Introduction There is evidence that biosimilar infliximab (BSI) has comparable efficacy and safety to originator infliximab (OI) and is significantly cheaper.
ECCO guidelines suggest therapeutic drug monitoring (TDM) can help determine whether infliximab (IFX) should be continued or dose-adjusted during maintenance treatment of inflammatory bowel disease (IBD).
Method Our unit developed a switch programme in order to take advantage of the cost savings associated with BSI.
We identified patients established on OI as IBD maintenance therapy (n=76). Our IBD nurses counselled patients, gained their consent to switch from OI to BSI, and obtained IFX TDM samples. We audited the usefulness of IFX TDM and whether concomitant immunomodulation (IM) or pretreatment with hydrocortisone were associated with lower rates of antibodies to infliximab (ATI).
Results 3 patients were excluded as their trough levels of IFX (TLI) were felt inaccurate due to the timing of the test. 73 were included: 16 (21.9%) had therapeutic TLI (3–7 µg/mL), 3 (4.12%) had high TLI (>7 µg/mL), 37 (50.68%) had low TLI (0.8–2.9 µg/ml) and 17 (23.3%) had TLI <0.8 µg/ml of whom 15 had ATI and 2 did not.
IFX TDM changed management in 46 (63%) patients: IFX was dose-optimised in 24 (32.9%) patients and discontinued in 14 (19.2%) others (7 were started on adalimumab or vedolizumab, and 7 stopped biological therapy altogether). 8 (10.9%) patients were re-staged with a view to stopping IFX.
No changes were made in 27 (37%) patients: 16 (21.9%) had optimal TLI, 4 (5.5%) were in remission with only marginally suboptimal TLI and no ATI, and 7 (9.6%) had not yet had their IFX TDM reviewed by the MDT.
Only one patient did not consent to switching from OI to BSI. 93.5% of patients continuing on IFX were switched from OI to BSI.
All patients received some form of co-treatment in an attempt to reduce the development of ATI (table 1). Despite this, 41 (53.9%) patients had ATI. The mean duration of IFX therapy was 34.3 months overall, 33 months in those with ATI, and 35.8 months in those without ATI.
Conclusion A switch programme facilitates cost savings, and is acceptable to patients if the rationale is properly explained.
IFX TDM altered management in 63% of our patients and therefore should be incorporated in switch programmes.
More than half of patients had ATI. This may be explained by the fact that patients had been on IFX for a prolonged time. In our cohort it appears that concomitant IM was better at preventing ATI than pretreatment with hydrocortisone.
Disclosure of Interest None Declared
- Therapeutic drug monitoring
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