Biomedical subjects

M F Stevens

Publications and source records attributed to M F Stevens.

At least 73 records · Page 4Linked to original sources

PubMed1989

A phase I study of meta-azidopyrimethamine ethanesulphonate (MZPES)--a new dihydrofolate reductase inhibitor.

A total of 68 patients were treated in a phase I study of meta-azidopyrimethamine ethanesulphonate (MZPES)--a novel lipophilic dihydrofolate reductase (DHFR) antagonist. The dose was increased from 5.4 mg/m2 to 460 mg/m2 given as a 1-h infusion, with 460 mg/m2, 600 mg/m2 and 800 mg/m2 given as a 24-h infusion. The dose-limiting toxicity was nausea and vomiting, which was marked at doses above 360 mg/m2 by 1-h infusion and 600 mg/m2 by 24-h infusion. Above 250 mg/m2 patients also described subjective neurological symptoms, although no objective signs were apparent. Myelosuppression was not consistent at any dose level. No objective responses were seen. In view of the lack of anti-folate activity at toxic levels, no phase II trials are currently proposed; toxicological and in vitro studies will continue.

Antineoplastic Agents↗

PubMed1989

Structural studies on bioactive compounds. 8. Synthesis, crystal structure, and biological properties of a new series of 2,4-diamino-5-aryl-6-ethylpyrimidine dihydrofolate reductase inhibitors with in vivo activity against a methotrexate-resistant tumor cell line.

A series of 2,4-diamino-5-aryl-6-ethylpyrimidines embracing basic substituents in the 5-aryl ring was synthesized and evaluated for inhibitory activity against rat liver dihydrofolate reductase (DHFR). Maximal enzyme inhibition was observed for compounds bearing a benzylamino (19) or N-alkylbenzylamino substituent (29 and 30) in the 4-position of the phenyl ring and a nitro group in the 3-position, the corresponding 3-amino, 3-azido, or unsubstituted analogues proving only weakly active or inactive as DHFR inhibitors. Selected compounds were also screened in vivo against a methotrexate-resistant tumor, the M5076 murine reticulosarcoma, and antitumor activity in general paralleled activity against DHFR, the (3,4-dichlorobenzyl)amino analogue 26 proving the least toxic compound to exhibit significant antitumor activity. The X-ray crystal structure of the ethanesulfonic acid salt of the N-methylbenzylamino compound 29 has been determined to facilitate future molecular modeling studies in this new series of DHFR inhibitors.

Animals↗

PubMed1988

Direct 19F NMR observation of the conformational selection of optically active rotamers of the antifolate compound fluoronitropyrimethamine bound to the enzyme dihydrofolate reductase.

The molecular basis of the binding of the lipophilic antifolate compound fluoronitropyrimethamine [2,4-diamino-5-(4-fluoro-3-nitrophenyl)-6-ethylpyrimidine] to its target enzyme dihydrofolate reductase has been investigated using a combination of 19F NMR spectroscopy and molecular mechanical calculations. 19F NMR reveals the presence of two different conformational states for the fluoronitropyrimethamine-Lactobacillus casei enzyme complex. MM2 molecular mechanical calculations predict restricted rotation about the C5-C1' bond of the ligand and this gives rise to two slowly interconverting rotamers which are an enantiomeric pair. The results of 19F NMR spectroscopy reveal that both these isomers bind to the enzyme, with different affinities. There is no detectable interconversion of the bound rotamers themselves on the NMR timescale. The effect of the addition of co-enzyme to the sample is to reverse the preference the enzyme has for each rotamer.

Folic Acid Antagonists↗

PubMed1987

Antitumor activity and pharmacokinetics in mice of 8-carbamoyl-3-methyl-imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one (CCRG 81045; M & B 39831), a novel drug with potential as an alternative to dacarbazine.

