PMC6312603_01
Patient samples and control sera assayed for eculizumab-C5 (E-C5) complexes and total complement activity. Three samples from the aHUS patient were examined: (1) sample obtained 1 hr before eculizumab infusion ("1 hr before ecu"), (2) sample obtained 1 hr after eculizumab infusion ("1 hr after ecu"), and (3) sample obtained 1 week after and 2 weeks before eculizumab infusion ("between ecu"). Control sera were obtained from 20 healthy controls. (a) Samples were incubated with increasing concentrations of eculizumab (0-100 mug/mL) and E-C5 complexes were measured (concentration is given in eculizumab-equivalent amounts). (b) Samples were incubated with increasing concentrations of eculizumab (0-100 mug/mL) and classical pathway complement activation was measured by the Wieslab  assay, detected as % of a normal human standard sera by the kit, defined to contain 100% activity (% of NHS).
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fig1
No changes in E-C5 concentrations were observed in the three patient samples, whereas the pooled control sera exhibited a dose-dependent increase in E-C5 from zero to the levels corresponding closely to the patient samples, indicating that a maximum of E-C5 complexes were present in all three patient samples (Figure 1(a)). The three patient samples were completely negative from time zero, consistent with full blockade, whereas the control sera displayed a dose-response inhibition from normal activity to zero at eculizumab concentrations of 50-100 mug/mL (Figure 1(b)).