Task: Question Answering
Input (English): Context: Giant-cell tumor of bone is a rare, locally aggressive tumor that typically occurs in the bones of skeletally mature young adults in their second to fourth decades. Traditionally, surgery has been the mainstay of therapy for this disease, but the disease can recur even with optimal procedures. Furthermore, it may occur in locations where a surgical approach would be morbid. The maturation of the understanding of the role of the receptor activator of nuclear factor-B ligand (RANKL) in the pathophysiology of giant-cell tumor of bone has led to the use of denosumab, a monoclonal antibody against RANKL, in this disease. In 2013, the US Food and Drug Administration approved denosumab for use in patients with recurrent/unresectable/metastatic giant-cell tumor of bone or for patients in whom surgery would be morbid. 
 Question: Which is the target of the drug Denosumab?
Output (English): rankl