ADAMTS-13 mutant

1. A method of reducing reactivity of ADAMTS-13 (a disintegrin-like domain, and metalloprotease) to an anti-ADAMTS-13 neutralizing antibody, with an isolated human thrombospondin type 1 motif, member 13, the method comprising substituting the following positions in the isolated human ADAMTS-13 with a different charged or uncharged amino acid: arginine at position 326, aspartic acid at position 330, aspartic acid at position 343 and arginine at position 349 in the disintegrin-like domain, aspartic acid at position 480, arginine at position 488, arginine at position 498, arginine at position 507, aspartic acid at position 533 and aspartic acid at position 543 in the cysteine-rich domain, and glutamic acid at position 641 and arginine at position 66o in the spacer domain, in the amino acid sequence encoded by the nucleotide sequence of SEQ ID NO: 1.

2. The method according to claim 1 , wherein the different amino acid is an uncharged amino acid.

3. The method according to claim 1 wherein the charged amino acid to be substituted is present in or around the neutralizing antibody recognition epitope, including at least one of arginine at position 312, lysine at position 318, arginine at position 568, glutamic acid at position 569, arginine at position 589, lysine at position 608, glutamic acid at position 634, aspartic acid at position 635 or arginine at position 639.

4. The method according to claim 1 , wherein the charged amino acid to be substituted is selected from the group consisting of aspartic acid at position 298, arginine at position 312, arginine at position 326, glutamic acid at position 327, arginine at position 370, arginine at position 452, aspartic acid at position 504, arginine at position 514, aspartic acid at position 537, arginine at position 568 and arginine at position 659.

5. The method according to claim 1 , wherein the uncharged amino acid is selected from the group consisting of alanine, glycine, proline, serine and threonine.