The aim of this study was to investigate the potential predictors of switching tumor necrosis factor (TNF)- inhibitors in Korean patients with ankylosing spondylitis (AS). more likely to be prescribed disease-modifying anti-rheumatic drugs than non-switchers. A history of joint surgery and complete ankylosis of the sacroiliac joint was more frequent in switchers. Multivariate Coxs proportional hazard analysis showed that the use of adalimumab as the first TNF- inhibitor was less likely to lead to switching and complete ankylosis of the sacroiliac joints was more likely to lead to switching. The principal reasons for switching were drug inefficacy and adverse events, but the differences in the clinical data of these two groups of switchers were not significant. In AS patients who are candidates for TNF- inhibitor therapy, switching Spinorphin may improve the therapeutic outcome based on clinical information. Introduction Ankylosing spondylitis (AS) is an inflammatory rheumatic disorder mainly affecting the axial skeleton. Inflammation of the sacroiliac joint, spine, and entheses is the main characteristic of AS and it eventually leads to ankylosis of the affected joint. Tumor necrosis factor (TNF)- inhibitors are a major advance in the treatment of AS and their efficacy has been proven in several randomized controlled trials Spinorphin [1C3]. However, according to nationwide registries of the drug continuation rate in several countries, the rate of treatment failure is considerable [4C6], with drug survival in the range of 63C82%. Moreover, many national recommendations and guidelines do not address drug discontinuation or switching in AS patients initially treated with TNF- inhibitors. In Korea, infliximab, etanercept, and adalimumab are the commercially available TNF- inhibitors. Etanercept for patients with AS was approved by the Spinorphin Korean Health Insurance Review & Assessment Service (HIRA) in Spinorphin May 2005, followed by infliximab in November 2006 and adalimumab in April 2007. Head-to-head trials comparing the safety and efficacy of these three TNF- inhibitors are lacking but their efficacies are considered to be similar. Infliximab is an IgG1 chimeric monoclonal antibody with its Fab portion derived from mouse; it is administered by intravenous infusion. Both etanercept, a recombinant 75-kDa TNF receptor IgG1 fusion protein, and adalimumab, a humanized monoclonal antibody, are given by subcutaneous injection. The different molecular structures and routes of administration of these three drugs could influence both their efficacies and their association with adverse events in patients receiving them. Accordingly, patients who do not respond to a TNF- inhibitor or suffer an adverse event during its use may benefit by switching to one of the other inhibitors. For ethical reasons, the switching rate of TNF- inhibitors and its effects cannot be investigated through randomized placebo-controlled studies. However, the many nationwide drug registries, such as BIOBADASER (Spanish Registry of Adverse Events of Biological Therapies in Rheumatic Diseases), BSRBR (The British Society for Rheumatology Biologics Registers), DANBIO (a nationwide registry of biological therapies in Denmark), and NOR-DMARD (Norwegian DMARD register) provide the basis for observational studies. To date, there is no well-organized registry of similar information in Asia. Therefore, in this work our primary objectives were: (1) to analyze the switching percentage, the order of switching, and the clinical characteristics of AS patients in Korea who had switched TNF- inhibitors and 2) to identify the predictors for switching TNF- inhibitors. Materials and Methods This retrospective cohort study was conducted in a single tertiary center. Patients diagnosed with AS according to the modified New York Criteria  and in whom TNF- inhibitors were first initiated between January 2002 and December 2013 were eligible. Those who received biological agents other than TNF- inhibitors and with a follow-up of less than 3 months were excluded. The TNF- inhibitors investigated in this study were infliximab, etanercept, and adalimumab. According to the Korean HIRA guidelines, the dose and interval of Rabbit Polyclonal to SCARF2 each TNF- inhibitor are predetermined. The dose or frequency of TNF- inhibitors was not escalated arbitrarily. Infliximab was administered as an intravenous infusion at a dose of 5 mg/kg at weeks 0, 2, and 6 and then every 6C8 weeks. Etanercept was administered as a subcutaneous injection of 25 mg twice per week or 50 mg once per week. Adalimumab was administered as a subcutaneous injection of 40 mg every other week. This study was approved by the Institutional Review Board of Chonnam National University Hospital (CNUH-2014-073), Republic of Korea. Although informed consent was waived due to retrospective study design, patient health information was de-identified prior to analysis and patient anonymity was preserved during the study period. Patients in whom standard treatment failed and who had active disease were eligible for TNF- inhibitor therapy, according to the Korean HIRA.