PubMed Health⌕ Search

Biomedical subjects

G A Curt

Publications and source records attributed to G A Curt.

At least 19 recordsLinked to original sources
PubMed1990

A phase I and pharmacokinetic study of trimetrexate using a 24-hour continuous-injection schedule.

Trimetrexate (TMTX) is an analog of methotrexate and a potent inhibitor of the enzyme dihydrofolate reductase. In this phase I study, TMTX was given intravenously to 32 patients as a constant infusion over 24 hours every 28 days. The maximum-tolerated dose of TMTX was 200 mg/m2, with myelosuppression as the dose-limiting toxicity. Other toxicities included nausea and vomiting, stomatitis, erythema and phlebitis at the site of infusion, rash and skin hyperpigmentation, and elevated serum hepatic enzymes. Two drug-related deaths occurred secondary to leukopenia and sepsis. Twenty-six patients were evaluable for antitumor response. Twenty-one patients had progressive disease, while three patients had disease stabilization. There were two partial responses observed--one in a patient with breast cancer and a second in a patient with nasopharyngeal carcinoma. TMTX pharmacokinetics were studied in 15 patients. The drug had a mean terminal half-life of 13 hours. Steady-state was not achieved during the 24-hour infusions. Only 6% of the parent compound was excreted unchanged in the urine, and CSF levels averaged less than 2% of simultaneously measured plasma levels. A dose of 150 mg/m2 is recommended for phase II trials of TMTX using this 24-hour infusion schedule.

Adult↗
PubMed1988

Phase I and clinical pharmacology study of intravenous flavone acetic acid (NSC 347512).

We have conducted a Phase I and pharmacological study of flavone acetic acid, one of a series of novel flavonoids. The drug was administered i.v. weekly for 4 weeks, with a 2-week rest and then repeated. Flavone acetic acid was given initially in a 1-h infusion, but at the 3900-mg/m2 dose level, the infusion time was lengthened to 3 h. A total of 31 patients were treated with 9 different dose levels, ranging from 330 to 6400 mg/m2. Dose-limiting toxicity was acute hypotension that began after about one-third of each drug dose had been infused and rarely lasted more than a few minutes after the infusion was discontinued. In addition, subjective fatigue and asthenia causing unacceptable patient discomfort was dose limiting. A significant side effect noted that was not dose limiting was diarrhea during the infusion. This drug exhibited nonlinear pharmacokinetic behavior. Plasma levels exceeded 300 micrograms/ml during the infusion at the maximally tolerated dose. After the infusion ended the principal half-life was about 2 h. In 24-h urine collections 27% of the flavone acetic acid dose was recovered as intact drug and an additional 37% was recovered as a metabolite. The maximally tolerated dose determined in this study is 6400 mg/m2 given i.v. over 3 h.

Adult↗
PubMed1987

Effect of calcium channel blockers on human CFU-GM with cytotoxic drugs.

Calcium channel blockers (CCBs) such as verapamil and nitrendipine are capable of increasing drug sensitivity in resistant murine and human tumor cells. This finding has potential value in the treatment of acquired drug resistance in human malignancies. Thus, we tested the ability of CCBs of two different structural classes to enhance the toxicity of doxorubicin (DOX), vinblastine (VBL), and vincristine (VCR) for normal myeloid and macrophage colony formation (marrow colony forming units-granulocyte-monocyte [CFU-GM]). Drug effects on colony formation from 35 normal volunteer marrows and from seven patient marrows in the recovery phase after cytotoxic chemotherapy were determined. No enhancement of toxicity was mediated by verapamil or nitrendipine when these drugs were co-incubated with the cytotoxic drugs for one hour or 24 hours before plating marrow cells in a semisolid agar system.

Adolescent↗
PubMed1987

Antimetabolites.

Explore the source record for details and available documents.

Animals↗
PubMed1986

Skin reactions induced by trimetrexate, an analog of methotrexate.

We have observed three forms of skin toxicity induced by the new antifol trimetrexate in a Phase I trial. They are: radiation recall, cellulitis at the infusion site, and generalized skin eruptions with erythroderma. A total of 25 episodes of some form of skin reaction occurred in 31 patients. The generalized eruption began about four days after drug administration and cleared within a week. The mechanism of skin toxicity of trimetrexate and other antifols is unknown.

Cellulitis↗
PubMed1985

Formation of methotrexate polyglutamates in purified myeloid precursor cells from normal human bone marrow.

