Critical appraisals of approaches for predictive designs in anticancer drugs.

The present review provides a critical appraisal of the most important areas in cancer drug research and, ultimately, in clinical oncology and therapy, with emphasis on the elucidation of possible predictive designs for the development of new anticancer drugs. These assessments encompass the well-established anticancer drugs and congeners which have been employed over the years in clinical therapy, and the more recent exploratory agents still requiring further rigorous scrutiny in the clinical environment. These areas mainly include the bioreversible redox carriers, the boron neutron capture compounds, some new mitosis-interactive agents, cell cycle modifiers, biological-response mpdifiers, oncogene inhibitors, drug-antibody conjugates, cancer cell suppression and destruction agents, antiangiogenesis and antimetastasis agents, apoptosis-promoting agents, and gene therapy and vaccines.

In the search for new anticancer drugs. 29. A study on the correlation of lipophilicities, ionization constants and anticancer activities of aminoxyl labeled TEPA congeners.

Ionization constants for a series of sterically hindered pyrrolidine, pyrroline and piperidine derivatives were determined by potentiometric titrations. The pKa values for the secondary amines as a group ranged from about 7.7 to 11.

In the search for new anticancer drugs. 28. Synthesis and evaluation of highly active aminoxyl labeled amino acid derivatives containing the [N'-(2-chloroethyl)-N'-nitrosoamino]carbonyl group.

The aminoxyl (nitroxyl) labeled (2-chloroethyl)nitrosocarbamoyl (CNC) derivatives of amino acids, i.e., N-[[N'-(2-chloroethyl)-N'-nitrosoamino]carbonyl]-A-(1-oxy-2,2,6,6- tetramethylpiperidin-4-yl)amides, A = glycyl (10a), A = L-alanyl (10b), A = L-valyl (10c), A = L-phenylalanyl (10d), were synthesized and evaluated in vitro for their anticancer activities against the murine lymphocytic leukemia P388.

In the search for new anticancer drugs. 27. Synthesis and comparison of anticancer activity in vivo of amino acids, carbohydrates, and carbohydrate-amino acid conjugates containing the [N'-(2-chloroethyl)-N'-nitrosoamino]carbonyl group.

The [N'-(2-chloroethyl)-N'-nitrosoamino]carbonyl [(2-chloroethyl)nitrosocarbamoyl, CNC] moiety containing compounds CNC-glycinamide 2d, CNC-amino acid derivatives 7a-d, and carbohydrate-CNC-amino acid conjugates 13, 18, 22, 23, 27, and 28 were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388 using the National Cancer Institute (NCI) protocol. The most active compound was 2d with a 520% increase in life span (%ILS) and 6/6 survivors after 60 days. The CNC-amino acid analogs 7a-d possessed high to moderate activities with maximum %ILS values of 270, 174, 141 and 132, respectively.

In the search for new anticancer drugs. 26. A comparison of anticancer activities of several TEPA, thio-TEPA, Seleno-TEPA, and azetidine analogs, including congeners containing an aminoxyl moiety.

A series of TEPA, Thio-TEPA, Seleno-TEPA, and azetidine analogs, including congeners containing an aminoxyl moiety, were synthesized and evaluated in vivo for anticancer activity against the murine lymphocytic leukemia P388. All aziridine derivatives were found to be active with an increase in life span ranging from 42% to 272%, and all azetidine analogs were rated as inactive with one marginal exception. An attempt was made to rationalize the results on the basis of the lipophilic properties of the compounds.

In the search for new anticancer drugs. XXV: Role of N-nitrosated amadori compounds derived from glucose-amino acid conjugates in cancer promotion or inhibition.

Earlier investigators found that some N-nitrosated Amadori compounds, derived from glucose and amino acid condensation reactions, exhibit mutagenic properties and theorized that these potentially carcinogenic compounds might be formed in the human digestive system. To further investigate these compounds, N-nitrosated Amadori compounds [i.e.

In the search for new anticancer drugs. XXIV: Synthesis and anticancer activity of amino acids and dipeptides containing the 2-chloroethyl- and [N'-(2-chloroethyl)-N'-nitroso]-aminocarbonyl groups.

A series of L,L- (42, 44, 46, and 60) and D,D- (43, 45, 47, and 61) dipeptide derivatives composed of phenylglycine, phenylalanine, homophenylalanine, and valine and containing a 2-chloroethylamino group at the C-terminus and an N'-(2-chloroethyl)-N'-nitroso-aminocarbonyl group at the N-terminus of the dipeptides were prepared. The dipeptide derivatives (42-47, 60, and 61) were first evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 42, 44, 46, and 60 possessed activities ranging from 46 to 111 percent increase in life span (%ILS), whereas 43 was marginal (%ILS = 31) and 45, 47, and 61 were inactive.

