Inflammatory Arthritis Stable after Switch to Biosimilar Infliximab Save

The DANBIO registrys has demonstrated that switching from infliximab (Remicade) to biosimilar CT-P13 (Inflectra in the U.S., Remsima in Europe) does not appear to have any negative effect on inflammatory arthritis disease activity, Danish researchers reported.

In Annals of the Rheumatic Diseases, Bente Glintborg, MD, of the Rigshospitalet in Glostrup, and colleagues wrote that inflammatory arthritis disease activity was similar 3 months before and after the switch. CT-P13's crude 1-year retention rate of 84.1% (95% CI 81.3%-86.5%) was similar to infliximab's crude retention rate of 86.2% (95% CI 84.0%-88.0%; P=0.22).

Adjusted absolute retention rates were 83.4% for CT-P13 (95% CI 80.8%-86.2%) and 86.8% (95% CI 84.8%-88.8%; P=0.03) for infliximab, indicating an absolute difference of 3.4%.

The observational study originated from a nationwide, non-medical switch in Denmark from infliximab to biosimilar CT-P13 for patients who had rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (AxSpA). A national guideline that all patients treated with infliximab should switch to CT-P13 for economic reasons by May 2015 dictated the switch. Patients and physicians had no say in the matter.

The DANBIO registry provided the sample for the study. DANBIO covers more than 95% of Danish adults with rheumatic disease who are treated in routine care with biologic disease-modifying anti-rheumatic drugs. Under national treatment guidelines, disease activity and outcomes are monitored at least biannually and whenever medication is changed.

"To our knowledge, this is the first study of large-scale, non-medical switching in routine care with prospective data collection," the authors wrote. "The availability of historic DANBIO data enabled us to use the patients as their own controls regarding fluctuations in disease activity before and after switch, and to identify a historic infliximab cohort for comparison of retention rates."

The researchers examined disease activity of 802 patients 3 months before switch, at the time of switch, and 3 months after the switch. Of that sample, 403 had RA; 120 had PsA; and 279 had AxSpA. The study group had a median age of 55 and consisted of 51% females. Patients had been treated previously with infliximab for an average of more than 6 years. The follow-up period was 413 days, during which 16% stopped CT-P13, mostly due to lack of effect or adverse events.

RA patients received a biosimilar dose of 3.3 mg/kg every 8 weeks. PsA patients received 4.6 mg/kg every 7 weeks, and AxSpA patients received 4.8 mg/kg every 8 weeks.

The researchers found that disease activity did not change from 3 months before the switch to 3 months after, with no clinically meaningful differences observed. Flare rates also were similar in that period.

Adjusted 1-year retention rates were slightly lower in the in CT-P13 group (83.4%) than the infliximab group (86.8%), with an adjusted absolute risk difference of 3.4%. "This difference is not necessarily attributable to CT-P13, but could represent a 'nocebo-effect,' that is, negative expectations toward the drug, or residual confounding," the authors wrote.

Patients whose previous infliximab treatment was longer than 5 years had a greater CT-P13 retention rate. CT-P13 retention rates across diagnoses were comparable, though slightly lower for RA patients.

Similar results of largely unchanged disease activity after a switch to CT-P13 have been reported in other studies with few negative outcomes. In the Norwegian randomized NOR-SWITCH trial, biosimilar CT-P13 was found to be non-inferior to infliximab after 52 weeks. The proportion of patients with flare in NOR-SWITCH was 26.2% for infliximab and 29.6% for CT-P13, which might have been partly due to the fact that patients with inflammatory bowel disease were included in this trial.

Overall retention rates differed between the two studies. In the DANBIO registry study, approximately 84% of patients were still on CT-P13 after 1 year, which was lower than the 96% retention rate in NOR-SWITCH. This variance also might reflect differences in the sample of each study, since gastroenterology, rheumatology and dermatology patients were included in NOR-SWITCH, not just people with inflammatory arthritis.

Limitations of the DANBIO registry research included the potential for incomplete data due the study's observational nature. The researchers used a time interval of 13 weeks around the baseline to minimize missing data at that point, but in most cases, patient data were available within a few days before or after the switch date.

The FDA approved CT-P13 in April 2016. In January 2017, the FDA issued a draft guidance about biosimilar interchangeability to address concerns about safety and efficacy that physicians have raised in the past year. The draft guidance is being reviewed by the American College of Rheumatology (ACR).