A number of 3-alkyl analogues of the experimental antitumor drug mitozolomide [8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H )-one] have been screened against murine tumors in vivo. Only the compounds with a 3-methyl- or 3-bromoethyl group possessed significant antitumor activity against the TLX5 lymphoma. The 3-methyl analogue, 8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one (CCRG 81045), was investigated further and found to possess good activity, when administered i.p., against the L1210 and P388 leukemias, the M5076 reticulum cell sarcoma, B16 melanoma, and ADJ/PC6A plasmacytoma. The drug was also active when administered p.o. to mice bearing the L1210 leukemia. A daily for 5 days schedule of 100 mg/kg CCRG 81045 produced increases of survival time of treated animals compared to controls of 176 and greater than 235% against the P388 and L1210 leukemias, respectively. In the female C57BL x DBA/2 F1 mouse the 10% lethal dose was 125 mg/kg daily for 5 days. CCRG 81045 was found to undergo mild alkaline hydrolysis and ring fission to form the linear triazene 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide, which is the putative metabolite formed upon metabolic activation of the antitumor drug dacarbazine [5-(3,3-dimethyltriazen-1-yl)imidazole-4-carboxamide]. The half-life of CCRG 81045 at 37 degrees C in 0.2 M phosphate buffer (pH 7.4) was 1.24 h, whereas that of 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide at 25 degrees C was reported to be 8 min (F. H. Shealy and C. A. Krauth, J. Med. Chem., 9:34-37, 1966). The half-life of CCRG 81045 in human plasma in vitro at 37 degrees C was 0.42 h. Pharmacokinetic experiments conducted in BALB/c mice produced plasma profiles of CCRG 81045, administered i.p. or p.o., which showed a rapid absorption phase, elimination half-lives of 1.13 h (i.p.) and 1.29 h (p.o.), and a bioavailability of 0.98.

Animals↗

PubMed1987

Antitumor imidazotetrazines. 14. Synthesis and antitumor activity of 6- and 8-substituted imidazo[5,1-d]-1,2,3,5-tetrazinones and 8-substituted pyrazolo[5,1-d]-1,2,3,5-tetrazinones.

The systematic variation of the potent antitumor agent mitozolomide (1) is extended to cover alteration of substituents at positions 6 and 8 and to change the imidazo[5,1-d]-1,2,3,5-tetrazinone (1) skeleton to the isomeric pyrazolo-[5,1-d]-1,2,3,5-tetrazinone (17) skeleton. The series of eight 6-alkyl and 6-aralkyl derivatives of 1 showed optimal antitumor activity when the group was small or linear, but activity diminished as size and branching of this substituent increased. This may reflect altered transport characteristics, or failure of the enlarged derivatives to fit a binding site, or possibly a reduced tendency for the derivatives having bulky groups at position 6 to hydrolytically generate the putatively active triazenes (21). Testing of 14 derivatives of 1 differently substituted at position 8 revealed a complex structure-activity relationship, with good antitumor activity obtained for carbamoyl and sulfamoyl groups bearing small substituents. The 8-methylsulfonyl compound had noteworthy activity, but the 8-cyano, 8-nitro, and 8-phenyl derivatives were devoid of useful antitumor activity in these tests. From the limited number of pyrazolotetrazinones (17) reported here, it is suggested that the same conclusions as regards activity also hold true for this ring system.

Animals↗

PubMed1987

Structural studies on bio-active compounds. Part 9. 2,4-Diamino-6-azidoquinazoline hydrochloride.

C8H7N7.HCl has a formula weight Mr237.7, and crystallizes in space group P21/n with a = 6.498(1), b = 10.333(8), c = 15.406(5) A, beta = 91.72(2) degrees. The final R factor was 0.049 for 1010 unique observed reflections. The azido substituent is almost linear, coplanar with the heterocycle, and parallel to the C(7)-C(6) ring bond. The heterocycle is protonated at N(1) and extensively hydrogen bonded. The 6-azido compound is at least a 100-fold better inhibitor of Escherichia coli dihydrofolate reductase than the analogue lacking the azido group, according to I50 values. Superimposing the quinazoline moiety upon the pteridine ring of the methotrexate-dihydrofolate reductase (E. coli) complex reveals two orientations of the N3 group in which it can fit the enzyme, making van der Waals contacts. Ab initio molecular orbital calculations suggest that one of these conformations, with torsion angle phi = C(5)-C(6)-N(61)-N(62) = -163.8 degrees, is low in energy.

Crystallography↗

PubMed1987

The aromatic azido group in anti-cancer drug design: application in the development of novel lipophilic dihydrofolate reductase inhibitors.

Two properties of the aromatic azido group have been exploited in the design of a novel dihydrofolate reductase inhibitor--lipophilicity and biotransformability. 2,4-Diamino-5-(3-azido-4-chlorophenyl)-6-ethylpyrimidine (MZP, 4), which can be prepared in three high-yielding synthetic steps from the antimalarial drug pyrimethamine (1), has a pKa of 7.19, a log P of 2.81 and inhibitory activity against the P388, L1210, B16 and M5076 tumours in vivo. The ethanesulphonic acid salt of MZP (MZPES, 6) is a potent inhibitor of rat liver dihydrofolate reductase (Ki 1.60 nM) and L1210 cells in vitro. Injections of MZPES in water (10 mg ml-1) at pH 4.1 can be sterilised by filtration and are stable provided they are protected from light.

