Retrospective Study on the Use of Infliximab and Adalimumab Drug and Antibody Levels for Clinical Decision Making in IBD Patients at a University-Based Single-Center Practice

Abstract

Introduction: Anti TNF agents are now first line medications to treat moderate to severe Crohn's disease (CD) and Ulcerative colitis (UC). However, primary and secondary treatment failure still frequently occur due to immunogenicity1,2. Antibodies to infliximab (ATIs), also known as human anti-chimeric antibodies (HACAs), form immune complexes with the drug and are associated with decreased infliximab levels, shorter duration of response, and higher risk of infusion reactions3-5. Assays developed to detect anti-drug antibodies and drug levels for both infliximab and adalimumab were initially used for research but several commercially available tests are now on the market for clinical use6. Individualized therapy based on antibody and drug level testing has been found to be more cost effective than empiric dose escalation in patients with Crohns disease who lost response to infliximab7,8. However, data on utilization of testing in routine clinical practice is newly emerging. We present the outcomes of drug and antibody testing for 80 patients on anti TNF therapy at a single center gastroenterology practice within a university hospital setting. Methods: All patients that had infliximab and adalimumab drug level and antibody testing using the AnserTM assay by Prometheus laboratories between August 2012 and March 2015 were identified and their charts were retrospectively reviewed. Demographic characteristics, disease activity, current therapy, serum drug and antibody levels, and management after testing were recorded and analyzed. Results: Drug and antibody tests were obtained from 80 patients. The majority of patients had IBD for over 2 years. Sixity one percent had Crohn's disease with a mean age of 37.2. The most common reason for checking levels was loss of response (63.8%). 61.3% of patients were secondary nonresponders to anti TNF, and 35% of patients were responding. Therapeutic drug levels were found in 76.3% of patients and antibodies were detected in 20% of patients. Dose changes and anti TNF discontinuation occurred in 29% and 30% of patients, respectively while 41.3 % had no change to the anti TNF regimen. Conclusion: Serum infliximab and adalimumab drug and antibody level testing frequently aids clinical decision making in the real world setting resulting in medication changes in a majority of cases.Table 1Table 2: Testing results n =80