Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: Bone pain is a common symptom in bone metastases. The therapies that are currently available include nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, steroids and gabapentin which have been demonstrated to improve neuropathic pain. In addition, preclinical studies indicate that agents such as transient receptor potential vanilloid 1 antagonists and cannabinoid 2 receptor agonist could be considered as adjuncts in ameliorating opioid side effects. New drugs are in the clinical phase of development, among which the most promising molecules seem to be anti-nerve growth factor (NGF) antibodies. Anti-NGF antibody therapy may be particularly effective in blocking bone cancer pain because NGF appears to be integrally involved in the upregulation, sensitization and disinhibition of multiple neurotransmitters, ion channels and receptors in the primary afferent nerve. The best way to treat bone metastases pain is to improve the control of skeletal disease burden. Recently, denosumab, a noncytotoxic IgG2 monoclonal antibody with high affinity for human RANKL, has been demonstrated to significantly prevent clinically relevant increase in pain compared with zoledronic acid across the tumor types. Based on these data, it has been suggested that denosumab has the potential to become a new standard of treatment in bone metastases management.
Question: To the ligand of which receptors does Denosumab (Prolia) bind?
rankl