Abstract: In some aspects, the present invention provides methods for predicting whether a subject will develop autoantibodies to an anti-TNF? drug during the course of anti-TNF? drug therapy. In other aspects, the present invention provides methods for predicting the level of an anti-TNF? drug in a subject during the course of anti-TNF? drug therapy. Systems for predicting anti-TNF? drug levels and the likelihood of autoantibody formation during the course of anti-TNF? drug therapy are also provided herein. The present invention further provides methods for predicting a clinical outcome (e.g., endoscopic response) of a subject on anti-TNF? drug therapy.