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NCI Monographs : a Publication of the... 1987Piritrexim (PTX) is a second-generation, lipid-soluble inhibitor of dihydrofolate reductase (DHFR). Metabolic inhibition occurs within seconds after rapid diffusion into... (Clinical Trial)
Clinical Trial
Piritrexim (PTX) is a second-generation, lipid-soluble inhibitor of dihydrofolate reductase (DHFR). Metabolic inhibition occurs within seconds after rapid diffusion into human cancer cells. We describe the initial phase I studies with iv and oral forms of this drug given on a daily basis for 5 days to patients with cancer. The dose-limiting toxicity is primarily hematologic (leukopenia, granulocytopenia, thrombocytopenia), but phlebitis is also encountered with iv administration and gastrointestinal problems (nausea, vomiting) with oral administration. Oral toxicity can be reduced by giving the daily dose in 2 divided doses. The maximum tolerated dose (MTD) for the iv route is 170 mg/m2 per day for 5 days; for the oral route it is 480 mg/m2 per day for 5 days. Unlike an earlier lipid-soluble folate antagonist, piritrexim did not cause neurologic or histamine-like disorders.
Topics: Administration, Oral; Clinical Trials as Topic; Dose-Response Relationship, Drug; Folic Acid Antagonists; Humans; Injections, Intravenous; Pyrimidines
PubMed: 3323908
DOI: No ID Found -
Journal of Medicinal Chemistry Mar 1999Nineteen previously undescribed 2,4-diamino-6-(arylmethyl)-5,6,7, 8-tetrahydroquinazolines (5a-m, 10-12) were synthesized as part of a larger effort to assess the...
Nineteen previously undescribed 2,4-diamino-6-(arylmethyl)-5,6,7, 8-tetrahydroquinazolines (5a-m, 10-12) were synthesized as part of a larger effort to assess the therapeutic potential of lipophilic dihydrofolate reductase (DHFR) inhibitors against opportunistic infections of AIDS. Condensation of appropriately substituted (arylmethyl)triphenylphosphoranes with 4, 4-ethylenedioxycyclohexanone, followed by hydrogenation (H2/Pd-C) and acidolysis, yielded the corresponding 4-(arylmethyl)cyclohexanones, which were then condensed with cyanoguanidine to form the tetrahydroquinazolines. Three simple 2, 4-diamino-6-alkyl-5,6,7,8-tetrahydroquinazoline model compounds (9a-c) were also prepared in one step from commercially available 4-alkylcyclohexanones by this method. Enzyme inhibition assays against rat liver DHFR, Pneumocystis carinii DHFR, and the bifunctional DHFR-TS enzyme from Toxoplasma gondii were carried out, and the selectivity ratios IC50(rat)/IC50(P. carinii) and IC50(rat)/IC50(T. gondii) were compared. The three most potent inhibitors of P. carinii DHFR were the 2,5-dimethoxybenzyl (5j), 3, 4-dimethoxybenzyl (5k), and 3,4,5-trimethoxybenzyl (5l) analogues, with IC50 values of 0.057, 0.10, and 0.091 microM, respectively. The remaining compounds generally had IC50 values in the 0.1-1.0 microM range. However all the compounds were more potent against the rat liver enzyme than the P. carinii enzyme and thus were nonselective. The T. gondii enzyme was always more sensitive than the P. carinii enzyme, with most of the analogues giving IC50 values of 0.01-0.1 microM. Moderate 5-10-fold selectivity for T. gondii versus rat liver DHFR was observed with five compounds, the best combination of potency and selectivity being achieved with the 2-methoxybenzyl analogue 5d, which had an IC50 of 0.014 microM and a selectivity ratio of 8.6. One compound (5l) was tested for antiproliferative activity against P. carinii trophozoites in culture at a concentration of 10 microgram/mL and was found to completely suppress growth over 7 days. The suppressive effect of 5l was the same as that of trimethoprim (10 microgram/mL) + sulfamethoxazole (250 microgram/mL), a standard clinical combination for the treatment of P. carinii pneumonia in AIDS patients. Four compounds (5a,h,k,l) were tested against T. gondii tachyzoites in culture and were found to have a potency (IC50 = 0.1-0.5 microM) similar to that of pyrimethamine (IC50 = 0.69 microM), a standard clinical agent for the treatment of cerebral toxoplasmosis in AIDS patients. Compound 5h was also active against T. gondii infection in mice when given qdx8 by peritoneal injection at doses ranging from 62.5 (initial dose) to 25 mg/kg. Survival was prolonged to the same degree as with 25 mg/kg clindamycin, another widely used drug against toxoplasmosis. Three compounds (5j-l) were tested for antiproliferative activity against human tumor cells in culture. Among the 25 cell lines in the National Cancer Institute panel for which data were confirmed in two independent experiments, the IC50 for at least two of these compounds was <10 microM against 17 cell lines (68%) and in the 0. 1-1 microM range against 13 cell lines (52%). One compound (5j) had an IC50 of <0.01 microM against four of the cell lines. The activity profiles of 5k,l were generally similar to that of 5j except that there were no cells against which the IC50 was <0.01 microM.
