Abstract
ADEPT is an antibody-based targeting strategy for the treatment of cancer. We have developed two new prodrugs, 4-[N,N-bis(2-chloroethyl)amino]-phenoxycarbonyl-L- glutamic acid (PGP) and (S)-2-[N-[4-[N,N-bis(2-chloroethyl)amino]- phenoxycarbonyl]amino]-4-(5-tetrazoyl)butyric acid (PTP), which are cleaved by the bacterial enzyme CPG2 to release the 4-[N,N-bis(2-chloroethyl)amino] phenol drug. In vitro, both prodrugs are approximately 100- to 200-fold less potent than the parent drug (1 h IC50 = 1.4 microM) in LoVo colorectal tumour cells. These prodrugs have been evaluated for utility in ADEPT when used in combination with a conjugate of CPG2 and the F(ab')2 fragment of the anti-CEA monoclonal antibody, A5B7. The conjugate was shown to localise specifically to established LoVo tumour xenografts growing in nude mice and optimal tumour-normal tissue ratios were achieved after 72 h. Administration of either prodrug, at doses which cause 6-8% body weight loss, 72 h after administration of the A5B7-CPG2 conjugate to the LoVo tumour-bearing mice resulted in tumour regressions and growth delays of 14-28 days. The PTP prodrug in combination with a high dose of conjugate (10 mg kg-1) gave the best anti-tumour activity despite being a 10-fold worse substrate for CPG2 than PGP. Prodrug alone, active drug alone or prodrug in combination with a non-specific conjugate had minimal anti-tumour activity in this tumour model.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Aniline Mustard / analogs & derivatives*
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Aniline Mustard / pharmacokinetics
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Aniline Mustard / therapeutic use
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Animals
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Antibodies, Monoclonal / administration & dosage*
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Antibodies, Monoclonal / immunology
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Antibodies, Neoplasm / administration & dosage*
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Antibodies, Neoplasm / immunology
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Antineoplastic Agents, Alkylating / pharmacokinetics
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Antineoplastic Agents, Alkylating / therapeutic use*
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Bacterial Proteins / administration & dosage*
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Bacterial Proteins / metabolism
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Biotransformation
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Carcinoembryonic Antigen / immunology*
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Colorectal Neoplasms / drug therapy*
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Colorectal Neoplasms / pathology
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Drug Screening Assays, Antitumor
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Female
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Humans
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Immunoconjugates / therapeutic use*
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Immunoglobulin Fab Fragments / administration & dosage
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Immunoglobulin Fab Fragments / immunology
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Mice
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Mice, Nude
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Neoplasm Transplantation
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Prodrugs / pharmacokinetics
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Prodrugs / therapeutic use*
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Pseudomonas / enzymology
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Substrate Specificity
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Tumor Cells, Cultured
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gamma-Glutamyl Hydrolase / administration & dosage*
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gamma-Glutamyl Hydrolase / metabolism
Substances
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(4-(N,N-bis(2-chloroethyl)amino)phenoxycarbonyl)glutamic acid
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2-(N-(4-(N,N-bis(2-chloroethyl)amino)phenoxycarbonyl)amino)-4-(5-tetrazolyl)butyric acid
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Antibodies, Monoclonal
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Antibodies, Neoplasm
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Antineoplastic Agents, Alkylating
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Bacterial Proteins
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Carcinoembryonic Antigen
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Immunoconjugates
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Immunoglobulin Fab Fragments
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Prodrugs
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hydroxyaniline mustard
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Aniline Mustard
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gamma-Glutamyl Hydrolase