Pronounced antitumor efficacy of doxorubicin when given as the prodrug DOX-GA3 in combination with a monoclonal antibody beta-glucuronidase conjugate.
A glucuronide doxorubicin prodrug N-[4-doxorubicin-N-carbonyl (oxymethyl) phenyl] O-beta-glucuronyl carbamate (DOX-GA3) has been developed to improve the antitumor effects of doxorubicin (DOX). The prodrug was originally designed to be activated into drug by human beta-glucuronidase (GUS) released from tumor cells in necrotic areas of tumor lesions. The aim of this study was to further improve the antitumor effects of DOX-GA3 by means of antibody-directed enzyme prodrug therapy (ADEPT). We thus investigated if the administration of an enzyme-immunoconjugate prepared from the pancarcinoma Ep-CAM specific monoclonal antibody (MAb) 323/A3 and beta-glucuronidase would result in improved antitumor effects because of additional enzyme localization in tumor tissue. In vitro, the prodrug DOX-GA3 was found to be 12-times less toxic than the parent drug DOX in a human ovarian cancer cell line. Immunospecific and complete activation of the prodrug took place when the cells were pretreated with 323/A3-beta-glucuronidase conjugate. In nude mice bearing s.c. human ovarian cancer xenografts (FMa) the maximum tolerated dose (MTD) of DOX-GA3 (500 mg/kg weekly x 2) was much higher when compared with that of DOX (8 mg/kg weekly x 2). In mice bearing well-established FMa xenografts, the standard treatment of DOX at the MTD (8 mg/kg weekly x 2) resulted in a tumor growth inhibition of 67%. Treatment with DOX-GA3 at a single dose of 500 mg/kg resulted in a better tumor growth inhibition of 87%. The combination of DOX-GA3 (500 mg/kg) with 323/A3-mGUS conjugate and anti-GUS MAb 105, to clear circulating conjugate, improved the antitumor effect even further to 98%. At the lower dose of 250 mg/kg DOX-GA3 tumor growth inhibition (34%) was not better than that of DOX. The combination, however, of DOX-GA3 at 250 mg/kg and 323/A3-mGUS conjugate plus MAb 105 again greatly improved the antitumor effect (growth inhibition of 93%). DOX given at 8 mg/kg weekly x 2 did not result in tumor regressions. As a result of ADEPT, the number of regressions of tumors improved from 0 out of 12 to 9 out of 11 at a dose of 250 mg/kg DOX-GA3. At the higher prodrug dose (500 mg/kg) the number of regressions improved from 2 out of 12 to 9 out of 10 as a result from the addition of enzyme-immunoconjugate. Our studies show that the efficacy of the widely used anti-cancer agent DOX may be improved by using the prodrug DOX-GA3, in combination with the tumor-specific enzyme-immunoconjugate 323/A3-mGUS and a conjugate clearing antibody.
Department of Medical Oncology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
P H
PH
Houba
E
E
Boven
I H
IH
van der Meulen-Muileman
R G
RG
Leenders
J W
JW
Scheeren
H M
HM
Pinedo
H J
HJ
Haisma
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001835:Body Weight / Q000187:drug effects; D002455:Cell Division; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D005260:Female; D005965:Glucuronates / Q000627:therapeutic use*; D005966:Glucuronidase / Q000378:metabolism / Q000627:therapeutic use*; D006801:Humans; D020714:Maximum Tolerated Dose; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008819:Mice, Nude; D008956:Models, Chemical; D009336:Necrosis; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000188:drug therapy*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000628:therapy; D011355:Prodrugs / Q000627:therapeutic use*; D013997:Time Factors; D014407:Tumor Cells, Cultured
C064108:323-A3 antigen, human; D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D005965:Glucuronates; D008562:Membrane Glycoproteins; C407038:N-(4-doxorubicin-N-carbonyl(oxymethyl)phenyl)-O-glucuronyl carbamate; D011355:Prodrugs; D004317:Doxorubicin; D005966:Glucuronidase