Topics: Animals; Antifungal Agents; Antineoplastic Agents; Antiprotozoal Agents; Cell Line; Drug Screening Assays, Antitumor; Folic Acid Antagonists; Humans; Liver; Lung; Mice; Pneumocystis; Pyrimidines; Quinazolines; Rats; Tetrahydrofolate Dehydrogenase; Toxoplasma; Toxoplasmosis, Animal; Tumor Cells, Cultured
PubMed: 10090784
DOI: 10.1021/jm980572i -
The disposition and metabolism of [14C]piritrexim in dogs after intravenous and oral administration.Drug Metabolism and Disposition: the... 1991The disposition of [14C]piritrexim ([14C]PTX) in male dogs after iv and po doses of 1.8 mg/kg was examined. After either route of administration, greater than 90% of the...
The disposition of [14C]piritrexim ([14C]PTX) in male dogs after iv and po doses of 1.8 mg/kg was examined. After either route of administration, greater than 90% of the dose was recovered in the exreta within 72 hr; approximately 20% was recovered in urine and 70% in feces. [14C]PTX was extensively metabolized by dogs; unchanged drug accounted for less than 15% of the dose in the excreta. The O-demethylated metabolites, 2'- and 5'-demethyl PTX, the glucuronide conjugate of 2'-demethyl PTX, and the sulfate conjugate of 5'-demethyl PTX were the major metabolites. Unchanged drug accounted for a large proportion of the drug-related radiocarbon in plasma. The average plasma half-life of PTX after iv administration was 2.6 +/- 0.3 hr, and the average total body clearance was 0.33 +/- 0.13 liter/hr/kg. After po administration, peak plasma concentrations of 0.9 +/- 0.3 micrograms/ml occurred about 1.1 hr after the dose; the absolute oral bioavailability of PTX was 0.63 +/- 0.14. Because the O-demethyl metabolites were active dihydrofolate reductase inhibitors, 2'- and 5'-demethyl PTX were synthesized, and the pharmacokinetics and bioavailability of these compounds in dogs after iv and po administration (5 mg/kg) were examined. The plasma concentration-time data for both compounds after iv doses were described by a two-compartment model, with t1/2 beta = 1.3 and 0.8 hr for the 2'- and 5'- demethyl compounds, respectively. Neither compound showed significant advantages over PTX in terms of pharmacokinetics or bioavailability.
Topics: Administration, Oral; Animals; Antineoplastic Agents; Biological Availability; Carbon Radioisotopes; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Dogs; Feces; Injections, Intravenous; Male; Pyridines; Pyrimidines; Tetrahydrofolate Dehydrogenase
PubMed: 1687022
DOI: No ID Found -
European Journal of Medicinal Chemistry Dec 2004Piritrexim (PTX) (1), a lipophilic inhibitor of the human dihydrofolate reductase, has been evaluated as an anticancer agent. The synthesis of four structural variations...
