Patent ID: 7919273

Claim:
A method of improving a chimeric or humanized anti-CD20 antibody or antigen-binding fragment thereof comprising making at least one amino acid substitution in the third complementarity determining region (CDR) sequence of the heavy chain of a chimeric or humanized or human anti-CD20 antibody or antigen binding fragment thereof to make a substituted antibody or antigen binding fragment thereof, wherein the substitution results in at least one improved characteristic selected from the group consisting of a slower off-rate, slower antigen dissociation rate, higher CDC activity, higher ADCC activity, higher apoptotic activity, greater ability to induce cell death in vitro in the absence of cross-linking and greater ability to kill or inhibit the growth of CD20-positive cells in vivo when administered to a subject with CD20-positive cells, wherein the CDR sequences of the unsubstituted anti-CD20 antibody or antigen-binding fragment thereof comprise the light chain CDR sequences CDRL1 (RASSSVSYIH; SEQ ID NO:1), CDRL2 (ATSNLAS; SEQ ID NO:2) and CDRL3 (QQWTSNPPT; SEQ ID NO:3) and heavy chain CDR sequences CDRH1 (SYNMH; SEQ ID NO:4), CDRH2(AIYPGNGDTSYNQKFKG; SEQ ID NO:5) and CDRH3(STYYGGDWYFNV; SEQ ID NO:32) and wherein the substitution comprises replacing the asparagine residue at Kabat position 101 of the heavy chain CDR3 (CDRH3) of the antibody with an aspartate residue.