The unique genetic, environmental and medical backgrounds of people in Japan might influence the effectiveness and safety of biologic agents in patients with rheumatoid arthritis (RA). Indeed, clinical trials revealed higher response rates to some biologic agents (including infliximab, etanercept and tocilizumab) in patients with RA in Japan than patients treated with the same agents in Western countries, although response rates to adalimumab were comparable in both populations. The reasons why response rates to some biologic agents differ in Japanese individuals is currently under investigation. Post-marketing surveillance data have been collected for all patients with RA who were treated with biologic agents in Japan to monitor drug safety. These data clearly demonstrated that only ∼5% of these patients experienced adverse drug reactions to biologic agents, which were well tolerated. Pneumonia, tuberculosis, Pneumocystis jirovecii pneumonia and interstitial pneumonitis are considered important severe adverse reactions and risk factors for these adverse effects have been identified. Adverse drug reactions could exaggerate the risks associated with biologic therapy in Japanese patients with RA. Attempts have, therefore, been made to predict clinical response and adverse effects to enable personalized therapy with biologic agents and to optimize the outcomes of these patients.
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