Therapeutic Drug Monitoring in Perianal Fistulizing Crohn’s Disease

Retrospective Cohort Study on the Predictive Value of Primary Non-response to Initial Biologic for Future Biologic Use in Patients with Inflammatory Bowel Disease

BACKGROUND

The armamentarium of medical therapies to treat inflammatory bowel disease (IBD) continues to grow, which has expanded treatment options, particularly after first biologic failure. Currently, there are limited studies investigating the predictive value of first biologic primary non-response (PNR) on subsequent biologic success. Our objective was to determine if PNR to the first biologic for IBD is predictive of response to subsequent biologic therapy.

METHODS

A multicenter retrospective chart review study was performed with patients with IBD that received two or more biologics. PNR was defined as no clinical or symptomatic improvement after at least six weeks of treatment leading to cessation of drug. Patients who stopped their first biologic due to adverse side effects were classified in the intolerance group. Patients with initial significant response to biologic followed by a loss of response were classified as secondary loss of response (SLOR). Data analysis was performed with Python and Excel.

RESULTS

Of the 249 patients that met inclusion criteria, there were 87 patients with PNR, 96 patients with SLOR, and 66 patients with intolerance to their first biologic exposure. Patients with ulcerative colitis (UC: 41.3%, p = 0.0083) and IBD-unclassified (IC: 56.3%, p = 0.0099) were found to have a significantly higher rate of primary non-response compared to patients with Crohn's disease (CD: 25.0%). Patients on adalimumab for their first biologic had a significantly (p = 0.0014) higher rate of PNR (42.7%, UC: 50.0%, CD: 32.7%) compared to those on infliximab (23.0%, UC: 31.0%, CD: 12.1%). Patients with PNR did not have a higher rate of second biologic nonresponse when compared to patients who had SLOR or intolerance to their first biologic. Univariate analyses demonstrated no difference in rates of response to second biologic when switching intra-class or out-of-class.

CONCLUSION

Ulcerative colitis and IBDU have higher rates of PNR compared to Crohn's disease, but still have high response rates to second biologic agents. Adalimumab may be a suboptimal initial biologic given its higher PNR rate compared to infliximab. Our results support that there is an equally likely chance of response to second biologic after first biologic PNR. Subanalyses evaluating intraclass and out-of-class medication switching showed similar success.

Management of Perianal Fistulizing Crohn's Disease

Perianal fistulizing Crohn's disease (CD) represents a severe phenotype of CD that is associated with significant morbidity and reduction in quality of life. Perianal fistulizing CD is caused by a complex interplay of genetic predisposition, immune dysregulation, gut dysbiosis, and various unknown physiological and mechanical factors. A multidisciplinary approach is hence required for optimal management . A detailed anatomical description and classification of perianal fistula, including comprehensive clinical, endoscopic, and radiological diagnostic workup, is an important prerequisite to treatment. For simple perianal fistulas, use of antibiotics and immunomodulators, with or without fistulotomy, are appropriate measures. The medical management of complex perianal fistula, on the other hand, requires adequate control of infection before initiation of therapy with immunomodulators. In active complex perianal fistula, anti-tumor necrosis factors remain the most accepted therapy, with concomitant use of antibiotics or immunomodulators enhancing the efficacy. For patients refractory to anti-tumor necrosis factors, treatment with anti-integrins, anti-interleukins, and small molecules is being evaluated. Mesenchymal stem cells, hyperbaric oxygen therapy, and exclusive enteral nutrition have also been investigated as adjunct therapies. Despite the expansion of the medical armamentarium, a large proportion of the patients require surgical interventions. In this review, we provide an up-to-date overview of the pathophysiology, clinical presentation, diagnosis, and medical management of perianal fistulizing CD. A brief overview of the surgical management of perianal fistulizing CD is also provided.

The potential for medical therapies to address fistulizing Crohn's disease: a state-of-the-art review

INTRODUCTION

Crohn's disease (CD) is a chronic, relapsing immune mediated disease, which is one of the two major types of inflammatory bowel disease (IBD). Fistulizing CD poses a significant clinical challenge for physicians. Effective management of CD requires a multidisciplinary approach, involving a gastroenterologist and a GI surgeon while tailoring treatment to each patient's unique risk factors, clinical representations, and preferences.

AREAS COVERED

This comprehensive review explores the intricacies of fistulizing CD including its manifestations, types, impact on quality of life, management strategies, and novel therapies under investigation.

EXPERT OPINION

Antibiotics are often used as first-line therapy to treat symptoms. Biologics that selectively target TNF-α, such infliximab (IFX), have shown high efficacy in randomized controlled trials. However, more than 50% of patients lose response to IFX, prompting them to explore alternative strategies. Current options include adalimumab and certolizumab pegol combination therapies, as well as small-molecule drugs targeting Janus kinases such as Upadacitinib. Furthermore, a promising treatment for complex fistulas is mesenchymal stem cells such as Darvadstrocel (Alofisel), an allogeneic stem cell-based therapy. However, surgical interventions are necessary for complex cases or intra-abdominal complications. Setons and LIFT procedures are the most common surgical options.

Perianal fistulizing Crohn's disease: Current perspectives on diagnosis, monitoring and management with a focus on emerging therapies

Crohn's disease (CD), a chronic inflammatory bowel disorder, manifests in various phenotypes, with fistulizing perianal CD (CD-PAF) being one of its most severe phenotypes. Characterized by fistula formation and abscesses, CD-PAF impacts 17% to 34% of all CD cases and with a significantly deleterious impact on patient's quality of life, while increasing the risk for anorectal cancers. The pathogenesis involves a complex interplay of genetic, immunological and environmental factors, with cytokines such as tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β) playing pivotal roles. Diagnostic protocols require a multi-disciplinary approach including colonoscopy, examination under anesthesia and magnetic resonance imaging. In terms of treatment, biologics alone often prove inadequate, making surgical interventions such as setons and fistula surgeries essential. Emerging therapies such as mesenchymal stem cells are under study. The South Asian context adds layers of complexity, including diagnostic ambiguities related to high tuberculosis prevalence, healthcare access limitations and cultural stigma toward perianal Crohn's disease and ostomy surgery. Effective management necessitates an integrated, multi-disciplinary approach, especially in resource-constrained settings. Despite advances, there remain significant gaps in understanding the disease's pathophysiology and a dearth of standardized outcome measures, underscoring the urgent need for comprehensive research.

Subcutaneous Infliximab [CT-P13], a True Biologic 2.0. Real Clinical Practice Multicentre Study

BACKGROUND

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is characterized by chronic relapsing intestinal inflammation. There are few data on the efficacy and safety in clinical practice of infliximab (CT-P13) in subcutaneous formulation (SC) for the treatment of patients with IBD.

METHODS

Multicenter, prospective study of patients with IBD in clinical remission, who had their treatment changed from intravenous (IV) infliximab to SC. Two groups of patients were evaluated according to whether they were on IV infliximab treatment at standard or intensified doses before the switch.

RESULTS

A total of 30 patients were on standard dosing and another 30 in intensified therapy. Treatment persistence in both groups at 6 months was greater than 95%. In both groups after the change, neither the biomarkers of inflammation nor the activity indices underwent significant changes at 3 and 6 months compared to the baseline value. Similarly, in both groups, infliximab trough levels showed a significant increase 3 and 6 months after the change to SC. No serious adverse events were registered.

CONCLUSIONS

The CT-P13 SC brings a new anti-TNF era. Achieving much higher drug levels that are constant over time opens new paths to explore the management of patients with IBD: less immunogenicity, better perianal disease control and higher achievement of mucosal healing.