A recent study aimed to investigate the applicability of therapeutic drug monitoring (TDM) as a potential tool for examining the transition from infliximab innovator (INX) to infliximab biosimilar (INB) concluded that TDM can be a helpful tool to monitor patients switching from INX to INB. The patients who were treated with INX treatment and ≥18 years shifted to INB as a part of routine treatment regimen but at a controlled state.

Monitoring of patient was done by collecting blood samples before the first infusion of INB (T1), and after the second (T2), fourth (T3), and seventh (T4) infusion of INB. Then after ~12 months, the patient’s status was considered by using T4. Measurement of infliximab trough levels, antibodies-to-infliximab (ATI), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and validated disease activity scores (if possible) was done.

The population to be screened consisted of 27 patients suffering from 7 different rheumatic diseases. These patients were administered with INX for 143 (58–161) months (median (IQR)) with half of the patients (52%) administered with concomitant immunosuppressives. Patients were screened for varying infliximab levels, and 56% of them contained levels of 1-5 μg/mL. High ATI levels (>880 au/ml) were found in one patient whereas low ATI levels (≤30 au/ml) were found in two patients. The transition to INB leads to discontinuation of therapy in seven patients (26%) due to some subjective reasons. There was no difference observed in infliximab levels, CRP levels, and disease activity scores between the four-time points (p ≥ 0.2460).

At last, it can be concluded that there were no pharmacokinetic or clinical differences between INX and INB in our diverse rheumatic cohort.