6 ADVERSE REACTIONS The following adverse reactions are discussed below and elsewhere in the labeling: Hypocalcemia [s ee Warnings and Precautions ( 5.3 )] Osteonecrosis of the Jaw [see Warnings and Precautions ( 5.4 )] Hypercalcemia following treatment discontinuation in patients with growing skeletons [see Warnings and Precautions ( 5.6 )] The most common adverse reactions in patients (per-patient incidence greater than or equal to 25%) were fatigue/asthenia, hypophosphatemia, and nausea (see Table 1). The most common serious adverse reaction was dyspnea. The most common adverse reactions resulting in discontinuation of Xgeva were osteonecrosis and hypocalcemia. Bone Metastasis from Solid Tumors: Most common adverse reactions (per-patient incidence greater than or equal to 25%) were fatigue/asthenia, hypophosphatemia, and nausea (6.1) Giant Cell Tumor of Bone: Most common adverse reactions (per-patient incidence greater than or equal to 10%) were arthralgia, headache, nausea, back pain, fatigue, and pain in extremity (6.1) Hypercalcemia of Malignancy: Adverse reactions in greater than 20% of patients were nausea, dyspnea, decreased appetite, headache, peripheral edema, vomiting, anemia, constipation, and diarrhea (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Amgen Inc. at 1-800-77-AMGEN (1-800-772-6436) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Bone Metastasis from Solid Tumors The safety of Xgeva was evaluated in three randomized, double-blind, double-dummy trials [see Clinical Trials ( 14.1 )] in which a total of 2841 patients with bone metastasis from prostate cancer, breast cancer, or other solid tumors, or lytic bony lesions from multiple myeloma received at least one dose of Xgeva. In Trials 1, 2, and 3, patients were randomized to receive either 120 mg of Xgeva every 4 weeks as a subcutaneous injection or 4 mg (dose adjusted for reduced renal function) of zoledronic acid every 4 weeks by intravenous (IV) infusion. Entry criteria included serum calcium (corrected) from 8 to 11.5 mg/dL (2 to 2.9 mmol/L) and creatinine clearance 30 mL/min or greater. Patients who had received IV bisphosphonates were excluded, as were patients with prior history of ONJ or osteomyelitis of the jaw, an active dental or jaw condition requiring oral surgery, non-healed dental/oral surgery, or any planned invasive dental procedure. During the study, serum chemistries including calcium and phosphorus were monitored every 4 weeks. Calcium and vitamin D supplementation was recommended but not required. The median duration of exposure to Xgeva was 12 months (range: 0.1 - 41) and median duration on-study was 13 months (range: 0.1 - 41). Of patients who received Xgeva, 46% were female. Eighty-five percent were White, 5% Hispanic/Latino, 6% Asian, and 3% Black. The median age was 63 years (range: 18 - 93). Seventy-five percent of patients who received Xgeva received concomitant chemotherapy. Table 1. Per-patient Incidence of Selecteda Adverse Reactions of Any Severity (Trials 1, 2, and 3) Body System Xgeva n = 2841 % Zoledronic Acid n = 2836 % GASTROINTESTINAL Nausea 31 32 Diarrhea 20 19 GENERAL Fatigue/Asthenia 45 46 INVESTIGATIONS Hypocalcemiab 18 9 Hypophosphatemiab 32 20 NEUROLOGICAL Headache 13 14 RESPIRATORY Dyspnea 21 18 Cough 15 15 a Adverse reactions reported in at least 10% of patients receiving Xgeva in Trials 1, 2, and 3, and meeting one of the following criteria: At least 1% greater incidence in Xgeva-treated patients, or Between-group difference (either direction) of less than 1% and more than 5% greater incidence in patients treated with zoledronic acid compared to placebo (US Prescribing Information for zoledronic acid) b Laboratory-derived and below the central laboratory lower limit of normal [8.3 - 8.5 mg/dL (2.075 - 2.125 mmol/L) for calcium and 2.2 - 2.8 mg/dL (0.71 - 0.9 mmol/L) for phosphorus] Severe Mineral/Electrolyte Abnormalities Severe hypocalcemia (corrected serum calcium less than 7 mg/dL or less than 1.75 mmol/L) occurred in 3.1% of patients treated with Xgeva and 1.3% of patients treated with zoledronic acid. Of patients who experienced severe hypocalcemia, 33% experienced 2 or more episodes of severe hypocalcemia and 16% experienced 3 or more episodes [see Warnings and Precautions ( 5.3 ) and Use in Specific Populations ( 8.6 )]. Severe hypophosphatemia (serum phosphorus less than 2 mg/dL or less than 0.6 mmol/L) occurred in 15.4% of patients treated with Xgeva and 7.4% of patients treated with zoledronic acid. Osteonecrosis of the Jaw (ONJ) In the primary treatment phases of Trials 1, 2, and 3, ONJ was confirmed in 1.8% of patients in the Xgeva group (median exposure of 12.0 months; range 0.1-40.5) and 1.3% of patients in the zoledronic acid group. The trials in patients with breast (Trial 1) or prostate (Trial 3) cancer included an Xgeva open label extension treatment phase where patients were offered Xgeva 120 mg once every 4 weeks (median overall exposure of 14.9 months; range 0.1-67.2). The patient-year adjusted incidence of confirmed ONJ was 1.1% during the first year of treatment, 3.7% in the second year, and 4.6% per year thereafter. The median time to ONJ was 20.6 months (range: 4-53) [see Warnings and Precautions ( 5.4 )]. In a placebo-controlled clinical trial with an extension treatment phase evaluating Xgeva for the prevention of bone metastases in patients with non-metastatic prostate cancer (a patient population for which Xgeva is not indicated), with longer treatment exposure of up to 