A membranoproliferative pattern of glomerular injury is frequently observed in patients with
complement-mediated disorders, such as C3 glomerulopathies (C3G) and primary
immune complex-mediated
membranoproliferative glomerulonephritis (IC-MPGN). The outcomes of C3G and -IC-MPGN are poor, independently of immunosuppressive therapy. However, two 48-week treatment periods with the anti-C5
monoclonal antibody eculizumab, divided by a -12-week washout period, achieved remission of
proteinuria and stabilization/improvement of the glomerular filtration rate (GFR), measured through
iohexol plasma clearance, in 3 of 10 patients with biopsy-proven MPGN,
nephrotic syndrome and
terminal complement complex sC5b-9 plasma levels >1,000 mg/mL, at inclusion. Baseline and end-of-study kidney biopsies were available for 2 patients with IC-MPGN, and their baseline characteristics were similar. However, in 1 patient
proteinuria and GFR did not improve during the study, whereas in the other
proteinuria decreased from 4.84 to 2.12 g/24-h and GFR increased from 91.5 to 142.7 mL/min/1.73 m2. Glomerular
inflammation improved and median (interquartile range) glomerular staining for
C5b-9 decreased in both cases: from 23.6 to 18.2% (p = 0.021) in the patient who achieved remission and from 15.8 to 10.7% (p = 0.019) in the patient with persistent
proteinuria. Chronic glomerular lesions progressed and C3 glomerular staining and electron-dense deposits did not change appreciably in either case. However, in the patient who achieved remission, ultrastructural evaluation revealed features of glomerular microangiopathy at inclusion, which fully recovered posttreatment. Podocyte foot process effacement was observed in both patients at inclusion, but recovered only in the patient with microangiopathy. Thus, in 2 patients with -IC-MPGN, chronic glomerular changes progressed despite
eculizumab-induced amelioration of glomerular
inflammation and inhibition of sC5b-9 deposition, and independently of treatment effects on
proteinuria and podocytes. The finding that the regression of microangiopathic changes was associated with improved clinical outcomes suggests that C5 blockade might have a therapeutic role in patients with IC-MPGN displaying microangiopathic endothelial injury.