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Nitroreductase: A prodrug-activating enzyme for cancer gene therapy

Lookup NU author(s): Professor Paul RaceORCiD


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1. The prodrug CB1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide) is activated by Escherichia coli nitroreductase (NTR) to a potent DNA-crosslinking agent. 2. Virus-mediated expression of NTR in tumour cells sensitizes them to CB1954 in vitro and in vivo, providing the basis for a strategy of cancer gene therapy. 3. A phase I trial of CB1954 in cancer patients has been completed, documenting the pharmacokinetics and establishing an acceptable dose. Subsequent trials of the replication-defective adenovirus CTL102 in patients with resectable tumours have documented expression of NTR in injected colorectal liver metastases, hepatocellular carcinoma, head and neck cancer and prostate cancer. Trials combining CTL102 and CB1954 are underway. 4. An oncolytic (replication- competent) adenovirus vector allowed increased expression of NTR in vitro and in a mouse tumour model, resulting in a greater reduction in tumour growth when combined with CB1954 treatment. 5. Alternative prodrugs may eventually prove superior to CB1954; a nitroaryl phosphoramide mustard prodrug activated by NTR shows a greater therapeutic index than CB1954 in a human ovarian carcinoma. 6. The crystal structure of NTR provided the basis for site-directed mutagenesis, which has identified a number of mutants with improved kinetics of CB1954 activation. These can provide improved cell sensitization to CB1954. Combinations of these are being tested. 7. The basis for a positive selection for improved NTR variants has been demonstrated.

Publication metadata

Author(s): Searle PF, Chen M-J, Hu L, Race PR, Lovering AL, Grove JI, Guise C, Jaberipour M, James ND, Mautner V, Young LS, Kerr DJ, Mountain A, White SA, Hyde EI

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: 37th Annual Scientific Meeting of the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists

Year of Conference: 2004

Pages: 811-816

Online publication date: 25/11/2004

ISSN: 0305-1870

Publisher: John Wiley & Sons, Inc.


DOI: 10.1111/j.1440-1681.2004.04085.x

PubMed id: 15566399

Series Title: Clinical and Experimental Pharmacology and Physiology