Piritrexim (PTX) (1), a lipophilic inhibitor of the human dihydrofolate reductase, has been evaluated as an anticancer agent. The synthesis of four structural variations (2-5) of PTX is reported. The PTX analogues 2-5 were obtained by reaction of suitable C3-building blocks with pyrimidine-2,4,6-triamine (14) or with cyanacetamide (7) and guanidine (10). The evaluation of 2-4 for antitumor activity against a panel of 60 human cancer cell lines showed inhibitory effects on the growth of the cell lines. These data are supported by molecular modeling and docking studies, which show that compounds 2-4 share the same binding mode within the DHFR active site. Moreover, the estimated ligand binding energies are in good agreement with the experimental activity data.
Topics: Antineoplastic Agents; Binding Sites; Cell Line, Tumor; Drug Screening Assays, Antitumor; Folic Acid Antagonists; Humans; Models, Molecular; Molecular Structure; Protein Binding; Protein Conformation; Pyridines; Pyrimidines; Tetrahydrofolate Dehydrogenase
PubMed: 15571870
DOI: 10.1016/j.ejmech.2004.09.001 -
American Journal of Clinical Oncology Oct 1994Four patients with advanced or metastatic bladder cancer progressing after MVAC chemotherapy were treated with oral piritrexim. Three of the four patients were evaluable...
Four patients with advanced or metastatic bladder cancer progressing after MVAC chemotherapy were treated with oral piritrexim. Three of the four patients were evaluable for response, and all three had a partial response to treatment. Piritrexim may be an effective drug for bladder cancer after progression on MVAC chemotherapy.
Topics: Administration, Oral; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Transitional Cell; Cisplatin; Doxorubicin; Female; Humans; Male; Methotrexate; Middle Aged; Pyrimidines; Urinary Bladder Neoplasms; Vinblastine
PubMed: 8092120
DOI: 10.1097/00000421-199410000-00019 -
NCI Monographs : a Publication of the... 1987Piritrexim (PTX), 2,4-diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido[2,3-d]pyrimidin e, formerly called BW 301U, is a potent small-molecule inhibitor of dihydrofolate... (Comparative Study)
Comparative Study
Piritrexim (PTX), 2,4-diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido[2,3-d]pyrimidin e, formerly called BW 301U, is a potent small-molecule inhibitor of dihydrofolate reductase (DHFR) that enters cells rapidly by passive diffusion and thus does not depend upon the transport-mediated uptake that can limit cell entry of methotrexate (MTX). PTX is as active as MTX in inhibiting DHFR and mammalian cell growth. In vivo, PTX is active against Walker 256, L1210, P388, Sarcoma 180, and Ehrlich ascites tumors. After iv administration of [14C]PTX to rats, the elimination profile of intact drug from plasma was first order with a half-life (t1/2) of 38 minutes. PTX penetrates extensively into tissues and its tissue:plasma concentration ratios are generally 10-fold higher than those reported for MTX. When administered systemically, PTX inhibits the DHFR-dependent conversion of sepiapterin or 7,8-dihydrobiopterin (BH2) to tetrahydrobiopterin (BH4), demonstrating that PTX enters brain at pharmacologically relevant concentrations. Pharmacokinetic studies in the dog indicated a mean plasma t1/2 (after iv dose) of 2.15 hours, total body clearance of 0.625 liters/hr/kg and steady-state volume of distribution of 1.82 liters/kg; the absolute bioavailability was 0.64. Toxicologic studies were conducted in rats and dogs that received daily doses for 1, 5, or 90 days. In dogs, oral doses of 480 (single dose), 25 (5 daily doses), and 2.5 mg/kg (90 daily doses) were lethal, whereas 240 (single dose), 2.5 (5 daily doses), and 0.5 mg/kg (90 daily doses) produced reversible alterations in clinical toxicity and histopathologic parameters. The lethal toxicity of PTX in dogs given 25 mg/kg/day for 5 days is prevented by oral calcium leucovorin rescue with either 0.75 or 3.0 mg/kg every hour for 4 hours on any of the 5 treatment days. The general pharmacologic profile indicates that PTX should be free of CNS, cardiovascular, and respiratory side effects at clinically useful doses.