Immature myeloid precursor cells were preferentially selected from normal human bone marrow by using immune rosette techniques that employed monoclonal antibodies against mature granulocytes, monocytes, T and B lymphocytes, and erythroid precursors (Mo5, M3, OKT3, B1, and EP1, respectively). We examined the formation, retention, and cytotoxic effects of methotrexate (MTX) polyglutamates (MTX-PGs) in these purified myeloid precursor cells. After 1- and 24-h exposures to MTX, with thymidine and deoxyinosine as rescue, the intracellular MTX-PG profile was examined by high-pressure liquid chromatography. Efflux patterns of MTX-PGs were also studied after additional 1- and 24-h incubations in drug-free media. Cytotoxic effects of retained MTX-PGs on bone marrow myeloid precursors were examined by colony formation in drug-free semisolid agar. Normal myeloid precursor cells converted MTX to MTX-PGs in a concentration- and time-dependent manner, preferentially retaining MTX-PGs with three to five glutamyl moieties. At low concentrations of MTX (1 microM), MTX-PG formation was insufficient to maintain saturation of the target enzyme dihydrofolate reductase after removal of drug from the incubation medium, and there was no decrease in myeloid colony formation. At higher concentrations of MTX (10 microM), formation of higher molecular weight polyglutamates was sufficient to allow for 24-h saturation of intracellular binding capacity after removal of extracellular drug and resulted in a 35% reduction in the formation of colony-forming units in culture. Comparison of MTX metabolism in normal bone marrow cells and the MTX-sensitive HL-60 human leukemia cell line showed twofold greater PG formation by these tumor cells after 24-h exposure to 1 or 10 microM MTX, and a marked (greater than 30-fold) increase in cytotoxicity for the HL-60 cells as compared with normal myeloid precursors, suggesting that the MTX polyglutamation may be important to its selective antitumor action.

Bone Marrow↗
PubMed1985

Determinants of the sensitivity of human small-cell lung cancer cell lines to methotrexate.

We have characterized the determinants of methotrexate (MTX) responsiveness in eight patient-derived cell lines of small-cell lung cancer (SCLC). Clonogenic survival was correlated with factors known to affect sensitivity to drug. NCI-H209 and NCI-H128 were most drug sensitive, with drug concentrations required to inhibit clonogenic survival by 50% with less than 0.1 microM MTX. Six cell lines (NCI-H187, NCI-H345, NCI-H60, NCI-H524, NCI-H146, and NCI-N417D) were relatively drug resistant. In all cell lines studied, higher molecular weight MTX-polyglutamates (MTX-PGs) with 3-5 glutamyl moieties (MTX-Glu3 through MTX-Glu5) were selectively retained. Relative resistance to low (1.0 microM) drug concentrations appeared to be largely due to decreased intracellular metabolism of MTX. Five of the six resistant lines were able to synthesize polyglutamates at higher (10 microM) drug concentrations, although one resistant cell line (NCI-N417D) did not synthesize higher molecular weight MTX-PGs, even after exposure to 10 microM drug. Two cell lines with resistance to 10 microM MTX (NCI-H146 and NCI-H524) synthesized and retained higher molecular weight MTX-PGs in excess of binding capacity after exposure to 10 microM drug. However, the specific activity of thymidylate synthase in these cell lines was low. MTX sensitivity in patient-derived cell lines of SCLC requires the ability of cells to accumulate and retain intracellular drug in the form of polyglutamate metabolites in excess of dihydrofolate reductase, as well as a high basal level of consumption of reduced folates in the synthesis of thymidylate.

Biological Transport, Active↗
PubMed1985

A phase I and pharmacokinetic study of dihydro-5-azacytidine (NSC 264880).

5,6-Dihydro-5-azacytidine (DHAC; NSC 264880) is an analogue of 5-azacytidine that does not possess the hydrolytically unstable 5,6-imino bond of the parent compound. Thus, unlike 5-azacytidine, DHAC is stable in aqueous solution and may be administered by prolonged i.v. infusion, potentially avoiding acute toxicities associated with bolus administration of 5-azacytidine. In this study, patients with advanced cancer were treated with DHAC administered as a 24-h constant i.v. infusion every 28 days. Treatment began at a dose of 1 g/sq m and was escalated to the maximum-tolerated dose of 7 g/sq m, where the limiting toxicity was pleuritic chest pain. Other toxicities included nausea and vomiting, which were not limiting. There was no evidence for myelosuppression, nephrotoxicity, or hepatotoxicity. DHAC was measured in plasma, urine, and ascites by a sensitive and specific reverse-phase high-performance liquid chromatography assay capable of detecting 50 ng of drug per ml. Steady-state plasma levels were achieved with 8 h and ranged from 10.0 to 20.5 micrograms of DHAC per ml at the maximum-tolerated dose. Total-body clearance of 311 +/- 76 ml/min/sq m and postinfusion half-lives between 1 and 2 h were observed. Between 8 and 20% of the administered dose was excreted unchanged in urine. While ascites DHAC levels in a patient with ovarian cancer were comparable to plasma levels, postinfusion elimination was slower from this compartment than from plasma. No correlation was observed between DHAC plasma levels and duration or intensity of dose-limiting pleuritic chest pain. One patient with progressive Hodgkin's lymphoma demonstrated stabilization of disease for seven treatment cycles, and two patients with aggressive lymphoma demonstrated dramatic, although transient, disease responses. A dose of 7 g/sq m is recommended for Phase II trials of DHAC using this schedule.

