Radium Ra 223 Dichloride

Xofigo is indicated for the treatment of patients with castration-resistant prostate cancer, symptomatic bone metastases and no known visceral metastatic disease. Xofigo is an alpha particle-emitting radioactive therapeutic agent indicated for the treatment of patients with castration-resistant prostate cancer, symptomatic bone metastases and no known visceral metastatic disease. ( 1 )

Xofigo (radium Ra 223 dichloride injection) is available in single-dose vials containing 6 mL of clear, colorless solution at a concentration of 1,100 kBq/mL (30 microcurie/mL) at the reference date with a total radioactivity of 6,600 kBq/vial (178 microcurie/vial) at the reference date. Single-dose vial at a concentration of 1,100 kBq/mL (30 microcurie/mL) at the reference date with a total radioactivity of 6,600 kBq/vial (178 microcurie/vial) at the reference date. ( 3 )

None. None.

• Bone Marrow Suppression: Measure blood counts prior to treatment initiation and before every dose of Xofigo. Discontinue Xofigo if hematologic values do not recover within 6 to 8 weeks after treatment. Monitor patients with compromised bone marrow reserve closely. Discontinue Xofigo in patients who experience life-threatening complications despite supportive care measures. ( 5.1 )
• Increased Fractures and Mortality in Combination with Abiraterone plus Prednisone/Prednisolone: Xofigo is not recommended in combination with abiraterone acetate plus prednisone/prednisolone. ( 5.2 )
• Embryo-Fetal Toxicity: Xofigo can cause fetal harm. Advise males with female partners of reproductive potential to use effective contraception. ( 5.3 , 8.1 , 8.3 )

5.1 Bone Marrow Suppression In the randomized trial, 2% of patients on the Xofigo arm experienced bone marrow failure or ongoing pancytopenia compared to no patients treated with placebo. There were two deaths due to bone marrow failure and for 7 of 13 patients treated with Xofigo, bone marrow failure was ongoing at the time of death. Among the 13 patients who experienced bone marrow failure, 54% required blood transfusions. Four percent (4%) of patients on the Xofigo arm and 2% on the placebo arm permanently discontinued therapy due to bone marrow suppression. In the randomized trial, deaths related to vascular hemorrhage in association with myelosuppression were observed in 1% of Xofigo-treated patients compared to 0.3% of patients treated with placebo. The incidence of infection-related deaths (2%), serious infections (10%), and febrile neutropenia (<1%) were similar for patients treated with Xofigo and placebo. Myelosuppression; notably thrombocytopenia, neutropenia, pancytopenia, and leukopenia; has been reported in patients treated with Xofigo. In the randomized trial, complete blood counts (CBCs) were obtained every 4 weeks prior to each dose and the nadir CBCs and times of recovery were not well characterized. In a separate single-dose phase 1 study of Xofigo, neutrophil and platelet count nadirs occurred 2 to 3 weeks after Xofigo administration at doses that were up to 1 to 5 times the recommended dose, and most patients recovered approximately 6 to 8 weeks after administration [see Adverse Reactions ( 6 )] . Hematologic evaluation of patients must be performed at baseline and prior to every dose of Xofigo. Before the first administration of Xofigo, the absolute neutrophil count (ANC) should be ≥ 1.5 x 10 9 /L, the platelet count ≥ 100 x 10 9 /L and hemoglobin ≥ 10 g/dL. Before subsequent administrations of Xofigo, the ANC should be ≥ 1 x 10 9 /L and the platelet count ≥ 50 x 10 9 /L. If there is no recovery to these values within 6 to 8 weeks after the last administration of Xofigo, despite receiving supportive care, further treatment with Xofigo should be discontinued. Patients with evidence of compromised bone marrow reserve should be monitored closely and provided with supportive care measures when clinically indicated. Discontinue Xofigo in patients who experience life-threatening complications despite supportive care for bone marrow failure. The safety and efficacy of concomitant chemotherapy with Xofigo have not been established. Outside of a clinical trial, concomitant use with chemotherapy is not recommended due to the potential for additive myelosuppression. If chemotherapy, other systemic radioisotopes or hemibody external radiotherapy are administered during the treatment period, Xofigo should be discontinued.

