Development and validation of an enzyme-linked immunosorbent assay to measure free eculizumab concentration in serum.

Aim: Eculizumab is a monoclonal antibody toward C5 fraction of the complement system. It is approved to treat paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. To perform pharmacokinetic studies and therapeutic drug monitoring, a validated assay is required.
Materials & Methods: An indirect ELISA with recombinant human C5 sensitized microtiter plates were developed.
Results: The assay allows the measurement of free eculizumab concentration in human serum. The LOD, LLOQ and ULOQ were 0.091, 0.25 and 82.35 mg/l, respectively. The assay meets EMA and US FDA guidelines criteria for the validation of a ligand-binding assay.
Conclusion: This method is validated and can be used in PK and PK-PD studies as well as to perform therapeutic drug monitoring of free eculizumab.