Endocrine Pharmacology USMLE Step 1 Practice Question

A 55-year-old man with end-stage renal disease on hemodialysis three times weekly presents with BP 148/92, HR 88, RR 16, temp 37°C, and SpO2 98%. Laboratory studies reveal persistently elevated PTH (156 pg/mL), serum phosphate 6.2 mg/dL, and serum calcium 8.1 mg/dL despite dietary phosphate restriction and active vitamin D supplementation. Physical examination reveals mild periarticular soft tissue deposits at the shoulders bilaterally. Chest X-ray shows no pulmonary edema. He denies bone pain. His physician prescribes a medication that sensitizes calcium-sensing receptors on parathyroid cells to suppress PTH secretion. Which drug was most likely prescribed?