Increasing Anticarcinoma Activity of an Anti-erbB2 Recombinant Immunotoxin by the Addition of an Anti-EpCAM sFv

Abstract

Purpose: erbB2, the product of the Her2-neu gene, is a well-established therapeutic target for antibody-based biologicals, but anti-erbB2 antibody-toxin fusion proteins are limited in their activity. The goal of this study was to determine if genetically adding an sFv targeting epithelial cell adhesion molecule (EpCAM) to an anti-Her2 sFv immunotoxin would result in enhanced antitumor activity. Experimental Design: In vitro studies were done in which the new bispecific immunotoxin DTEpCAM23 was compared with monospecific immunotoxins (DTEpCAM and DT23) to quantitate immunotoxin activity. Mixtures of monospecific immunotoxins were tested to determine if they were as effective as the bispecific immunotoxin. Binding and internalization studies were also done. In vivo, bispecific immunotoxins were given i.t. to athymic nude mice bearing HT-29 human colon cancer flank tumors and i.p. to mice with i.p. tumors. Results: DTEpCAM23 bispecific immunotoxins showed far greater activity than monospecific immunotoxin (sometimes over 2,000-fold) against most tumor lines. Bispecific immunotoxin was superior and selective in its activity against different carcinoma cell lines. Bispecific immunotoxin had greater activity than monospecific immunotoxin indicating an advantage of having both sFv on the same single-chain molecule. Binding and internalization studies did not explain the differences between bispecific immunotoxin and monospecific immunotoxin activity. Orientation of the sFvs on the molecule had a significant effect on in vitro and in vivo properties. The bispecific immunotoxins were more effective than the monospecific immunotoxin in the flank tumor mouse model. Conclusions: The synthesis of bispecific immunotoxin created a new biological agent with superior in vitro and in vivo activity (over monospecific immunotoxin), more broad reactivity, more efficacy against tumors in vivo, and diminished toxic effects in mice.

A Bispecific Recombinant Cytotoxin (DTEGF13) Targeting Human Interleukin-13 and Epidermal Growth Factor Receptors in a Mouse Xenograft Model of Prostate Cancer

“…Another bispecific immunotoxin simultaneously targeted EpCAM and erbB2, resulting in a hybrid that again had significantly greater activity against the two monomeric immunotoxins. Unlike DTEGF13, internalization studies of DTEpCAM/anti-erbB2 hybrid revealed a higher level of internalization with the bispecific immunotoxin rather than the monomeric immunotoxin (43). A bispecific immunotoxin was reported that selectively and simultaneously targeted human CD22 and CD19 on B cells and was effective in the therapy of systemic B-cell malignancy in a scid/hu mouse model (12).…”

Claudin-7 Regulates EpCAM-Mediated Functions in Tumor Progression

“…Anti-EpC has been reported to be of therapeutic efficacy in several types of human cancer (35,(44)(45)(46)(47)(48)(49). The most striking effect was observed with a bispecific antibody on ascites production by ovarian cancer (46).…”

A dual-targeting triplebody mediates preferential redirected lysis of antigen double-positive over single-positive leukemic cells

“…33 An impressive array of similar agents has been designed and tested using bispecific scFvs against EpCAM, various growth-factor and cytokine receptors, as well as an urokinase-type plasminogen activator receptor (uPAR), to import toxic cargo into various types of human cancer cells in culture and in mice xenografted with human cancer tissues. [34][35][36][37][38] For most of these agents, investigators have shown that the dualtargeting proteins had more potent anti-cancer activity than the corresponding mono-targeting control agents. We are not aware, however, of any studies attempting to demonstrate directly that the dual-targeting agent indeed preferentially eliminated antigen dp over sp cells when both were present in the same reaction mixture, mimicking the simultaneous presence of both types of cells in an infiltrated cancerous tissue.…”