National Cancer Institute Formulary: A Public-Private Partnership Providing Investigators Access to Investigational Anticancer Agents.

As part of the White House Cancer Moonshot Initiative, the National Cancer Institute (NCI) has developed a drug formulary to provide investigational anticancer agents to the extramural research community. This article describes how the NCI Formulary functions, how researchers may apply for access to drugs in the formulary, and the NCI's initial goals for formulary participation. Approved investigators may apply for access to formulary agents at: https://nciformulary.cancer.gov.

The effects of interleukin 2 and alpha-interferon administration on hepatic drug metabolism in mice.

We have administered the cytokines interleukin 2 (IL-2), alpha-interferon (IFN-alpha), and gamma-interferon (IFN-gamma) to mice and measured the alterations in hepatic drug-metabolizing enzyme activities. For comparative purposes and to understand the mechanism of diphtheria and tetanus toxoids and pertussis (DTP) vaccine-induced inhibition of drug metabolism, we also studied the effects of vaccine administration in mice. The administration of IL-2 alone or in combination with IFN-alpha or IFN-gamma causes dose-dependent increases in hexobarbital-induced sleep times. These increases correlate well with the inhibition of specific microsomal mixed-function oxidase activities. Sublethally irradiated mice and athymic nude mice receiving injections of IL-2 or IL-2 plus IFN-alpha do not show the inhibition of drug metabolism seen in normal mice. However, the inhibition of drug metabolism in DTP vaccine-treated mice was similar in all three groups. These observations indicate a possible role for immune cells (probably T-lymphocytes) in the inhibition of drug metabolism caused by administration of these cytokines, which is different from the inhibition of drug metabolism caused by DTP vaccine.

Formation of quaternary amines by N-methylation of azaheterocycles with homogeneous amine N-methyltransferases.

Catalytic activities of two amine N-methyltransferases were documented for the following azaheterocycles: isomeric phenyl- and bispyridyls; 2-, 3- and 4-mono-substituted pyridines; and a miscellaneous group of azaheterocycles that included mono- and diazabenzenes and mono- and diazanaphthalenes. The broad substrate specificities of the two amine N-methyltransferases for primary and secondary amines are here extended to a large number of aromatic azaheterocycles in which N-methylation results in the formation of quaternary ammonium metabolites. Pyridine was the best substrate for both enzymes. Substitution in the ring at the 2-position sterically hindered methylation of the pyridyl nitrogen; 2-phenylpyridine and 2,2'-bispyridyl were not substrates.

Role of N-methyltransferases in the neurotoxicity associated with the metabolites of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and other 4-substituted pyridines present in the environment.

Amine N-methyltransferases in the brains of humans, monkeys, mice, rabbits and rats, as well as two homogeneous enzymes isolated from rabbit liver, are capable of N-methylating 4-phenyl-1,2,3,6-tetrahydropyridine to 1-methyl-4-phenyltetrahydropyridine (MPTP), and 4-phenylpyridine to 1-methyl-4-phenylpyridinium ion (MPP+). The product in each instance is a neurotoxin. The suggestion is offered that the known long half-life of methylpyridinium compounds in brain may be due to limitations in transport of such charged metabolites out of this tissue and to metabolic recycling of the desmethyl species by amine N-methyltransferases. The methylation of pyridines to quaternary amines is suggested as a means by which lipophilic compounds, having gained entrance to the cell, are converted to charged species that efflux much less readily.

The Cancer Therapy Evaluation Program (CTEP) at the National Cancer Institute: industry collaborations in new agent development.

The mission of the Cancer Therapy Evaluation Program (CTEP), a clinical research program of the National Cancer Institute (NCI), is to reduce the burden of cancer. CTEP plans, reviews, and coordinates clinical trials for investigational anticancer agents, from the inception of protocols through the preparation and submission of Investigational New Drug Applications (INDs) to the Food and Drug Administration (FDA). CTEP also serves as a liaison to the FDA for the extramural clinical research community and industry collaborators. Other CTEP functions include managing, tracking, and reviewing clinical protocols as well as monitoring, planning, and maintaining regulatory compliance of the clinical trials. In addition, CTEP coordinates the distribution of the investigational agents from industry collaborators for use in all NCI-sponsored clinical trials. The advantages of collaborating with CTEP are described as well as details about the contractual framework, either a Clinical Trials Agreement (CTA) or a Cooperative Research and Development Agreement (CRADA), for such a collaboration. Many of the concerns raised by industry collaborators with respect to intellectual property, data access, and publications are also addressed.

Biochemical effects of dithiolthiones.

Administration of dithiolthiones to mice in single intragastric doses (2-4 mmol/kg body weight) or in the diet (0.5% for 14 days), and to rats in the diet (0.1% for 14 days) was found to increase glutathione levels and the activities of a number of enzymes in various tissues including the liver and lung. The enzymes affected were glutathione transferases (with chlorodinitrobenzene or dichloronitrobenzene), quinone and glutathione reductase, and glucose-6-phosphate and 6-phosphogluconate dehydrogenase, all of which are involved directly or indirectly in the detoxication of xenobiotics, including carcinogens. The dithiolthiones tested in mice were oltipraz, ADT, 116L and 129L, and in rats, oltipraz. Intragastric administration of dithiolthiones (oltipraz, ADT or 116L; two doses each of 1 g/kg body weight) did not increase glutathione levels or enzyme activities in murine mammary adenocarcinoma transplants. Increases in glutathione levels and enzyme activities similar to those found with dithiolthiones were observed when a semi-synthetic diet containing 10-40% lyophilized cabbage was fed to mice for 30 days. Dithiolthiones that are present in cabbage may play a role in the protective actions of diets high in vegetables against the toxic actions of xenobiotics. The biochemical effects of dithiolthiones reported here may account for the protective actions of these compounds.

