Treatment of Moderate Crohn's Disease

First-Line Treatment Options

• The American Gastroenterological Association recommends anti-TNF therapy (infliximab, adalimumab) as first-line therapy for patients with moderate Crohn's disease, particularly for those with risk factors for poor prognosis 1, 2
• Anti-TNF agents (infliximab, adalimumab) are recommended as first-line therapy for moderate-to-severe Crohn's disease with risk factors of poor prognosis, with a strength of evidence rated as high 3, 2
• Infliximab is administered intravenously at 5 mg/kg at weeks 0, 2, and 6 for induction, followed by maintenance every 8 weeks, as recommended by the Crohn's and Colitis Foundation 4
• Adalimumab is given subcutaneously with an induction dose of 160 mg, then 80 mg two weeks later, followed by 40 mg every two weeks for maintenance, with a moderate level of evidence supporting its use 4
• Patients should be evaluated for response to anti-TNF induction therapy between 8-12 weeks to determine if therapy modification is needed, as suggested by the Clinical Gastroenterology and Hepatology society 3, 2

Combination Therapy

• The Gastroenterology society recommends combination therapy with a thiopurine when starting infliximab to improve efficacy and reduce immunogenicity, with a high strength of evidence 4, 1
• For adalimumab, combination with methotrexate may be more effective than monotherapy, though evidence is less robust, with a moderate level of evidence supporting its use 1, 5
• Combination therapy has shown better outcomes for remission induction compared to monotherapy, as reported by the Gastroenterology society, with a high strength of evidence 1, 5

Alternative First-Line Options

• Ustekinumab is recommended for induction of remission in patients with moderate-to-severe Crohn's disease, particularly in those who have inadequate response to conventional therapy or anti-TNF therapy, with a moderate level of evidence supporting its use 4, 1
• Vedolizumab is suggested as an alternative to certolizumab pegol for induction of remission, with a moderate level of evidence supporting its use, and may be considered in patients who prioritize a potentially better safety profile over speed of action 1, 5

Second-Line Treatments

• Ustekinumab is strongly recommended for patients who never responded to anti-TNF therapy, with a high strength of evidence supporting its use, as suggested by the Gastroenterology society 1, 5
• Vedolizumab is suggested as an alternative for induction of remission in primary non-responders, with a moderate level of evidence supporting its use, and may be considered in patients who have failed anti-TNF therapy 1
• For patients who initially responded but later lost response to infliximab, adalimumab or ustekinumab are recommended, with a moderate level of evidence supporting their use, as suggested by the Gastroenterology society 1, 5
• If adalimumab was the first-line drug with subsequent loss of response, infliximab may be considered as a second-line agent, with a moderate level of evidence supporting its use, as reported by the Gastroenterology society 1, 6

Corticosteroids

• In patients with moderate Crohn's disease who have failed budesonide, prednisone 40-60 mg/day is suggested to induce remission, with a moderate level of evidence supporting its use, as recommended by the Clinical Gastroenterology and Hepatology society 7, 8
• Patients should be evaluated for response to prednisone between 2-4 weeks, with a moderate level of evidence supporting this approach, as suggested by the Clinical Gastroenterology and Hepatology society 7, 8
• Corticosteroids are NOT recommended for maintenance of remission due to significant side effects, including bone loss, metabolic complications, increased intraocular pressure, and increased risk of infections, with a high strength of evidence supporting this recommendation, as reported by the Clinical Gastroenterology and Hepatology society 7, 8

Immunomodulators

• Thiopurines (azathioprine, 6-mercaptopurine) are not recommended as monotherapy for induction of remission, with a high strength of evidence supporting this recommendation, as suggested by the Clinical Gastroenterology and Hepatology society and the Gastroenterology society 7, 1, 2
• Thiopurines may be used for maintenance of remission in selected patients who achieved remission on corticosteroids, with a moderate level of evidence supporting their use, as recommended by the Clinical Gastroenterology and Hepatology society 7, 2
• Parenteral (subcutaneous or intramuscular) methotrexate is suggested for induction and maintenance of remission, with a moderate level of evidence supporting its use, as recommended by the Gastroenterology society 1, 2
• Oral methotrexate is not recommended due to limited efficacy, with a high strength of evidence supporting this recommendation, as reported by the Gastroenterology society 1, 5

Treatment Algorithm

• First-line therapy: Anti-TNF (infliximab or adalimumab), preferably in combination with thiopurine or methotrexate, with a high strength of evidence supporting this approach, as recommended by the Journal of Crohn's and Colitis and the Gastroenterology society 4, 3, 1
• Alternative first-line: Ustekinumab or vedolizumab, especially in patients with contraindications to anti-TNF therapy, with a moderate level of evidence supporting their use, as suggested by the Journal of Crohn's and Colitis and the Gastroenterology society 4, 1
• For primary non-response to anti-TNF: Switch to ustekinumab or vedolizumab, with a high strength of evidence supporting this approach, as recommended by the Gastroenterology society 1, 5
• For secondary non-response to anti-TNF: Switch to adalimumab or ustekinumab if on infliximab, or consider infliximab or ustekinumab if on adalimumab, with a moderate level of evidence supporting these approaches, as suggested by the Gastroenterology society 1, 6

