WYOST

What it is

WYOST is a biosimilar medicine to Xgeva, containing denosumab . Denosumab is a human IgG2 monoclonal antibody with high affinity and specificity for RANK ligand (RANKL) . Each vial contains a deliverable dose of 120 mg denosumab in 1.7 mL of solution (70 mg/mL) . WYOST is supplied as a sterile, preservative-free, clear, colourless to slightly yellowish or slightly brownish solution for injection at pH approximately 5.2 .

Approved indications

— Prevention of skeletal related events in patients with multiple myeloma and in patients with bone metastases from solid tumours . — Treatment of giant cell tumour of bone in adults or skeletally mature adolescents that is recurrent, or unresectable, or resectable but associated with severe morbidity . — Treatment of hypercalcaemia of malignancy that is refractory to intravenous bisphosphonate .

Dosing overview

For prevention of skeletal related events, the recommended dose is 120 mg administered as a single subcutaneous injection once every 4 weeks into the thigh, abdomen or upper arm . For treatment of giant cell tumour of bone and hypercalcaemia of malignancy, the recommended dose is 120 mg administered as a single subcutaneous injection once every 4 weeks into the thigh, abdomen or upper arm with a loading dose of 120 mg on days 8 and 15 of the initial 4-week treatment period . Daily supplementation with at least 500 mg calcium and 400 IU vitamin D is required in all patients, unless hypercalcaemia is present .

Key safety warnings

Pre-existing hypocalcaemia must be corrected prior to initiating therapy with denosumab . Hypocalcaemia can occur at any time during therapy with denosumab, and monitoring of calcium levels should be conducted prior to the initial dose, within two weeks after the initial dose, and if suspected symptoms of hypocalcaemia occur . In the post-marketing setting, severe symptomatic hypocalcaemia including fatal cases has been reported, with most cases occurring in the first weeks of initiating therapy, but can occur later . Osteonecrosis of the jaw has occurred in patients treated with denosumab, with the majority of cases occurring within 5 months after the last dose . An oral examination should be performed by the prescriber prior to initiation of WYOST treatment and a dental examination with appropriate preventive dentistry is recommended prior to treatment, especially in patients with risk factors for osteonecrosis of the jaw . Patients should avoid invasive dental procedures during treatment with WYOST . Atypical femoral fracture has been reported with denosumab, and these fractures may occur with little or no trauma in the subtrochanteric and diaphyseal regions of the femur and may be bilateral . During treatment, patients should be advised to report new or unusual thigh, hip, or groin pain . Clinically significant hypercalcaemia requiring hospitalisation and complicated by acute renal injury has been reported in denosumab-treated patients with giant cell tumour of bone and patients with growing skeletons weeks to months following treatment discontinuation . Multiple vertebral fractures, not due to bone metastases, may occur following discontinuation of treatment with WYOST, particularly in patients with risk factors such as osteoporosis or prior fractures .

Contraindications

Pregnancy is a contraindication . Hypersensitivity to the active substance, to CHO-derived proteins or to any of the excipients is a contraindication . Severe untreated hypocalcaemia is a contraindication . Unhealed lesions from dental or oral surgery are a contraindication .

PBS listing

WYOST 120 mg in 1.7 mL is listed on the PBS as 2 items with streamlined restriction at an ex-manufacturer price of A$296.93 .

Regulatory history

WYOST denosumab 70 mg/mL (120 mg/1.7 mL) solution for injection vial was first listed on the ARTG on 23 August 2024 . The AusPAR approval date was 7 August 2024 .