Design and modification of EGF4KDEL 7Mut, a novel bispecific ligand-directed toxin, with decreased immunogenicity and potent anti-mesothelioma activity.
BACKGROUND
Potency, immunogenicity, and toxicity are three problems that limit the use of targeted toxins in solid tumour therapy.


METHODS
To address potency, we used genetic engineering to develop a novel bispecific ligand-directed toxin (BLT) called EGF4KDEL, a novel recombinant anti-mesothelioma agent created by linking human epidermal growth factor (EGF) and interleukin-4 (IL-4) to truncated pseudomonas exotoxin (PE38) on the same single-chain molecule. Immunogenicity was reduced by mutating seven immunodominant B-cell epitopes on the PE38 molecule to create a new agent, EGF4KDEL 7Mut.


RESULTS
In vitro, bispecific EGF4KDEL showed superior anti-mesothelioma activity compared with its monospecific counterparts. Toxicity in mice was diminished by having both ligands on the same molecule, allowing administration of a 10-fold greater dose of BLT than a mixture of monomeric IL4KDEL and EGFKDEL. EGF4KDEL 7Mut, retained all of its functional activity and induced about 87% fewer anti-toxin antibodies than mice given the parental, non-mutated form. In vivo, intraperitoneal (IP) injection of the BLT showed significant (P<0.01) and impressive effects against two aggressive, malignant IP mesothelioma models when treatment was begun 14-16 days post tumour innoculation.


CONCLUSIONS
These data show that EGF4KDEL 7Mut is a promising new anti-mesothelioma agent that was developed to specifically address the obstacles facing clinical utility of targeted toxins.
Stish
B J
BJ
Department of Therapeutic Radiology-Radiation Oncology, Section on Molecular Cancer Therapeutics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
Oh
S
S
Chen
H
H
Dudek
A Z
AZ
Kratzke
R A
RA
Vallera
D A
DA
D036002:ADP Ribose Transferases / Q000627:therapeutic use*; D000818:Animals; D001427:Bacterial Toxins / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000627:therapeutic use*; D005098:Exotoxins / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D000922:Immunotoxins / Q000276:immunology / Q000627:therapeutic use*; D015847:Interleukin-4 / Q000627:therapeutic use*; D008297:Male; D008654:Mesothelioma / Q000188:drug therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D010534:Peritoneal Neoplasms / Q000188:drug therapy; D011994:Recombinant Proteins / Q000627:therapeutic use; D037521:Virulence Factors / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D004815:Epidermal Growth Factor; D005098:Exotoxins; D000922:Immunotoxins; D015847:Interleukin-4; D011994:Recombinant Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A