Biological agents for the treatment of Crohn’s disease

What is Crohn’s disease?

Crohn’s disease, an autoimmune gastrointestinal disorder, is one of two types of inflammatory bowel disease characterized by possible inflammation throughout the entire thickness of the bowel wall. It has the potential to affect the entire gastrointestinal tract, ranging from the mouth to the colon. This disease typically exhibits wide variability among patients and follows a pattern of recurring flare-ups and periods of remission, with overall disease progression.

Biological agents for the treatment of Crohn's disease 1

Although the exact cause of Crohn’s disease remains unknown, it is believed to stem from an inappropriate immune response to environmental factors within the gastrointestinal tract. It demonstrates a bimodal distribution, affecting individuals between the ages of 15 and 30, as well as those between 40 and 60 years old. As our understanding of the disease continues to grow, treatment approaches have evolved, with biologic monoclonal antibodies playing a crucial role in evidence-based medicine and treatment guidelines.

Presently, the American Gastroenterological Association and the American College of Gastroenterology recommend the use of biologic agents as essential components of therapy for patients with moderate to severe Crohn’s disease. Moderate to severe Crohn’s disease is defined by a high risk of disease-related complications, significant impact on quality of life, burden of inflammation and gastrointestinal tract involvement, hospitalization, or the need for surgery.

Scoring and Treatment Approaches for Moderate to Severe Crohn’s Disease

The Crohn’s Disease Activity Index (CDAI) Score is a widely accepted scoring system that helps determine the severity of Crohn’s disease in patients. It takes into account various factors including demographics, subjective symptoms, laboratory values, and extraintestinal findings, providing scores ranging from 0 to 600. A score falling within the range of 220 to 450 indicates moderate disease, while a score over 450 indicates severe disease.

For the treatment of moderate to severe Crohn’s disease, several biologic immunomodulator pharmacotherapy agents have been approved. First-line agents include infliximab, adalimumab, and certolizumab-pegol. Second-line agents are vedolizumab and ustekinumab. However, natalizumab is no longer recommended due to the risk of progressive multifocal leukoencephalopathy.

In cases where conventional therapy options, such as corticosteroids, thiopurines, or methotrexate, fail to provide a satisfactory response, biologic agents are often initiated as an alternative treatment approach.

Biologic Agents for the Treatment of Moderate to Severe Crohn Disease


A Chimeric TNF-alpha Inhibitor Infliximab, the first monoclonal antibody approved for Crohn disease therapy, is indicated for moderately to severely active Crohn disease in patients aged 6 and older. Clinical trials have shown its efficacy in inducing and maintaining remission, with higher rates of clinical response compared to placebo. It is also effective in reducing and maintaining fistulas in adult patients.


A Fully Human Tumor Necrosis Factor Blocker Adalimumab, approved for both pediatric and adult patients with moderate to severe Crohn disease, is used for induction and maintenance treatment. It has shown superiority over placebo in inducing remission and response, with higher doses leading to greater reduction in CDAI scores. Adalimumab is recommended for patients who have not responded adequately to infliximab or have shown intolerance.


A First-Line Option Certolizumab-pegol is considered as a first-line option for patients with moderate to severe Crohn disease who have not responded adequately to infliximab or adalimumab. It has demonstrated a reduction in CDAI scores and clinical response compared to placebo. Although it has less immunogenicity potential than infliximab, it is found to be less effective in induction and maintenance treatment.

Vedolizumab and Ustekinumab

Second-Line Agents Vedolizumab and ustekinumab are alternative options for patients who have failed TNF-alpha inhibitors. Vedolizumab, a humanized integrin receptor inhibitor, showed no significant difference in CDAI scores during induction but demonstrated efficacy for maintenance treatment. Ustekinumab, an interleukin-12 and interleukin-23 inhibitor, has evidence for both induction and remission but limited data in patients with Crohn disease.

Advancements in Biologic Therapy

Biologic agents have revolutionized the treatment of Crohn disease, providing options beyond conventional therapies. They offer significant reductions in CDAI scores and improve overall quality of life. Early initiation of biologic therapy may lead to a decrease in disease complications.

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