Catalytic activity of an in vivo tumor targeted anti-cea scFv: :carboxypeptidase G2 fusion protein

• Published in: International journal of cancer Vol. 85; no. 4; pp. 571 - 577
• Main Authors: BHATIA, J, SHARMA, S. K, CHESTER, K. A, PEDLEY, R. B, BODEN, R. W, READ, D. A, BOXER, G. M, MICHAEL, N. P, BEGENT, R. H. J
• Format: Journal Article
• Language: English
• Published: New York, NY Wiley-Liss 15.02.2000
• Subjects: Animals; Antineoplastic agents; Biological and medical sciences; Carcinoembryonic Antigen - immunology; Cloning, Molecular; Colonic Neoplasms - drug therapy; Colonic Neoplasms - metabolism; Escherichia coli; gamma-Glutamyl Hydrolase - metabolism; gamma-Glutamyl Hydrolase - therapeutic use; General aspects; Humans; Immunoglobulin Variable Region - immunology; Medical sciences; Mice; Mice, Nude; Pharmacology. Drug treatments; Prodrugs - pharmacokinetics; Prodrugs - therapeutic use; Recombinant Fusion Proteins - pharmacokinetics; Recombinant Fusion Proteins - therapeutic use; scFv; Tissue Distribution; Transplantation, Heterologous; Antineoplastic agent; Enzyme; Prodrug; Malignant tumor; Biological activity; Colonic disease; Peptidases; Carcinoembryonic antigen; In vivo; Treatment; Carboxypeptidase A; Established cell line; Digestive diseases; Hydrolases; Intestinal disease; Colon; Recombinant protein; Fusion protein; Metallocarboxypeptidases; Single chain antibody
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/(SICI)1097-0215(20000215)85:4<571::AID-IJC20>3.3.CO;2-T

Antibody-directed enzyme prodrug therapy (ADEPT) targets an enzyme selectively to a tumor where it converts a relatively non-toxic prodrug to a potent cytotoxic drug. Previous clinical work using antibody-enzyme chemical conjugates has been limited by the moderate efficiency of tumor targeting of these molecules. To address this a recombinant fusion protein composed of MFE-23, an anti-carcinoembryonic antigen (CEA) single chain Fv (scFv) antibody, fused to the amino-terminus of the enzyme carboxypeptidase G2 (CPG2) has been constructed to achieve ADEPT in CEA-producing tumors. MFE-23::CPG2 fusion protein was overexpressed in Escherichia coli and purified using CEA affinity chromatography. Efficacy of MFE-23::CPG2 delivery to tumors in vivo was assessed by measuring catalytic activity after intravenous injection of purified MFE-23::CPG2 into nude mice bearing CEA-positive LS174T human colon adenocarcinoma xenografts. Recombinant MFE-23::CPG2 cleared rapidly from circulation and catalytic activity in extracted tissues showed tumor to plasma ratios of 1.5:1 (6 hr), 10:1 (24 hr), 19:1 (48 hr) and 12:1 (72 hr). (125)I-MFE-23::CPG2 was retained in kidney, liver and spleen but MFE-23::CPG2 catalytic activity was not, resulting in excellent tumor to normal tissue enzyme ratios 48 hr after injection. These were 371:1 (tumor to liver), 450:1 (tumor to lung), 562:1 (tumor to kidney), 1,477:1 (tumor to colon) and 1,618:1 (tumor to spleen). Favorable tumor : normal tissue ratios occurred at early time points when there was still 21% (24 hr) and 9.5% (48 hr) of the injected activity present per gram of tumor tissue. The high tumor concentrations and selective tumor retention of active enzyme delivered by MFE-23::CPG2 establish that this recombinant fusion protein has potential to give improved clinical efficiency for ADEPT.