Recombinant immunotoxin against B-cell malignancies with no immunogenicity in mice by removal of B-cell epitopes.

Abstract

Many nonhuman proteins have useful pharmacological activities, but are infrequently effective in humans because of their high immunogenicity. A recombinant immunotoxin (HA22, CAT8015, moxetumomab pasudotox) composed of an anti-CD22 antibody variable fragment fused to PE38, a 38-kDa portion of Pseudomonas exotoxin A, has produced many complete remissions in drug-resistant hairy-cell leukemia when several cycles of the agent can be given, but has much less activity when antibodies develop. We have pursued a strategy to deimmunize recombinant immunotoxins by identifying and removing B-cell epitopes. We previously reported that we could eliminate most B-cell epitopes using a combination of point mutations and deletions. Here we show the location and amino acid composition of all of the B-cell epitopes in the remaining 25-kDa portion of Pseudomonas exotoxin. Using this information, we eliminated these epitopes to produce an immunotoxin (HA22-LR-8M) that is fully cytotoxic against malignant B-cell lines, has high cytotoxic activity against cells directly isolated from patients with chronic lymphocytic leukemia, and has excellent antitumor activity in mice. HA22-LR-8M does not induce antibody formation in mice when given repeatedly by intravenous injection and does not induce a secondary antibody response when given to mice previously exposed to HA22. HA22-LR-8M also has greatly reduced antigenicity when exposed to sera from patients who have produced antibodies to HA22. The properties of HA22-LR-8M make it an excellent candidate for further clinical development.

• Authors: Masanori Onda, Richard Beers, Laiman Xiang, Byungkook Lee, John E Weldon, Robert J Kreitman, Ira Pastan
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 108 Issue 14 Pg. 5742-7 (Apr 05 2011) ISSN: 1091-6490 [Electronic] United States
• PMID: 21436054 (Publication Type: Journal Article, Research Support, N.I.H., Intramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• Bacterial Toxins
• Epitopes, B-Lymphocyte
• Exotoxins
• Recombinant Fusion Proteins
• Virulence Factors
• immunotoxin HA22
• ADP Ribose Transferases
• Pseudomonas aeruginosa exotoxin A

Topics

• ADP Ribose Transferases (genetics, metabolism)
• Amino Acid Sequence
• Animals
• Antibodies, Monoclonal
• Bacterial Toxins (genetics, metabolism)
• Cell Line, Tumor
• Enzyme-Linked Immunosorbent Assay
• Epitopes, B-Lymphocyte (genetics)
• Exotoxins (genetics, metabolism)
• Immunization, Passive (methods)
• Leukemia, Lymphocytic, Chronic, B-Cell (drug therapy, immunology)
• Mice
• Mice, Inbred BALB C
• Models, Molecular
• Molecular Sequence Data
• Mutagenesis
• Protein Engineering (methods)
• Recombinant Fusion Proteins (biosynthesis, genetics, immunology, therapeutic use)
• Statistics, Nonparametric
• Virulence Factors (genetics, metabolism)