Advances in Therapeutic Drug Monitoring of Biologic Therapies in Inflammatory Bowel Disease: 2015 in Review

OPINION STATEMENT

Monoclonal antibody therapy directed against tumor necrosis factor-alpha (anti-TNFs) has revolutionized the care of patients with Crohn's disease and ulcerative colitis. These large proteins are potentially immunogenic. Early clinical trials demonstrated an association with both serum concentrations of these agents as well as the presence of antidrug antibodies generated by the host with loss of response. More recent research has provided further evidence to confirm the impact of low drug trough concentrations and antidrug antibodies on subsequent clinical course in CD and UC. Given these clinical implications, treatment algorithms have been developed to aid clinicians in interpreting trough drug levels and antibody concentrations in those with confirmed active disease. Several studies have demonstrated the utility of these approaches. Furthermore, there are growing data supporting the use of therapeutic drug monitoring in a prospective fashion in those patients who are clinically stable on anti-TNF therapies to ensure they are receiving appropriate dosing and have not yet developed antibodies. In addition, for those who have developed low-level antibodies, increasing the dose of an anti-TNF or adding an immunomodulator may help to overcome this immunologic response. Further research is required to assess these proposed strategies, as well as to determine the role of trough drug level assessment and antibody testing for new anti-TNFs and biologic medication with alternative mechanisms of action.

Can we get more from our current treatments?

Crohn's disease is a chronic incurable condition that normally requires lifelong treatment. Whilst the anti-TNF agents have revolutionised the management of Crohn's disease over the last fifteen years, they are not a panacea. In particular, in part due to their immunogenic nature, loss of response limits their long term effectiveness in many patients. The only other long term disease-modifying options are the immunomodulators, methotrexate, azathioprine and mercaptopurine. Therefore, given the limited number of drugs available to treat Crohn's disease, it is important that efforts are made to ensure that drugs are used in the best way possible as once a drug is deemed ineffective, it is rarely used again. For the growing number of patients who have active disease despite having been exposed to all standard therapies, failure to optimise drug therapy may lead to missed opportunities in the management of their disease. In this review, optimisation of drugs commonly used in the management of Crohn's disease will be discussed.