Background Almost half of childhood-onset SLE (cSLE) patients show damage within 5 years after disease onset, which is partially disease- and partially drug-related [1]. Therefore, the challenge in (c)SLE is not only to lower disease activity, but also to minimalize glucocorticoid toxicity. Treat-to-target (T2T) has been a new type of approach to improve long-term patient outcomes by adapting treatment regimens until the target is met. For T2T, the concept of Lupus-Low-Disease-Activity-State (LLDAS) as a target in SLE has been defined which contains a SLE disease activity index (SLEDAI) ≤ 4 and a maximum prednisolone use of 7.5mg/day [2]. This adult LLDAS (aLLDAS) has been shown to be a feasible target in cSLE patients and attainment leads to lowering risk for severe flare and cumulative damage [3]. Another cSLE cohort study demonstrated that all patients were able to reach aLLDAS (median 186 days) and 72.5% remained in aLLDAS >50% of time [4]. Recently, an international cSLE T2T Task Force has adapted the LLDAS definition specifically for cSLE patients (cLLDAS) by Delphi surveys and consensus meetings, with an addition of a calculated prednisolone dose per body weight in maximum dose of 0.15 mg/kg/day and an absolute maximum of 7,5 mg/day (Smith et al., submitted).

Objectives The first objective was to investigate if the time to reach first aLLDAS and cLLDAS differs in cSLE. The second objective was to observe if cSLE patients maintain in cLLDAS for 50% of follow-up time (cLLDAS-50).

Methods Data from a prospective longitudinal cSLE cohort were used, with patient/parent consent. Patients were classified as cSLE by SLICC 2012 criteria with a disease onset < 18 years old. Definitions were: aLLDAS according to Franklyn (2), disease activity score by SLEDAI-2K, cLLDAS by cLSE T2T Task Force (Smith et al. submitted) and damage according to SLICC Damage Index. cLLDAS-50 was defined as attainment of cLLDAS in more than 50% of follow-up. Binary regression analysis was used for testing co-variates for attaining cLLDAS-50 with significance for p<0.05.

Results 43 cSLE patients were studied, with a median age of symptom onset at 13.6 years, median age at diagnosis of 14.6 years and median follow-up of 4.6 years (range 1-13 years). Mean number of visits was 10.9 per patient. Mean SLEDAI at diagnosis was 15.4 (SD 10.4, range 2-43). Use of MMF was in 62.8%, AZA in 37.2%, and use of HCQ in 100% of patients. 41.9% of patients used a biologic (rituximab or belimumab) at any time point. Each patient reached aLLDAS and cLLDAS at least once during follow-up. Mean time to reach first aLLDAS/cLLDAS was 8.8 months and 9.7 months respectively. Only 58.1% (25/43) of patients were able to maintain cLLDAS-50. The use of biologic(s) had a inversely correlation on reaching cLLDAS-50 (p=0.005), but time to start biologic(s) was not taken into account. Shorter time to cLLDAS was correlated with attaining cLLDAS-50 (p=0.025). SLEDAI at diagnosis, renal/neurological disease and compliance problems were not correlated with attaining cLLDAS-50.

Conclusion In a longitudinal cSLE cohort, reaching cLLDAS occurred later than aLLDAS, emphasizing the need for an adapted LLDAS definition for cSLE. This study shows that reaching cLLDAS in cSLE is feasible, but attaining cLLDAS-50 is difficult. Earlier starting of glucocorticoid-sparing drugs (such as biologics) seems necessary in a severe subgroup not retaining, or not reaching, cLLDAS.

References [1]Holland et al. Measuring disease damage and its severity in childhood-onset systemic lupus erythematosus. Arthritis Care & Research Nov 2018; Vol. 70, No. 11: 1621-1629.

[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]Smith et al. Attainment of low disease activity and remission targets reduces the risk of severe flare and new damage in childhood lupus. Rheumatology 2022;61: 3378-3389.

[4]Wahadat et al. LLDAS is an attainable treat-to-target goal in childhood-onset SLE. Lupus Science & Medicine 2021;8:e000571. doi:10.1136.

Acknowledgements: NIL.

Disclosure of Interests None Declared.