Denosumab is a monoclonal antibody that inhibits which molecule on osteoclasts to reduce bone resorption?

• A. Raloxifene
• B. Teriparatide
• C. Denosumab (Prolia)
• D. Zoledronic acid

Answer: (C)

Denosumab reduces bone resorption by blocking RANKL, the molecule that binds to RANK on osteoclast precursors to drive their maturation and activity. By binding RANKL, denosumab prevents this signal, so osteoclast formation and function are diminished, leading to decreased bone resorption and greater bone mass.

RANKL is produced by osteoblasts and stromal cells, and its interaction with RANK on osteoclasts is the key trigger for osteoclast development and activity. Other options describe different drugs with distinct mechanisms: a selective estrogen receptor modulator, a parathyroid hormone analog that promotes bone formation, and a bisphosphonate that inhibits osteoclasts via a separate pathway. The monoclonal antibody listed—denosumab—targets RANKL, making it the correct choice.