Topics: Animals; Behavior, Animal; Dogs; Folic Acid Antagonists; Heart; Metabolic Clearance Rate; Methotrexate; Mice; Muscle, Smooth; Neoplasms, Experimental; Pyrimidines; Rats; Solubility; Tissue Distribution; Tumor Cells, Cultured
PubMed: 3431588
DOI: No ID Found -
Journal of Medicinal Chemistry Oct 1993A series of eight previously undescribed 2,4-diaminothieno[2,3-d]pyrimidine analogues of the potent dihydrofolate reductase (DHFR) inhibitors trimetrexate (TMQ) and...
A series of eight previously undescribed 2,4-diaminothieno[2,3-d]pyrimidine analogues of the potent dihydrofolate reductase (DHFR) inhibitors trimetrexate (TMQ) and piritrexim (PTX) were synthesized as potential drugs against Pneumocystis carinii and Toxoplasma gondii, which are major causes of severe opportunistic infections in AIDS patients. 2,4-Diamino-5-methyl-6-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 3,4,5-trimethoxy or 2,5-dimethoxy substitution in the aryl/aralkyl moiety and 2,4-diamino-5-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 2,5-dimethoxy substitution in the aryl/aralkyl moiety were obtained by reaction of the corresponding 2-amino-3-cyanothiophenes with chloroformamidine hydrochloride. The aryl group in the 5,6-disubstituted analogues was either attached directly to the hetero ring or was separated from it by one or two carbons, whereas the aryl group in the 5-monosubstituted analogues was separated from the hetero ring by two or three carbons. 2-Amino-3-cyano-5-methyl-6-(aryl/alkyl)thiophene intermediates for the preparation of the 5,6-disubstituted analogues were prepared from omega-aryl-2-alkylidene-malononitriles and sulfur in the presence of a secondary amine, and 2-amino-3-cyano-4-(aryl/aralkyl)thiophene intermediates for the preparation of the 5-monosubstituted analogues were obtained from omega-aryl-1-chloro-2-alkylidenemalononitriles and sodium hydrosulfide. Synthetic routes to the heretofore unknown ylidenemalononitriles, and the ketone precursors thereof, were developed. The final products were tested in vitro as inhibitors of DHFR from Pneumocystis carinii, Toxoplasma gondii, rat liver, beef liver, and Lactobacillus casei. A selected number of previously known 2,4-diaminothieno[2,3-d]pyrimidines lacking the 3,4,5-trimethoxyphenyl and 2,5-dimethoxyphenyl substitution pattern of TMQ and PTX, respectively, were also tested for comparison. None of the compounds was as potent as TMQ or PTX, and while some of them showed some selectivity in their binding to Pneumocystis carinii and Toxoplasma gondii versus rat liver DHFR, this effect was not deemed large enough to warrant further preclinical evaluation.
Topics: Animals; Antineoplastic Agents; Folic Acid Antagonists; Humans; Liver; Pneumocystis; Pyrimidines; Rats; Structure-Activity Relationship; Toxoplasma; Trimetrexate
PubMed: 8230096
DOI: 10.1021/jm00073a009 -
Archives of Dermatology Apr 1991Methotrexate is an effective and convenient treatment for severe psoriasis whose use is limited by the development of hepatic fibrosis and cirrhosis in a small number of... (Clinical Trial)
Clinical Trial
Methotrexate is an effective and convenient treatment for severe psoriasis whose use is limited by the development of hepatic fibrosis and cirrhosis in a small number of patients. The mechanism of hepatotoxicity is unknown, but it is believed to be the result of intracellular polyglutamation and prolonged retention of methotrexate within the cell. Piritrexim isethionate is a lipid-soluble antifolate that has a mechanism of action similar to that of methotrexate. Since it is not polyglutamated, piritrexim could be effective in the treatment of psoriasis without the associated long-term hepatotoxicity. A 12-week phase I/II clinical trial of severe chronic plaque psoriasis assessed the safety and efficacy of oral piritrexim therapy. Based on experience gained from oncologic trials, each patient received a twice-daily dosage for 5 consecutive days every 2 weeks. Dosages ranged from 25 to 100 mg twice a day. Improvement in both lesion scores and percentage of body involvement was significant at a dose of 50 mg or more twice daily. Fifteen of 19 patients who completed 12 weeks of therapy demonstrated greater than 50% improvement in lesion scores. Improvement was limited by recrudescence of lesions over the 9-day rest period. Adverse experiences were minimal and dose related. Piritrexim is efficacious in the treatment of psoriasis.