The ability of amine N-methyltransferases from rabbit liver to N-methylate azaheterocycles.

The substrate specificity of two homogeneous amine N-methyltransferases from rabbit liver has been demonstrated to extend to the azaheterocycles pyridine, R-(+)-nicotine and S-(-)-nicotine. Both enzymes methylate R-(+)-nicotine at the pyridyl nitrogen to afford the N-methylnicotinium salt, whereas S-(-)-nicotine does not act as a substrate for either enzyme. Surprisingly, R-(+)-nicotine is methylated at either the pyridyl nitrogen, or the pyrrolidine nitrogen, to afford the two isomeric monomethylate nicotinium ions when an enzymic preparation containing both methyl transferase activities was used. Under similar conditions S-(-)-nicotine was methylated only at the pyridyl nitrogen. The production of charged metabolites in-vivo, from the large number of pyridino-compounds that are used as drugs, or are present in the environment, may be of toxicological significance, in view of the reported toxicities of several such quaternary ammonium compounds.

Amine N-methyltransferases from rabbit liver.

N-Methylation of amines has been ascribed to enzymes listed as amine N-methyltransferase, indolethylamine N-methyltransferase, and arylamine N-methyltransferase. All of these activities are accomplished by each of two related enzymes present in rabbit liver. The two N-methyltransferases have a very broad and overlapping specificity for primary and secondary amines. Both have a molecular mass of 30,000 daltons and react with an antibody formed to one of them, but have different isoelectric points.

Modulation of hepatic mRNA levels after administration of lipopolysaccharide and diphtheria and tetanus toxoids and pertussis vaccine adsorbed (DTP vaccine) to mice.

Administration of whole-cell diphtheria and tetanus toxoids and pertussis vaccine adsorbed (DTP vaccine) caused marked depression in the expression of mRNA for isozymes of cytochrome P-450 in the livers of endotoxin-responsive and nonresponsive mice. The levels of expression of mRNA for a polycyclic aromatic hydrocarbon-inducible (CYP1A2) and an ethanol-inducible (CYP2E1) form of P-450 were reduced by 70% to 80% 8 to 12 hr after vaccination or Bordetella pertussis endotoxin administration. These effects are preceded by marked increases (threefold to sixfold) in mRNA expression for interleukin-6, interleukin-1 and tumor necrosis factor in both strains of mice, with maximal increases 1 to 2 hr after injection. This is the first demonstration that levels of cytokine mRNA are altered in the liver in response to DTP vaccine administration. The finding of increased cytokine mRNA in the livers of mice injected with vaccine supports a role for cytokines as mediators of the decreased levels of cytochrome P-450. In addition, inducible nitric oxide synthase mRNA expression is also increased after vaccine administration, with a peak at 4 hr. The temporal relationship of the increased cytokine mRNA expression, increased nitric oxide synthase and decreased expression of P-450 mRNAs suggests a mechanism by which cytokines mediate the induction of nitric oxide synthase, which increases nitric oxide and decreases the activities of some cytochromes P-450.

Chemoprotective effects of two dithiolthiones and of butylhydroxyanisole against carbon tetrachloride and acetaminophen toxicity.

Administration of tert-butyl-4-hydroxyanisole or of two dithiolthiones to female CD-1 mice protected against the acute toxic effects of two hepatotoxic agents, acetaminophen and carbon tetrachloride. Reduced mortality of mice was observed following pretreatment with tert-butyl-4-hydroxyanisole or dithiolthiones. Pretreatment reduced or prevented hepatic glutathione depletion produced by these two hepatotoxic agents. Liver damage, i.e., as determined by serum transaminase and sorbitol dehydrogenase activities, was less after pretreatment with tert-butyl-4-hydroxyanisole or dithiolthiones. Administration of dithiolthiones resulted in increased (from four- to over six-fold) activities of liver glutathione-S-transferases.

N-methylation: potential mechanism for metabolic activation of carcinogenic primary arylamines.

Two amine N-methyltransferases isolated from rabbit liver catalyze S-adenosylmethionine-dependent N-methylation of benzidine and 4-aminobiphenyl but not of 4-aminoazobenzene or 2-aminobiphenyl. The enzymatic reaction products were analyzed and found to be identical to synthetic N-methylbenzidine and N-methyl-4-aminobiphenyl. N-Methylation may be a critical step in the metabolic activation of primary arylamines because N-methylarylamines, unlike primary arylamines, are readily N-oxygenated by the NADPH- and oxygen-dependent microsomal flavin-containing monooxygenase. Kinetic studies carried out with the purified porcine liver monooxygenase demonstrate that, while activity with primary arylamines could not be detected, N-methyl derivatives of benzidine, 4-aminoazobenzene, and 4-aminobiphenyl are substrates. Products formed from N-methyl-4-aminobiphenyl had the properties of the hydroxylamine and/or nitrone in that the enzyme- and time-dependent incubation product(s) reduced Fe3+ to Fe2+, and formaldehyde was formed during the course of the reaction. These data suggest that N-methyl-4-aminobiphenyl is oxidized to N-hydroxy-N-methyl-4-aminobiphenyl, which can undergo further oxidation to a nitrone that hydrolyzes to formaldehyde and N-hydroxy-4-aminobiphenyl.