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Updated: Feb 8, 2026

Synthesis of an Intein-mediated Artificial Protein Hydrogel
Published on: January 27, 2014
Generation of Potent Anti-HER1/2 Immunotoxins by Protein Ligation Using Split Inteins
Thomas Pirzer1, Kira-Sophie Becher2, Marcel Rieker3,4
1Institute for Organic Chemistry and Biochemistry , Technische Universität Darmstadt , Alarich-Weiss-Strasse 4 , D-64287 Darmstadt , Germany.
Abstract:
Cell targeting protein toxins have gained increasing interest for cancer therapy aimed at increasing the therapeutic window and reducing systemic toxicity. Because recombinant expression of immunotoxins consisting of a receptor-binding and a cell-killing moiety is hampered by their high toxicity in a eukaryotic production host, most applications rely on recombinant production of fusion proteins consisting of an antibody fragment and a protein toxin in bacterial hosts such as Escherichia coli ( E. coli). These fusions often lack beneficial properties of whole antibodies like extended serum half-life or efficient endocytic uptake via receptor clustering. Here, we describe the production of full-length antibody immunotoxins using self-splicing split inteins. To this end, the short (11 amino acids) N-terminal intein part of the artificially designed split intein M86, a derivative of the Ssp DnaB intein, was recombinantly fused to the heavy chain of trastuzumab, a human epidermal growth factor receptor 2 (HER2) receptor targeting antibody and to a nanobody-Fc fusion targeting the HER1 receptor, respectively. Both antibodies were produced in Expi293F cells. The longer C-terminal counterpart of the intein was genetically fused to the protein toxins gelonin or Pseudomonas Exotoxin A, respectively, and expressed in E. coli via fusion to maltose binding protein. Using optimized in vitro splicing conditions, we were able to generate a set of specific and potent immunotoxins with IC50 values in the mid- to subpicomolar range.
Insights
Researchers developed a novel method to create potent antibody immunotoxins for cancer therapy. This technique uses split inteins for efficient production of full-length antibody toxins, enhancing therapeutic potential.
Area of Science:
- Biotechnology
- Molecular Biology
- Cancer Therapeutics
Background:
- Cell-targeting protein toxins are promising for cancer therapy, aiming to improve efficacy and reduce side effects.
- Current methods often use antibody fragments produced in bacteria, which may lack optimal properties like longer circulation times.
- Producing full-length antibody immunotoxins is challenging due to toxicity in eukaryotic hosts.
Purpose of the Study:
- To develop a method for producing full-length antibody immunotoxins using self-splicing split inteins.
- To overcome limitations of current immunotoxin production methods.
- To generate specific and potent immunotoxins for potential cancer treatment.
Main Methods:
- Recombinant fusion of an N-terminal intein fragment to antibody heavy chains (trastuzumab, HER2-targeting; nanobody-Fc, HER1-targeting).
- Expression of antibody fragments in Expi293F cells and toxin fragments (fused to maltose binding protein) in E. coli.
- In vitro splicing of intein fragments to assemble full-length antibody immunotoxins.
Main Results:
- Successfully produced full-length antibody immunotoxins targeting HER2 and HER1 receptors.
- Achieved specific and potent immunotoxin activity.
- Generated immunotoxins with IC50 values in the mid- to subpicomolar range.
Conclusions:
- Self-splicing split inteins enable efficient production of full-length antibody immunotoxins.
- This method overcomes toxicity issues associated with eukaryotic expression of immunotoxins.
- The generated immunotoxins show high potency and specificity, offering a promising approach for cancer therapy.
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