Study Evaluating the Long-term Safety and Efficacy of ABX464 in Active Ulcerative Colitis

This study is an open-label study aiming at evaluating the long-term safety and the efficacy profile of ABX464 given once a day (o.d) at 50 mg in subjects who have been previously enrolled in the ABX464-101 clinical study (induction study) and who are willing to continue their treatment.

All subjects will receive ABX464 given at 50 mg o.d irrespective of their previous treatment received in the ABX464-101 study (i.e. ABX464 or Placebo).

The actual treatment received by a subject throughout the previous study (ABX464-101) will not be known at the time the subjects enter this follow-up study. This treatment group will be communicated (throughout the investigators) to the subjects at the end of the ABX464-101 study (planned in Q3/2018).

The enrolment in this follow-up study will be based on the willingness of the subject to carry on his/her participation and also based on investigator's judgement.

Subjects will be treated with ABX464 for an overall period of 48 months. Subjects will be followed up weekly during the first month, every two weeks during the second month and then on a monthly basis until M24, then quaterly from M24 to M48.

Inclusion criteria

A subject will be eligible for inclusion in this study only if ALL of the following criteria apply:

• Subjects previously enrolled in the ABX464-101 clinical study who have completed the initial 2-month treatment phase;
• Subjects able and willing to comply with study visits and procedures;
• Subjects with hematological and biochemical laboratory parameters as follows at the D56 visit of the ABX464-101 study:

• Hemoglobin > 9.0 g dL-1;
• Absolute neutrophil count ≥ 750 mm-3;
• Platelets ≥ 100,000 mm-3;
• Total serum creatinine ≤ 1.3 x ULN (upper limit of normal);
• Creatinine clearance > 50 mL min-1 by the Cockcroft-Gault equation;
• Total serum bilirubin < 1.5 x ULN;
• Alkaline phosphatase, AST (SGOT) and ALT (SGPT) < 1.5 x ULN;
• Subjects should understand, sign and date the written voluntary informed consent form at the enrolment visit prior to any protocol-specific procedures being performed;
• Subjects should be affiliated to a social security regimen (for French sites only);
• Females and males receiving the study treatment and their partners must agree to use a highly effective contraceptive method during the study and for 3 months after end of study or early termination. Contraception should be in place at least 3 months prior to study participation. Women must be either postmenopausal (at least 12 months of amenorrhea), 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), intrauterine hormone-releasing system (IUS), hormonal contraception (estrogen and progestogen or progestogen only) associated with inhibition of ovulation, bilateral tubal occlusion, vasectomized partner. True abstinence is defined when this is in line with the preferred and usual lifestyle of the subject. 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 infrequent or irregular menstrual cycle.

Exclusion criteria

The following criterion should be checked at the time of screening. If this exclusion criterion applies, the subject will not be included in the study:

▪ Any condition, which in the opinion of the investigator, could compromise the subject's safety or the adherence to the study protocol.