Topics: Adult; Aged; Drug Administration Schedule; Female; Folic Acid Antagonists; Humans; Male; Middle Aged; Psoriasis; Pyrimidines
PubMed: 2006875
DOI: No ID Found -
Chest Feb 2008Antineoplastic agent-induced pulmonary toxicity is an important cause of respiratory failure. Although the incidence of antineoplastic agent-induced pulmonary toxicity... (Review)
Review
Antineoplastic agent-induced pulmonary toxicity is an important cause of respiratory failure. Although the incidence of antineoplastic agent-induced pulmonary toxicity seems to be low, more cases can be expected, with increasing numbers of patients receiving the new generations of antineoplastic agents. Antineoplastic agents have previously been associated with bronchospasm, hypersensitivity reactions, venous thromboembolism, and pulmonary hemorrhage. Physicians should be aware of the clinical and radiographic presentations of the pulmonary toxicities associated with the newer antineoplastic agents. The approach to diagnosis, risk factors, and possible mechanisms of antineoplastic agent-induced pulmonary toxicity are discussed in this article.
Topics: Antibiotics, Antineoplastic; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antimetabolites, Antineoplastic; Antineoplastic Agents; Bevacizumab; Deoxycytidine; Doxorubicin; Epirubicin; Etoposide; Everolimus; Humans; Lung; Lung Diseases; Mitoxantrone; Neoplasms; Pneumonia; Pyrimidines; Risk Factors; Sirolimus; Teniposide; Trastuzumab; Gemcitabine
PubMed: 18252919
DOI: 10.1378/chest.07-0851 -
The disposition and metabolism of [14C]piritrexim in rats after intravenous and oral administration.Drug Metabolism and Disposition: the... 1991The disposition of [14C]piritrexim in male rats after iv (5 and 10 mg/kg) and po (5, 10, and 20 mg/kg) doses was studied. After an iv dose of 10 mg/kg, rats excreted an...
The disposition of [14C]piritrexim in male rats after iv (5 and 10 mg/kg) and po (5, 10, and 20 mg/kg) doses was studied. After an iv dose of 10 mg/kg, rats excreted an average of 57% of the dose in feces and 32% in urine; after a po dose of 10 mg/kg, 84% of the dose was excreted in feces and 9% in urine. After iv doses, the elimination of unchanged drug from plasma was first order, with a t1/2 of 0.6 hr; at any time point, unchanged drug accounted for less than 50% of the total radiocarbon in the plasma. Oral bioavailability of unchanged drug was less than 5%. O-Demethylation and subsequent conjugation were the main pathways of metabolism; the demethyl metabolites of piritrexim were potent inhibitors of dihydrofolate reductase and were cytotoxic to cells in culture. Concentrations of radiocarbon were highest in liver 24 hr after an iv dose, but less than 1% of the radiocarbon was unchanged drug. Concentrations of radiocarbon in liver after po doses were approximately 40% of those attained after equivalent iv doses.
Topics: Administration, Oral; Animals; Biological Availability; Biotransformation; Cell Survival; Folic Acid Antagonists; Injections, Intravenous; Iodine Radioisotopes; Male; Pyrimidines; Rats; Tetrahydrofolate Dehydrogenase; Tissue Distribution
PubMed: 1680625
DOI: No ID Found