Biomedical subjects

Aleem Gangjee

Publications and source records attributed to Aleem Gangjee.

23 records · Page 2Linked to original sources

PubMed2003

Design, synthesis, and biological activities of classical N-[4-[2-(2-amino-4-ethylpyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid and its 6-methyl derivative as potential dual inhibitors of thymidylate synthase and dihydrofolate reductase and as potential antitumor agents.

Two novel analogues, N-[2-amino-4-ethyl[(pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid (2) and N-[2-amino-4-ethyl-6-methyl[(pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-l-glutamic acid (4), were designed and synthesized as potent dual inhibitors of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) and as antitumor agents. Compound 2 had inhibitory potency against human DHFR similar to N-[4-[2-(amino-3,4-dihydro-4-oxo-7H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid (LY231514) and 1, whereas 4 was inactive against human DHFR. Both 2 and 4 were more potent than LY231514 against E. coliTS. Against human TS, 2 was 7-fold less potent than LY231514 and 4 showed similar inhibitory activity as LY231514. In contrast to 2, which was an efficient substrate of human folypolyglutamate synthetase (FPGS), 4 was a poor substrate of FPGS. Compound 2 showed GI50 values in the nanomolar range against more than 18 human tumor cell lines in the standard NCI preclinical in vitro screen.

Antineoplastic Agents↗

PubMed2002

Synthesis of classical and nonclassical, partially restricted, linear, tricyclic 5-deaza antifolates.

Seven novel 2,4-diamino-5-deaza-6,7,8,9-tetrahydropyrido[3,4-g]pteridine derivatives 3-9 with different benzyl and a benzoyl substitution at the N7 position were designed and synthesized, as classical and nonclassical, partially restricted, linear tricyclic 5-deaza antifolates. The purpose was to investigate the effect of conformational restriction of the C6-C9 (tau(1)) and C9-N10 (tau(2)) bonds via an ethyl bridge from the N10 to the C7 position of 5-deaza methotrexate (MTX) on the inhibitory potency against dihydrofolate reductase (DHFR) from different sources and on antitumor activity. The synthetic methodology for most of the target compounds was a concise five-step total synthesis to construct the tricyclic nucleus, 2,4-diamino-5-deaza-7H-6,7,8,9-tetrahydropyrido[3,4-g]pteridine (23), followed by regioselective alkylation of the N7 nitrogen. Biological results indicated that this partial conformational modification for the classical analogue N-[4-[(2,4-diamino-5-deaza-6,7,8,9-tetrahydropyrido[3,4-g]pteridin-7-yl)methyl]benzoyl]-L-glutamic acid 3 was detrimental to DHFR inhibitory activity as well as to antitumor activity compared to MTX or 5-deaza MTX. However, the classical analogue 3 was a better substrate for folypolyglutamate synthetase (FPGS) than MTX. These results show that a classical 5-deaza folate partially restricted via a bridge between the N10 and C7 positions retains FPGS substrate activity and that the antitumor activity of classical tricyclic analogues such as 3 would be influenced by FPGS levels in tumor systems. Interestingly, the nonclassical analogues 4-9 showed moderate to good selectivity against DHFR from pathogenic microbes compared to recombinant human DHFR. These results support the idea that removal of the 5-methyl group of piritrexim along with restriction of tau(1) and tau(2) can translate into selectivity for DHFR from pathogens.

Animals↗

PubMed2002

Analysis of quinazoline and pyrido[2,3-d]pyrimidine N9-C10 reversed-bridge antifolates in complex with NADP+ and Pneumocystis carinii dihydrofolate reductase.

