Recombinant anti-carcinoembryonic antigen antibodies for targeting cancer

Abstract

Antibodies can be used to target cancer therapies to malignant tissue; the approach is attractive because conventional treatments such as chemo- and radiotherapy are dose limited due to toxicity in normal tissues. Effective targeting relies on appropriate pharmacokinetics of antibody-based therapeutics, ideally showing maximum uptake and retention in tumor and rapid clearance from normal tissue. We have studied the factors influencing these dynamics for antibodies against carcinoembryonic antigen (CEA). Protein engineering of anti-CEA antibodies, in vivo biodistribution models, and mathematical models have been employed to improve understanding of targeting parameters, define optimal characteristics for the antibody-based molecules employed, and develop new therapies for the clinic. Engineering antibodies to obtain the desired therapeutic characteristics is most readily achieved using recombinant antibody technology, and we have taken the approach of immunizing mice to provide high-affinity anti-CEA single-chain Fv antibodies (sFvs) from filamentous bacteriophage libraries. MFE-23, the most characterized of these sFvs, has been expressed in bacteria and purified in our laboratory for two clinical trials: a gamma camera imaging trial using 123I-MFE-23 and a radioimmunoguided surgery trial using 125I-MFE-23, where tumor deposits are detected by a hand-held probe during surgery. Both these trials showed that MFE-23 is safe and effective in localizing tumor deposits in patients with cancer. We are now developing fusion proteins that use the MFE-23 antibody to deliver a therapeutic moiety; MFE-23:: carboxypeptidase G2 (CPG2) targets the enzyme CPG2 for use in the antibody-directed enzyme prodrug therapy system and MFE::tumor necrosis factor alpha (TNFalpha) aims to reduce sequestration and increase tumor concentrations of systemically administered TNFalpha.

Tumor‐targeting properties of antibody–vascular endothelial growth factor fusion proteins

“…These results are significantly less impressive than the results obtained by the same group with an scFv fragment specific for carcinoembryonic antigen [scFv(MFE-23)], 55 an agent that has moved into clinical development. 56,57 Cutting-edge genomic research has devoted a great deal of attention to the search for markers specifically expressed in the luminal aspect of tumor endothelium, but not in normal endothelial cells, 58,59 for use as targets for biomolecular intervention. While such markers may prove invaluable for discovering novel functions of the tumor endothelium and for the design of inhibitory molecules, their use as targets for ligand-based targeting may be limited, based on the following simple chemical and pharmacokinetic considerations.…”

Adenovirus Tumor Targeting and Hepatic Untargeting by a Coxsackie/Adenovirus Receptor Ectodomain Anti–Carcinoembryonic Antigen Bispecific Adapter

“…Bispecific adapters with a CEA-binding domain should untarget adenovirus vectors from normal tissues and retarget them to CEA-positive tumors. MFE-23, a single-chain antibody with high affinity for CEA, is currently in phase I studies both as an imaging agent for radioimmunoguided surgery and as a tumor-targeting agent for antibody-directed enzyme prodrug therapy (20)(21)(22). To retarget CEA-positive cells, MFE-23 has been fused to sCAR to form sCAR-MFE, a bispecific transductional reagent.…”

Characterization of Monoclonal Antibodies Against Carcinoembryonic Antigen (CEA) and Expression inE. coli

“…(2)(3)(4) CEA is expressed at greatly increased levels in nearly all human colorectal carcinomas, as well as many other malignancies of epithelial origin such as breast, lung, and ovarian carcinomas. (2)(3)(4)(5) CEA gene family belongs to the immunoglobulin gene superfamily and consists of approximately 30 genes, of which 17 are transcriptionally active. (2,4,6) Antibodies are highly specific recognition molecules and the development of monoclonal antibodies (MAbs) (7) has revolutionized the medical applications of antibodies in research and clinical laboratories.…”