Infliximab and adalimumab concentrations are associated with important outcomes in inflammatory bowel disease (IBD). Antibodies to infliximab (ATI) and adalimumab (ATA) are associated with reduced drug concentrations and worse outcomes. Because the efficacy of dose escalation to overcome antibodies is unclear, we assessed the impact of this strategy to overcome immunogenicity in IBD.
Infliximab and adalimumab dosing, drug, and antibody concentrations were extracted from a database of patients with IBD having specimens collected for therapeutic drug monitoring. The primary outcome compared proportions with either infliximab ≥5 μg/mL or adalimumab ≥7.5 μg/mL and undetectable antibodies between dose-escalated and non-escalated patients. Area under the receiver operating characteristic curve analyses determined antibody concentrations below which dose escalation was associated with the primary outcome.
The study included 63,176 patients treated with infliximab and 46,429 patients treated with adalimumab. We detected ATI and ATA in 23.6% (n = 14,900) of patients treated with infliximab and 19.6% (n = 9101) of patients treated with adalimumab. In patients with ATI, infliximab dose escalation (n = 453) yielded higher proportions achieving the primary outcome (47.5% vs 30.9%; P < 0.001), greater drug concentration increases (5.9 μg/mL vs 0.2 μg/mL; P < 0.001), and ATI reductions (4.3 U/mL vs 1.9 U/mL; P = 0.002) compared to no escalation (n = 204). An ATI threshold of 8.55 U/mL was associated with achieving the primary outcome with dose escalation (area under the curve = 0.66). For patients with ATI ≤8.55 U/mL (n = 274), higher proportions (59.1% vs 29.6%; P < 0.001) achieved the primary outcome compared with those with ATI >8.55 U/mL (n = 179). No patients treated with adalimumab achieved the primary outcome (0/390), regardless of dose escalation (n = 87).
Dose escalation increased drug concentrations and eliminated antibodies with infliximab but not adalimumab. Initial ATI ≤8.55 U/mL was associated with increased efficacy of dose escalation using this assay.