Complement-targeted therapy: development of C5- and C5a-targeted inhibition.

The complement system is a major effector of humoral immunity and natural immunity. The complement system has three independent pathways of complement activation: a classical pathway, an alternative pathway, and a lectin pathway. These pathways converge to a common pathway that activates C3. This pathway also leads to the formation of various bioactive molecules such as C5a and the formation of membrane attack complex on the surface of target cells. In the past, the only preparations with anti-complementary action were C1 inhibitors (C1-INH), but an anti-C5 monoclonal antibody (eculizumab) appeared a few years ago, and this antibody has yielded encouraging results. In addition, a C5a receptor (C5aR) antagonist is in the clinical trial phase, and this antagonist should also prove efficacious. Anti-complement agents have garnered attention as a new treatment strategy for refractory inflammatory diseases.