The current study is the first from our registry to report the retention rates of the anti-TNFα biologics and the factors associated with withdrawal of the drugs. Our results are similar to those reported in European registries in which IFX had the lowest retention rate among the anti-TNFα biological agents.[19-21] More recently, data from the REAL RA registry in Japan also reported lower retention rates of IFX and TCZ as ZD1839 supplier compared to ETN.[22] Although the exact reasons for the difference in the retention rates of the anti-TNFα

biologics remain unclear, one important cause is the development of anti-drug antibodies (immunogenicity) which lower the serum levels of the corresponding drugs. Immunogenicity of the anti-TNFα biological agent has been implicated

for the development of secondary treatment failure[23] and BGJ398 research buy infusion reaction (drug–anti-drug immune complexes).[24] This is illustrated by the high withdrawal rate of IFX over time because it is a chimeric monoclonal antibody that is associated with the highest incidence of anti-drug antibodies.[25] In our registry, a substantial proportion of withdrawals of IFX were due to infusion reaction, which could also be related to the development of immunogenicity to the drug. The rate of TB and serious non-TB infections combined was 2.26 per 100 patient-years of follow-up in our registry. This figure is lower than those reported in the British (4.2 per 100 patient-year)[11] and French registries (5.0 per 100 patient-year)[15] but similar to that of the Dutch DREAM registry (2.59 per 100 patient-year).[26] The major sites of infection were similar with the European registries,[15, 26, 27] with lower respiratory tract and skin/soft tissue infection being most common. Herpes zoster reactivation and opportunistic infections like candidiasis reported to our registry was also similar to those presented in the European[28-30]

and Japanese registries.[31] Tuberculosis is endemic in Asia, including our locality. There are around 6000 new cases of TB in Hong Kong every year and this rate has been constant Selleck Vorinostat over the past decade.[32] We calculated that the odds ratio of having TB in users of the anti-TNFα biologics was 3.71 (95% CI 2.62–5.25) when compared to our local general population. Given the increasing number of patients who are receiving the anti-TNFα biologics, this figure is not alarming at this juncture. The low relative risk of TB can be attributed to universal screening and treatment of latent TB before commencement of the anti-TNFα biologics, as well as the preference of using ETN in patients at risk of TB reactivation. Combined methotrexate (MTX) and the anti-TNF biologics has been shown to enhance clinical efficacy in RCTs.[33] The concomitant use of MTX has also been reported to reduce the incidence of immunogenicity and hence may help in reducing the rate of termination due to secondary treatment failure.