ABTECT - Maintenance

All eligible subjects who have completed either one of the induction studies above mentioned, will be given the opportunity to take part in the present ABX464-107 study which consists of 2 treatment phases. This study consists of a 44-week maintenance treatment phase (Part 1 and Part 2), followed by a 4-year Long Term Extension (LTE) treatment phase and a 28-days follow-up period consisting in the End of Study (EOS) visit. The maintenance phase is a 44-week double blind, placebo-controlled, phase. Subjects who are clinical responders after 8 weeks induction will be randomized to Part 1, and those who are non-clinical responders will be randomized to Part 2. At the end of the 44-week maintenance phase, subjects will continue their allocated treatment until the maintenance phase is unblinded. Once the study is unblinded, all subjects receiving obefazimod will continue their allocated treatment. Subjects receiving placebo will be allocated to obefazimod 25 mg or can terminate the study.