5.2 Increased Fractures and Mortality in Combination with Abiraterone plus Prednisone/Prednisolone Xofigo is not recommended for use in combination with abiraterone acetate plus prednisone/prednisolone outside of clinical trials. The clinical efficacy and safety of concurrent initiation of Xofigo treatment and abiraterone acetate plus prednisone/prednisolone treatment was assessed in a randomized, placebo-controlled multicenter phase 3 study (ERA-223 trial) in 806 patients with asymptomatic or mildly symptomatic castration resistant prostate cancer with bone metastases. The study was unblinded early based on an Independent Data Monitoring Committee recommendation. At the primary analysis, an increased incidence of fractures (28.6% vs 11.4%) and deaths (38.5% vs 35.5%) have been observed in patients who received Xofigo in combination with abiraterone acetate plus prednisone/prednisolone compared to patients who received placebo in combination with abiraterone acetate plus prednisone/prednisolone. Safety and efficacy with the combination of Xofigo and agents other than gonadotropin-releasing hormone analogues have not been established. -167640120650005.3 Embryo-Fetal Toxicity The safety and efficacy of Xofigo have not been established in females. Based on its mechanism of action, Xofigo can cause fetal harm when administered to a pregnant female. Advise pregnant females and females of reproductive potential of the potential risk to a fetus. Advise male patients to use condoms and their female partners of reproductive potential to use effective contraception during and for 6 months after completing treatment with Xofigo [see Use in Specific Populations ( 8.1 , 8.3 ) and Clinical Pharmacology ( 12.1 )].

The following serious adverse reactions are discussed in greater detail in another section of the label:

• Bone Marrow Suppression [see Warnings and Precautions ( 5.1 )] The most common adverse drug reactions (≥ 10%) in patients receiving Xofigo were nausea, diarrhea, vomiting, and peripheral edema. The most common hematologic laboratory abnormalities (≥ 10%) were anemia, lymphocytopenia, leukopenia, thrombocytopenia, and neutropenia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Bayer HealthCare Pharmaceuticals Inc. at 1-888-842-2937 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. In the randomized clinical trial in patients with metastatic castration-resistant prostate cancer with bone metastases, 600 patients received intravenous injections of 55 kBq/kg (1.49 microcurie/kg) of Xofigo and best standard of care and 301 patients received placebo and best standard of care once every 4 weeks for up to 6 injections. Prior to randomization, 58% and 57% of patients had received docetaxel in the Xofigo and placebo arms, respectively. The median duration of treatment was 20 weeks (6 cycles) for Xofigo and 18 weeks (5 cycles) for placebo. The most common adverse reactions (≥ 10%) in patients receiving Xofigo were nausea, diarrhea, vomiting, and peripheral edema (Table 3). Grade 3 and 4 adverse events were reported among 57% of Xofigo-treated patients and 63% of placebo-treated patients. The most common hematologic laboratory abnormalities in Xofigo-treated patients (≥ 10%) were anemia, lymphocytopenia, leukopenia, thrombocytopenia, and neutropenia (Table 4). Treatment discontinuations due to adverse events occurred in 17% of patients who received Xofigo and 21% of patients who received placebo. The most common hematologic laboratory abnormalities leading to discontinuation for Xofigo were anemia (2%) and thrombocytopenia (2%). Table 3 shows adverse reactions occurring in ≥ 2% of patients and for which the incidence for Xofigo exceeds the incidence for placebo. Table 3: Adverse Reactions in the Randomized Trial System/Organ Class Preferred Term Xofigo (n=600) Placebo (n=301) Grades 1-4 % Grades 3-4 % Grades 1-4 % Grades 3-4 % Blood and lymphatic system disorders Pancytopenia 2 1 0 0 Gastrointestinal disorders Nausea 36 2 35 2 Diarrhea 25 2 15 2 Vomiting 19 2 14 2 General disorders and administration site conditions Peripheral edema 13 2 10 1 Renal and urinary disorders Renal failure and impairment 3 1 1 1 Laboratory Abnormalities Table 4 shows hematologic laboratory abnormalities occurring in > 10% of patients and for which the incidence for Xofigo exceeds the incidence for placebo. Table 4: Hematologic Laboratory Abnormalities Hematologic Laboratory Abnormalities Xofigo (n=600) Placebo (n=301) Grades 1-4 % Grades 3-4 % Grades 1-4 % Grades 3-4 % Anemia 93 6 88 6 Lymphocytopenia 72 20 53 7 Leukopenia 35 3 10 <1 Thrombocytopenia 31 3 22 <1 Neutropenia 18 2 5 <1 Laboratory values were obtained at baseline and prior to each 4-week cycle. As an adverse reaction, grade 3-4 thrombocytopenia was reported in 6% of patients on Xofigo and in 2% of patients on placebo. Among patients who received Xofigo, the laboratory abnormality grade 3-4 thrombocytopenia occurred in 1% of docetaxel naïve patients and in 4% of patients who had received prior docetaxel. Grade 3-4 neutropenia occurred in 1% of docetaxel naïve patients and in 3% of patients who have received prior docetaxel. Fluid Status Dehydration occurred in 3% of patients on Xofigo and 1% of patients on placebo. Xofigo increases adverse reactions such as diarrhea, nausea, and vomiting which may result in dehydration. Monitor patients’ oral intake and fluid status carefully and promptly treat patients who display signs or symptoms of dehydration or hypovolemia. Injection Site Reactions Erythema, pain, and edema at the injection site were reported in 1% of patients on Xofigo. Secondary Malignant Neoplasms Xofigo contributes to a patient’s overall long-term cumulative radiation exposure. Long-term cumulative radiation exposure may be associated with an increased risk of cancer and hereditary defects. Due to its mechanism of action and neoplastic changes, including osteosarcomas, in rats following administration of radium-223 dichloride, Xofigo may increase the risk of osteosarcoma or other secondary malignant neoplasms [see Nonclinical Toxicology ( 13.1 )] . However, the overall incidence of new malignancies in the randomized trial was lower on the Xofigo arm compared to placebo (<1% vs. 2%; respectively), but the expected latency period for the development of secondary malignancies exceeds the duration of follow up for patients on the trial. Subsequent Treatment with Cytotoxic Chemotherapy In the randomized clinical trial, 16% patients in the Xofigo group and 18% patients in the placebo group received cytotoxic chemotherapy after completion of study treatments. Adequate safety monitoring and laboratory testing was not performed to assess how patients treated with Xofigo will tolerate subsequent cytotoxic chemotherapy.

