P526 Sampling not at trough: adalimumab serum drug and antibody levels remain relatively stable in between injections
B. Ungar*1, M. Yavzori1, O. Picard1, E. Fudim1, U. Kopylov1, Y. Chowers2, R. Eliakim1, S. Ben-Horin1
1Sheba Medical Centre & Sackler School of Medicine, Gastroenterology, Tel Hashomer, Israel, 2Rambam Health Care Campus, Bruce & Ruth Rappaport School of Medicine, Technion Institute of Technology, Department of Gastroenterology, Haifa, Israel
Pharmacokinetics of adalimumab have been extensively studied in recent years. Decreased adalimumab levels and increased anti-adalimumab-antibody (AAA) levels have been associated with loss of clinical response. Monitoring self-administered adalimumab drug and AAA levels is often encumbered in clinical practice by the need to measure at trough time point. Subcutaneous administration of adalimumab may potentially result in less pharmacokinetic variability within the administration cycle. However, only scant data exist as to variations in serum adalimumab and AAA levels in between injections. We aimed to determine whether non-trough serum adalimumab and AAA levels differ from trough levels in IBD patients treated with adalimumab.
A prospective pharmacokinetic analysis of 10 IBD patients treated with adalimumab every 2 weeks was performed. Five patients had positive drug levels and negative AAA, whilst the others had positive AAA and low drug levels. Serum levels were measured at home-visits every 3 days from one trough level to the next. For the purpose of comparative analysis, results were grouped into samples obtained day 1 (early cycle), at 5 days (mid-cycle), and at 10–13 days (late cycle) and compared with levels obtained at trough (day 14). An additional retrospective analysis of 10 patients with in between injections drug and AAA levels was performed. Serum drug and AAA levels were measured by a drug-tolerant anti-lambda ELISA and compared at predefined time points using the Wilcoxon non-parametric test.
Collectively, 20 patients regularly treated with adalimumab were studied. No significant difference in drug levels was identified between the 4 time points (median 3.7, 3.95, 4.4, and 4.25, respectively, p > 0.1 for all 6 comparisons). AAA were also similar for all 4 time points (median 1.2, 0.95, 1.3, and 0.78, respectively, p > 0.1 for all comparisons). Additional sub-analyses demonstrated that drug levels did not significantly diverge for both patients with and without AAA (p > 0.1 for all comparisons). Moreover, there was no difference in AAA levels amongst AAA positive patients (p > 0.1 for all comparisons). As to AAA negative patients, all AAA values at the different time points were below the assay-positivity threshold.
Adalimumab and AAA levels remain relatively stable at different time points in between adalimumab injections. Provided these results are repeated by additional studies, the timing and logistics of drug and AAA monitoring could be substantially simplified. * Supported in part by unrestricted research grant from AbbVie