Dose-Ranging Phase 2b Study of ABX464 in Moderate to Severe Ulcerative Colitis

Inclusion Criteria:

* Men or women age 18 - 75 years;
* Diagnosis of moderate to severe active UC (including ulcerative proctitis if proximal extension of disease occurs beyond 10 cm) confirmed by endoscopy and histology at least 12 Weeks prior to screening visit. Moderate to severe active UC defined by Modified Mayo Score (MMS) of 5 to 9 inclusive (on a scale of 0-9). Moderate to severe active UC should be confirmed at screening visit with a centrally read endoscopy sub-score of at least 2 (on a scale of 0-3);
* Patients having either a documented inadequate response, no response, a loss of response, or an intolerance (defined as the occurrence of at least one Adverse Reaction leading to treatment discontinuation) to either immunosuppressant treatment (i.e., azathioprine, 6-mercaptopurine, methotrexate), tumor necrosis factor \[TNF\] inhibitors, vedolizumab, JAK inhibitors and/or corticosteroid treatment. Inadequate response, no response, loss of response is defined as:

  i. Active disease or relapse in spite of thiopurines or methotrexate given at an appropriate dose for at least 3 months (i.e. azathioprine 2-2.5 mg/kg/day or mercaptopurine 1-1.5 mg/kg/day in the absence of leukopenia), and/or ii. Active disease despite corticosteroids treatment (prednisolone up to 0.75 mg/kg/day) over a period of 4 Weeks, and/or iii. Active disease or relapse in spite of adequate treatment (as defined in the SmPC) with tumor necrosis factor \[TNF\] inhibitors or vedolizumab, and/or iv. Active disease or relapse in spite of adequate treatment with JAK inhibitors over a period of at least 6 Weeks.
* Patients receiving oral corticosteroids must have been on a stable dose of prednisone or prednisone equivalent (≤20 mg/day) or on beclomethasone diproprionate (≤5mg/day) or on budesonide MMX (≤9 mg/day) for at least 2 Weeks prior to the screening visit;
* Topical corticosteroids and topical 5-aminosalicylic acid preparations must have been withdrawn at least 2 Weeks prior to the screening visit;
* Patients who are on oral 5-aminosalicylic acid must have been on a stable dose for at least 4 Weeks prior to the screening visit;
* Patients who are receiving immunosuppressants in the form of azathioprine, 6-mercaptopurine, or methotrexate needed to be on a stable dose for at least 4 Weeks prior to screening visit. Patients taking methotrexate also are advised to take folic acid 1 mg/day (or equivalent) supplementation if there is no contraindication;
* Patients on probiotics (e.g., Culturelle® \[Lactobacillus GG, i-Health, Inc.\], Saccharomyces boulardii) must be on stable doses for at least 2 Weeks prior to the screening visit;
* Patients on antidiarrheals (e.g., loperamide, diphenoxylate with atropine) must be on stable doses for at least 2 Weeks prior to the screening visit;
* Patients who have received tumor necrosis factor \[TNF\] inhibitors, vedolizumab or other biologics must have discontinued therapy at least 8 Weeks prior to the screening visit due to lack or insufficient efficacy or intolerance;
* Patients previously treated with cyclosporine, tacrolimus or JAK inhibitors must have discontinued therapy at least 4 Weeks prior to the screening visit due to lack or insufficient efficacy or intolerance;
* Patients previously treated with tube feeding, defined formula diets, or parenteral alimentation/nutrition must have discontinued treatment 3 Weeks before the screening visit and must be able to take, orally, appropriate amount of food (calories) and liquids to maintain body weight;
* Patients with surveillance colonoscopy defined as per ECCO guidelines;
* Patients with the following hematological and biochemical laboratory parameters obtained at screening:

  i. Hemoglobin \> 9.0 g dL-1; ii. Absolute neutrophil count ≥ 750 mm-3; iii. Platelets ≥ 100,000 mm-3; iv. Total serum creatinine ≤ 1.3 x ULN (upper limit of normal); v. Creatinine clearance \> 90 mL min-1 by the Cockcroft-Gault equation within 60 days prior to baseline; vi. Total serum bilirubin \< 1.5 x ULN; vii. Alkaline phosphatase, AST (SGOT) and ALT (SGPT) \< 2 x ULN;
* Patients are able and willing to comply with study visits and procedures as per protocol;
* Patients should understand, sign and date the written voluntary informed consent form at the screening visit prior to any protocol-specific procedures are performed;
* Patients should be affiliated to a social security regimen (for French sites only);
* Females and males receiving the study treatment (potentially in combination with immunosuppressant) and their partners must agree to use a highly effective contraceptive method during the study and for 6 months after end of study or early termination. Contraception should be in place at least 2 Weeks prior to study participation. Women must be surgically sterile or if of childbearing potential must use a highly effective contraceptive method. Women of childbearing potential (WOCBP) will enter the study after confirmed menstrual period and a negative pregnancy test. Highly effective methods of contraception include true abstinence, intrauterine device (IUD) or hormonal contraception aiming at inhibition of ovulation, intrauterine hormone releasing system, bilateral tubal ligation, vasectomized partner. True abstinence is defined when this is in line with the preferred and usual lifestyle of the patient. In each case of delayed menstrual period (over one month between menstruations) confirmation of absence of pregnancy is required. This recommendation also applies to WOCBP with an infrequent or irregular menstrual cycle. Female and male patients must not be planning pregnancy during the trial and for 6 months post completion of their participation in the trial. In addition, male participants should use condoms and not donate sperm as long as contraception is required.

Exclusion Criteria:

* Patients with Crohn's Disease (CD) or presence or history of fistula, indeterminate colitis (IC), infectious/ischemic colitis or microscopic colitis (lymphocytic and collagenous colitis);
* History of toxic megacolon, abdominal abscess, symptomatic colonic stricture or stoma; history or imminent colectomy, colonic malignancy;
* History or current evidence of colonic dysplasia or adenomatous colonic polyps. Patient with severe gastrointestinal complications; e.g., short bowel syndromes, recent or planned bowel surgery, Ileostomy and/or colostomy, recent bowel perforation;
* History of more than one episode of herpes zoster or a history (single episode) of disseminated zoster;
* Patients with active infections at screening such as infected abdominal abscess, Clostridium difficile (stool antigen and toxin required), CMV (positive IgM), TB and recent infectious hospitalization;
* Patients previously treated with ABX464;
* Acute, chronic or history of clinically relevant pulmonary, cardiovascular, hepatic, pancreatic or renal functional abnormality, encephalopathy, neuropathy or unstable CNS pathology such as seizure disorder, angina or cardiac arrhythmias, active malignancy or any other clinically significant medical problems as determined by physical examination and/or laboratory screening tests and/or medical history;
* Acute, chronic or history of immunodeficiency or autoimmune disease;
* History of malignancy excluding patients considered cured (5 years disease free survivors);
* Serious illness requiring systemic treatment and/or hospitalization within 3 Weeks prior to baseline;
* Pregnant or breast-feeding women;
* Illicit drug or alcohol abuse or dependence;
* Patients who received live vaccine 30 days or fewer before first dose of study treatment and/or who's planning to receive such a vaccine during the study duration;
* Use of any investigational or non-registered product within 3 months or within 5 half-lives preceding baseline, whichever is longer and during the study;
* Any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol.