Background Some recent publications support the fact that there is no clinically meaningful difference between infliximab biosimilar and the originator in naïve patients, but sole a few of them actually assessed the transition itself. Since May 2016, according to the European guidelines, the French Health Authorities have allowed interchangeability between a biotherapy reference product and its biosimilar. According to the last studies focusing on the safety and efficacy issues, avoiding the transition to biosimilar looks no longer justified.
Objectives This work aimed to understand to which extent the use of infliximab biosimilar may result in the failure of the switch strategy in spondyloarthritis patients.
Methods This is a retrospective study conducted from June to December 2016. Only were included the adult patients with rheumatoid arthritis (RA), spondyloarthritis (SpA) or psoriatic arthritis (PsA) having accepted the transition from Infliximab reference product (IFXR) to its biosimilar (IFXB). For SpA patients, transition monitoring was based on the end-of-dose “wearing off” (WO) phenomenon assessment before and after the switch, disease activity score BASDAI and also the inflammatory marker CRP. Transition was considered as unsuccessful after 2 IFXB infusions with patient complain. In this case, the drug level was determined using ELISA before switching back to IFXR, and any spacing infusions because a concomitant health disorder was sought.
Results Of the 99 patients treated with IFXR for more than 2 years, 91% (90/99) accepted the transition: 53 SpA, 23 RA and 14 PsA. Fourteen patients (12 SpA, 2 RA) didn't reach the 3rd IFXB administration. SpA patients reported the occurrence of arthralgia (12/12) and a partial (8/12) or total (4/12) efficacy loss. Only 5 patients reported a 2 point-increase or more regarding the BASDAI score, and only 3 patients had an increase in the CRP level (Cf. Table 1). Except for P1, the efficacy loss was associated in each case with WO phenomenon already reported before the transition (8/12) or undetectable IFX level (3/12). For these 3 last patients, the IFXB drug administration rate was increased by at least 2 weeks than usual because of a concomitant infection.
Conclusions This observational study showed a transition failure rate at 16% (76/90) in global, which reached 23% (12/53) if limited to SpA. All SpA patients with supposed transition failure reported either a disease escape beforehand or a concomitant infection requiring to spacing infusions. In order to complete these results, an anti-IFX antibodies monitoring is in progress so to highlight any IFX activity loss. Any failure observed with the transition would be actually more complex than the presumably inefficacy of the biosimilar IFXB especially for SpA patients. So, it seems difficult to assess robustly the inefficacy of the transition to IFXB in SpA patients only according to patient complain.
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Disclosure of Interest None declared