Infliximab Biosimilar Maintains Remission, Trough Levels After Switch in IBD

More than 95% of patients with inflammatory bowel disease (IBD) stayed on therapy a year after being switched, without a clinical reason, from the infliximab originator (Remicade; Janssen) to the biosimilar CT-P13, with remission rates and drug levels holding steady through 56 weeks.¹

A Japanese study found high remission and continuation rates, plus noninferior trough levels, after patients with IBD were switched to the infliximab biosimilar CT-P13. | Image credit: mi_viri - stock.adobe.com

Little Real-World Data From Japan

Infliximab, an anti–tumor necrosis factor-alpha antibody, transformed treatment for Crohn disease and ulcerative colitis, but its cost remains a barrier to access worldwide. Japan's Ministry of Health, Labour and Welfare recommends biosimilars to ease that burden, and the biosimilar CT-P13 (Infliximab BS in Japan; Nippon Kayaku, under license from developer Celltrion) has been available there for IBD since 2014. Yet only a handful of postmarketing and retrospective studies have examined nonmedical switching (NMS)—moving stable patients to a biosimilar for nonclinical reasons—in Japanese patients with IBD, leaving physicians and patients hesitant.

The stakes extend beyond Japan: expanding biosimilar use in the US has already reshaped the infliximab market, saving commercial insurers an estimated $259.5 million to $842.2 million from 2018 to 2021 as originator prices fell more than half amid competition, according to a claims analysis of more than 42,000 patients.² Researchers at Fukuoka University sought prospective, real-world evidence on whether switching can succeed elsewhere without compromising disease control.

The prospective observational study enrolled 167 patients with IBD—136 with Crohn disease, 31 with ulcerative colitis—who underwent NMS from the originator to CT-P13 at Fukuoka University Chikushi Hospital starting in April 2021.¹ Patients had a median age of 43 years and median disease duration of 16.1 years, and most had been on originator therapy for nearly a decade (median, 9.8 years).

The primary end point was clinical remission at 56 weeks, defined as a Crohn's Disease Activity Index below 150 or a partial Mayo score of 2 or lower—thresholds below which disease activity is considered quiescent.

High Continuation and Remission Rates

The treatment continuation rate at 56 weeks was 95.6% overall: 94.7% among patients with Crohn disease and 100% among those with ulcerative colitis. Of the 132 patients in remission at baseline, 84.1% remained in remission at week 56 in an intention-to-treat analysis, with remission-maintenance rates of 85.7% for Crohn disease and 77.8% for ulcerative colitis.

Adverse events occurred in 22.8% of patients (38 of 167), most commonly infections (14.4%), and only 2 were classified as serious: an infusion reaction after the fourth dose that led the team to withhold a fifth dose and a case of sepsis considered related to CT-P13.

“This adverse event was considered to be related to CT-P13; however, administration was subsequently continued, and it has since been possible to safely maintain the treatment,” the researchers wrote.

Trough Concentrations Remained Noninferior

Among 119 patients in the per-protocol pharmacokinetic analysis, median infliximab trough concentrations were 3.9 µg/mL at baseline, then 4.3, 3.8, and 4.1 µg/mL at weeks 8, 24, and 56, respectively. As a ratio to baseline, trough levels measured 115.6%, 101.2%, and 123.5% at those time points—noninferior to baseline at every measurement above the study's 85% inferiority threshold.

Albumin declined modestly by week 56 (P < .001), and leucine-rich alpha-2 glycoprotein—a biomarker used as a proxy for disease activity since the study omitted endoscopy—dipped at 24 weeks before returning near baseline by week 56, without a matching change in remission rates.

Patients Knew Little About Biosimilars, but Few Objected

A companion questionnaire given to all 167 patients found awareness of biosimilars was strikingly low: 85.0% said they “did not know” about biosimilars at baseline, 9.0% had “heard” of them, and 6.0% said they “knew” about them. No patient proactively requested the switch, but 57.5% said they were “not bothered” by it, and 54.5% agreed with the recommendation vs 3.6% who disagreed.

Anxiety about the switch, scored on an 11-point scale, fell significantly by week 24 and stayed lower through week 56 vs baseline (P < .001 for both), even as median satisfaction scores dipped slightly, from 10 at baseline to 9 at weeks 24 and 56 (P < .001). The researchers suggested direct experience with the biosimilar, more than preswitch counseling, is what ultimately reassures patients.

Small, Single-Center Design Limits Generalizability

The authors acknowledged limitations: a single-center design with a relatively small ulcerative colitis subgroup (31 patients), no endoscopy or fecal calprotectin testing, and no measurement of antidrug antibodies, which limited formal assessment of immunogenicity. They noted the low rate of loss of response makes it unlikely antidrug antibodies played a major role.

For payers and health systems weighing formulary strategy around infliximab, the findings add to a growing international evidence base—alongside cost data from more competitive markets such as the US—suggesting stable patients can move to a lower-cost biosimilar without sacrificing disease control, even where switching itself doesn't directly lower a patient's costs.

References

1. Nomaru R, Takeda T, Takahashi A, et al. Effectiveness, safety, and pharmacokinetics of the infliximab biosimilar CT-P13 after non-medical switch from the infliximab originator in patients with inflammatory bowel disease. Intest Res. 2026;24(3):552-562. doi:10.5217/ir.2025.00118
2. Paglinco SR, Abdel-Rasoul M, McNicol M, at al. The biosimilar shift: trending infliximab biosimilar utilization and associated cost savings for commercial insurance. Am J Manag Care. 2025;31(10):295. doi:10.37765/ajmc.2025.89811