7 years, the patient-year adjusted incidence of confirmed ONJ was 1.1% during the first year of treatment, 3.0% in the second year, and 7.1% per year thereafter. Atypical Subtrochanteric and Diaphyseal Fracture Atypical femoral fracture has been reported with Xgeva [see Warnings and Precautions ( 5.5 )] . Giant Cell Tumor of Bone The safety of Xgeva was evaluated in two single arm trials (Trials 4 and 5) [see Clinical Trials ( 14.2 )] in which a total of 304 adult or skeletally mature adolescent patients with giant cell tumor of bone received at least 1 dose of Xgeva. Patients received 120 mg Xgeva subcutaneously every 4 weeks with additional 120 mg doses on Days 8 and 15 of the first month of therapy. Patients receiving concurrent bisphosphonate therapy were excluded from enrollment in both studies. Patients with prior history of ONJ or osteomyelitis of the jaw, an active dental or jaw condition requiring oral surgery, non-healed dental/oral surgery, or any planned invasive dental procedure were excluded from enrollment in Trial 5. During the trial, serum chemistries including calcium and phosphorus were monitored every 4 weeks. Calcium and vitamin D supplementation was recommended but not required. Of the 304 patients who received Xgeva, 145 patients were treated with Xgeva for ≥ 1 year, 44 patients for ≥ 2 years, and 15 patients for ≥ 3 years. The median number of doses received was 14 (range: 1 to 60 doses) and the median number of months on study was 11 (range: 0 to 54 months). Fifty-eight percent of the enrolled patients were women and 80% were White. The median age was 33 years (range: 13 to 83 years); a total of 10 patients were skeletally mature adolescents (13 to 17 years of age). The adverse reaction profile of Xgeva in patients with giant cell tumor of bone was similar to that reported in Trials 1, 2, and 3. The most common adverse reactions in patients (per-patient incidence ≥ 10%) were arthralgia, headache, nausea, back pain, fatigue, and pain in extremity. The most common serious adverse reactions were osteonecrosis of the jaw and osteomyelitis (per-patient incidence of 0.7%). The most common adverse reactions resulting in discontinuation of Xgeva were osteonecrosis of the jaw (per-patient incidence of 0.7%), and tooth abscess or tooth infection (per-patient incidence of 0.7%). The adverse reaction profile appeared similar in skeletally mature adolescents and adults. Hypocalcemia and Hypophosphatemia Moderate hypocalcemia (corrected serum calcium less than 8 to 7 mg/dL or less than 2 to 1.75 mmol/L) occurred in 2.6% of patients treated with Xgeva. Severe hypophosphatemia (serum phosphorus less than 2 to 1 mg/dL or less than 0.6 to 0.3 mmol/L) occurred in 29 patients (9.5%). Osteonecrosis of the Jaw (ONJ) In Trials 4 and 5, ONJ was confirmed in 4 of 304 (1.3%) patients who received Xgeva. The median time to ONJ was 16 months (range: 13 to 20 months) [see Warnings and Prec autions ( 5.4 )]. Hypercalcemia of Malignancy Xgeva was evaluated in an open-label, single-arm trial (Trial 6) in which 33 patients with hypercalcemia of malignancy (with or without bone metastases) refractory to treatment with intravenous bisphosphonate therapy were enrolled [see Clinical Trials ( 14.3 )]. The adverse reaction profile of Xgeva in patients with hypercalcemia of malignancy was similar to that reported in Trials 1, 2, 3, 4, and 5. Adverse reactions occurring in greater than 20% of patients were nausea (30%), dyspnea (27%), decreased appetite (24%), headache (24%), peripheral edema (24%), vomiting (24%), anemia (21%), constipation (21%), and diarrhea (21%). The following adverse reactions of Grade 3 or greater severity related to study therapy were reported on study: fatigue (3%) and infection (6%). Grade 3 laboratory abnormalities included hypomagnesemia (3%), hypokalemia (3%), and hypophosphatemia (76%) of patients. No deaths on study were related to Xgeva therapy. 6.2 Postmarketing Experience The following adverse reactions have been identified during postapproval use of Xgeva. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Hypocalcemia: Severe symptomatic hypocalcemia, including fatal cases [see Contraindications ( 4.1 ) and Warnings and Precautions ( 5.3 )]. Hypersensitivity, including anaphylactic reactions [see Contraindications ( 4.2 ) and Warnings and Precautions ( 5.2 )]. Musculoskeletal pain, including severe musculoskeletal pain. Positive rechallenge has been reported. 6. 3 Immunogenicity As with all therapeutic proteins, there is potential for immunogenicity. Using an electrochemiluminescent bridging immunoassay, less than 1% (7/2758) of patients with osseous metastases treated with denosumab doses ranging from 30-180 mg every 4 weeks or every 12 weeks for up to 3 years and none of the 304 patients with giant cell tumor of bone in Trials 4 and 5 tested positive for binding antibodies. No patient with positive binding antibodies tested positive for neutralizing antibodies as assessed using a chemiluminescent cell-based in vitro biological assay. There was no evidence of altered pharmacokinetic profile, toxicity profile, or clinical response associated with binding antibody development. The incidence of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of a positive antibody (including neutralizing antibody) test result may be influenced by several factors, including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of antibodies to denosumab with the incidence of antibodies to other products may be misleading.