New modular delivery system for diagnostic and therapeutic pre-targeting using tautomer-specific monoclonal antibody EM-6-47 and 3-substituted adenines.
We have developed a new modular affinity system for the 2-step delivery of functional molecules to target cells. The system is based on the tautomer-specific monoclonal antibody (MAb) EM-6-47, which binds to 3- and 3,8-substituted adenines with high affinity (Ka > 10(9) l/mol) without cross-reacting with naturally occurring purine derivatives. This MAb serves as the hapten-specific fusion partner to produce bispecific MAbs (bs-MAbs) recognizing a target cell antigen and a low-m.w. hapten as carrier molecule for, e.g., radionuclides. Either the C-8 or the N-3 position of adenines can be used for conjugation with effector molecules; the remaining position may be substituted with different moieties to modulate the pharmacokinetics of the haptens. Different 3- and 3,8-substituted adenines conjugated to the chelates DOTA and DTPA or to the drug daunomycin were synthesized. Adenine-chelate derivatives were efficiently labeled with (111)In and 90Y, while high-affinity binding of 3-substituted adenines to MAb EM-6-47 remained almost unaffected by the conjugation to radiochelates. To confirm the validity of the delivery system, a prototype bs-MAb, EM-168-47, was generated by somatic cell fusion of MAb EM-6-47 and MAb EM-168-2, the latter recognizing a surface antigen on canine hematopoietic cells. Two-step targeting assays in vitro verified the bs-MAb-mediated, dose-dependent delivery of (111)In-labeled adenine-chelate derivatives to myeloid cells. This system represents a powerful tool for new pre-targeting approaches relying on bs-MAbs and low-m.w. haptens. Suitable cellular antigens can be targeted by fusing the appropriate MAbs with hapten-specific MAb EM-6-47, and tailor-made 3-substituted adenines may be labeled with diagnostic or therapeutic radionuclides, cytotoxic drugs or other functional molecules.
Krüger
K
K
Institute of Cell Biology (Cancer Research), Center of Cancer Research and Cancer Therapy, University of Essen Medical School, Germany.
Jochum
C
C
Glüsenkamp
K H
KH
Krüsemann
C
C
Lorenz
P
P
Eberle-Adamkiewicz
G
G
Drosdziok
W
W
Beelen
D W
DW
Coenen
H H
HH
Rajewsky
M F
MF
D000225:Adenine / Q000737:chemistry; D000818:Animals; D018033:Antibodies, Bispecific / Q000627:therapeutic use*; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D004285:Dogs; D016503:Drug Delivery Systems; D006241:Haptens / Q000378:metabolism; D000922:Immunotoxins / Q000008:administration & dosage*; D007205:Indium Radioisotopes / Q000627:therapeutic use
D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D006241:Haptens; D000922:Immunotoxins; D007205:Indium Radioisotopes; D000225:Adenine