Inhibition of poly-LacNAc biosynthesis with release of CMP-Neu5Ac feedback inhibition increases the sialylation of recombinant EPO produced in CHO cells

Sialylation of recombinant therapeutic glycoproteins modulates their pharmacokinetic properties by affecting their in vivo half-life. N- glycanbranching on glycoproteins increases the number of potential attachment sites for sialic acid. Here, we introduce a new approach for increasing the sialylation of recombinant human erythropoietin (rhEPO) produced in CHO cells by modulating poly- N-acetyllactosamine(poly-LacNAc) biosynthesis. We did not observe an increase in rhEPO sialylation, however, until the feedback inhibitionby intracellular cytidine monophosphate- N-acetylneuraminic acid(CMP-Neu5Ac), which is a limiting factor for sialylation, was released. Thus, we found that a combined approach inhibiting poly-LacNAc biosynthesis and releasing CMP-Neu5Ac feedback inhibitionproduces the most significant increase in rhEPO sialylation in metabolically engineeredCHO cells. Furthermore, a detailed analysis of the resulting N- glycanstructures using LC/MS revealed increased tri- and tetra- sialylated N- glycanstructures accompanied by a reduction of di-sialylated N- glycanstructures. These results validate our new approach for glycosylation engineering, and we expect this approach will be useful in future efforts to enhance the efficacy of other therapeutic glycoproteins.