Biomedical subjects

B R Leyland-Jones

Publications and source records attributed to B R Leyland-Jones.

8 recordsLinked to original sources

PubMed1998

Synthesis and structure-activity relationships of 2-pyrazinylcarboxamidobenzoates and beta-ionylideneacetamidobenzoates with retinoidal activity.

The structure-activity relationships of two series of novel retinoids (2-pyrazinylcarboxamidobenzoates and beta-ionylideneacetamidobenzoates) have been investigated by evaluating their ability to induce differentiation in both human promyelocytic leukemia (HL60) cells and mouse embryonal carcinoma (P19) cells. The most active compound (ED50 = 8.3 x 10(-9) M) of the 2-pyrazinylcarboxamidobenzoates is 4-[2-(5,6,7,8-tetrahydro-5,5,8, 8-tetramethylquinoxalyl)carboxamido]benzoic acid (9u), while the most active analogue of the beta-ionylideneacetamidobenzoates is 4-[3-methyl-5-(2',6',6'-trimethyl-1'-cyclohexen-1'-yl)-(2E, 4E)-pentadienamido]benzoic acid (10a, ED50 = 3.2 x 10(-8) M). Our studies identify an absolute requirement for the carboxylic acid moiety on the aromatic ring to be para relative to the amide linkage for activity. Benzoate substitutions in the ortho position relative to the terminal carboxylate (9d,k,r) are well-tolerated; however, a methoxy substituent meta relative to the terminal carboxylate gives rise to only weakly active analogues (9x). Conformational studies (NMR, X-ray crystallography) of the 2-pyrazinylcarboxamidobenzoates indicate that the preferred conformation exhibits a trans-amide bond and an internal hydrogen bond between the quinoxaline N1 and HN amide which locks the torsional angle between C2 and CO in the s-trans conformation. N-Methylation (9y) results in loss of activity. Studies indicate that there is now a cis-amide bond present which redirects the carboxylate toward the pharmacophoric gem-dimethyl groups. The distance between the gem-dimethyl group and the terminal carboxylate appears to be too short to activate the retinoid receptor. N-Methylation in the beta-ionylideneacetamidobenzoate series (10c) also results in the formation of a cis-amide bond and loss of activity.

Animals↗

PubMed1991

Antineoplastic drug sensitivity of human MCF-7 breast cancer cells stably transfected with a human alpha class glutathione S-transferase gene.

Studies have suggested that the alpha class glutathione S-transferase (GST) may protect cells from the chemotherapeutic drugs chlorambucil and melphalan. In order to further define the function of human alpha class GST, a complementary DNA which encodes it was ligated into an expression vector under the direction of the human metallothionein-IIA promoter and stably transfected into human MCF-7 breast cancer cells in conjunction with the G418-selectable plasmid pSV2neo. Clonal cell lines were identified which expressed increased levels of GST enzyme activity (2.2- to 5.6-fold). The transfected cell lines also had increased peroxidase activity using cumene hydroperoxide as the substrate (1.9- to 3.8-fold) which is consistent with the intrinsic peroxidase activity of alpha class GSTs. Southern blot analysis indicated that genomic DNA from these cells contained a fragment indistinguishable from the transfected alpha class GST complementary DNA (850 base pairs); Northern blot analysis of total cellular RNA indicated that these cells contained appropriately sized alpha class GST RNA (980 nucleotides); and Western blot analysis indicated that, while MCF-7 cells contained no detectable alpha class GST protein, the transfected cells contained markedly elevated levels of alpha class GST but no detectable mu or pi class GST. These alpha class GST transfected cells had increased resistance to ethacrynic acid (2.1- to 3.0-fold). However, the transfected cells failed to show any increased resistance measured at the drug dosage which inhibited 50% of the colony formation to the chemotherapeutic drugs chlorambucil, melphalan, Adriamycin, or cisplatin under conditions of either continuous or 1-h drug exposure. Neither was there any change in sensitivity to the cytotoxins benzo(a)pyrene, benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (anti), or 1-chloro-2,4-dinitrobenzene. These studies indicate that expression of this human alpha class GST by itself in MCF-7 human breast cancer cells does not confer resistance to the chemotherapeutic drugs tested under the conditions used in these studies.

Antineoplastic Agents↗

PubMed1986

Central nervous system toxicity of fludarabine phosphate.

Fourteen patients developed severe central nervous system (CNS) toxicity after receiving an investigational antitumor agent, fludarabine phosphate (FAMP). The CNS toxicity has the distinctive features of delayed onset and progressive clinical course. Visual deficits were the most common presenting symptom and developed eventually in most cases. Deterioration of mental status and progressive encephalopathy were also observed. The development of clinical CNS toxicity appears dose-related; thirteen of 36 patients (36.1%) who received FAMP at high doses (greater than or equal to 96 mg/m2/day for 5-7 days per course) developed neurotoxicity, while only one of 443 patients (0.2%) who received the drug at low doses (less than or equal to 125 mg/m2 per course) developed similar toxicity. Although the precise mechanism responsible for this toxicity is yet unknown, progressive demyelination appears to be the responsible process. Extensive review of the clinical data failed to identify factors which might contribute to the development of CNS toxicity. Patients on trials of FAMP should be meticulously monitored for the possible development of neurotoxicity.

