Modified Forms of Pseudomonas Exotoxin A

Abstract

Pseudomonas exotoxin A or “PE” is a 66 kD, highly potent, cytotoxic protein secreted by the bacterium Pseudomonas aeruginosa. Various forms of PE have been coupled to other proteins, such as antibodies, to generate therapeutically useful cytotoxin conjugates that selectively target cells of a desired phenotype (such as tumor cells). In the present invention, peptides spanning the sequence of an approximately 38 kD form of Pseudomonas exotoxin A protein were analyzed for the presence of immunogenic CD4+ T cell epitopes. Six immunogenic T cell epitopes were identified. Residues were identified within each epitope for introduction of targeted amino acid substitutions to reduce or prevent immunogenic T-cell responses in PE molecules which may be administered to a heterologous host.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Appl. No. 61 / 531,576, filed Sep. 6, 2011 which is herein incorporated by reference in its entirety.REFERENCE TO RELATED APPLICATION[0002]This application claims benefit of and priority based on U.S. Provisional Patent Application Ser. No. 61 / 531,576, filed Sep. 6, 2011, the contents of which are herein incorporated by reference in their entirety.NAMES OF THE PARTIES IN A JOINT RESEARCH AGREEMENT[0003]The claimed invention was made pursuant to a joint research agreement, as defined in 35 U.S.C. §103 (c)(3), that was in effect on or before the date the claimed invention was made, and as a result of activities undertaken within the scope of die joint research agreement, by or on behalf of the Intrexon Corp. (Foster City, Calif., U.S.A.) and Antitope Ltd. (Cambridge, UK).REFERENCE TO SEQUENCE LISTING SUBMITTED ELECTRONICALLY[0004]A Sequence Listing is submitted electronically via EFS-Web...

AI Technical Summary

Benefits of technology

The patent text describes a study on a protein called Pseudomonas exotoxin A (PE38) and its potential immunogenicity. The researchers analyzed peptides from the PE38 sequence and tested them for their ability to stimulate CD4+ T cells. They found six immunogenic peptides, which were used to create a T cell map of the PE38 sequence. Next, they identified specific residues within these peptides that might trigger an immune response. Based on these findings, the researchers made targeted amino acid substitutions to reduce or prevent PE38-induced immunogenicity. This would allow for multiple therapeutic administrations of cytotoxic PE, which could be used to target cancer cells in vivo.

Problems solved by technology

These responses include those that elicit a weak clinical effect and those that limit efficacy which can occasionally result in morbidity or even mortality in patients.

In particular, serious complications can arise with the production of neutralizing antibodies, especially when they target recombinant self proteins and therefore have the potential to cross react with the patient's own endogenous protein (Lim, 2005).

PE-A typically produces death by causing liver failure.

A significant disadvantage in using PE-A for treatment of disease, however, is that

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