- Design
- Single-centre retrospective cohort with paired-biopsy subgroup
- Population
- 43 patients with lupus nephritis not in complete response at belimumab start
- Primary outcome
- Deep clinical renal response (uPCR <200 mg/g, no active haematuria, stable function)
- Effect
- 38.5% at 12 months; 53.8% at 24 months
This single-centre retrospective study followed 43 patients with biopsy-proven lupus nephritis not in complete response when add-on belimumab was started. It tested a stringent 'deep' response: protein-creatinine ratio below 200 mg/g, no active glomerular haematuria and stable kidney function.
Deep response was reached by 38.5% at 12 months and 53.8% at 24 months, against 66.7% and 76.9% for conventional complete response. Deep responses took longer (median 17.7 vs 7.5 months). SLEDAI fell from 13 to 2, and glucocorticoids were reduced in 72%. In eight paired biopsies, activity fell while chronicity rose.
The sample is small and uncontrolled, and whether deeper response protects kidneys in the long term is unknown.
The finding is a reason not to judge belimumab's renal effect too early, and to keep aiming for lower proteinuria in the second year.
- Deep renal response reached about half of patients by 24 months on add-on belimumab.
- Deep responses took a median of about 18 months to appear.
- Glucocorticoids were reduced in nearly three-quarters of patients.
- Keep measuring proteinuria into the second year rather than judging response at 6-12 months.
- Whether deep response improves long-term kidney survival is not yet known.
Why it matters
It challenges the habit of declaring lupus nephritis treatment a success or failure at one year.
Don't overread it
This small uncontrolled cohort cannot show that belimumab, rather than time and standard therapy, produced the deep responses.
The statistics, in plain English
These are proportions in 43 uncontrolled patients, so there is no comparison group. Paired biopsy findings in eight patients are exploratory.
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