The present invention relates to mutated factor (FX) polypeptides and uses thereof for the treatment of haemophilia. In particular, the present invention relates to a mutated factor X (FX) polypeptide wherein the heavy chain comprises at least one mutation selected from the group consisting of: —the mutation which consists of the substitution of the glutamic acid residue (E) at position 255 of Seq. ID No. 1 by a glutamine residue (Q), an asparagine residue (N), a serine residue (S), an alanine residue (A), or a tyrosine residue (Y); —the mutation which consists of the substitution of the glutamic acid residue (E) at position 256 of Seq. ID No. 1 by a glutamine residue (Q); and —the mutation which consists of the substitution of the glutamic acid residue (E) at position 258 of Seq. ID No. 1 by a glutamine residue (Q).