Mutated anti-cd22 antibodies with increased affinity to cd22-expressing leukemia cells

A method of inhibiting growth of a CD22+ cancer cell by contacting said cell with an anti-CD22 antibody with a variable light (VL) chain having the sequence of a VL of antibody RFB4 and a variable heavy (VH) chain having the sequence a VH chain of antibody RFB4, provided that residues 100, 100A and 100B of CDR3 of the VH chain of said anti-CD22 antibody, have an amino acid sequence selected from the group consisting of:

• THW, YNR, TTW, and STY and further provided that residue 100 of the VL chain of said anti-CD22 antibody is C and residue 44 of the VH chain of said anti-CD22 antibody is C, as the residues of the VL and VH chains are numbered in the column of FIG. 2 or FIG. 3 labeled “Kabat Numbering”, which antibody is fused or conjugated to a therapeutic moiety, which therapeutic moiety inhibits growth of said cell.

A kit for detecting the presence of a CD22+ cancer cell in a biological sample, said kit comprising:

• (a) a container, and
• (b) an anti-CD22 antibody with a variable light (VL) chain having the sequence of a VL chain of antibody RFB4 and a variable heavy (VH) chain having the sequence of a VH chain of antibody RFB4, provided that residues 100, 100A and 100B of CDR3 of the VH chain of said anti-CD22 antibody have an amino acid sequence selected from the group consisting of:
• THW, YNR, TTW, and STY and further provided that residue 100 of the VL chain of said anti-CD22 antibody is C and residue 44 of the VH chain of said anti-CD22 antibody is C, as the residues of the VL and VH chains are numbered in the column of FIG. 2 or FIG. 3 labeled “Kabat Numbering”, which antibody is fused or conjugated to a detectable label.