mg/1.7mL solution for injection vial was first listed on the ARTG on 2025-07-09 .