The Fc fusion technology has been introduced to generate long-acting antagonistic drugs such as Enbrel, Orencia and Amevive. Here, Genexine created a novel noncytolytic hybrid Fc (hyFc) as a carrier of agonistic protein drugs using naturally existing IgD and IgG4 Fcs without any mutation in the hyFc region. The erythropoietin (EPO) fused with hyFc exhibited little binding activity to $Fc{gamma}R$ and C1q molecules that are main mediators for death of target cells. The EPO-hyFc showed higher in vitro and in vivo bioactivities than EPO-IgG1 Fc and highly glycosylated EPO (Aranesp). Phase I clinical trial with EPO-hyFc is currently undergoing in Korea.