Overview

Unfortunately, some patients with Crohn's disease (CD) fail to respond to the best clinical treatments and some only experience temporary benefit. For severe Crohn's disease, there is an experimental treatment called "high dose immunoablation" followed by autologous hematopoietic stem cell transplantation (HSCT). This study removes over active lymphocytes (immunoablation) and replaces them using blood stem cells that have been taken from the patient's own body. The aim of the study is to reset or reprogram the patient's immune system to its state prior to diagnosis.

Eligibility

Inclusion Criteria:

1. Aged 13-28 years are eligible
2. Confirmed diagnosis of active Crohn's disease:
   1. Diagnosis of Crohn's disease based on typical radiological appearances and / or typical histology at least 6 months prior to screening.
   2. Active disease at the time of registration to the trial, defined as
   3. PCDAI > 30, and ii) Two of the following:
   4. elevated CRP
   5. endoscopic evidence of active disease confirmed by histology
   6. clear evidence of active small bowel Crohn's disease on CT or MR enterography.
3. Unsatisfactory course despite 3 immunosuppressive agents (usually azathioprine,

   methotrexate and infliximab, adalimumab and/or certolizumab) in addition to corticosteroids. Patients should have relapsing disease (i.e. 1 exacerbation/year) despite thiopurines, methotrexate and/or infliximab/adalimumab/certolizumab maintenance therapy or clear demonstration of intolerance / toxicity to these drugs.

4. Current problems unsuitable for surgery or patient at risk for developing short bowel syndrome.
5. Accepted by a majority of the members of the combined IBD Center as an appropriate candidate (see Selection description below).
6. Informed consent
   1. Prepared to undergo additional study procedures as per trial schedule
   2. Patient has undergone intensive counseling about risks

Exclusion Criteria:

1. Pregnancy or unwillingness to use adequate contraception during the study, in women of childbearing age. Unwillingness of using appropriate contraceptive measures in males.
2. Concomitant severe disease
   1. renal: creatinine clearance < 30 mL/min (measured or estimated)
   2. cardiac: clinical evidence of refractory congestive heart failure; left ventricular ejection fraction < 40% by cardiac echo; chronic atrial fibrillation necessitating oral anticoagulation; uncontrolled ventricular arrhythmia; pericardial effusion with hemodynamic consequences as evaluated by an experienced echo cardiographer
   3. pulmonary: diffusion capacity <40%
   4. psychiatric disorders including active drug or alcohol abuse
   5. concurrent or recent history of malignant disease (excluding non-melanoma skin cancer)
   6. uncontrolled hypertension, defined as resting systolic blood pressure ≥ 140 and/or resting diastolic pressure ≥ 90 despite at least 2 anti-hypertensive agents.
   7. any infection with HIV, HTLV-1 or 2, hepatitis viruses, or any other infection the investigators consider a contraindication to participation.
   8. other chronic disease causing significant organ failure.
3. Infection or risk thereof:
   1. Current clinical relevant abscess or significant active infection.
   2. Perianal fistula without free drainage. Perianal fistulas is not an exclusion provided there is natural free drainage or a seton suture(s) have been placed.
   3. History of tuberculosis or at current increased risk of tuberculosis
   4. Quantiferon Gold test result or other investigations that the investigators regard as evidence of active tuberculosis.
   5. Abnormal chest X-ray (CXR) consistent with active infection or neoplasm.
   6. Significant malnutrition: Body Mass Index (BMI) ≤ 18, serum albumin < 20 g/l.
   7. Previous poor compliance. 8) Concurrent enrollment in any other protocol using an investigational drug or hematopoietic growth factor up to four weeks before study entry.