Clinical characteristics and response to standard-of-care treatment in systemic lupus erythematosus patients with or without anti-ribonucleoprotein (RNP) antibodies: An Australian, multi-centre cohort study

Background: Anti-ribonucleoprotein (RNP) (auto)antibodies are frequently detected in patients with systemic lupus erythematosus (SLE) although their associations with SLE disease activity remain incompletely understood. We compared socio-demographics and clinical characteristics between adult patients with SLE with or without anti-RNP antibodies (RNP+ vs. RNP-). Methods: We used data from a national, multicentre registry of SLE patients in Australia, collected prospectively between 2007 and 2023. Anti-RNP status and other serological profiles along with demographics were recorded at enrolment. At each routine clinic visit, medication details and disease activity indicators (SLEDAI-2K, PGA) were captured, and treat-to-target (T2T) states, lupus low disease activity state (LLDAS) and DORIS remission (REM), were determined. Clinical characteristics were compared between RNP+ and RNP- patients at 6 months (182±30 days) and 12 months (365±30 days) from enrolment. Results: A total of 587 patients were studied. 174 (29.6% (95%CI: 26.1%, 33.4%)) were RNP+ with significantly higher disease activity and more medication use at enrolment compared with RNP- patients (SLEDAI-2K median [IQR]: 8.0 [4.0, 10.0] vs. 4.0 [2.0, 8.0], p<0.001; PGA: 0.9 [0.4, 1.2] vs. 0.5 [0.2, 1.0], p<0.001; daily glucocorticoid dose 6.8 [0.0, 15.0] vs. 3.0 [0.0, 10.0] mg/day, p<0.001). RNP+ group had more patients with vasculitis, renal, cutaneous, serological, and constitutional activity. At enrolment, a greater proportion of RNP+ patients had active disease (SLEDAI-2K ≥6) compared with RNP- patients (53% versus 41%, p<0.007). Accordingly, significantly fewer RNP+ patients were in LLDAS (20% vs. 32.2%, p-value=0.004) or REM (11.6% vs. 22.6%, p-value=0.006). Follow-up data were available for 344 patients at 6 months (n=101, 29.4% RNP+), and for 298 patients at 12 months (n=87, 29.2% RNP+). Disease activity indicators between RNP+ and RNP- groups converged within the first 12 months following enrolment. While significantly fewer RNP+ patients achieved T2T states at 6 months, comparable proportions of RNP+ and RNP- patients were in T2T states by 12 months. Glucocorticoid and immunosuppressant use remained significantly higher in RNP+ patients throughout follow-up. Conclusions: Anti-RNP positive patients presented with a higher burden of disease activity at enrolment, and required more intensive treatment with glucocorticoids and immunosuppressants during the first year since study of follow-up.