Clinical relevance
To see whether their findings had clinical implications, the investigators conducted a case-cohort study nested within the Human Microbiome Project 2 cohort. They saw that, after adjusting for age, sex, IBD type, smoking, and N-acetyltransferase (NAT2) phenotype, 4 of the 12 acetyltranfserase candidates were associated with a roughly threefold increase in steroid use, suggesting that 5-ASA treatment had failed the patients.
“So then to take it one step further, we turned to the SPARC IBD cohort,” Dr. Mehta said.
SPARC IBD is an ongoing prospective cohort of patients who provide stool samples and detailed medication and symptom data.
They identified 208 cohort members who were on 5-ASA, were free of steroids at baseline, and who had fecal metabolomic data available. In this group, there were 60 cases of new corticosteroid prescriptions after about 8 months of follow-up.
The authors found that having three or four of the suspect acetyltransferases in gut microbiota was associated with a an overall odds ratio for 5-ASA treatment failure of 3.12 (95% confidence interval, 1.41-6.89).
“Taken together, I think this advances the idea of using the microbiome for personalized medicine in IBD,” Dr. Mehta said.
“Right now it’s an ideal outcome for a patient with [ulcerative colitis] to retain a robust remission on 5-ASA alone,” commented session moderator Michael J. Rosen, MD, MSCI, a pediatric gastroenterologist at Stanford University Medical Center in Palo Alto, Calif., who was not involved in the study.
Asked in an interview whether the findings would be likely to change clinical practice, Dr. Rosen replied that “I think it’s fairly early stage, but I think it’s wonderful that they sort of rediscovered this older data and are modernizing it to understand why [5-ASA] may not work for some patients. It certainly seems like it might be a tractable approach to use the microbiome to personalize therapy and potentially increase the effectiveness of 5-ASA.”
The study was supported by grants from Pfizer, the National Institutes of Health, American College of Gastroenterology, and the Crohn’s & Colitis Foundation. Dr. Mehta disclosed that his team has filed a provisional patent application related to the work. Dr. Rosen reported no relevant conflict of interest.
