RANK ligand (RANKL) inhibitors

Antibodies that block RANKL, the signal that makes osteoclasts form and work. Strong antiresorptives, but the effect wears off quickly when stopped.

Updated Nov 1, 2026

What they are

Monoclonal antibodies against RANKL, the cytokine that osteoblasts and other cells use to switch on osteoclasts through the RANK receptor. Denosumab is the member in use: a subcutaneous injection for osteoporosis at high fracture risk, bone loss from hormone therapy for prostate or breast cancer and, in another product, bone metastases, myeloma and giant cell tumour of bone.

Mechanism of action

RANKL binds RANK on osteoclast precursors and mature osteoclasts and drives their formation, activity and survival; osteoprotegerin is the body's own decoy that limits it. Denosumab mimics osteoprotegerin: it binds RANKL so it cannot reach RANK, and bone resorption falls sharply. Unlike bisphosphonates it is not stored in bone, so resorption comes back, often overshooting, when doses stop.

Target: RANK ligand (RANKL, TNFSF11), the cytokine that activates osteoclasts

Drugs in this class

DenosumabAn antibody against RANKL, injected under the skin, that strongly lowers bone resorption. Stopping it without a…RANK ligand (RANKL), the cytokine that switches on osteoclasts

Test yourself

Think of the answer, then tap the question to see it.

What natural protein does denosumab imitate?

Osteoprotegerin, the decoy receptor that binds RANKL and keeps it from activating RANK on osteoclasts.

Why is a bisphosphonate usually given after denosumab is stopped?

Denosumab is not stored in bone; when it wears off resorption rebounds and multiple vertebral fractures can occur, so another antiresorptive is needed.

In which patients is the hypocalcaemia from denosumab most dangerous?

Advanced chronic kidney disease, especially on dialysis or with CKD-mineral bone disorder; it can be severe and fatal.

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