Design: Retrospective case-control study in 5828 patients (2171 cases, 1445 controls). Subjects needed to have consecutively orders of 2 anti-TNF therapies (infliximab (IFX) prior to adalimumab (ADM) or vice versa).
Key findings:
Before switch from IFX to ADM, median (interquartile range) IFX serum concentrations were lower in cases versus control subjects (1.0 μg/mL [1.0–1.0] vs 11.7 μg/mL [4.2–27.1]; P < .0001).
As noted in figure below, prior antidrug antibodies ADAb) to anti-TNF agent was associated with development of ADAb with 2nd anti-TNF agent. This risk was >2-fold higher when switching from IFX to ADM (B in Figure) and even more when switching from ADM to IFX (D in Figure)
Increasing concentrations of ADAb to IFX were associated with higher proportions of patients developing ADAb to ADM (P < .0001). In contrast, increasing concentrations of ADAb to ADM did not result in a significantly higher proportion of patients developing ADAb to IFX.
My take:
In my experience, many patients with subtherapeutic anti-TNF levels, even those with ADAb, can remain on initial anti-TNF with more frequent dosing and often with combination therapy. So before jumping off the initial treatment, make sure it has been optimized.
In those who do start a 2nd anti-TNF agent, the authors recommend using combination therapy (with an immunomodulator) which “leads to lower rates of clinical failure and more favorable pharmacokinetics, compared with monotherapy.”
“Alternatively, a strategy with optimized monotherapy using proactive TDM may be effective as well, but remains to be assessed in a prospective manner.”
Kaplan-Meier curves representing proportion of patients who developed ADAb when (A) switched from infliximab to adalimumab and (C) switched from adalimumab to infliximab. Difference in rate of ADAb formation between cases (red) and control subjects (teal) for those patients who (B) switched from infliximab to adalimumab and (D) switched from adalimumab to infliximab.
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