Background: The introduction of biosimilar infliximab with CT-P13 offers substantial potential cost savings with opportunities of gain share to gastrointestinal units. Data on switching from Remicade to CT-P13 are only just emerging and were not available in early 2016. Therapeutic drug monitoring (TDM) is increasingly recognised as an effective means to optimize patient outcomes on anti-TNF therapy, but is not widely adopted in the UK. All bio-naive patients in our unit scheduled for infliximab received CT-P13 from September 2015 (n=73), saving approximately £480,000 in year 1. Following discussions with hospital management, we took the opportunity to implement TDM whilst switching patients established on Remicade to biosimilar CT-P13.
Methods: A switch pathway was agreed (see Figure 1) and implemented June 2016, with all data collected prospectively. Routine blood tests, disease activity scores (Partial Mayo/HBI), faecal calprotectin (FC) and serum for infliximab trough levels and antibodies to infliximab (ATI) were obtained. TDM was performed with the IDKmonitor® ELISA assay. Results were reviewed in a virtual biologics clinic (GI consultant/specialist pharmacist) and decision made on further management as per NICE DG-22 TDM algorithm. Clinical response was defined as a change in HBI ≥3 and Partial Mayo ≥2. Clinical remission was defined as HBI <5 and Partial Mayo <2.
Results: 160/161 (99%) patients currently receiving Remicade agreed to our switch process. 86/160 (54%) patients were switched to CT-P13 with no dose change whilst 15/160 (9%) switched with dose escalation and 8/160 (5%) with dose de-escalation. 27/160 (17%) patients stopped biologic therapy altogether due to a combination of immunogenicity (infliximab trough levels <3 μg/ml; ATI >8μg/ml), clinical and biochemical remission. 24/160 (15%) patients had immunogenicity with infliximab but were not in clinical and biochemical remission and therefore switched to an alternative biologic (adalimumab n=18; vedolizumab n=6). Data on trough levels and ATIs post switch (pre-infusion 3 and 6) are presently being analysed.
Conclusions: The local experience combining the sequential introduction of TDM with switching of Remicade to CT-P13 has not resulted in any immediate complications in our cohort of IBD patients. Health-economic evaluation of the switch process is on-going with a projected saving of approximately £710,000 in year 1.