The investigational product, named Ovasave (Ova-Treg), is a cell-based therapy, consisting of an autologous antigen-specific regulatory type 1 T lymphocyte expanded population administered via the intravenous route as an infusion.

The study is a multicenter, randomised, double-blinded, placebo-controlled, multi-dose and multi-injection study; followed with a 16-week phase with either the possibility for an open-label treatment part or a safety follow-up part with no injection.

Then, the patients will be followed in an additional long-term safety follow-up, of maximum duration of 3 years from the first administration.

During double-blinded phase, the treatment consists of 2 intravenous (i.v.) administrations of antigen-specific autologous T regulatory cells or placebo:

• Group A: 1.10e4 cells and 1.10e4 cells
• Group B: 1.10e6 cells and 1.10e6 cells
• Group C: 1.10e7 cells and 1.10e7 cells
• Group D: Placebo and Placebo

During double-blinded phase, two i.v. administrations of study drug (Ova-Treg) will be administered, one at week 0 and another one at week 8 for the group A, B and C. Two injections of Placebo will be administered, one at week 0 (V4) and another one at week 8 for the group D. During double-blinded phase, all the patients will be followed during 16 weeks. This will be followed by an additional period of 16 weeks when the patient is expected to receive two additional administrations of Ovasave at 10e6 cells dose (Open-label phase), except if refused by the patient or not recommended by the Investigator, representing the follow-up phase. These third and fourth administrations will be performed for all groups (A, B, C and D) with an injection of Ovasave at 1.10e6 cells administered at week 16 and week 24. A patient who didn't receive the 2 first administrations during the double-blinded phase cannot receive the third and the fourth administration during Open-label phase.

Main Inclusion Criteria:

1. Active Crohn's Disease diagnosis defined as patients with medical history of signs, symptoms and biological evidence of active bowel inflammation:

   • Documented endoscopic evidence of inflammatory bowel disease (IBD), compatible with Crohn's diagnosis at least 1 year prior to screening and
   • High sensitive C-reactive protein (hs-CRP) > 10 mg/L at V1.

2. Failure or intolerance to conventional treatments including corticosteroid, immunosuppressant and at least one biologics; and had not responded (primarily failure) or responded and then lost response completely (no response or need to increase the dose / secondary failure) or were intolerant to this therapy at a dose indicated for CD

3. Documented CDAI (Crohn's Disease Activity Index) above 250 points (CDAI ≥ 250) at screening or within the past 3 months;