Recombinant NY-ESO-1 cancer antigen: production and purification under cGMP conditions.

The cancer-testis antigen, NY-ESO-1, has been engineered into a bacterial expression plasmid which incorporates a His6-tag. The plasmid was transfected into E. coli strain BL21 and Master and Working cell banks generated from this expression system. Three 15-litre fermentations were performed under cGMP (code of Good Manufacturing Practice) conditions and the crude NY-ESO-1 tagged protein isolated as solubilised inclusion bodies. A three-step cGMP chromatography process (immobilised metal affinity, anion exchange, and hydrophobic interaction) was utilised to purify the protein. The purified NY-ESO-1 is being used in early stage human cancer vaccine trials in Australia and the U.S.A.

Engineering and characterisation of chimeric monoclonal antibody 806 (ch806) for targeted immunotherapy of tumours expressing de2-7 EGFR or amplified EGFR.

We report the generation of a chimeric monoclonal antibody (ch806) with specificity for an epitope on the epidermal growth factor receptor (EGFR) that is different from that targeted by all other anti-EGFR therapies. Ch806 antibody is reactive to both de2-7 and overexpressed wild-type (wt) EGFR but not native EGFR expressed in normal tissues at physiological levels. Ch806 was stably expressed in CHO (DHFR -/-) cells and purified for subsequent characterisation and validated for use in preliminary immunotherapy investigations. Ch806 retained the antigen binding specificity and affinity of the murine parental antibody. Furthermore, ch806 displayed enhanced antibody-dependent cellular cytotoxicity against target cells expressing the 806 antigen in the presence of human effector cells. Ch806 was successfully radiolabelled with both iodine-125 and indium-111 without loss of antigen binding affinity or specificity. The radioimmunoconjugates were stable in the presence of human serum at 37 degrees C for up to 9 days and displayed a terminal half-life (T(1/2beta)) of approximately 78 h in nude mice. Biodistribution studies undertaken in BALB/c nude mice bearing de2-7 EGFR-expressing or amplified EGFR-expressing xenografts revealed that (125)I-labelled ch806 failed to display any significant tumour retention. However, specific and prolonged tumour localisation of (111)In-labelled ch806 was demonstrated with uptake of 31%ID g(-1) and a tumour to blood ratio of 5 : 1 observed at 7 days postinjection. In vivo therapy studies with ch806 demonstrated significant antitumour effects on established de2-7 EGFR xenografts in BALB/c nude mice compared to control, and both murine 806 and the anti-EGFR 528 antibodies. These results support a potential therapeutic role of ch806 in the treatment of suitable EGFR-expressing tumours, and warrants further investigation of the potential of ch806 as a therapeutic agent.

Construction, production, and characterization of humanized anti-Lewis Y monoclonal antibody 3S193 for targeted immunotherapy of solid tumors.

The Lewis Y (Ley) antigen is a blood group-related antigen that is expressed in a high proportion of epithelial cancers (including breast, colon, ovary, and lung cancer) and is an attractive target for monoclonal antibody-directed therapy. The murine monoclonal 3S193 (IgG3) was generated in BALB/c mice by immunization with Ley-expressing cells of the MCF-7 breast carcinoma cell-line. The murine 3S193 showed high specificity for Ley in ELISA tests with synthetic Ley and Ley-containing glycoproteins and glycolipids and also reacted strongly in rosetting assays and cytotoxic tests with Ley-expressing cells. We generated a humanized form of the murine 3S193 antibody by linking cDNA sequences encoding the variable region of murine 3S913 with frameworks of the human KOL heavy chain and REI K chain. The genes for the humanized 3S193 monoclonal antibody IgG1 were transfected into mouse myeloma NS0 cells and cloned for the establishment of high antibody-producing colonies. Humanized 3S193 antibody was subsequently produced through in vitro culture and under good manufacturing practice conditions using hollow-fiber bioreactors. The purified humanized 3S193 (hu3S193) was subsequently characterized and validated for use in preliminary immunotherapy investigations. hu3S193 reacted specifically with Ley antigen, with similar avidity to the murine form. hu3S193 demonstrated potent immune effector function, with higher antibody-dependent cell-mediated cytotoxicity than its murine counterpart and potent complement-dependent cytotoxicity (ED50, 1.0 microg/ml). The in vivo immunotherapeutic potential of hu3S193 was assessed in a human breast xenograft model using MCF-7, Ley-positive cells. Six i.v. doses of up to 1 mg of hu3S193 were administered to animals bearing established tumors (120-130 mm3) with no significant effect on tumor growth. In contrast, in an MCF-7 xenograft preventive model, a 1-mg hu3S193 dosage schedule was able to significantly slow tumor growth compared with placebo and isotype-matched control IgG1 antibody. hu3S193 has promise for immunotherapy of Ley-positive tumors and is currently entering Phase I clinical trials.