Correlation of Infliximab Levels With Outcomes in Ulcerative Colitis

Infliximab is approved for induction and maintenance of clinical remission and mucosal healing in patients with moderate to severe active ulcerative colitis, in those who have an inadequate response to conventional therapy such as IV steroids. It is typically dosed at 5 mg/kg at 0, 2, and 6 weeks, followed by 5 mg/kg every 8 weeks thereafter. The alternative to rescue medical therapy with infliximab is proctocolectomy with ileal pouch anastomosis, which carries risks including pouchitis, fecal incontinence, pouch failure requiring further surgical procedures and female infertility, or proctocolectomy with permanent end-ileostomy, which many patients wish to avoid. The induction regimen of 3 doses of Infliximab followed by a maintenance dose every 8 weeks is used to achieve response in hopes of avoiding colectomy. Unfortunately, a large proportion of patients are unable to achieve or sustain a clinical response over time and end up getting a colectomy.

Potential implicated pathways in non-responders include fecal wasting of infliximab and factors that accelerate drug clearance such as a large TNF (tumor necrosis factor) or CRP (C reactive protein) burden, anti-infliximab antibodies (ATI), low serum albumin, male sex and larger body size. Patients with severe ulcerative colitis who fail corticosteroids and standard dosing with infliximab usually proceed to proctocolectomy. Optimizing early infliximab blood levels in patients with moderate-severe ulcerative colitis by administering the second dose of infliximab before week 2 could improve the efficacy and further reduce the need for colectomy. However, there is a paucity in the literature as this is a relatively new school of thought. Our study will address this deficit by evaluating the relationship between early drug levels of infliximab in ulcerative colitis and colectomy rates at one and three months.