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Cancer Chemotherapy and Pharmacology

, Volume 40, Issue 3, pp 189–201 | Cite as

Antibody-directed enzyme prodrug therapy: pharmacokinetics and plasma levels of prodrug and drug in a phase I clinical trial

  • Janet Martin
  • Stephen M. Stribbling
  • Grace K. Poon
  • Richard H. J. Begent
  • Mark Napier
  • Surinder K. Sharma
  • C. J. Springer
ORIGINAL ARTICLE

Abstract

Antibody-directed enzyme prodrug therapy (ADEPT) was administered to ten patients in a phase I clinical trial. The aim was to measure plasma levels of the prodrug 4-[(2-chloroethyl)(2-mesyloxyethyl) amino] benzoyl-l-glutamic acid (CMDA) and the bifunctional alkylating drug (CJS11) released from it by the action of tumour-localised carboxypeptidase G2 (CPG2) enzyme. New techniques were developed to extract the prodrug and drug from plasma by solid-phase adsorbtion and elution and to measure CPG2 activity in plasma and tissue. All extracts were analysed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). CPG2 activity was found in metastatic tumour biopsies but not in normal tissue, indicating that localisation had been successful. The clearing agent SB43-gal, given at 46.5 mg/m2, achieved the aim of clearing non-tumour-localised enzyme in the circulation, indicating that conversion of prodrug to drug could take place only at the site of localised conjugate. Plasma prodrug did not always remain above its required threshold of 3 μM for the “therapeutic window” of 120 min after dosing, but the presence of residual prodrug after the first administration of each day indicated that this could be achieved during the remaining four doses over the following 8 h. Despite considerable inter-patient prodrug plasma concentration variability, the elimination half-life of the prodrug was remarkably reproducible at 18 ± 8 min. Rapid appearance of the drug in plasma indicated that successful conversion from the prodrug had taken place, but also undesirable leakback from the site of localisation into the bloodstream. However, drug plasma levels fell rapidly by at least 50% at between 10 and 60 min with a half-life of 36 ± 14 min. Analysis of the plasma extracts by LC/MS indicated that this technique might be used to confirm qualitatively the presence of prodrug, drug and their metabolites.

Key words ADEPT   Prodrug   Carboxypeptidase G2 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Janet Martin
    • 1
  • Stephen M. Stribbling
    • 1
  • Grace K. Poon
    • 1
  • Richard H. J. Begent
    • 2
  • Mark Napier
    • 2
  • Surinder K. Sharma
    • 2
  • C. J. Springer
    • 1
  1. 1.CRC Centre for Cancer Therapeutics, Institute of Cancer Research, CRC Laboratory, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK Tel.: 0181 643 8901 ext. 4214 Fax: 0181 770 7899GB
  2. 2.CRC Clinical Research Laboratories, Royal Free Hospital School of Medicine, Department of Clinical Oncology, Rowland Hill Street, London NW3 2PF, UKGB

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