The purpose of the study is to determine whether an investigational compound, ALX-0600, is safe and effective in treating Crohn's Disease.

The study is twelve weeks in duration and there are eight weeks of once-daily injections into your abdomen or thigh. There are a total of six visits.

Inclusion Criteria

1. Men and women, 18 years of age and older
2. Signed and dated informed consent to participate before any study-related procedures are performed
3. Diagnosis of Crohn's disease for at least 6 months that has been documented and confirmed
4. A Crohn's Disease Activity Index (CDAI) score of 220 to 450 inclusive
5. Female subjects who are not surgically sterile or postmenopausal must use medically acceptable methods of birth control during and for 30 days after the treatment period.
6. HCT 30% or greater
7. WBC 3.5 x 109/L or greater
8. Platelets 100 x 109/L or greater
9. Adequate renal function defined as: serum creatinine and BUN 1.5 x ULN or less
10. Adequate hepatic function defined as: ALT/SPGT, AST/SGOT 2.0 x ULN or less; total bilirubin 1.25 x ULN or less, alkaline phosphatase 1.5 x ULN or less
11. Female subjects of childbearing potential must have negative urine pregnancy test results prior to randomization
12. A stool sample must be taken at screening and analyzed by a local laboratory for enteric pathogens, pathogenic ova and parasites, and Clostridium difficile toxin, and reported negative prior to randomization.
13. C-reactive protein value must be 1.0 mg/dL or more, unless there are obvious manifestations of currently active Crohn's disease such as positive observations on endoscopy, other positive indications by laboratory test results, or the subject has had a previous intestinal resection for Crohn's disease.

Exclusion Criteria

1. Nutritionally compromised subjects requiring enteral or parenteral therapy to maintain weight
2. Body weight less than 40 kg or more than 100 kg
3. Bowel obstruction or any condition that may predispose to its development, intestinal perforation, or significant gastrointestinal hemorrhage
4. Current ileostomy or colostomy or extensive external fistulization (more than 3 external fistulae which are expressible with gentle compression)
5. Expected to require surgical therapy for Crohn's disease or Crohn's disease related complications within 12 weeks of screening. If an abscess is present, it should be drained at least 3 weeks before pre-screening
6. History of ulcerative colitis within 6 months of screening visit
7. Cushing's syndrome
8. Known HIV infection, or symptoms or signs of HIV infection
9. Acute systemic infection and/or intestinal infection requiring antibiotic therapy at time of screening or baseline
10. Evidence of chronic hepatitis B or C viral infection
11. Decompensated liver disease
12. Clinically significant ECG abnormalities
13. History of angina or cardiac arrhythmia requiring drug or device intervention or clinically significant congestive heart failure or other clinically significant cardiac disease
14. History of myocardial infarction within 12 months of screening
15. History of thromboembolic disease (e.g., phlebitis, pulmonary embolus) or known congenitally or acquired prothrombotic disorder (e.g., protein C deficiency)
16. History of cancer (other than resected cutaneous basal or squamous cell carcinoma or in situ cervical cancer) or clinically significant lymphoproliferative disease with fewer than 5 years documented disease-free state
17. Known substance abuse in the previous 2 years
18. Nursing mothers or pregnant women
19. Use of native GLP-2, growth hormone, or growth factors within 3 months of signing informed consent
20. Use of any of the prior or concomitant medications described in section 5.4, except as specified
21. Known hypersensitivity to any of the active or inactive constituents of ALX-0600