Efficacy, immunogenicity and cost analysis of a systematic switch from originator infliximab to biosimilar CT-P13 of all patients with inflammatory arthritis from a single center.

Biosimilar drugs are intended to be as effective as the originator product but with a lower cost to healthcare systems. In our center we promoted a switch from originator infliximab (IFXor) to biosimilar infliximab (CT-P13). We analyzed efficacy, safety, immunogenicity and cost savings of switching. Eligible patients were adults with the diagnosis of rheumatoid arthritis (RA), spondyloarthritis (SpA) and psoriatic arthritis (PsA) on therapy with IFXor for at least 6 months and with stable disease activity. Efficacy was measured considering change from baseline in Disease Activity Score in 28 joints (DAS28) for RA and PsA and in Ankylosing Spondylitis Disease Activity Score (ASDAS) for SpA. Disease worsening was considered when an increase of 1.2 from baseline in DAS28 or an increase of 1.1 in ASDAS occurred. Serum IFX levels (sIFX) were dichotomized as therapeutic (between 3-6 µg/mL), low (< 3 µg/mL), and high (> 6 µg/mL). Anti-drug antibody (ADA) levels were dichotomized into detectable (> 10 ng/ml) or non-detectable (< 10 ng/ml). A cost analysis was done based on the purchasing prices of the 2 drugs at our center. During a period of 1 year switch to CT-P13 was performed in 60 patients for non-medical reasons. We had a total of 36 patients with SpA, 16 with RA and 8 with PsA. Disease activity was stable over the observation period and similar to the values observed with IFXor. Median follow-up time was 15 months during which 5 patients stopped CT-P13. Forty two switchers had blood samples collected before and after switch. A total of 27 patients had unaltered sIFX levels and ADA status during follow up. Three patients had detectable ADA at baseline, with low sIFX levels. After switch, ADAs became negative in 2 of those patients, and the other patient kept detectable ADA levels. ADAs became positive in 5 patients after switch. The switch to CT-P13 represented a 26.4 % reduction of costs in the use of IFX therapy in these patients. The switch in routine care of a group of RA, SpA and PsA patients from IFXor to CT-P13 did not affect efficacy, safety, immunogenicity and reduced costs in 26.4%. The observed changes in blood samples were not associated with higher disease activity and did not lead to stopping IFX therapy.