Monitoring

• Evaluate response to anti-TNF induction therapy between 8-12 weeks, with a moderate level of evidence supporting this approach, as suggested by the Clinical Gastroenterology and Hepatology society 3, 2
• Assess response to prednisone between 2-

AGA Guidelines for Management of Moderate‑to‑Severe Crohn’s Disease

Disease Severity Classification

• Moderate‑to‑severe Crohn’s disease is defined by a Crohn’s Disease Activity Index (CDAI) ≥ 220 or a high risk of adverse outcomes (e.g., need for surgery, hospitalization, or disability) based on structural damage, inflammatory burden, and quality‑of‑life impact. (American Gastroenterological Association – strong recommendation) 9

First‑Line Biologic Therapy for Biologic‑Naïve Patients

Anti‑TNF + Thiopurine Combination (preferred)

• Infliximab 5 mg/kg IV at weeks 0, 2, 6 then every 8 weeks combined with azathioprine or 6‑mercaptopurine is recommended as the top regimen for induction and maintenance. (AGA – strong recommendation; moderate‑certainty evidence) [9][10]
• Adalimumab 160 mg subcutaneously (SC) then 80 mg at week 2, followed by 40 mg every 2 weeks combined with methotrexate is the second‑ranked regimen. (AGA – strong recommendation; moderate‑certainty evidence) [9][10]

Alternative Biologic Options

• Ustekinumab (IL‑12/23 inhibitor) is recommended with a strong recommendation and moderate‑certainty evidence. (AGA – strong recommendation) [10][11]12
• The AGA recommends infliximab, adalimumab, or ustekinumab over certolizumab pegol for biologic‑naïve patients because of superior efficacy (inflximab RR 0.54, adalimumab RR 0.82; moderate certainty). Certolizumab pegol has low‑certainty evidence and did not meet the minimal clinically important difference. (AGA – strong recommendation) [10][12][11][13]

Alternative Biologics for Specific Priorities

• Vedolizumab is conditionally suggested over no treatment and preferred over certolizumab pegol when safety is prioritized over rapid onset. Evidence is low certainty for induction but moderate certainty for maintenance. (AGA – conditional recommendation) [10][11]

Safety Considerations – Natalizumab

• The AGA advises against natalizumab because of the risk of progressive multifocal leukoencephalopathy (PML), despite modest efficacy (RR 0.88 for induction, RR 0.58 for maintenance). It may be considered only in JC‑virus‑antibody‑negative patients who can adhere to intensive monitoring and place high value on potential benefit. (AGA – conditional recommendation; low‑certainty evidence) [10][11][13][12]

Second‑Line Therapy After Anti‑TNF Failure

Primary Non‑Response (no initial response)

• Ustekinumab is strongly recommended (strong recommendation, moderate certainty) as the next line. (AGA – strong recommendation) 10
• Vedolizumab is suggested as an alternative option. (AGA – conditional recommendation) 10

Secondary Non‑Response (loss of response)

• After infliximab failure, switching to adalimumab or ustekinumab is conditionally recommended (low certainty). (AGA – conditional recommendation) 10
• After adalimumab failure, infliximab or ustekinumab may be considered based on indirect evidence. (AGA – conditional recommendation) 10

Perianal Fistulizing Disease

• Infliximab is strongly recommended for both induction and maintenance of fistula remission (strong recommendation, moderate certainty). (AGA – strong recommendation) 9
• Initiating biologic therapy early (rather than after failure of 5‑ASA or corticosteroids) is conditionally recommended (low certainty). (AGA – conditional recommendation) 9
• Combination of infliximab with antibiotics is strongly recommended for fistula induction (strong recommendation, moderate certainty). (AGA – strong recommendation) 9
• Antibiotics alone are strongly not recommended for fistula remission (strong recommendation against). (AGA – strong recommendation) 9

Role of Corticosteroids

• Corticosteroids are not recommended for maintenance of remission due to significant adverse effects (strong recommendation against). (AGA – strong recommendation) 9

Immunomodulators

Thiopurines (Azathioprine, 6‑Mercaptopurine)

• Do not use as monotherapy for induction (conditional recommendation against; very low certainty). (AGA – conditional recommendation) 10
• May be used for maintenance in patients who achieved remission with corticosteroids (conditional recommendation; low certainty). (AGA – conditional recommendation) 10

Methotrexate

• Parenteral methotrexate (subcutaneous or intramuscular) is suggested for both induction and maintenance (conditional recommendation, moderate certainty). (AGA – conditional recommendation) 10
• Oral methotrexate is not recommended because of limited efficacy (conditional recommendation, moderate certainty). (AGA – conditional recommendation) 10