Effect of CTAP101 Capsules on Ca/iPTH in Advanced Breast/Prostate Cancer Patients Treated With Denosumab/Zoledronic Acid

This is a multi-center, open-label, repeat-dose study to evaluate the safety, efficacy, and tolerability of CTAP101 Capsules in subjects with bone metastases who are receiving ongoing therapy with denosumab or zoledronic acid. Following screening, approximately 12 eligible subjects with breast cancer and approximately 12 eligible subjects with prostate cancer, all of whom have metastases to bone and are undergoing treatment with anti-resorptive therapies, will receive CTAP101 Capsules at an initial daily oral dose of 30 μg (1 capsule) for 4 weeks. The daily dose may be increased in 30 μg (1 capsule) increments at 4-week intervals to a maximum of 300 μg or until serum calcium reaches \>10.3 mg/dL for two consecutive visits (dose escalation phase) at which time the subject will suspend dosing until serum calcium is ≤10.0 mg/dL and will directly enter a 12-week maintenance phase, resuming treatment at a reduced daily dose, followed by a 2-week follow-up period. Subjects reaching the maximum dose without serum calcium reaching \>10.3 mg/dL, will directly enter the 12-week maintenance phase, followed by a 2-week follow-up period. Serum markers for monitoring bone metabolism (including plasma iPTH, PTHrP, and serum free calcifediol), immune function and tumor burden will be measured during the treatment period. The FACT-BP Quality of Life Measurement in Patients with Bone Pain questionnaire will be used to explore the effect of the treatment, if any, on musculoskeletal pain. The genotype of vitamin D binding protein (DBP) will also be determined. Safety will be monitored through adverse events, serum and urine chemistries, hematology, and ECGs.