Cooperative mixtures of bispecific F(ab')2 antibodies for delivering saporin to lymphoma in vitro and in vivo

• Published in: Cancer research (Chicago, Ill.) Ill.), 1991-05, Vol.51 (9), p.2353-2361
• Main Authors: FRENCH, R. R, COURTENAY, A. E, INGAMELLS, S, STEVENSON, G. T, GLENNIE, M. J
• Format: Article
• Language: English
• Subjects: AMINO ACIDS; ANIMAL CELLS; ANIMALS; ANTIBODIES; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - therapeutic use; Antibody Affinity - immunology; Antineoplastic agents; Antineoplastic Agents, Phytogenic - immunology; Antineoplastic Agents, Phytogenic - metabolism; Antineoplastic Agents, Phytogenic - therapeutic use; Biological and medical sciences; CARBOXYLIC ACIDS; DISEASES; Drug Synergism; General aspects; GUINEA PIGS; HYDROGEN COMPOUNDS; IMMUNE SYSTEM DISEASES; Immunoglobulin Fab Fragments - immunology; Immunoglobulin Fab Fragments - therapeutic use; IMMUNOLOGY; IMMUNOTHERAPY; Immunotoxins - immunology; Immunotoxins - metabolism; Immunotoxins - therapeutic use; Iodine Radioisotopes - pharmacokinetics; ISOTOPE APPLICATIONS; LEUCINE; Leucine - pharmacokinetics; LEUKEMIA; MAMMALS; Medical sciences; MEDICINE; MICE; Mice, Inbred BALB C; Mice, Inbred CBA; MONOCLONAL ANTIBODIES; N-Glycosyl Hydrolases; NEOPLASMS; NUCLEAR MEDICINE; ORGANIC ACIDS; ORGANIC COMPOUNDS; Pharmacology. Drug treatments; Plant Proteins - immunology; Plant Proteins - metabolism; Plant Proteins - therapeutic use; Precursor Cell Lymphoblastic Leukemia-Lymphoma - immunology; Precursor Cell Lymphoblastic Leukemia-Lymphoma - metabolism; Precursor Cell Lymphoblastic Leukemia-Lymphoma - therapy; RADIOIMMUNOLOGY; RADIOIMMUNOTHERAPY; RADIOLOGY; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Ribosome Inactivating Proteins, Type 1; RODENTS; SPECIFICITY; THERAPY; TRACER TECHNIQUES; TRITIUM COMPOUNDS; TUMOR CELLS; Tumor Cells, Cultured; VERTEBRATES 550604 > Medicine-- Unsealed Radionuclides in Therapy-- (1980-)
• ISSN: 0008-5472; 1538-7445

We report that selected combinations of two or more monoclonal bispecific F(ab')2 antibodies (BsAbs) far outperform single derivatives in the delivery of the ribosome-inactivating protein, saporin, to guinea pig L2C leukemic cells. Throughout the work, BsAbs were constructed by thioether-linking the hinges of two Fab'gamma, one from monoclonal anti-L2C-idiotype antibody and the other from anti-saporin antibody. The latter was either affinity-purified rabbit polyclonal or one of a panel of five mouse monoclonal antibodies. In vitro cytotoxicity studies showed that, though all derivatives were effective, the BsAb made with the polyclonal antibody was always 10 to 20 times more potent than those made with a monoclonal antibody in yielding 50% inhibition of [3H]leucine uptake. This superior activity could be matched by selective mixtures of two or more of the monoclonal derivatives. Furthermore, in immunotherapeutic delivery of saporin to tumor, a pair of BsAbs performed significantly better than did either individually. Binding and uptake studies with radiolabeled saporin demonstrated a 20-fold increase in functional affinity when saporin was held at the cell surface by an appropriate BsAb mixture rather than by a single BsAb. In contrast, only small differences were recorded in the rate at which saporin was internalized as a result of the same maneuver. We conclude that the improved performance of combinations of BsAbs arises from their ability to provide multiple linkages between saporin molecules and cell surfaces, significantly increasing the functional affinity with which saporin is tethered to the cell, but, in this system at least, having only a minor effect on the rate at which it is internalized. Cocktails of two or more BsAbs, selected to bind to multiple epitopes on ribosome-inactivating proteins and perhaps also on unwanted cells, could provide an important new strategy in immunotherapy.