Background/Purpose: Recently biosimilar infliximab was approved in South Korea and it has been commonly used for rheumatoid arthritis (RA) patients who are resistant to conventional DMARDs. The biosimilar infliximab have been shown to be equivalent to original infliximab in equivalent efficacy and safety in RA through several clinical trials, but its effectiveness and safety in daily practice has not yet been reported. This study aims to compare the characteristics of RA patients who use biosimilar infliximab with those of patients who start original infliximab and to identify the effectiveness and safety of biosimilar infliximab for RA patients in clinical practice.

Methods: Using the prospective biologic DMARDs registry in Korea: BIOlogics Pharmacoepidemiologic StudY (BIOPSY), we selected RA patients who started either biosimilar or original infliximab. Baseline characteristics including sociodemographics, disease activity, previous or concurrent medications, and comorbidities of two groups were compared. Treatment outcomes such as DAS28-ESR and HAQ-DI scores observed in 6 or 9 months after starting infliximab were compared between two groups. Drug retention rates of both groups were also compared using Kaplan-Meier analysis and the reasons of discontinuation were described in each group.

Results: A total of 98 RA patients who started either original or biosimilar infliximab were included in this analysis; 52 for biosimilar infliximab users (33.8 PY) and 46 of original infliximab users (50.2 PY). Baseline characteristics of two groups were quite similar in age, disease duration, and previous or current medications. Although baseline DAS28-ESR and HAQ-DI scores were not differed between two groups, swollen joints count was lower in biosimilar users than original users (6.1 ± 4.9 vs. 8.2 ± 5.4, P=0.05). Biologics-naïve patients were more common in biosimilar users but not significant statistically (92.3 % vs. 84.8 %, P=0.39). Early DAS28-ESR remission rate observed in 6 or 9 months after starting biosimilar and original infliximab were 18.6% and 15.6%, respectively (P =0.75). HAQ-DI changes were not different between two groups (0.4 ± 0.8 vs. 0.4 ± 0.7 P=0.85). The drug retention rates during 20 months were higher in biosimilar users, but there was no statistical significance (68.4% in biosimilar users vs. 53.1% in original users, p=0.16 by log-rank test). The most common reason of drug discontinuation was ineffectiveness in both groups (61.5% in biosimilar and 68.2% in original infliximab). Discontinuation due to infusion related reaction was only one case in each group. 

Conclusion: There was no significant difference in baseline characteristics of biosimilar infliximab users compared to original infliximab users in South Korea. Drug persistency of biosimilar infliximab for 20 months was comparable to that of original infliximab, and the reasons of drug discontinuation were similar between two groups.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/characteristics-and-outcomes-of-ra-patients-who-start-biosimilar-infliximab-in-south-korea/