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Individual clinical response to biologic therapy, particularly antiTNF, can be influenced by their pharmacokinetics and immunogenicity, so therapeutic monitoring of drug levels (TDM) can guide the biologic treatments.
Objectives:
Evaluation of the concordance of dose setting based on clinical response and serum infliximab trough levels (SITLs), as well as, anti-drug antibodies (ADA). Analysis of the utility of TDM to guide dose setting.
Study Design:
Prospective and descriptive study of patients with rheumatic diseases treated with infliximab and under TDM. Informed voluntary consent was obtained from all patients.
Methods:
Medical records were reviewed and dosage regimens were recorded. Dose schemes were established according to an index of clinical response (DAS28, BASDAI…). SITLs (Therapeutic range: 2.5-9 mcg/mL ) and ADA were measured by Elisa (Promonitor®). ADA presence was considered as a therapeutic failure indicator.
Results:
34 patients were included with median age of 57 years (range [30-83]). Infliximab standard dose according to clinical guidelines (3 mg/Kg or 5 mg/Kg every 8 weeks for rheumatoid arthritis or other diseases, respectively) were administered to 13 patients [69.2% showed SITLs under the therapeutic range, 61.5% with ADA]. In 19 patients with maintained good clinical response, dose decrease or interval elongation had been implemented [63.2% showed SITLs under the therapeutic range, 26.3% with ADA]. It had been necessary to increase the dose or shorten the interval in 2 patients due to inadequate clinical response [100% under the therapeutic range with ADA].
Conclusions:
Although optimization based on clinical response of biologic treatments in patients with rheumatic diseases can reduce the therapy costs is not always an effective strategy,since a high percentage of patients with SITLs under the therapeutic range and ADAs was found. TDM of infliximab and ADA is a tool to individualize infliximab treatments.