To Örebro University

Background: Each lupus nephritis (LN) flare causes nephron loss that equals a decade or more of reduction in renal function lifespan, making prompt initiation of therapy imperative and prevention of flares even more desirable. Identification of readily available signals of imminent flare is therefore expected to improve prognosis.

Objectives: In light of observed cases of de novo LN during belimumab treatment (1), we evaluated predictors of de novo renal flare occurrence in patients with systemic lupus erythematosus (SLE) and no prior history of renal disease undergoing standard therapy (ST) with or without add-on belimumab in clinical trial settings.

Methods: Data from five clinical trials of belimumab in SLE (BLISS-52 NCT00424476; BLISS-76 NCT00410384; BLISS-NEA NCT01345253; BLISS-SC NCT01484496; EMBRACE NCT01632241) were utilised. The study population comprised 1932 patients with a baseline renal British Isles Lupus Assessment Group (BILAG) score E. De novo renal flares were defined as a change from renal BILAG E to A or B within a 52-week follow-up. Comparisons of baseline data were made using the Mann-Whitney U test, Pearson’s chi-squared (χ2) test or Fisher’s exact test as appropriate. Predictors of renal flare occurrence were investigated using univariable and multivariable Cox regression analysis. p values <0.05 were considered statistically significant.

Results: De novo renal flares were documented in 146 (7.6%) patients. Among patients who developed at least one renal flare, greater proportions were Asians (30.8% versus 20.2%; p<0.003), had positive baseline anti-dsDNA levels (74.0% versus 61.3%; p=0.003), and had low baseline levels of C3 (51.4% versus 38.2%; p=0.002) and C4 (45.2% versus 35.8%; p=0.030) compared with patients who did not flare. In univariable Cox regression analysis, azathioprine use was protective against renal flares (HR: 0.70; 95% CI: 0.49–0.99; p=0.047), while anti-Sm positivity at baseline showed a trend towards an association with imminent renal flare (HR: 1.68; 95% CI: 0.99–2.85; p=0.057). In multivariable Cox regression analysis adjusting for age, sex, ethnicity, serum creatinine, and variables that differed significantly in univariable analysis, Asian ancestry (HR: 1.60; 95% CI: 1.03–2.49; p=0.036), high mean prednisone dose from baseline until renal flare occurrence or throughout the follow-up (HR: 1.03; 95% CI: 1.02–1.05; p<0.001), and baseline serum creatinine (HR: 1.02; 95% CI: 1.01–1.03; p=0.001) were associated with imminent de novo renal flare, while extra-renal clinical SLE Disease Activity Index 2000 (cSLEDAI) showed a negative association (HR: 0.92; 95% CI: 0.86–0.98; p=0.007). Notably, use of belimumab 1 mg/kg by intravenous (IV) infusion yielded a nearly 3 times decreased hazard of renal flare (HR: 0.37; 95% CI: 0.20–0.68; p=0.001), whereas IV belimumab 10 mg/kg and belimumab 200 mg administered subcutaneously (SC) displayed no clear protection.

Conclusion: Asian patients appeared particularly susceptible to new-onset renal involvement, corroborating the substantial vulnerability of Asian SLE populations to renal affliction. Add-on low-dose IV belimumab on top of ST appeared protective against renal flares in SLE patients with no prior history of nephritis, while addition of the approved 10 mg/kg IV belimumab dose and SC belimumab yielded no clear protection. Discrepant results between low and high/approved belimumab doses warrant in-depth mechanistic exploration of underlying reasons e.g., potential effects of belimumab on B cell subsets that acquire regulatory properties.

Reference: [1]Parodis I, Vital EM, et al. Rheumatology (Oxford). 2021;60(9):4348-54.