Modifications in synthesis strategy improve the yield and efficacy of geldanamycin-herceptin immunoconjugates.
Geldanamycin (GA) was modified with N-tert-butyloxycarbonyl-1,3-diaminopropane to introduce a latent primary amine. After deprotection, this primary amine provided a site for introduction of a maleimide group that enabled linkage to proteins. This maleimido derivative of geldanamycin (GMB-APA-GA) was linked to the monoclonal antibody Herceptin after the antibody had been modified with Traut's reagent to introduce thiol groups. By this sequence, a new immunoconjugate (H:APA-GA) was generated that showed greater antiproliferative activity than the previously reported analogous immunoconjugate created with a 1,4-diaminobutane spacer derivative of geldanamycin to form an immunoconjugate, H:ABA-GA. Both immunoconjugates inhibited in vitro the growth of MDA-361/DYT2 cells, a cell line overexpressing the HER2 antigen, while Herceptin alone was ineffective. However, H:APA-GA showed better efficacy than H:ABA-GA (IC(50) = 0.2 vs 0.58 mg/mL and cell doubling time >12 vs 6 days, respectively). Results of the in vivo therapy experiments in a xenograft model were consistent with the in vitro findings. Treatment with Herceptin prolonged the survival of the tumor-bearing mice when compared with the control group, but H:ABA-GA and H:APA-GA were each more efficacious than unmodified Herceptin. However, unlike H:ABA-GA, the immunoconjugate H:APA-GA caused stable tumor regression (in 25% of the recipients), showing a qualitative improvement with potential clinical relevance.
Mandler
Raya
R
Metabolism Branch, National Cancer Institute, NIH, Bethesda, Maryland 20982-1002, USA.
Kobayashi
Hisataka
H
Davis
Marie Y
MY
Waldmann
Thomas A
TA
Brechbiel
Martin W
MW
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D016227:Benzoquinones; D002455:Cell Division / Q000187:drug effects; D003959:Diamines / Q000737:chemistry; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D047029:Lactams, Macrocyclic; D051379:Mice; D009374:Neoplasms, Experimental / Q000188:drug therapy; D011809:Quinones / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D015996:Survival Rate; D013810:Therapeutic Equivalency; D014183:Transplantation, Heterologous; D000068878:Trastuzumab; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D016227:Benzoquinones; D003959:Diamines; D018796:Immunoconjugates; D047029:Lactams, Macrocyclic; D011809:Quinones; D000068878:Trastuzumab; C001277:geldanamycin