Adult↗
PubMed1985

Competitive protein-binding assay for trimetrexate.

A competitive protein-binding assay has been developed for trimetrexate (TMTX) based on the tight binding of this drug to human dihydrofolate reductase (tetrahydrofolate dehydrogenase). In this assay, TMTX competes with 3H-methotrexate for binding to the enzyme. Free drug is separated from that bound to reductase by adsorption with dextran-albumin-coated charcoal. TMTX is measurable over a range from 2 X 10(-9) to 5 X 10(-8) M in plasma, with a coefficient of variation of less than 10%. Measurements of TMTX in plasma, cerebrospinal fluid, and urine agreed closely with parallel determinations in aqueous solutions.

Animals↗
PubMed1985

Enrichment of myeloid progenitor cells from normal human bone marrow using an immune-rosette technique.

In this study we have developed methods for purification of myeloid progenitor cells (CFU-Cs) from normal human bone marrow cells. Bone marrow aspirates were obtained from volunteers, and mononuclear cells (MNCs) were separated by Ficoll-Hypaque gradient centrifugation. T- and B-lymphocytes, monocytes, mature granulocytes, and erythroid precursors were eliminated by an immune-rosette technique using a panel of murine monoclonal antibodies and immunoglobulin (Ig)-coated sheep red blood cells (SRBCs). MNCs were treated with OKT3, B1, M3, Mo5, and EP1 monoclonal antibodies, which are reactive with T cells, B cells, monocytes, granulocytes, and erythroid precursors, respectively. Antibody-treated MNCs were incubated with SRBCs that had been coated with goat antirabbit IgG F(ab')2 and rabbit antimouse Ig for immune rosetting. Rosetted cells were then separated from nonrosetted cells in Ficoll-Hypaque. Nonrosetted cells were, in the second step, treated with an OKIa1 monoclonal antibody and again separated into an Ia+ and Ia- cell fraction by the same manner; 39% +/- 19.2% (mean +/- 1 SD, range 16.3%-75.4%) of CFU-Cs (colonies plus clusters) were recovered in the OKT3-, B1-, M3-, Mo5-, EP1- cell fraction, and the number of CFU-Cs grown in semisolid agar was 149.6 +/- 73.0 (64.0-309.0)/10(4) plated cells in this purified fraction, representing an enrichment of 14.2 +/- 6.4 (6.0-27.3)-fold when compared with unseparated marrow cell fractions. CFU-Cs were enriched 17.7 +/- 8.6 (6.1-28.3)-fold in the Ia+ cell fraction. These purified myeloid precursors would be of value for in-depth studies of the interactions between hematopoietic progenitor cells and regulatory factors that influence their proliferation and differentiation and also of drug metabolism and determinants of cytotoxicity.

Adolescent↗
PubMed1984

Cancer chemotherapy. Progress and expectations, 1984.

Progress in the treatment of cancer with drugs has radically altered the clinical approach to patients with malignancy. Not only have new drugs produced promising results in hitherto untreatable tumors, but they have extended and enhanced the effectiveness of other modalities, including surgery and radiotherapy. In this article, the authors consider avenues of research that likely to aid in the discovery of new anticancer drugs and improve the effectiveness of established agents. Promising new efforts in drug development include the use of new screening systems, particularly those employing human tumor material; the development of improved analogs of existing active agents particularly those of the anthracycline and platinum complex types; and the search for agents that which promote differentiation or prevent metastasis. In an effort to improve the effectiveness of established agents, the authors consider the application of pharmacokinetic principles in developing regional perfusion routes, intraperitoneal chemotherapy, and central nervous system penetration. Finally, the contribution of biochemical pharmacology to the current understanding of drug action, mechanisms of resistance, and drug interactions are considered, and the impact of this knowledge on clinical protocol design is assessed.

Antineoplastic Agents↗