Study of OSE-127 vs Placebo in Patients With Moderate to Severe Active Ulcerative Colitis

Inclusion Criteria:

1. Provision of signed and dated informed consent document indicating that the patienthas been informed of all the pertinent aspects of the trial prior to enrollment

2. Willingness and ability to comply with scheduled visits, treatment plans, laboratorytests, and other study procedures

3. Willingness to refrain from live or attenuated vaccines during the study and for 12weeks after last dose

4. Male or female 18 to 75 years of age, inclusive

5. Diagnosis of moderate to severe active UC made at least 3 months before thescreening visit. The diagnosis of UC must have been confirmed by endoscopy, with aminimal extent of 15 cm from anal margin and histology (Moderate to severe active UCis defined by a modified Mayo score between 4 and 9, inclusive. The modified Mayoscore is defined by the addition of the rectal bleeding subscore, the stoolfrequency sub-score, and the endoscopic sub-score. Thus, to be included, a patientmust have the following:

6. a rectal bleeding score ≥ 1,

7. a stool frequency score ≥ 1 (sub-score calculated before bowel preparation),and

8. an endoscopic sub-score ≥ 2

9. No previous biologic therapy (i.e., TNF antagonists, vedolizumab or ustekinumab) andprior or current UC documented medication history that includes at least 1 of thefollowing:

10. Corticosteroids

11. Immunosuppressive agents

OR

Previous or current biologic therapy

Exclusion Criteria:

1. Stoma, proctocolectomy, or subtotal colectomy

2. Physician judgment that patient is likely to require any surgery for UC during thestudy duration, or double-blind phase duration at least

3. Evidence of fulminant colitis, toxic megacolon, or perforation

4. Current or recent (within 4 weeks prior to screening) hospitalization for UC careand/or treatment with IV steroids

5. The following laboratory results at screening:

6. Elevation at screening of aminotransferase (AST), alanine aminotransferase (ALT) > 3 × the upper limit of normal (ULN) or total bilirubin > 2 × ULN (unless due to Gilbert's disease) or evidence of chronic liver disease

7. Platelet count < 100,000/mm3

8. Hemoglobin (Hgb) < 8.5 g/dL

9. Neutrophils < 1500/mm3

10. Lymphocytes < 800/mm3

11. Absolute white blood cell (WBC) count < 3000/mm3

12. Crohn's disease or indeterminate colitis or any other diagnosis not consisting withUC

13. History or evidence of incompletely resected colonic dysplasia or unconventionallesion at risk of colonic adenocarcinoma

14. Stool culture or other examination positive for enteric pathogen, includingClostridium difficile (C. diff) toxin. If positive, the patient should be treatedand rescreening is allowed.

15. Men or women with childbearing potential not willing to use adequate birth controlduring the study. Adequate birth control includes surgical sterilization,intrauterine device, oral contraceptive, contraceptive patch, long-acting injectablecontraceptive, partner's vasectomy, double-barrier method (condom, diaphragm withspermicide), or abstinence during study and 30 days following the last follow-upvisit. Women of childbearing potential will enter the study after a negativepregnancy test.

16. Breastfeeding

17. Chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) from screening throughthe end of the study

18. Use of topical steroids and/or topical 5-aminosalicylic acid preparations within 2weeks before the screening visit (all such medications should be withdrawn at least 2 weeks prior to the screening visit)

19. Use of antidiarrheals within 2 weeks before the screening visit (all suchmedications should be withdrawn at least 2 weeks prior to the screening visit)

20. Treatment with azathioprine, 6-MP, methotrexate (MTX), cyclosporin, tacrolimus,sirolimus, leflunomide and/or mycophenolate mofetil within 4 weeks before thescreening visit (all such medications should be withdrawn at least 4 weeks prior tothe screening visit)