 Eculizumab is a recombinant humanized monoclonal antibody against the complement protein C5.It is an immunoglobulin G-kappa (IgGκ) consisting of human constant regions and murine complementarity-determining regions grafted onto human framework light and heavy chain variable regions.The compound contains two 448-amino acid heavy chains and two 214-amino acid light chains, and has a molecular weight of approximately 148 kilodaltons (kDa).