Simultaneous measurements of the intra- and extra-cellular oxygen concentration in viable cells.

An EPR method that can measure the intra- and extra-cellular oxygen concentration [O2] simultaneously in vitro has been developed using specially designed nitroxides. In the presence of Fe(CN)6(3-) in the medium, intracellular [O2] is measured by a neutral 15N-nitroxide and extracellular [O2] is measured by a negatively charged 14N-nitroxide, since charged species do not enter cells and the EPR spectrum of a 15N-nitroxide does not overlap with that of a 14N-nitroxide. The method is based in part on the minimal broadening of negatively charged nitroxides by Fe(CN)6(3-) and the very effective broadening of neutral nitroxides by the same paramagnetic ions.

A critical evaluation of the present status of toxicity of aminoxyl radicals.

The literature on the toxicity of aminoxyl radicals was critically reviewed. It was concluded that, in general, the aminoxyl radicals possess a very low toxicity and are not mutagenic. In support of this contention, several aminoxyl radicals were evaluated in vitro.

In the search for new anticancer drugs. XXIII: Exploration of a predictive design for anticancer drugs of carbohydrates containing N-nitrosochloroethylamino, N-nitrosomethyl, and N-nitrosoaminoxyl components.

The spin-labeled glucose nitrosoureas 13-16, streptozotocin (18), chlorozotocin (31), streptozotocin analogues of galactosyl 24 and mannosyl 28, and their tetra-O-acetyl derivatives 25 and 29, MCNU (Cymerin, 34), and glucamine (21) were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 13-16, 18, 24, 28, 31, and 34 possessed activities ranging from 33 to 603% increase in life span (%ILS), whereas 21, 25, and 29 were inactive (%ILS = 9 to 10). All CD2F1 male mice treated with the most active compounds (13, 14, and 34) at 20 mg/kg were alive after 30 days, whereas all mice treated with the clinical drug streptozotocin (18) and clinically tested chlorozotocin (31) succumbed.

Chemical and electrochemical reduction rates of cyclic nitroxides (nitroxyls).

The reduction rates of five-membered pyrrolidine and pyrroline, and six-membered piperidine nitroxides (alternatively termed nitroxyls) containing various substituents were determined under homogeneous conditions using ascorbate, and electrochemically under heterogeneous conditions. The results were compared with data from the literature. It was shown that the increased rates of reduction of six-membered nitroxides, compared with those of the five-membered nitroxides, cannot be explained on the basis of differences in electrochemical potentials but, rather, can be ascribed to differences in the accessibility of the nitroxide group.

Development of nitroxides for selective localization inside cells.

The use of nitroxides to measure intracellular phenomena, especially oxygen concentrations, is a new and potentially important approach to a number of physiological and pathophysiological studies. This study provides data indicating the feasibility of developing nitroxides that localize selectively in the intracellular compartment; it is based on the use of readily hydrolysed ester linkages, such that the nitroxides become converted intracellularly to ionic derivatives that do not cross cell membranes readily. Up to 120-fold increased concentrations of intracellular nitroxides (and their one electron reduction product, the hydroxylamines) were obtained.

Evaluation of spin labeled TEPA and CCNU analogs against osteosarcoma and MNU-induced mammary carcinoma of the SD-rat.

The effectiveness to reduce tumor growth by 1-(2-chloroethyl)-3-(1-oxyl-2,2,6,6-tetramethylpiperidinyl)- 1-nitrosourea (SLCNU) and N,N,N,'N'- bis(1,2-ethanediyl)-N"-(1-oxyl-2,2,6,6-tetramethyl- 2-piperidinylaminocarbonyl)-phosphoric triamide (SLDU) was studied in osteosarcoma and MNU-induced mammary carcinoma in the SD-rat. Both compounds elicited neither an inhibitory effect on these tumors nor an increase in the mean/median life span as compared to the control group.

Cellular pharmacology of N,N',N''-triethylene thiophosphoramide.

N,N',N''-triethylene thiophosphoramide (Thio-TEPA) is an alkylating agent whose antineoplastic activity has been known for nearly 30 years. Human plasma pharmacokinetic studies revealed the presence of TEPA, a Thio-TEPA metabolite which after 4 h achieved plasma concentrations equal to those of the parent compound. We studied the activity of both Thio-TEPA and TEPA against murine leukemia P388 cells in culture.

In the search for new anticancer drugs, XXI. Spin labeled nitrosoureas.

