Eculizumab Serum Concentrate Assay
Commercial Mail-out Laboratory
|Red top tube 5 mL (Clot Activator)
Preferred Minimum: 1 mL serum
Absolute Minimum: 0.5 mL serum
Freeze thaw > 2 cycles and refrigerated samples.
Test performed on Mondays, Wednesdays and Fridays.
24 hours upon receipt at reference laboratory (upon receipt in laboratory)
Eculizumab is considered to be present in a therapeutic level in aHUS
if the trough serum concentration is >99 μg/mL (Legendre CM et al,
NEJM 2013), and in PNH if the serum concentration is >35
μg/mL (Hillmen P et al, NEJM 2004).
The eculizumab level (free anti-C5) is a measurement of the serum level
of eculizumab (Soliris®, Alexion Pharmaceuticals), a humanized
IgG4 monoclonal antibody directed against the complement protein C5.
By binding to C5, eculizumab prevents cleavage of C5 to its active
fragments C5a and C5b, thereby preventing formation of C5b-9 and
halting the process of complement-mediated cell destruction.
Adequate dosage and dosing interval of eculizumab results in a complete
blockade of activation of the terminal complement pathway. If a
patient is not being adequately dosed with eculizumab, breakthrough
activation of the complement system and subsequently disease
reactivation may occur. Along with clinical markers of disease
activity and other laboratory measures of terminal complement pathway
activity (such as CH50, C5a, and sC5b-9), the eculizumab level may be
used to guide therapeutic decision making as to adequate dosage and