Biologics in Crohn's disease: searching indicators for outcome

Balancing the risks and benefits of biologic therapy in inflammatory bowel diseases

INTRODUCTION

The incidence of Inflammatory Bowel Diseases (IBD) is rising and overall epidemiology is changing. Goals of IBD therapy are also fast changing to reflect the concept of mucosal healing. IBD management is increasingly revolving around questions of ideal positioning of biologic therapies.

AREAS COVERED

This paper covers important concepts regarding two classes of biologic medications approved for treatment of IBD in the United States - anti-TNF-α agents and lymphocyte-homing antagonists. Topics covered include drug mechanism of action, pharmacokinetic considerations for the clinician including therapeutic drug monitoring, summary of current evidence of drug efficacy in IBD focusing on randomized, controlled trial data. Additionally, nuanced discussion of medication side-effects and adverse reactions is presented.

EXPERT OPINION

Paradigms of treatment goals in IBD are changing with increasing focus on mucosal healing. Concomitantly, our understanding of important factors that impact drug pharmacokinetic/pharmacodynamics relationships with biologic agents has increased which will help eventually develop personalized algorithms to optimize the efficacy of these agents. Though direct head-to-head comparisons between these agents are lacking, biologic agents can be considered the safest and most effective therapies introduced for IBD.

Adeno-associated virus mediated delivery of Tregitope 167 ameliorates experimental colitis

AIM

To explore the anti-inflammatory potential of adeno-associated virus-mediated delivery of Tregitope 167 in an experimental colitis model.

METHODS

The trinitrobenzene sulfonate (TNBS) model of induced colitis was used in Balb/c mice. Subsequently after intravenous adeno-associated virus-mediated regulatory T-cell epitopes (Tregitope) delivery, acute colitis was initiated by intra-rectal administration of 1.5 mg TNBS in 40% ethanol followed by a second treatment with TNBS (0.75 mg in 20% ethanol) 8 d later. Control groups included mice not treated with TNBS (healthy control group) and mice treated by TNBS only (diseased group). At the time of sacrifice colon weight, the disease activity index and histology damage score were determined. Immunohistochemical staining of the colonic tissues was performed to asses the cellular infiltrate and the presence of transcription factor forkhead Box-P3 (Foxp3). Thymus, mesenteric lymph nodes, liver and spleen tissue were collected and the corresponding lymphocyte populations were further assessed by flow cytometry analysis for the expression of CD4+ T cell and regulatory T cell associated markers.

RESULTS

The Tregitope 167 treated mice gained an average of 4% over their initial body weight at the time of sacrifice. In contrast, the mice treated with TNBS alone (no Tregitope) developed colitis, and lost 4% of their initial body weight at the time of sacrifice (P < 0.01). The body weight increase that had been observed in the mice pre-treated with Tregitope 167 was substantiated by a lower disease activity index and a decreased colon weight as compared to the diseased control group (P < 0.01 and P < 0.001, respectively). Immunohistochemical staining of the colonic tissues for CD4+ showed that inflammatory cell infiltrates were present in TNBS treated mice with or without administration with tregitope 167 and that these cellular infiltrates consisted mainly of CD4+ cells. For both TNBS treated groups CD4+ T cell infiltrates were observed in the sub-epithelial layer and the lamina propria. CD4+ T cell infiltrates were also present in the muscularis mucosa layer of the diseased control mice, but were absent in the Tregitope 167 treated group. Numerous Foxp3 positive cells were detected in the lamina propria and sub-epithelium of the colon sections from mice treated with Tregitope 167. Furthermore, the Foxp3 and glycoprotein A repetitions predominant markers were significantly increased in the CD4+ T lymphocyte population in the thymus of the mice pre-treated with adeno-associated virus serotype 5 (cytomegalovirus promoter-Tregitope 167), as cytomegalovirus promoter compared to lymphocyte populations in the thymus of diseased and the healthy control mice (P < 0.05 and P < 0.001, respectively).

CONCLUSION

This study identifies adeno-associated virus-mediated delivery of regulatory T-cell epitope 167 as a novel anti-inflammatory approach with the capacity to decrease intestinal inflammation and induce long-term remission in inflammatory bowel disease.

New insights into the role of STAT3 in IBD

Although it is clear that inflammatory bowel disease (IBD) involves an inappropriate immune response to floral components, the molecular determinants that mediate the gene transcription underlying and aggravating disease remain poorly understood. There is building momentum, however, that implicates differential regulation of the signal transducer and activator of transcription (STAT) 3 as an important factor in mediating pathogenic gene transcription in IBD, and this notion was reinforced by studies presented at the recent 2011 Digestive Disease Week (DDW) conference in Chicago. In the present report we integrate the existing body of literature with the novel data presented at this meeting to present a kaleidoscopic scheme so as to provide further insight into the role of STAT3 in IBD. A genetic propensity to its overactivation in the monocyte and epithelial compartment compromises the innate defense to allow low-level bacterial infection to fester and eventually initiate disease. The subsequent STAT3 activation in various relevant mucosal immune compartments, in particular epithelial cell proliferation and survival, and the function of the regulatory T cells and Th17 cells allow the mucosal immune system to fight the infection and return to steady state. As such, the action of STAT3 in IBD is highly context-dependent but always important.

Diagnosis and management of fistulizing Crohn's disease

The transmural inflammation characteristic of Crohn's disease predisposes patients to the formation of fistulas. Up to 50% of patients with Crohn's disease are affected by fistulas, which is a major problem given the considerable morbidity associated with this complication. Appropriate treatment of fistulas requires knowledge of specific pharmacological and surgical therapies. Treatment options depend on the severity of symptoms, fistula location, the number and complexity of fistula tracts, and the presence of rectal complications. Internal fistulas, such as ileoileal or ileocecal fistulas, are mostly asymptomatic and do not require intervention. By contrast, perianal fistulas can be painful and abscesses may develop that require surgical drainage with or without seton placement, transient ileostomy, or in severe cases, proctectomy. This Review describes the epidemiology and pathology of fistulizing Crohn's disease. Particular focus is given to external and perianal fistulas, for which treatment options are well established. Available therapeutic options, including novel therapies, are discussed. Wherever possible, practical and evidence-based treatment regimens for Crohn's disease-associated fistulas are provided.