E153 Drug survival of infliximab in psoriatic arthritis with and without methotrexate at North Bristol NHS Trust Rheumatology Department

Abstract Background/Aims Infliximab, an anti-tumour necrosis factor (TNF) monoclonal antibody, is an established biologic therapy for psoriatic arthritis (PsA). Treatment persistence varies in practice. Although not mandated by NICE for infliximab treatment, concomitant methotrexate (MTX) has been shown to improve drug survival by reducing anti-drug antibody formation. Not all patients can tolerate or receive MTX. This study evaluated infliximab survival among PsA patients at North Bristol NHS Trust, comparing outcomes between those treated with and without MTX, and explored reasons for not receiving MTX. Methods This retrospective review utilised anonymised data from the hospital’s biologics database. Patients with PsA who met NICE eligibility criteria and started infliximab therapy between 2005-2025 were included. Data collected included treatment start and stop dates, route of administration (intravenous vs. subcutaneous after intravenous loading), concurrent MTX use, current treatment status (ongoing, discontinued, or switched), and any reasons for not being on MTX (categorised as intolerance, contraindication or patient preference). Drug survival was calculated annually up to ten years, based on the duration from treatment initiation to discontinuation or last follow-up. Patients were included only for the number of years they had been observed. Results 35 eligible patients received infliximab in the study period. At baseline, 21 (60%) were on concomitant MTX and 14 (40%) were not. Among those not receiving MTX, 8 (57%) had prior intolerance or toxicity, 3 (14%) had clinical contraindications (including liver disease, already on other csDMARD and inefficacy), and 3 (21%) without clear documentation. Only 1 out of 8 (12.5%) had attempted a rechallenge with a lower dose of methotrexate after previous intolerance. After one year of treatment, 25 patients (71.4%) remained on infliximab, with survival higher in the MTX group (76%) than the non-MTX group (64%). At year three, 10 patients (37%) remained on infliximab, with survival higher in the MTX group (53%) than the non-MTX group (17%). Main reasons for discontinuation were inefficacy (52%), adverse effect (26%), and remission or other factors (21%). Concomitant MTX use is associated with improved persistence of infliximab for treatment of PsA, consistent with European registry data such as DANBIO. The lower survival among those unable to take MTX may reflect increased immunogenicity. As a proportion of patients cannot tolerate MTX, this analysis poses a rationale for considering rechallenge of a lower dose of MTX if appropriate or alternative csDMARD co-therapy. Further work could explore the impact of methotrexate dose on infliximab drug survival in PsA. Conclusion In this local real-world cohort, infliximab demonstrated moderate long-term survival in PsA, with greater persistence among those on MTX. The most common reasons for not receiving MTX were intolerance and contraindications. These findings support current NICE TA199, which recommends MTX co-therapy when feasible, and emphasise the importance of individualised treatment approaches to optimise biologic persistence. Disclosure C. Lau: None. N. Mathews: None. T. Dean: None. E. Rose-Parfitt: None.