Pos0138 efficacy and safety of belimumab in adults with childhood-onset systemic lupus erythematosus: preliminary results from a prospective observational study

Background Childhood-onset Systemic Lupus Erythematosus (cSLE) is a rare autoimmune disease with multi-system manifestations, more severe disease course and higher frequency of morbidity than adult-onset SLE. Belimumab is the first treatment for cSLE approved for children ≥5 years of age. Objectives To investigate the efficacy and safety of Belimumab in adult patients with cSLE. Methods A prospective observational (non-interventional) study, involving adult patients with cSLE was conducted. During the 9-yearstudy period (01/2015 to 12/2022), adults with a cSLE diagnosis and Belimumab receivers (by intravenous or subcutaneous administration) for >12 consecutive months were enrolled. All patients met the revised 1997 American College of Rheumatology (ACR) or 2012 Systemic Lupus International Collaborating Clinics (SLICC) classification criteria and were followed at regular intervals (up to 6 months) in the Transition Rheumatology Outpatient Clinic. SLE activity was defined according to SLEDAI-2K and the SELENA-SLEDAI Physician Global Assessment (PGA), scale 0–3 [1]. At the last follow-up visit, response to therapy was assessed by Lupus Low Disease Activity State (LLDAS), remission state and SLE Responder Index (SRI4). LLDAS was defined as: i) SLEDAI-2K ≤4, with no activity in major systems ii) no new lupus disease activity compared to previous evaluation iii) a SELENA-SLEDAI PGA ≤1 iv) current prednisolone (or equivalent) dose ≤7.5 mg daily and v) standard maintenance doses of immunosuppressive drugs. [2]. Remission was defined as i) clinical SLEDAI-2K=0 ii) dose of prednisone ≤5 mg/day according to the DORIS definition [3]. SRI4 was defined as i) ≥4-point reduction from baseline in SELENA-SLEDAI score, ii) no worsening in PGA and iii) no new BILAG A organ domain score or 2 new BILAG B organ domain scores compared with baseline [4]. Results A total of 15 patients (14 females) were enrolled in the study. At baseline, the patients’ current mean (SD) age was 25.4 (7) years and the interval from disease onset to first Belimumab administration 12.4 (7.3) years. Half of the patients had a history of lupus nephritis and 42.8% were aPL positive. All patients were under hydroxychloroquine treatment and 80% of them were additionally receiving a second immunosuppressive agent (Methotrexate, MMF, Azathioprine). Glucocorticoids (GCs) were concomitantly administered in 13 (86.6%) patients in a dose of ≥7.5mg in 57.1% of them. The patients’ SLEDAI-2K mean (SD) score before Belimumab initiation was 12.1 (2.3), indicating high disease activity. The mean (SD) duration of Belimumab administration was 36.2 (1.9) months. At the last follow up visit, ongoing therapy with Belimumab was recorded in 66.7% of the cohort. SLEDAI-2K mean (SD) score was reduced to 3.5 (2.3), 1 patient (6.6 %) was in remission, 9 (60%) patients had mild and none high disease activity. The majority (78.5%) met the LLDAS definition and 78.5% were SRI4 Responders. Half of the patients (53.8%) achieved lower doses or discontinuation of GCs and 26.7% accomplished a reduction of the immunosuppressant’s dose. Reasons for Belimumab discontinuation included pregnancy issues, infection and low adherence (3, 1, 1 patient respectively). None of the patients experienced a serious adverse event. Conclusion In this cohort of adult patients with cSLE, Belimumab was well-tolerated and effectively reduced disease activity allowing the downstream of GCs’s dose. References [1]MOSCA M, BOMBARDIERI S: Assessing remission in systemic lupus erythematosus. Clin Exp Rheumatol. 2006;24:99-104. [2]FRANKLYN K, et al: Definition and initial validation of a Lupus Low Disease Activity State (LLDAS). Ann Rheum Dis. 2016;75:1615-21. [3]VAN VOLLENHOVEN R et al: A framework for remission in SLE: consensus findings from a large international task force on definitions of remission in SLE (DORIS). Ann Rheum Dis. 2017;76:554-61. [4]KMA C Luijten et al: The systemic Lupus Erythematosus Responder Index (SRI); a new SLE disease activity assessment. Autoimmun Rev 2012;11:326-9 Acknowledgements: NIL. Disclosure of Interests None Declared.