title: Delivery of the ribosome-inactivating protein, gelonin, to lymphoma cells via CD22 and CD38 using bispecific antibodies.
abstract: It is well established that bispecific antibodies (BsAbs) can be used effectively in targeting the ribosome-inactivating protein (RIP), saporin, against neoplastic B cells. We have now extended this delivery system for use with gelonin. By measuring antigen-binding characteristics and epitope mapping a panel of anti-gelonin MAbs using the IAsys resonant mirror bisensor, we were able to rapidly select the most suitable for making BaAbs. The Fab' fragments from these MAbs were chemically conjugated with Fab' from either anti-CD22 or anti-CD38. Cytotoxicity assays showed that BsAbs were highly efficient at delivering gelonin to cultured Daudi cells and achieved levels of toxicity which correlated closely with the affinity of the BsAbs. Using pairs of anti-CD22 BsAbs we were able to generate bivalent BsAb-gelonin complexes which achieved IC50 values of 2 x 10(-11) M gelonin, a potency which is equivalent to that reached by saporin in this targeting system. However, because gelonin is 5-10 times less toxic than saporin, the therapeutic ratio for gelonin is superior, making it potentially a more useful agent for human treatment. Cytotoxicity assays and kinetic analysis showed that targeting gelonin via CD38 was 2-5 times less effective than delivery through CD22. However, with a pair of BsAbs designed to co-target gelonin via CD22 and CD38, the cytotoxicity achieved equalled that obtained with a pair of anti-CD22 BsAbs (IC50 = 1 x 10(-11) M). This important result suggests that the anti-CD38 helps bind the gelonin to the cell and is then 'dragged' or 'piggy-backed' into the cell by the anti-CD22 BsAb. The implication of these findings for cancer therapy is discussed.
authors.affiliation: Lymphoma Research Unit, Tanovus Laboratory, General Hospital, Southampton, UK.
authors.forename: R R
authors.initials: RR
authors.lastname: French
authors.forename: C A
authors.initials: CA
authors.lastname: Penney
authors.forename: A C
authors.initials: AC
authors.lastname: Browning
authors.forename: F
authors.initials: F
authors.lastname: Stirpe
authors.forename: A J
authors.initials: AJ
authors.lastname: George
authors.forename: M J
authors.initials: MJ
authors.lastname: Glennie
mesh_terms: D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology / Q000378:metabolism; D015703:Antigens, CD / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology*; D002051:Burkitt Lymphoma / Q000188:drug therapy* / Q000276:immunology* / Q000378:metabolism; D015815:Cell Adhesion Molecules; D000922:Immunotoxins / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D007700:Kinetics; D037102:Lectins; D007930:Leucine / Q000493:pharmacokinetics; D008562:Membrane Glycoproteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D009699:N-Glycosyl Hydrolases; D010940:Plant Proteins / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000633:toxicity*; D011500:Protein Synthesis Inhibitors / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000633:toxicity*; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D051918:Sialic Acid Binding Ig-like Lectin 2; D014316:Tritium
chemical_list: D018033:Antibodies, Bispecific; D015703:Antigens, CD; D000943:Antigens, Differentiation; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D000922:Immunotoxins; D007457:Iodine Radioisotopes; D037102:Lectins; D008562:Membrane Glycoproteins; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D054789:Ribosome Inactivating Proteins, Type 1; D051918:Sialic Acid Binding Ig-like Lectin 2; D014316:Tritium; C025674:GEL protein, Gelonium multiflorum; D009699:N-Glycosyl Hydrolases; D000076985:Saporins; D036541:ADP-ribosyl Cyclase; C498155:Cd38 protein, mouse; D051997:ADP-ribosyl Cyclase 1; D007930:Leucine