Optimization of biologic therapy in Crohn's disease.

INTRODUCTION: Crohn's disease (CD) is a manifestation of inflammatory bowel disease (IBD), which can result in significant morbidity. Biologic therapy with anti-TNF medication has been effective in treating inflammation and reducing complications in CD. It is important for clinicians to have better knowledge of the various biologic therapies including mechanisms of action and optimization strategies. Areas covered: The review describes optimization of biologic therapy in CD including different mechanisms of loss of response, therapeutic drug monitoring in CD, clinical implications and management strategies which utilize drug monitoring, and areas of future development and research in optimization of biologic therapy. Expert opinion: Achieving adequate levels of the drug (antibody unbound) is one of the most important determinants of attaining clinical remission and mucosal healing. Drug level is also critical in determining if a patient requires combination therapy with an immunomodulator. Certain populations, including those with active perianal disease, may require higher serum levels to achieve healing or closure. Treat to target level is an algorithm that is not universally accepted and more data is need. Additionally, there are numerous assays that don't always correlate, especially regarding measuring anti-drug antibodies.