Acute Disease↗

PubMed1985

Phase I study of elliptinium (2-N-methyl-9-hydroxyellipticinium).

Elliptinium (2-N-methyl-9-hydroxyellipticinium), a chemotherapeutic agent whose mechanism of action has not been completely elucidated, intercalates into DNA. In this Phase I clinical trial, the schedule of drug administration consisted of weekly intravenous infusions. Twenty-nine patients were evaluable for toxicity. The initial dose level was 40 mg/m2 and was escalated to 150 mg/m2 through six levels. The dose-limiting side effects were emesis, xerostomia, and azotemia. The lack of myelosuppression was the most striking feature. Objective responses (partial remission, minor response) were seen in one patient each with Hodgkin's disease, non-Hodgkin's lymphoma, breast cancer, and nasopharyngeal carcinoma. We recommend a Phase II evaluation of elliptinium at a dose of 100 mg/m2 on a weekly schedule.

Adolescent↗

PubMed1983

N-acetyl-beta-glucosaminidase and beta 2-microglobulin. Their urinary excretion in patients with renal parenchymal disease.

The urinary excretion of N-acetyl-beta-glucosaminidase (NAG) and beta 2-microglobulin (beta 2M) was studied in 43 patients with various forms of renal parenchymal disease. Patients with membranous nephropathy, membranoproliferative glomerulonephritis, focal segmental glomerulosclerosis, obstructive pyelonephritis, nephrosclerosis, and minimal change nephropathy generally had urinary NAG and beta 2M levels more than 3 SDs above those seen in normal subjects. Patients with progressive renal disease averaged higher NAG and beta 2M urinary levels than those with the same renal lesion and stable function. Since elevated urinary levels of NAG and beta 2M suggest renal tubular injury or dysfunction, our observations suggest tubulointerstitial involvement in a wide variety of renal diseases.

Acetylglucosaminidase↗

PubMed1982

Specific determination of pentamethylmelamine and its demethylated metabolites in human plasma by high pressure liquid chromatography.

Pentamethylmelamine (PMM) and its demethylated metabolites tetra-N2246, tri-N246 and tri-N224 have comparable relative antitumor potencies in animal systems. We have developed a sensitive and specific high pressure liquid chromatography (HPLC) assay for these compounds in the plasma of patients receiving pentamethylmelamine, a cytotoxic S-triazine derivative now undergoing clinical trials. The method involves analysis of an ethyl acetate extract of plasma by a high pressure liquid chromatograph containing a reverse-phase column and ultraviolet detection at 240 nm. The mobile phase is acetonitrile and KH2PO4 buffer (pH 5.5); gradient elution over 25 min yields relative retention times to hexamethylmelamine as internal standard of 0.36, 0.40, 0.54 and 0.70 for tri-N246, tri-N224, tetra-N2246 and PMM. The lower limit of sensitivity for each is 300 ng/ml. Pharmacokinetic studies on four patients receiving a 24-h infusion of PMM (doses 900-3000 mg/m2) showed a mean terminal half-life of PMM of 101 +/- 28 (SD) min, a mean volume of distribution of 2036 +/- 75 ml/kg, and a metabolic clearance rate of 14.2 +/- 3.7 (ml/min)/kg. Mean areas under the plasma-vs-time curves of tri-N246, tri-N224 and tetra-N2246 were 126%, 41% and 56% of PPM, demonstrating extensive formation of these metabolites in man.

Altretamine↗

PubMed1982

Deoxycytidine and deoxythymidine kinase activities in plasma of mice and patients with neoplastic disease.

In C57BL x DBA/2 F1 (hereafter called BD2F1) mice inoculated with P815 neoplasms and in AKR mice with spontaneously developing leukemia, significant amounts of plasma deoxycytidine and thymidine kinase activities were detected in advanced disease. Undetectable or low levels of such kinase activities were observed in normal BD2F1 and in control AKR mice. Initial studies with leukemia patients revealed increased amounts of plasma deoxycytidine and thymidine kinase activities correlating favorably with the peripheral white blood cell counts. Initial studies with small numbers of patients with solid tumors revealed significant activities of both kinases in plasma of patients with four different cancers. Healthy volunteers revealed enzyme activities only insignificantly above background.

Adolescent↗

PubMedDate not supplied

Azacitidine: 10 years later.

Azacitidine has been undergoing clinical trials for almost 20 years and is internationally considered to have a useful place in the treatment of acute nonlymphocytic leukemia. However, its role in the various combinations for induction, intensification, maintenance, or relapse regimens has not yet been clearly defined. This review outlines the last 10 years' clinical experience with the drug in acute nonlymphocytic leukemia, analyzes what critical information has yet to be obtained, and suggests what phase III trials may still be feasible to gather that information.

Acute Disease↗