The present invention relates to a method for the production of in vitro glycoengineered erythropoiesis stimulating protein, comprising the steps of providing sialic acid free erythropoiesis stimulating protein, treating the erythropoiesis stimulating protein with N-Acetyl-Glucosamin-transferase B3GNT2, treating the erythropoiesis stimulating protein with galactosyltransferase, and treating the erythropoiesis stimulating protein with sialyltransferase.
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