Eculizumab Case Study

Figure 1. In vivo C3 binding on red cells of PNH patients on eculizumab.
(A) Kinetics of C3 binding on red cells from a representative PNH patient during eculizumab treatment. Before treatment (0 wks) no red cell binds C3, whereas starting from 1 weeks of treatment three populations of red cells are displayed: one population of normal red cells (CD59+C3-) and two distinct populations of PNH (CD59-negative) red cells, one with (C3+) and one without (C3-) fragments bound on their surface.
(B) Characterization of C3 fragment bound to erythrocytes from PNH patient on eculizumab. The left panel shows the normal (CD59-positive) and PNH (CD59-negative) populations (gated by the elliptic mark). The PNH (CD59-negative) population (see gate in the
The bar diagram shows the average (+SD) proportion of PNH (CD59-negative) red cells bound with C3 in a series of patients not on eculizumab after 3 and after 5 days of incubation at 37°C in ABO-compatible sera with eculizumab. n: number of different patients studied at the indicated time points. Empty bars show the experiments without addition of MgCl2 whereas the filled bars show the experiments with the addition of MgCl2 (1.25 mM). C3 binding on PNH red cells increased significantly along the time (Wilcoxon signed paired test: P<0.005 at 30 minutes, 2, 6 and 24
(B) Kinetics of C3 binding on PNH red cells from a series of PNH patients on eculizumab after complement activation in vitro by mild acidification in presence of eculizumab. The line diagram shows the average (+SD) proportion of C3-negative PNH red cells that became bound with C3 in a series of eculizumab treated patients at different time points (from 1 to 24 hours) since complement activation in their own sera (continuous line without MgCl2; dotted line with 1.25 mM MgCl2). In this 7 patients the percentage PNH red cells that in vivo were already bound with C3 was 30.3±24.5%. n: number of different patients studied at the indicated time points.
(C) Effect of in vitro complement activation on C3- PNH red cells from patients on eculizumab. RBCs without C3 binding have been sorted by FACS from a patient on eculizumab and subjected to complement activation in presence of eculizumab. Analysis of RBC with anti-CD59 and anti-C3d: just after sample drawing (left panel); after FACS sorting of C3- RBC (middle panel); sorted C3- RBC after 2 hours from complement activation in presence of eculizumab (right panel). HCl: serum acidification: ECU: