C

Etanercept, leflunomide and methotrexate are established disease-modifying therapies for rheumatoid arthritis [Cole 2004, PMID 15190385; Sanders 2002, PMID 12003373; Weinblatt 2013, PMID 23874006]. Febuxostat, a xanthine-oxidase inhibitor, is approved for hyperuricemia and gout, not for rheumatoid arthritis management [Gaffo 2010, PMID 20694062].