Animals↗

PubMed1986

Structural studies on bioactive compounds. 4. A structure-antitumor activity study on analogues of N-methylformamide.

A series of derivatives of N-methylformamide (NMF), an experimental antitumor agent, has been prepared, having the general formula R3C(X)NR1R2 where R1 = H, CH3, CD3, CH2CF3, CH2CH2Cl, cyclopropyl, C2H5, CH2OH, CH2OR, CH2N(CH3)2; R2 = H, CH3; R3 = H, CF3, CCl3, CH3, Ph, NHCH3, N(CH3)2; and X = O, S, NH. A further short series of "push-pull" olefins of the general formula R1R2C = CHNR3R4 has been synthesized where R1 = H, CH3 and R2 = H, NO2, CN, CHO, CH3 and R3 = H and R4 = H, CH3, morpholino. These compounds have been tested for activity against the M5076 ovarian sarcoma and the TLX5 lymphoma in mice. NMF was by far the most potent agent of both series with activity against both tumors. Some other compounds showed weak activity, but there is a rigorous structural requirement for activity and most analogues were inactive. Certain members of the series exist as equilibrium mixtures of rotamers about the amide or pro-amide bonds as shown by NMR.

Animals↗

PubMed1985

N-Methylformamide (NSC 3051): a potential candidate for combination chemotherapy.

N-Methylformamide (NMF) was found to be non-toxic to the bone marrow as reflected in the absence of leukopenia in mice, even when the marrow had been compromised by prior administration of cyclophosphamide. Thus recovery from the leukopenic nadir after 160 mg/kg of cyclophosphamide was unaffected by 200 mg/kg X 10 of NMF. This combination, given to animals bearing the M5076 sarcoma, proved to have an additive antitumour effect as measured by tumour growth delay and was superior to the antitumour effect of two doses of cyclophosphamide, a regime which prolonged the leukopenia. Furthermore, the hepatotoxicity of NMF was not augmented by the addition of cyclophosphamide. When hepatotoxicity was induced in BALB/c mice bearing the NMF-resistant ADJ/PC6A plasmacytoma, cyclophosphamide fully maintained its antitumour effect. The results show NMF to be a highly specific antiproliferative agent with potential for use in the therapy of patients with a compromised bone marrow and/or in combination chemotherapy.

Animals↗

PubMed1985

Studies on the toxicity of the antitumour agent N-methylformamide in mice.

Aspects of the toxicology of N-methylformamide (NMF), an investigational antitumour agent, were studied in mice. After injection of NMF at its LD10 (800 mg/kg) dosage the total peripheral white blood cell and platelet counts were unchanged in BALB/c mice. A mild granulocytosis was seen in this strain after administration of the LD50 (2300 mg/kg) dosage. Plasma activity of the enzyme sorbitol dehydrogenase in BDF1 mice was markedly increased after either a single injection of not less than 800 mg/kg or a chronic treatment of not less than 400 mg/kg/day over 5 days indicating the drug to be hepatotoxic. Plasma activities of L-alanine and L-aspartate aminotransferases were also increased after the chronic treatment. Chronic administration of NMF was less hepatotoxic than single dose administration of the same total dose and also increased the antitumour efficacy of NMF against the M5076 sarcoma. These results indicate that the maximum therapeutic benefit of NMF might be obtained by the use of chronic schedules and that the drug is not myelosuppressive.

Alanine Transaminase↗

PubMed1985

Antitumour imidazotetrazines, Part IX. The pharmacokinetics of mitozolomide in mice.

Mitozolomide is a novel antitumour agent showing a broad spectrum of activity against murine tumours and is currently undergoing Phase I clinical evaluation in the UK. We have conducted an animal pharmacokinetic study using male BALB/c mice as a pre-requisite to the clinical work. Mice were dosed i.p. at 5 dose levels (0.25-20 mg kg-1) and the oral and transdermal routes of administration were investigated at 20 mg kg-1. The analytical data produced a good fit to a simple open one-compartment pharmacokinetic model with an elimination half-life of the drug from plasma of between 0.68 and 0.88 h over the 0.25-20 mg kg-1 range covered. There was no evident dose dependency over this range and studies with two formulations showed mitozolomide to have good systemic availability when administered via the oral route (F values of 0.66 and 0.81). The drug was also found to be systemically available when administered topically in dimethylsulfoxide (F = 0.47). Mitozolomide shows many biochemical and biological similarities to the clinically used nitrosoureas BCNU and CCNU but our results show that it differs markedly in its kinetics from these two agents, with mitozolomide having relatively sustained plasma levels. It is hoped that this may be of therapeutic benefit if these levels are reflected in relative tumour concentrations.

