E105 Comparative effectiveness of leflunomide in deforming versus non-deforming rheumatoid arthritis forms

Background/Aims Deforming forms of rheumatoid arthritis (RA) are associated with greater severity and more frequent use of biologics. Leflunomide, although indicated as a second-line treatment after failure of conventional synthetic DMARDs, may represent an effective alternative even in these advanced cases. The aim of this study was to evaluate the efficacy, tolerability, and need for biologic therapy in patients with deforming RA compared to those with non-deforming forms, all treated with leflunomide. Methods This was a retrospective observational study including patients with seropositive RA who received Leflunomide. Patients were divided into two groups based on the presence of clinical joint deformities: deforming RA and non-deforming RA. Comparisons of collected data were performed using Student’s t-test and chi-square test, with statistical significance set at p < 0.05. Results Among the 154 patients included, 69% had deforming RA and 31% had non-deforming RA. In the deforming group, the mean age was 56 years with a female-to-male ratio of 0.06; in the non-deforming group, the mean age was 55 years with a sex ratio of 0.02. Patients with deforming RA had a longer disease duration (17 vs 13 years) and higher mean rheumatoid factor titers (345 vs 245 IU/mL). Extra-articular manifestations were also more frequent in this group (52% vs 44%). Under leflunomide, both groups showed improvement in DAS28 over time: from 5.1 to 2.71 at 12 months in the deforming group, and from 4.8 to 2.5 in the non-deforming group, with no significant difference in final scores. Treatment duration was longer in the deforming RA group (49 vs 30 months, p < 0.05). Adherence and tolerability were similar between groups (good adherence: 72% vs 79%; good tolerability: 73% vs 77%). However, the use of biologic therapy was significantly more frequent in the deforming group (43% vs 23%, p < 0.01). Conclusion Despite greater clinical severity, patients with deforming RA achieved a satisfactory response to leflunomide, with notable clinical improvement and acceptable tolerability. These findings suggest that leflunomide remains a viable therapeutic option in severe RA, potentially delaying or reducing the need for biologic agents, especially in settings with limited resources. Disclosure H. Bakadir: None. S. Zaher: None. A. Ajerouassi: None. W. Rachidi: None. K. Nassar: None. S. Janani: None.