Antifolate inhibitor

Structural, Conformational, and Electronic Properties of Antifolate Inhibitors of Dihydrofolate Reductase. ... 

Antifog agents Antifoggants Antifolate TS inhibitor Antifouling agents Antifreeze... 

Fig. 8. Thymidylate synthase inhibitors designed to fit into the A/, AJ -methylenetetrahydrofolate binding site. The best inhibitors from each class are the classical antifolate TS inhibitor (31), the naphthostyril-based lead compound (32), and the tetrahydroquinoline-based lead compound (33), iC values (in nAI)...

In malaria chemotherapy, resistant parasites have significantly reduced the efficiency of classic antifolate drugs. In the search for novel inhibitors of... 

Among these drugs, the dihydrofolate reductase (DHFR) inhibitors are used clinically with a certain amount of success. They belong to two major classes the classical antifolates which feature a polar amino-acid side chain terminus and those containing nonpolar side chains, called lipophilic or nonclassical anti-folates. 

The enzyme mediating remethylation, 5-methyltetrahy-drofolate-betaine methyltransferase (Fig. 40-4 reaction 4), utilizes methylcobalamin as a cofactor. The kinetics of the reaction favor remethylation. Faulty remethylation can occur secondary to (1) dietary factors, e.g. vitamin B12 deficiency (2) a congenital absence of the apoenzyme (3) a congenital inability to convert folate or B12 to the methylated, metabolically active form (see below) or (4) the presence of a metabolic inhibitor, e.g. an antifolate agent that is used in an antineoplastic regimen. 

Other Fluorinated Antitumor Drugs in Development A number of totally synthetic fluorinated molecules are also in clinical development for cancer therapies. There are numerous inhibitors of kinases, some apoptosis inductors, and antifolates. 

ZD-9331 is a non-nucleosidic inhibitor of thymidylate synthase. It is also an antifolate, in which the quinazoline moiety replaces the pteridine entity, structurally close to methylene tetrahydrofolate (i.e., the second substrate of thymidylate synthase). Moreover, replacement of the acid function of glutamic acid by a tetrazole renders polyglutamination impossible. Consequently, ZD-9331 is active on tumors that are resistant to the usual antifolates. ... 

Lee TS, Kollman PA (2000) Theoretical studies suggest a new antifolate as a more potent inhibitor of thymidylate synthase, J Am Chem Soc, 122 4385-93... 

One of the most common infections in man is caused by the protozoan, Toxoplasma gondii, which is transmitted to humans when they consume raw or inadequately cooked, infected meat. Infected pregnant women can transmit the organism to the fetus. Cats are the only animals that shed oocysts that can infect other animals as well as man. The treatment of choice for this condition is the antifolate drug, pyrimethamine [peer i METH a meen] (see p. 353). A combination of sulfadiazine (see p. 289) and pyrimethamine is also efficacious. Leucovorin is often administered to protect against folate deficiency. Other inhibitors of folate biosynthesis, such as trimethoprim (see p. 293) and sulfamethoxazole (see p. 289) are without therapeutic efficacy in toxoplasmosis. [Note At the first appearance of a rash, pyrimethamine should be discontinued since hypersensitivity to this drug can be severe.]... 

Covalent bonds are not as important in drug-receptor binding as noncovalent interactions. Alkylating agents in chemotherapy tend to react and form an immonium ion, which then alkylates proteins, preventing their normal participation in cell divisions. Baker s concept of active site directed irreversible inhibitors was well established by covalent formation of Baker s antifolate and dihydrofolate reductase (46). 

HIV protease inhibitors/ of metoprolol as an antihypertensive/ and of methotrexate as an antifolate antitumor therapy. 

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