Infliximab is a chimeric (human-murine) antibody to tumor necrosis factor (anti-TNF). Some patients may develop antibodies to the drug, reducing its effectiveness.
When to suspect formation of antibodies to infliximab:
(1) The patient requires escalating doses to achieve the same effect.
(2) The duration of effect for a previously effective dose is much shorter.
(3) The patient does not respond (treatment failure).
(4) Undetectable or greatly reduced serum infliximab levels shortly after a dose.
Possible risk factors for formation of antibodies:
(1) history of anti-mouse antibodies
(2) little or no immunosuppression
When interpreting results of tests for antibodies to infliximab, it is important to know if the presence of infliximab in the serum interferes with the assay (page 32). If infliximab interferes with the assay, then detection of infliximab in the sample makes any result indeterminate.
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