Therapeutic Drug Monitoring of Tumor Necrosis Factor Antagonists in Inflammatory Bowel Disease

Although tumor necrosis factor (TNF) antagonists have shown clear benefits over conventional treatments for inducing and maintaining clinical remission in both Crohn's disease and ulcerative colitis, a high proportion of patients lose response over time. Given the scarce alternative of treatments when treatment failure occurs, it is highly desirable to optimize both initial response and long-term continuation of TNF antagonists. One of the most well-characterized factors associated with loss of response to these agents is the development of immunogenicity, whereby the production of neutralizing antidrug antibodies accelerates drug clearance, leading to subtherapeutic drug concentrations and, ultimately, to treatment failure. However, other patient-related factors, such as sex and/or body size, and disease severity, including TNF burden and serum albumin concentration among others, also may influence the pharmacokinetics of these agents. Nevertheless, the evidence generated to date about these complex interactions is scarce, and further prospective studies evaluating their influence on the pharmacokinetics of TNF antagonists are needed. Drug adjustment empirically based on clinical symptoms often is inaccurate and may lead to suboptimal outcomes. Recent evidence shows that maintenance of an optimal therapeutic drug concentration is associated with improved clinical outcomes. Therefore, incorporation of therapeutic drug monitoring into clinical practice may allow clinicians to optimize treatment by maintaining effective drug concentrations over time.