The present invention relates to Factor IX polypeptides conjugated to heparosan (HEP) polymers, methods for the manufacture thereof and uses of such conjugates. The resultant conjugates may be used - for example - in the treatment or prevention of bleeding disorders such as haemophilia B.本發明係關於與肝素前體(HEP)聚合物共軛之因子IX多肽、其製造方法及此類共軛物之用途。所得共軛物可用於例如治療或預防出血病症,諸如血友病B。