Patent ID: 7129332

Claim:
An isolated polypeptide comprising an antibody heavy chain variable region (“VH”) and an antibody light chain variable region (“VL”), each region comprising three complementarity determining regions (“CDRs”), which CDRs of each region are numbered sequentially CDR1 to CDR3 starting from the amino terminus, the polypeptide when made into an immunotoxin with a Pseudomonas exotoxin A or cytotoxic fragment thereof (“PE”) forming an immunotoxin which binds to epidermal growth factor receptor type III (“EGFRvIII”) antigen and which has a cytotoxicity to cells expressing said antigen at least equal to the cytotoxicity to said cells of an immunotoxin of parental antibody MR1 (SEQ ID NO.:18) and said PE, and a higher yield, when made into an immunotoxin with said PE, than that of MR1 when made into an immunotoxin with said PE, wherein: (a) CDRs 1–3, respectively of the V H of the polypeptide have the sequence of CDRs 1–3, respectively of parental antibody MR1 V H , except for: (i) substitution of an amino acid selected from the group consisting of proline and tryptophan for the serine at position 98 of the CDR3 of the heavy chain variable region of antibody MR1, and (ii) substitution of an amino acid selected from the group consisting of: tyrosine, asparagine, tryptophan, isoleucine, phenylalanine, serine, and valine for the threonine at position 99 of the CDR3 of the heavy chain variable region of antibody MR 1 and, optionally, (iii) a substitution in CDR1 or CDR2 of said heavy chain variable region of at least one amino acid encoded by a codon that comprises a nucleotide belonging to a hot spot motif selected from AGY or RGYW, wherein R is A or G, Y is C or T and W is A or T; and (b) CDRs 1–3, respectively, of the V L of the polypeptide have: (i) the sequence of CDRs 1–3, respectively, of antibody MR1 V L or, (ii) the sequence of CDRs 1–3, respectively, of antibody MR1 V L except for a substitution in one or more of said CDRs 1–3 of said polypeptide at least one amino acid encoded by a codon that comprises a nucleotide belonging to a hot spot motif selected from AGY or RGYW, wherein R is A or G, Y is C or T and W is A or T.