The spin labeled nitrosoureas 7a-e and 12 were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 7a-c, 7e and 12 possessed activities ranging from 31 to 542 percent increase in life span (%ILS), whereas compound 7d was marginal (%ILS = 21). All CD2F1 male mice treated with the most active compounds (7a and 12) at 35 mg/kg for 9 days were alive after 30 days, whereas all mice treated with the clinical drug CCNU (1c) succumbed.

In the search for new anticancer drugs. XX: A comparison of the in vitro growth inhibition of P388 cells by TEPA and N,N;N',N'-bis (1,2-ethanediyl)-N''-(1-oxyl-2,2,6,6-tetramethyl-4- piperidinylaminocarbonyl) phosphoric triamide and congeners.

We tested the in vitro growth inhibitory activity of TEPA, and three analogs against P388 murine lymphocytic leukemia cells in culture. The analogs consist of spin-labeled TEPA and two reduced forms containing the NH and NOH groups instead of the nitroxyl function. Spin label TEPA was obtained by replacing one of the aziridine groups in TEPA with spin-labeled urea.

In the search for new anticancer drugs. 19. A predictive design of N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide (TEPA) analogues.

The nitroxyl-labeled analogues of N,N:N',N':N",N"-tri-1,2-ethanediylphosphoric triamide (TEPA), N,N:N',N'-bis(1,2-ethanediyl)-N"-[[(2,2,6,6-tetramethyl-1-oxypiperidi n-4- yl)amino]carbonyl]phosphoric triamide (5a) and N,N:N',N'-bis(1,2-ethanediyl)-N"-[[(2,2,5,5-tetramethyl-1-oxypyrrolid in-3- yl)amino]carbonyl]phosphoric triamide (11a), possess therapeutic indexes that are 8-12 times higher than those of thio-TEPA (1) and TEPA (2). The introduction of methyl groups into the aziridine ring, or the replacement of the nitroxyl moiety with hydroxylamine or amine derivatives, or with an adamantane moiety, results in compounds of lesser activity. An attempt is made to rationalize these results using a lipophilicity scale.

In the search for new anticancer drugs. XVIII. Various mono- and bis-anthraquinone hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl)phosphoric diamide moiety.

The structure-anticancer activity and the activity-lipophilicity relationship of 8 mono- and bis-anthraquinone hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl) phosphoric diamide moiety were evaluated. These compounds were tested in vivo, using murine lymphocytic leukemia P388. Seven of these compounds were active and one was marginal at optimum doses.

In the search for new anticancer drugs. 17. Linear and cyclic polyether analogues of N,N:N',N':N'',N''-tri-1,2-ethanediylphosphoric triamide and N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide.

Linear and cyclic polyether derivatives of N,N:N',N':N'',N''-tri-1, 2-ethanediylphosphoric triamide (TEPA) and N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide (thio-TEPA) are synthesized and evaluated for their antineoplastic activity against the murine lymphocytic leukemia P388. All compounds, except for 7d, were active ranging from 42% to 287% increase in life span (% ILS). All CD2F1 male mice treated with the most active compound (7a) at 90 mg/kg per day for 9 days were alive after 30 days, whereas all mice treated with the clinical drug thio-TEPA were dead.

Human erythrocyte membrane permeability and nitroxyl spin-label reduction.

Nitroxyl spin labels are paramagnetic compounds that have demonstrated utility as contrast enhancing agents in proton magnetic resonance imaging. The time-course of contrast enhancement depends on distribution and elimination of these agents. Reduction, resulting in formation of the diamagnetic hydroxylamine, is the major metabolic pathway observed in vivo.

Diradical nitroxyl spin label contrast agents for magnetic resonance imaging. A comparison of relaxation effectiveness.

The proton relaxation enhancement characteristics of seven potential MRI contrast agents containing two nitroxyl spin labels per molecule (diradicals) were compared with eight similar agents with only one spin label per molecule (monoradicals). Diradical nitroxyls were evaluated to test the hypothesis that multiple paramagnetic centers in one molecule will result in stronger proton relaxation enhancement characteristics, allowing effective contrast enhancement at lower molar concentrations and thus a reduced osmotic load and greater safety. The acute toxicity of these agents is believed to be largely related to osmotic load.

In the search for new anticancer drugs. XV. Various aliphatic and aromatic hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl)phosphoric diamide moiety.

The scope of the structure-anticancer activity relationship among various aliphatic and aromatic hydrazones containing the N,N,N',N'-bis(1,2-ethanediyl)-phosphoric diamide moiety was studied. A total of 19 compounds were tested in vivo, using murine lymphocytic leukemia P388. At optimum dose all these compounds were active.