No formal clinical drug interaction studies have been performed. Subgroup analyses indicated that the concurrent use of bisphosphonates or calcium channel blockers did not affect the safety and efficacy of Xofigo in the randomized clinical trial.

8.1 Pregnancy Risk Summary The safety and efficacy of Xofigo have not been established in females. Based on mechanism of action, Xofigo can cause fetal harm when administered to a pregnant female [see Clinical Pharmacology ( 12.1 )] . While there are no human or animal data on the use of Xofigo in pregnancy, maternal use of a radioactive therapeutic agent could affect development of a fetus. Advise pregnant females and females of reproductive potential of the potential risk to a fetus.

8.2 Lactation Risk Summary The safety and efficacy of Xofigo have not been established in females. There is no data on the presence of radium-223 dichloride in human milk, the effects on the breastfed child, or the effects on milk production.

8.3 Females and Males of Reproductive Potential Contraception Males Because of potential effects on spermatogenesis associated with radiation, advise male patients to use condoms and their female partners of reproductive potential to use effective contraception during and for 6 months after completing treatment with Xofigo [see Use in Specific Populations ( 8.1 )] . Infertility Males Based on mechanism of action, Xofigo may impair fertility in males of reproductive potential [see Clinical Pharmacology (12.1) and Nonclinical Toxicology ( 13.1 )] .

8.4 Pediatric Use The safety and efficacy of Xofigo in pediatric patients have not been established. In single- and repeat-dose toxicity studies in rats, findings in the bones (depletion of osteocytes, osteoblasts, osteoclasts, fibro-osseous lesions, disruption/disorganization of the physis/growth line) and teeth (missing, irregular growth, fibro-osseous lesions in bone socket) correlated with a reduction of osteogenesis that occurred at clinically relevant doses beginning in the range of 22 – 88 kBq (0.59 – 2.38 microcurie) per kg body weight.

8.5 Geriatric Use Of the 600 patients treated with Xofigo in the randomized trial, 75% were 65 years of age and over and while 33% were 75 years of age and over. No dosage adjustment is considered necessary in elderly patients. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

8.6 Patients with Hepatic Impairment No dedicated hepatic impairment trial for Xofigo has been conducted. Since radium-223 is neither metabolized by the liver nor eliminated via the bile, hepatic impairment is unlikely to affect the pharmacokinetics of radium-223 dichloride [see Clinical Pharmacology ( 12.3 )] . Based on subgroup analyses in the randomized clinical trial, dose adjustment is not needed in patients with mild hepatic impairment. No dose adjustments can be recommended for patients with moderate or severe hepatic impairment due to lack of clinical data.

8.7 Patients with Renal Impairment No dedicated renal impairment trial for Xofigo has been conducted. Based on subgroup analyses in the randomized clinical trial, dose adjustment is not needed in patients with existing mild (creatinine clearance [CrCl] 60 to 89 mL/min) or moderate (CrCl 30 to 59 mL/min) renal impairment. No dose adjustment can be recommended for patients with severe renal impairment (CrCl less than 30 mL/min) due to limited data available (n = 2) [see Clinical Pharmacology ( 12.3 )] .

The active moiety of Xofigo is the alpha particle-emitting isotope radium-223 (as radium Ra 223 dichloride), which mimics calcium and forms complexes with the bone mineral hydroxyapatite at areas of increased bone turnover, such as bone metastases (see Table 2). The high linear energy transfer of alpha particles (80 keV/micrometer) leads to a high frequency of double-strand DNA breaks in adjacent cells including tumor cells, osteoblasts and osteoclasts, resulting in an anti-tumor effect on bone metastases. The alpha particle range from radium-223 dichloride is less than 100 micrometers (less than 10 cell diameters) which limits damage to the surrounding normal tissue.