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Lookup NU author(s): Professor Alan Calvert
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Heterocyclic para-aminobenzoate modifications of 2-desamino-2-methyl-5,8-dideazafolic acid and a series of its N10-substituted analogs have produced a number of interesting compounds that have enabled a deeper understanding of the biochemical events required for activity in this class of antimetabolite. There is a relationship that has become apparent between compound potency and both uptake via the reduced-folate carrier and FPGS substrate activity. Rapid cellular uptake and metabolism to polyglutamate forms that are 100-fold more potent as inhibitors of TS can translate a modest TS inhibitor such as ICI D1694 into a very potent inhibitor of cell growth (500- and 10-fold more potent than CB3717 or ICI 198583, respectively). Polyglutamation may therefore act as an almost essential activation step and ICI D1694 may be highly specific for tumors expressing both the reduced-folate carrier and FPGS. Polyglutamation of folate analogs also leads to drug retention which may play a major role in the pharmacodynamics of TS inhibition by ICI D1694 in vivo. Current studies with 3H-ICI D1694 are aimed at demonstrating metabolism to polyglutamates in tumor cells. The serious toxic limitations of CB3717, i.e., liver and kidney toxicities, are not seen with ICI D1694 reflecting the good water solubility of the drug compared with CB3717. The toxicities observed in mice are however to hematological tissues and are due to its TS inhibitory effects (37). Thus ICI D1694 may elicit toxicities in man more typical of an antimetabolite than of CB3717. The clinical evaluation of ICI D1694 may further our understanding of the role that metabolism to polyglutamates may have in therapeutic activity.
Author(s): Jackman AL, Marsham PR, Moran RG, Kimbell R, O'Connor BM, Hughes LR, Calvert AH
Publication type: Article
Publication status: Published
Journal: Advances in Enzyme Regulation
Year: 1991
Volume: 31
Pages: 13-27
ISSN (print): 0065-2571
ISSN (electronic): 1873-2437
URL: http://dx.doi.org/10.1016/0065-2571(91)90006-8
DOI: 10.1016/0065-2571(91)90006-8
PubMed id: 1877386
Notes: Presented at the 31st Symposium on Regulation of Enzyme Activity and Synthesis in Normal and Neoplastic Tissues. Indiana University, Indianapolis, Indiana, USA. 1-2nd October 1990.
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