Methotrexate analogues--XVII. Antitumor activity of 4-amino-4-deoxy-N10-methylpteroyl-D,L-homocysteic acid and its dual inhibition of dihydrofolate reductase and folyl polyglutamate synthetase.
A new analogue of methotrexate was synthesized from 4-amino-4-deoxy-N10-methylpteroic acid and D,L-homocysteic acid. The product (mAPA-HCysA) was bound tightly to L1210 mouse leukemia dihydrofolate reductase (IC50 = 1 nM), inhibited L1210 cell proliferation in culture (IC50 = 0.3 microM), and prolonged the survival of L1210 leukemic mice (98% increase in lifespan at 120 mg/kg, qdx9). Studies on the interaction of mAPA-HCysA with partially purified mouse liver folyl polyglutamate synthetase revealed that mAPA-HCysA was not a substrate. Hence, the increased dose of mAPA-HCysA required to inhibit tumor growth in vitro and in vivo relative to methotrexate may reflect, in part, the inability of this compound to form non-effluxing polyglutamates. Folyl polyglutamate synthetase was competitively inhibited by mAPA-HCysA (K1 = 190 +/- 70 microM) when folate was the variable substrate. Thus, mAPA-HCysA is the first known compound to inhibit both mammalian dihydrofolate reductase and mammalian folyl polyglutamate synthetase.
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D005493:Folic Acid Antagonists; D007939:Leukemia L1210 / Q000188:drug therapy; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D010453:Peptide Synthases / Q000037:antagonists & inhibitors*
D000970:Antineoplastic Agents; D005493:Folic Acid Antagonists; C040719:methotrexate-homocysteic acid; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D008727:Methotrexate