Structural studies of two ternary complexes of Pneumocystis carinii dihydrofolate reductase (pcDHFR) with the cofactor NADP(+) and potent antifolates, the N9-C10 reversed-bridge inhibitor 2,4-diamino-6-[N-(2',5'-dimethoxybenzyl)-N-methylamino]quinazoline (1) and its 3',5'-dimethoxypyrido[2,3-d]pyrimidine analog (2), were carried out. Data for the monoclinic crystals were refined to 1.90 A resolution for the complex with (1) (R = 0.178) and to 2.1 A resolution for the complex with (2) (R = 0.193). The effect of the N9-C10 reversed-bridge geometry is to distort the bridge from coplanarity with the pyrido[2,3-d]pyrimidine or quinazoline ring system and to twist the C10 methylene conformation toward a gauche conformation. This change also influences the conformation of the methoxybenzyl ring, moving it away from a trans position. This change places the 5'-methoxy group deeper within the hydrophobic pocket made by Ile65, Pro66 and Phe69 of the pcDHFR active site. These results also revealed the first observation of an unusual conformation for the reversed-bridge geometry (C5-C6-N9-C10 torsion angle) in antifolate (2). The electron density is consistent with the presence of two models (conformers 2-1 and 2-2) that result from inversion of the geometry at N9. The four examples of N9-C10 reversed-bridge antifolates cluster in two conformations, with the structure of quinazoline (1) similar to that previously reported for its 2',5'-dimethoxypyrido[2,3-d]pyrimidine analog (3). The two conformers of (2) differ from these and each other by a twisted-bridge geometry that results in the dimethoxybenzyl ring occupying the same conformational space. Conformer 2-2 also has the N9-C10 reversed bridge perpendicular to the pyrido[2,3-d]pyrimidine plane, in contrast to the gauche-trans conformation normally observed. As a result of these changes, the N9 methyl probes conformational space in the active site not normally occupied by antifolate structures. The N9 methyl of conformer 2-2 makes close contacts to the conserved Leu25 as well as the hydroxyl O atoms of the nicotinamide ribose and Ser64, whereas the other three reversed-bridge conformers make weak hydrophobic contacts with Ile123, Thr61 and Ile65. These antifolates are ten times more selective for pcDHFR than the C9-N10 bridge parent trimetrexate. However, pyrido[2,3-d]pyrimidines (2) and (3) are three times more selective for pcDHFR than quinazoline (1) is for rat liver DHFR. These data suggest that the loss of hydrogen-bonding interactions with N8 is more important to potency than the interactions of the methoxybenzyl substituents.

Crystallography, X-Ray↗

PubMed2002

Synthesis of N-[4-[1-ethyl-2-(2,4-diaminofuro[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid as an antifolate.

N-[4-[1-Ethyl-2-(2,4-diaminofuro[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-L-glutamic acid 3 was designed and synthesized to investigate the effect of homologation of a C9-methyl to an ethyl on dihydrofolate reductase (DHFR) inhibition and on antitumor activity. Compound 3 was obtained via a concise seven step synthesis starting from palladium-catalyzed carbonylation of 4-propionylphenol, followed by a Wittig reaction with 2,4-diamino-5-(chloromethyl)furo[2,3-d]pyrimidine (6), catalytic hydrogenation, hydrolysis, and standard peptide coupling with diethyl L-glutamate. The biological results indicated that extending the C9-methyl group to an ethyl on the C8-C9 bridge region (analogue 3) doubled the inhibitory potency against recombinant human (rh) DHFR (IC(50) = 0.21 microM) as compared to the C9-methyl analogue 1 and was 4-fold more potent than the C9-H analogue 2. As compared to 1, compound 3 demonstrated increased growth inhibitory potency against several human tumor cell lines in culture with GI(50) values < 1.0 x 10(-8) M. Compound 3 was also a weak inhibitor of rh thymidylate synthase. Compounds 1 and 3 were efficient substrates of human folylpolyglutamate synthetase (FPGS). Further evaluation of the cytotoxicity of 3 in methotrexate-resistant CCRF-CEM cell sublines and metabolite protection studies implicated DHFR as the primary intracelluar target. Thus, alkylation of the C9 position in the C8-C9 bridge of the classical 5-substituted 2,4-diaminofuro[2,3-d]pyrimidine is highly conducive to DHFR and tumor inhibitory activity as well as FPGS substrate efficiency.

Antineoplastic Agents↗

PubMed2002

Recent advances in the chemistry and biology of folypoly-gamma-glutamate synthetase substrates and inhibitors.

The importance of folylpoly-gamma-glutamate synthetase (FPGS) in cancer chemotherapy arises from its function of adding gamma-L-glutamate moieties to classical antifolates which contain an L-glutamate. Polyglutamylation of classical antifolates used in cancer chemotherapy have certain advantages. The polyglutamylated antifolates are trapped within the cell and hence are retained for a longer duration. In addition some polyglutamylated forms of classical antifolates also inhibit the target folate-dependent enzyme to a greater extent than those monoglumate form. There are however certain drawbacks to this enzymatic transformation of classical antifolates. For those analogs which need polyglutamylation for activation either for retention within tumor cells or to increase inhibitory activity against the target folate-dependent enzyme(s) (both of which could contribute to the antitumor activity of the analog), resistance to the antifolates can be manifested by reduction in the level of FPGS activity. In addition retention of polyglutamate forms of antifolates within normal cells may be a cause of toxicity. Thus the structural requirements for substrate activity for FPGS are of critical importance in the design of classical antifolates as cancer chemotherapeutic agents. In addition classical antifolates which lack the necessity of polyglutamation could circumvent the resistance due to a decrease in the level and activity of FPGS. FPGS activity on natural folate is essential to cell proliferation and survival. Thus inhibition of FPGS activity itself has been suggested as a chemotherapeutic strategy. Structural requirement for inhibition of FPGS have also been studied extensively. This review highlights the synthesis and the structural requirement for substrate and inhibitory activity of classical antifolates for FPGS and their relevance to cancer chemotherapy.

Animals↗