Folate analogues. 34. Synthesis and antitumor activity of non-polyglutamylatable inhibitors of dihydrofolate reductase.
Five analogues of methotrextate (MTX), 10-deazaaminopterin (10-DAM), and 10-ethyl-10-deazaaminopterin (10-EDAM) in which the glutamate moiety was replaced by either a gamma-methyleneglutamate or beta-hydroxyglutamate were synthesized and evaluated for their antifolate activity. These analogous are 4-amino-4-deoxy-N10-methylpteroyl-beta-hydroxyglutamic acid (1), 4-amino-4-deoxy-10-deazapteroyl-beta-hydroxyglutamic acid (2), 4-amino-4-deoxy-N10-methylpteroyl-gamma-methyleneglutamic acid (3, MMTX), 4-amino-4-deoxy-10-deazapteroyl-gamma-methyleneglutamic acid (4, MDAM), and 4-amino-4-deoxy-10-ethyl-10-deazapteroyl-gamma-methyleneglutamic acid (5, MEDAM). None of these compounds were metabolized to the respective polyglutamate derivative as judged by their inability to serve as substrates for CCRF-CEM human leukemia cell folylpolyglutamate synthetase (FPGS) in vitro. All compounds inhibited recombinant human-dihydrofolate reductase (DHFR) at nearly equivalent magnitude as MTX. Growth-inhibition studies with H35 hepatoma, Manca human lymphoma, and CCRF-CEM human leukemia cells established greater cytotoxic effects with compounds 3-5 than with compounds 1 and 2. gamma-Methyleneglutamate derivatives 3-5 were transported to H35 hepatoma cells better than MTX or beta-hydroxyglutamate derivatives 1 and 2. Compound 3 was 2.5 times better than MTX in competing with folinic acid transport in H35 hepatoma cells. Compound 1 did not have a significant inhibitory effect on folinic acid transport even at 50 microM under identical conditions. The IC50 for compound 1 against H35-hepatoma cell growth was 8.5-fold higher than MTX. Compounds with the gamma-methyleneglutamate moiety (3-5) exhibited almost equal or lower IC50 values than MTX against the growth of CCRF-CEM human leukemia cells. These studies show that on continuous exposure, the non-polyglutamylatable inhibitors DHFR (3-5) can exhibit superior antifolate activity compared to the polyglutamylatable methotrexate, presumably due to their enhanced transport to these cell lines. Compounds 3-5 appear to be excellent models to study the role of polyglutamylation of antifolates in antitumor activity and host toxicity.
Abraham
A
A
Drug Development Laboratory, University of South Alabama, Mobile 36688.
McGuire
J J
JJ
Galivan
J
J
Nimec
Z
Z
Kisliuk
R L
RL
Gaumont
Y
Y
Nair
M G
MG
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004354:Drug Screening Assays, Antitumor; D005493:Folic Acid Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007202:Indicators and Reagents; D008727:Methotrexate / Q000494:pharmacology; D015394:Molecular Structure; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D013329:Structure-Activity Relationship
D000964:Antimetabolites, Antineoplastic; D005493:Folic Acid Antagonists; D007202:Indicators and Reagents; D011994:Recombinant Proteins; D008727:Methotrexate