Administration, Oral↗

PubMed1985

Experimental antitumor activity against murine tumor model systems of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one (mitozolomide), a novel broad-spectrum agent.

8-Carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H) -one (mitozolomide) demonstrates curative action against a range of murine tumor model systems. At single doses of between 20 and 40 mg/kg, the latter of which approximates the 10% lethal dose value in mice, the compound elicited cures against the L1210 and P388 leukemias irrespective of the route of tumor and/or drug administration; in these tests, animals receiving 10(5) cells i.p. survived greater than 60 days after treatment. Potent effects were also observed against the TLX5 lymphoma (s.c.) and B16 melanoma (i.p.). In other experiments, 7 of 10 animals implanted with 2 X 10(5) Lewis lung carcinoma cells survived greater than 60 days while 10 of 10 animals survived greater than 60 days after implantation of the Colon 26 tumor. Potent inhibition of the solid tumor models was also observed with complete cures of the Colon 38, M5076 sarcoma, and ADJ/PC6A plasmacytoma. In cross-resistance studies, the compound was ineffective against an L1210 leukemia made resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea and against a TLX5 lymphoma resistant to dimethyltriazenes but cured animals bearing the L1210 leukemia with derived resistance to cyclophosphamide.

Animals↗

PubMed1984

Studies of the mode of action of antitumour triazenes and triazines-V. The correlation of the in vitro cytotoxicity and in vivo antitumour activity of hexamethylmelamine analogues with their metabolism.

Experiments were conducted to ascertain whether the antitumour activity of hexamethylmelamine analogues correlated with their in vitro cytotoxicity and metabolism. Two analogues, namely pentamethylmelamine (PMM) and 2,2,4,4-tetramethylmelamine (TMM), and hexamethylmelamine (HMM) itself were shown to be active towards the murine ADJ/PC6A (PC6) plasmacytoma; another three, 2-chloro-4,6-bis(dimethylamino)-1,3,5-triazine (CBDT), 2,4-bis-(dimethylamino)-6-hydrazino-1, 3,5-triazine (HBDT) and 2,4,6-trimethylmelamine (TriMM) were inactive against the same tumour. The cytotoxicity of these compounds was examined against a PC6 tumour cell line in vitro. In the absence of liver microsomal activation only CBDT proved to be significantly cytotoxic at a concentration of 5 mM. In the presence of murine liver microsomes the three active antitumour agents were all cytotoxic at this concentration whereas HBDT and TriMM remained non-toxic. The degree of cytotoxicity correlated with the extent of metabolism for these analogues. The products of biotransformation of these compounds were stable precursors of formaldehyde (presumably N-hydroxymethyl intermediates) (FP) rather than formaldehyde itself. After injection of these 6 compounds to Balb/c mice the levels of FP generated in the plasma were markedly greater for the three active antitumour agents than for the inactive analogs. No free formaldehyde was detected in the plasma after administration of any of the compounds. These results suggest that for these compounds in vitro cytotoxicity correlates with in vitro biotransformation and their antitumour activity correlates with plasma levels of FP generated by metabolism in vivo.

Altretamine↗

PubMed1984

The chemosensitivity of a new experimental model--the M5076 reticulum cell sarcoma.

The M5076 reticulum cell sarcoma is a murine tumour of potential value in experimental chemotherapy. Experiments were conducted to ascertain the growth characteristics and chemosensitivity of this neoplasm in the BDF1 mouse. The intramuscular tumour proved to be responsive to the alkylating agents, nitrosoureas, procarbazine, DTIC and treosulphan, yet insensitive to the antimetabolites and only weakly responsive to adriamycin. Analogues of the antitumour agents hexamethylmelamine and N-methylformamide were tested against this neoplasm. The patterns of activity determined for these analogues against this tumour were identical to those previously reported against other model systems.

Altretamine↗

PubMed1984

Antitumor imidazotetrazines. 1. Synthesis and chemistry of 8-carbamoyl-3-(2-chloroethyl)imidazo[5,1-d]-1,2,3,5-tetrazin-4(3 H)-one , a novel broad-spectrum antitumor agent.

