A phase 2a open-label study to evaluate the long-term safety and efficacy of ABX464 50mg as maintenance therapy in patients with moderate to severe rheumatoid arthritis.

This Phase 2a open-label study aims at investigating the long-term safety and efficacy of an oral dose of ABX464 in patients who have been previously enrolled in the ABX464-301 clinical study and who are willing to continue their treatment.

All patients will receive ABX464 given at 50mg o.d. irrespectively of their previous treatment received in the ABX464-301 study (i.e. ABX464 or Placebo).

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.

Patients will be treated with ABX464 for a period of 52 weeks. If they achieve a clinical response on Week 52 (defined as DAS28-CRP ≤ 2,6 for anti-TNFα naïve patients or DAS-28-CRP ≤ 3,2 for patients previously treated by anti-TNFα), they will be eligible to continue treatment for up to 104 weeks.Patients will be followed up at week , week 2 and then, on a monthly basis the first year (up to W52), and quaterly the second year (up to W104).

Inclusion Criteria:

• Patients previously enrolled in the ABX464-301 clinical study who have completed the initial 12 weeks of treatment period;

Criteria that should be met by patients at week 52 to be eligible for 52 additional weeks of study treatment:

▪ Patients should be in clinical response. Clinical response is defined as: DAS28-CRP ≤ 2,6 for anti-TNFα naïve patients or DAS-28-CRP ≤ 3,2 for patients previously treated by anti-TNFα.

Exclusion Criteria:

• Any condition, which in the opinion of the investigator, could compromise the patient's safety or adherence to the study protocol