The US Food and Drug Administration (FDA) has approved a new indication for Amgen's Xgeva (denosumab) for the treatment of hypercalcemia of malignancy (HCM) refractory to bisphosphonate therapy. Xgeva was approved and granted Orphan Drug Designation by the FDA, which is reserved for drugs that are intended for the treatment of rare diseases affecting fewer than 200,000 people in the US.

HCM is a serious complication in patients with advanced cancer, including those with hematologic malignancies, and indicates poor prognosis. The condition results from cancer-driven increases in bone resorption, and if untreated, can lead to renal failure, progressive mental impairment, coma and death.

"Our continued study of Xgeva reinforces Amgen's ongoing commitment to address the unmet needs of cancer patients," said Sean E. Harper, MD, executive vice president of Research and Development at Amgen. "This latest FDA approval for Xgeva provides an important new therapeutic option for patients with a rare condition that cannot be resolved with bisphosphonate therapy."

The approval of Xgeva is based on positive results from an open-label, single-arm study, which enrolled patients with advanced cancer and persistent hypercalcemia after recent bisphosphonate treatment. The primary endpoint was the proportion of patients with a response, defined as albumin-corrected serum calcium (CSC) <11.5 mg/dL (2.9 mmol/L; Common Terminology for Adverse Events [CTCAE] grade <1) within 10 days after the first dose of Xgeva. Secondary endpoints included the proportion of patients who experienced a complete response (defined as CSC <10.8 mg/dL [2.7 mmol/L]) by day 10, time to response and response duration (defined as the number of days from the first occurrence of CSC <11.5 mg/dL). The study achieved its primary endpoint with a response rate at day 10 of 63.6 per cent in the 33 patients evaluated. The overall complete response rate was 63.6 per cent. The estimated median time to response (CSC <11.5 mg/dL) was nine days, and the median duration of response was 104 days.

The most common adverse reactions in patients receiving Xgeva for hypercalcemia of malignancy were nausea, dyspnea, decreased appetite, headache, peripheral edema, vomiting, anemia, constipation and diarrhoea.

For patients with HCM, Xgeva is administered as a subcutaneous injection (120 mg) every four weeks with additional doses of 120 mg on days eight and 15 of the first month of therapy.

Xgeva binds to RANK Ligand (RANKL), a protein essential for the formation, function and survival of osteoclasts, the cells responsible for bone resorption, thereby modulating calcium release from bone. Xgeva prevents RANKL from activating its receptor, RANK, on the surface of osteoclasts, thereby decreasing bone destruction and calcium release.

Hypercalcemia of malignancy (HCM) is a serious complication in patients with advanced cancer, including those with hematological malignancies.1 In 2012, the estimated prevalence of HCM in cancer patients in the US was 2.7 per cent. HCM is indicative of poor prognosis and occurs most often in patients with squamous cell cancer (e.g., lung cancer, head and neck cancer), breast cancer, kidney cancer, myeloma and lymphoma. HCM results from cancer-driven increases in bone resorption, and, if untreated, can lead to renal failure, progressive mental impairment, coma and death.

Xgeva was approved by the FDA for the prevention of skeletal-related events (SREs) in patients with bone metastases from solid tumors in 2010. Xgeva is not indicated for the prevention of SREs in patients with multiple myeloma. In clinical trials, Xgeva demonstrated a clinically meaningful improvement compared to the previous standard of care in preventing SREs. In 2013, Xgeva was approved by the FDA as the first-and-only treatment for adults and skeletally mature adolescents with giant cell tumour of bone that is unresectable or where surgical resection is likely to result in severe morbidity.

Pre-existing hypocalcemia must be corrected prior to initiating therapy with Xgeva. Xgeva can cause severe symptomatic hypocalcemia, and fatal cases have been reported. Monitor calcium levels and administer calcium, magnesium, and vitamin D as necessary. Monitor levels more frequently when Xgeva is administered with other drugs that can also lower calcium levels. Advise patients to contact a healthcare professional for symptoms of hypocalcemia.

Xgeva is contraindicated in patients with known clinically significant hypersensitivity to Xgeva, including anaphylaxis that has been reported with use of Xgeva. If an anaphylactic or other clinically significant allergic reaction occurs, initiate appropriate therapy and discontinue Xgeva therapy permanently.

Osteonecrosis of the jaw (ONJ) can occur in patients receiving Xgeva. Patients who are suspected of having or who develop ONJ while on Xgeva should receive care by a dentist or an oral surgeon. In these patients, extensive dental surgery to treat ONJ may exacerbate the condition.  In clinical trials in patients with osseous metastasis, the incidence of ONJ was higher with longer duration of exposure.

Atypical femoral fracture has been reported with Xgeva. These fractures can occur anywhere in the femoral shaft from just below the lesser trochanter to above the supracondylar flare and are transverse or short oblique in orientation without evidence of comminution.

Atypical femoral fractures most commonly occur with minimal or no trauma to the affected area. During Xgeva treatment, patients should be advised to report new or unusual thigh, hip, or groin pain. Patient presenting with an atypical femur fracture should also be assessed for symptoms and signs of fracture in the contralateral limb. Interruption of Xgeva therapy should be considered, pending a risk/benefit assessment, on an individual basis.

Xgeva can cause fetal harm when administered to a pregnant woman. Advise females of reproductive potential to use highly effective contraception during therapy, and for at least five months after the last dose of Xgeva.  

The most common adverse reactions in patients receiving Xgeva with bone metastasis from solid tumors were fatigue/asthenia, hypophosphatemia, and nausea. The most common serious adverse reaction was dyspnea.

The most common adverse reactions in patients receiving Xgeva for giant cell tumor of bone were arthralgia, headache, nausea, back pain, fatigue, and pain in extremity. The most common serious adverse reactions were osteonecrosis of the jaw and osteomyelitis. The most common adverse reactions resulting in discontinuation of Xgeva were osteonecrosis of the jaw and tooth abscess or tooth infection.

The most common adverse reactions in patients receiving Xgeva for hypercalcemia of malignancy were nausea, dyspnea, decreased appetite, headache, peripheral edema, vomiting, anaemia, constipation, and diarrhoea. Denosumab is also marketed as Prolia in other indications.