The Renal Activity Index for Lupus Identifies Active Renal Disease and Treatment Response in Adult Patients With Systemic Lupus Erythematosus and Lupus Nephritis

Objective We evaluated the ability of Renal Activity Index for Lupus (RAIL) to discriminate active lupus nephritis (LN) in adult patients with active systemic lupus erythematosus (SLE) and differentiate LN treatment response. Methods Urine samples from adults with biopsy‐proven active Class III and IV LN from TULIP‐LN (active‐LN‐group; NCT02547922) and adults with active, non‐renal SLE from TULIP‐1 (active‐SLE‐group; NCT02446912) were utilized and RAIL biomarkers (NGAL, KIM‐1, MCP‐1, adiponectin, hemopexin, ceruloplasmin) measured in the urine at baseline (both studies); and at Week 12 and Week 24 for TULIP‐LN only. The groups were compared at baseline, and changes in RAIL‐scores from baseline in the active‐LN‐group were compared between non‐responders and responders over time, i.e., those with complete renal response (CRR), partial renal response (PRR) and urine protein–creatine ratio decrease ≥50% [UPCR50]. Results At baseline, median [interquartile range (IQR)] concentrations of RAIL biomarkers were significantly higher ( P < 0.02) in the active‐LN‐group (n=128) versus the SLE‐control‐group (n=48), as were RAIL‐scores [5.59 (4.31–6.47) versus 3.57 (2.78–4.47); P <0.001]. At Week 12/Week 24 there were 25/31 patients achieving CRR, 39/54 with PRR and 41/63 with UPCR50, respectively. Changes of RAIL‐scores from baseline to Week 12/Week 24 significantly differed between non‐responders and responders (PRR, CRR, UPCR50: all P <0.0006) with lower scores in responders. For CRR versus non‐response, median [IQR] RAIL‐scores decreased by ‐1.3 (‐3.64/‐0.21) versus ‐0.39 at Week 12, and ‐2.30 (‐3.63/‐1.03) versus ‐0.88 (‐2.20/0.33) at Week 24, respectively. Conclusions The RAIL identifies active LN and longitudinally differentiates treatment response in adults with LN. image