Danish Registry Analysis Finds Consistent Safety After Switching to Infliximab Biosimilar GP1111

As biosimilars continue to replace originator biologics across Europe, clinicians and payers are increasingly looking to real-world data to confirm that large-scale switching strategies do not compromise patient safety. New national registry data from Denmark suggest that serious safety events remained uncommon among people with inflammatory arthritis treated with the infliximab biosimilar GP1111, including those who underwent biosimilar-to-biosimilar switching.¹

New Danish registry data confirm the safety of switching to infliximab biosimilars, showing low rates of serious adverse events in patients with inflammatory arthritis. | Image credit: Ilya - stock.adobe.com

The observational cohort study evaluated safety outcomes in routine clinical care among people with rheumatoid arthritis (RA), psoriatic arthritis (PsA), or axial spondyloarthritis (axSpA) who initiated GP1111 between April 2019 and April 2022. Investigators used data from DANBIO, Denmark’s nationwide rheumatology registry, linked with national hospital, prescription, and mortality registries to capture serious adverse events during the first year of treatment.

Although randomized controlled trials have shown comparable safety profiles between infliximab biosimilars and the originator product, evidence has been more limited for biosimilar-to-biosimilar switching, particularly in heterogeneous, real-world populations. Denmark’s national treatment guidelines have mandated several infliximab switches over the past decade, creating an opportunity to evaluate safety outcomes across multiple switching scenarios.² The authors noted that lingering concerns around immunogenicity and rare adverse events have contributed to clinician and patient hesitancy, underscoring the need for high-quality registry data.¹

The analysis included 2132 adults who initiated GP1111 during the study period. Of these, 1534 individuals (72%) had switched from another infliximab biosimilar, most commonly CT-P13. Participants were stratified into 5 mutually exclusive subcohorts based on prior biologic disease-modifying antirheumatic drug (bDMARD) exposure, including originator-experienced biosimilar switchers, originator-naïve biosimilar switchers, infliximab-experienced users, infliximab-naïve but bDMARD-experienced users, and bDMARD-naïve users.

Across indications, the median age ranged from the mid-40s to early 60s, and median disease duration ranged from 6 to 11 years. Approximately 23% of patients had at least 1 comorbidity at baseline, and 14% had used oral corticosteroids in the year prior to starting GP1111. Disease remission at baseline varied by diagnosis, occurring in 55% of people with RA, 54% of those with PsA, and 30% of those with axSpA.

During the 1-year follow-up period, serious safety events were infrequent across the overall cohort. Age- and sex-adjusted incidence rates per 100 person-years were 1.0 or lower for major adverse cardiovascular events (MACEs), venous thromboembolic events (VTEs), death, and severe allergic reactions.

A total of 19 MACE events were observed, corresponding to an adjusted incidence rate of 1.0 per 100 person-years. These events primarily occurred among older individuals, with a median age of 66 years. Venous thromboembolic events were rare, with 11 events recorded and an adjusted incidence rate of 0.6 per 100 person-years. Nine deaths occurred during follow-up, yielding an adjusted incidence rate of 0.6 per 100 person-years.

Severe allergic reactions were also uncommon, with 16 events reported. Although these reactions were observed more frequently among infliximab-naïve but bDMARD-experienced individuals, the overall adjusted incidence rate remained below 1.0 per 100 person-years.

Serious infections represented the most frequently observed adverse outcome. Fifty-eight serious infections requiring hospitalization were identified, corresponding to an adjusted incidence rate of 3.2 per 100 person-years in the overall cohort. Rates varied across treatment history subgroups, ranging from 2.1 to 5.6 per 100 person-years. In multivariable analyses, a history of serious infection prior to GP1111 initiation was associated with a higher risk of subsequent serious infection (HR, 2.06; 95% CI, 1.19-3.57). Other baseline factors, including prior biologic treatment history, were not significantly associated with infection risk.

The authors concluded that GP1111 demonstrated a favorable safety profile during the first year of treatment, regardless of prior infliximab or biosimilar exposure. They noted that serious infection rates were comparable to those previously reported for originator tumor necrosis factor inhibitors in similar populations.

Several limitations were acknowledged. The observational design precluded causal inference, and the low number of events limited the ability to adjust for multiple covariates or conduct detailed subgroup analyses for rare outcomes. Additionally, follow-up was limited to 1 year, and findings may not reflect longer-term safety. Nevertheless, the use of nationwide registries with near-complete coverage strengthened the reliability of event capture.

References

1. Nabi H, Jensen KY, Westermann R, et al. Safety outcomes in 2132 Danish patients with inflammatory arthritis treated with biosimilar infliximab (GP1111) in routine care. Ther Adv Musculoskelet Dis. Published online December 23, 2025. doi:10.1177/1759720X251393114

2. Nabi H, Hendricks O, Jensen DV, et al. Infliximab biosimilar-to-biosimilar switching in patients with inflammatory rheumatic disease: clinical outcomes in real-world patients from the DANBIO registry. RMD Open. 2022;8(2):e002560. doi:10.1136/rmdopen-2022-002560