Crohn's disease is a chronic inflammatory bowel disease. This disease can be treated with, among other things, biologicals such as adalimumab. Patients use adalimumab for a long time to maintain remission and to prevent relapse of the bowel inflammation. The disadvantages of this therapy are the high price and side effects (such as the higher risk of infection).

Currently, adalimumab is given every 2 weeks, by injection under the skin. The optimal time between two injections has never been investigated before. Prior research in patients with rheumatoid arthritis shows that disease remission can be maintained with longer injection-intervals. Our hypothesis is that this is the same for Crohn's disease patients. Our aim is to show non-inferiority of extending the adalimumab dosing interval, under strict disease monitoring in Crohn's disease patients in sustained (>9 months) clinical remission, compared to standard care.

During the trial,174 patients with stable Crohn's disease will be divided into 2 groups. One group continues adalimumab injections with the same 2-week interval. And the other group will incrementally extend the interval to 4 weeks, under strict disease monitoring. If a step-down leads to recurrence of disease activity patients will return to the preceding effective dosing interval. Thus, we will investigate whether, and for whom, it is safe to extend the adalimumab injection interval.

Rationale

Adalimumab is both an effective induction and maintenance therapy for Crohn's disease (CD). Due to the risk of side effects (infections, injection reaction) and high costs, an extension of the injection interval is an attractive option. However, this strategy has not been evaluated yet in a randomized controlled trial in CD patients.

Objective

To assess non-inferiority and cost-effectiveness of disease activity guided adalimumab interval lengthening in CD patients in sustained (>9 months) clinical remission, compared to standard dosing of every other week.

Study design

Multicenter, randomized controlled, open label non-inferiority trial, with two treatment arms.

Study population

Crohn's disease patients, in sustained clinical remission on adalimumab maintenance therapy.

Intervention

Intervention arm: The adalimumab injection interval during maintenance therapy (40 mg per 2 weeks) will be extended through a stepwise disease activity guided manner to 3 weeks and subsequently - after 24 weeks - to 4 weeks. If a step-down leads to recurrence of disease activity patients will return to the preceding effective dosing interval.

Control arm: patients will continue adalimumab maintenance treatment of 40mg per 2 weeks. Treatment decisions are made at the discretion of the treating physician.

Main study parameters/endpoints

Primary outcome: Cumulative incidence of persistent disease flares in 48 weeks of follow-up. A persistent flare is defined as two of three of the following criteria persisting for > 8 weeks, despite dose escalation of adalimumab; FC >250 µg/g, CRP≥10 mg/L, HBI ≥5. Non-inferiority is reached if the difference in cumulative incidence of persistent flares not exceeds the non-inferiority margin of 15%.

Secondary outcomes include cumulative incidence of transient flares, adverse events, predictors for successful dose reduction and cost-effectiveness.

Inclusion Criteria:

• Diagnosis of colonic and/or distal ileal CD

• Sustained steroid-free clinical remission for >9 months whilst being treated with adalimumab at a stable dose

• Adalimumab dosed at 40 mg sc every 2 weeks

• Full clinical response and disease control, all three criteria below need to be fulfilled prior to enrollment:

  • Absence of active inflammatory intestinal or extra-intestinal symptoms, as judged by both patient and physician
  • Fecal calprotectin (FC) < 150 μg/g and C reactive protein (CRP) <10 mg/L
  • Harvey Bradshaw Index (HBI) <5

Exclusion Criteria:

• Absence of written informed consent
• Concomitant corticosteroid usage
• Need for CD-related surgery
• Actively draining peri-anal fistula
• Pregnancy or lactation
• Other significant medical conditions that might interfere with this study (such as current/recent malignancy, immunodeficiency syndromes and psychiatric illness)
• Impossibility to measure outcomes, e.g. planned relocation, language issues, short life expectancy