Anti–tumor necrosis factor drugs, still the standard therapy for moderate to severe IBD, did not induce remission in 20% to 30% of patients and lost effectiveness within a year in another 30% to 40% of patients.3,4,5,6 Novel biological agents emerging in recent years can help some patients who do not respond to anti–tumor necrosis factor therapy,6 but these agents are ineffective in many others.7 Initial efforts to improve remission rates with these agents have focused on optimizing serum drug levels and screening for antidrug antibodies, and these efforts have had some success.3,5. This evidence concerns the gene TNF and inflammatory bowel disease.