Interaction of 5-diazoimidazole-4-carboxamide and alkyl and aryl isocyanates in the dark affords 8-carbamoyl-3-substituted-imidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-on es. In cold methanol or ethanol, the 3-(2-chloroethyl) derivative 7a decomposes to afford 2-azahypoxanthine (14) and methyl and ethyl N-(2-chloroethyl)carbamates, respectively. Compound 7a has curative activity against L-1210 and P388 leukemia and may act as a prodrug modification of the acyclic triazene 5-[3-(2-chloroethyl)triazen-1-yl]imidazole-4-carboxamide (MCTIC), since it ring opens to form the triazene in aqueous sodium carbonate.

Animals↗

PubMed1984

Studies of the mode of action of antitumor triazenes and triazines. 6. 1-Aryl-3-(hydroxymethyl)-3-methyltriazenes: synthesis, chemistry, and antitumor properties.

1-Aryl-3-(hydroxymethyl)-3-alkyltriazenes [ArN = NN(CH3)CH2OH] have been synthesized by diazonium coupling to the carbinolamine (RNHCH2OH), generated in situ from the alkylamine and formaldehyde mixtures. The (hydroxymethyl)triazene structure has been confirmed by IR, NMR, and mass spectral analysis and also by the preparation of a crystalline benzoate derivative. The mass spectra of the (hydroxymethyl)triazenes suggest that they fragment by loss of formaldehyde to give the methyltriazene, which is also the product of hydrolysis in solution. The degradation of the (hydroxymethyl)triazenes in solution has been followed by UV spectroscopy and by HPLC analysis, and the half-lives were determined under a variety of conditions. The half-lives of the corresponding methyl- and (hydroxymethyl)triazenes are very similar. Both methyl- and (hydroxymethyl)triazenes decompose on silica plates during TLC analysis to give products consistent with known diazo-migration reactions. The (hydroxymethyl)triazenes have pronounced antitumor activity against the TLX5 tumor in vivo; in vivo-in vitro bioassay experiments suggest that the (hydroxymethyl)triazenes exert their in vivo antitumor activity via the degradation product, the alkyltriazene.

Animals↗

PubMed1983

The formation and metabolism of N-hydroxymethyl compounds--IV. Cytotoxicity and antitumour activity of N-hydroxymethylformamide, a putative metabolite of N-methylformamide (NSC 3051).

Experiments were conducted to test the hypothesis that N-hydroxymethylformamide (HMF) is the active metabolite of the antitumour agent N-methylformamide (NMF). In an in vitro bioassay against the TLX5 lymphoma HMF was more cytotoxic than NMF; this cytotoxicity was abolished by preincubating the TLX5 cells with semicarbazide, a formaldehyde trapping agent. Similarly, the inhibition of incorporation of radiolabelled thymidine, uridine, formate and leucine into TLX5 cells elicited by HMF was eliminated by preincubation of the cells with semicarbazide. HMF is considerably less toxic to tumour-bearing BDF1 mice than NMF and, unlike NMF, does not reduce hepatic glutathione levels in vivo. HMF has no inhibitory activity against the TLX5 lymphoma or the Sarcoma 180 in mice in vivo and only marginal activity against the M5076 reticulum cell sarcoma; these tumours are highly sensitive to NMF. However, like NMF, HMF inhibits growth of the human mammary tumour MX-1 implanted in the subrenal capsule of mice.

Animals↗

PubMed1982

Studies of the mode of action of antitumour triazenes and triazines--IV. The metabolism of 1-(4-acetylphenyl)-3,3-dimethyltriazene.

The metabolism of 1-(4-acetylphenyl)-3,3-dimethyltriazene has been studied in vivo and in vitro in mice. This dimethyltriazene was extensively metabolised in vivo and HPLC analysis of the plasma revealed the presence of two metabolites, the monomethyltriazene, 1-(4-acetylphenyl)-3-methyltriazene, and the arylamine, 4-aminoacetophenone. The dimethyltriazene was also biotransformed in vitro by a 9000 g fraction of mouse liver homogenate to products which were selectively toxic to TLX5 lymphoma cells. HPLC analysis of the products of in vitro metabolism under these conditions showed the presence of the monomethyltriazene but in an amount insufficient to account for the observed cytotoxicity. The monomethyltriazene was itself rapidly biotransformed by a 9000 g fraction of mouse liver homogenate, and by isolated mouse hepatocytes.

Animals↗