How a cofactor-free protein environment lowers the barrier to O2 reactivity.

Molecular oxygen (O2)-utilizing enzymes are among the most important in biology. The abundance of O2, its thermodynamic power, and the benign nature of its end products have raised interest in oxidases and oxygenases for biotechnological applications. Although most O2-dependent enzymes have an absolute requirement for an O2-activating cofactor, several classes of oxidases and oxygenases accelerate direct reactions between substrate and O2 using only the protein environment. Nogalamycin monooxygenase (NMO) from Streptomyces nogalater is a cofactor-independent enzyme that catalyzes rate-limiting electron transfer between its substrate and O2 Here, using enzyme-kinetic, cyclic voltammetry, and mutagenesis methods, we demonstrate that NMO initially activates the substrate, lowering its pKa by 1.0 unit (ΔG* = 1.4 kcal mol-1). We found that the one-electron reduction potential, measured for the deprotonated substrate both inside and outside the protein environment, increases by 85 mV inside NMO, corresponding to a ΔΔG0' of 2.0 kcal mol-1 (0.087 eV) and that the activation barrier, ΔG‡, is lowered by 4.8 kcal mol-1 (0.21 eV). Applying the Marcus model, we observed that this suggests a sizable decrease of 28 kcal mol-1 (1.4 eV) in the reorganization energy (λ), which constitutes the major portion of the protein environment's effect in lowering the reaction barrier. A similar role for the protein has been proposed in several cofactor-dependent systems and may reflect a broader trend in O2-utilizing proteins. In summary, NMO's protein environment facilitates direct electron transfer, and NMO accelerates rate-limiting electron transfer by strongly lowering the reorganization energy.

Differential fluorescent staining of human chromosomes with daunomycin and adriamycin--the d-bands.

Human chromosome preparations were treated with a group of anthracycline antibiotics. Well-defined, orange-red fluorescent bands were observed on chromosomes after the slide was stained with daunomycin and adriamycin but not with nogalamycin. The characteristic differential bands appeared to be similar to the banding patterns obtained by the quinacrine techniques. Interaction of these antibiotics with DNA could provide information on the general mechanism of fluorescent banding. Further, these bands (D-bands) appeared to be more stable than the Q-bands and may have some usefulness for routine clinical cytogenetic analysis.

Enzymatic Synthesis of the C-Glycosidic Moiety of Nogalamycin R.

Carbohydrate moieties are essential for the biological activity of anthracycline anticancer agents such as nogalamycin, which contains l-nogalose and l-nogalamine units. The former of these is attached through a canonical O-glycosidic linkage, but the latter is connected via an unusual dual linkage composed of C-C and O-glycosidic bonds. In this work, we have utilized enzyme immobilization techniques and synthesized l-rhodosamine-thymidine diphosphate (TDP) from α-d-glucose-1-TDP using seven enzymes. In a second step, we assembled the dual linkage system by attaching the aminosugar to an anthracycline aglycone acceptor using the glycosyl transferase SnogD and the α-ketoglutarate dependent oxygenase SnoK. Furthermore, our work indicates that the auxiliary P450-type protein SnogN facilitating glycosylation is surprisingly associated with attachment of the neutral sugar l-nogalose rather than the aminosugar l-nogalamine in nogalamycin biosynthesis.

Human pharmacokinetics, excretion, and metabolism of the anthracycline antibiotic menogaril (7-OMEN, NSC 269148) and their correlation with clinical toxicities.

In a Phase I study, menogaril (7-OMEN) was administered daily for 5 days/course, every 21-28 days. Dosages of 3.5, 7, 11.5, 17, and 31.5 mg/m2 were infused over 1 h, and dosages of 42, 50, and 56 mg/m2 were infused over 2 h. Pharmacokinetics was studied at all dosages. Plasma and urine samples were collected from 24 patients, and bile samples were also collected from 2 patients. 7-OMEN and metabolites were measured by high performance liquid chromatography. 7-OMEN was the major plasma fluorescent species at all times, with only trace amounts of N-demethyl menogaril observed. 7-OMEN disappeared from plasma biexponentially with t1/2 alpha 0.19 +/- 0.04 (mean +/- SE) h and t1/2 beta 13.22 +/- 1.54 h. Plasma pharmacokinetics of 7-OMEN was linear from 3.5-56 mg/m2; area under the curve increased proportionally with dosage. Total body clearance of 7-OMEN was 28.18 +/- 3.33 liter/m2/h, Vc was 224 +/- 30.8 liter/m2, and Vss was 370 +/- 25.7 liter/m2. Plasma pharmacokinetics of 7-OMEN studied on multiple days of a given course were similar. Urinary excretion of 7-OMEN and fluorescent metabolites accounted for 5.4 +/- 0.4% of the daily dose. Parent compound still represented greater than or equal to 80% of urinary drug fluorescence after 24 h. N-demethyl menogaril was the only other fluorescent drug species detected in urine. In two patients with biliary tract drains, biliary excretion of drug fluorescence accounted for 2.2-4.2% of the daily dose. Only 7-OMEN and N-demethyl menogaril were detected in bile by high performance liquid chromatography and thin layer chromatography. 7-OMEN was the major fluorescent biliary species, but, by 24 h, N-demethyl menogaril accounted for approximately 40% of biliary drug fluorescence. When considered in light of each patient's observed toxicities, excellent relationships were observed between the plasma area under the curve of 7-OMEN and the percentage of decreases in WBC and absolute neutrophil count. These latter findings should be useful in developing more precise and intelligent dosing schemes for 7-OMEN.

Metabolism and disposition of menogaril (NSC 269148) in the rabbit.

We have investigated the metabolism and disposition, in rabbits, of menogaril (7-OMEN), a new anthracycline antibiotic recently introduced into clinical trials. 7-OMEN was administered by rapid i.v. injection at a dosage of 2.5 mg/kg. 7-OMEN and metabolites were assayed by high performance liquid chromatography. Plasma concentrations of 7-OMEN declined in biexponential fashion with a terminal half-life of 2.7 h. The area under the plasma concentration versus time curve was 1.3 microM X h. The systemic clearance of 7-OMEN was 57.6 ml/min/kg. No metabolite of 7-OMEN was detected in plasma. At 8 h after treatment, the cumulative urinary and biliary excretions of 7-OMEN equivalents amounted to 1.3 and 3.4% of the total administered dose, respectively. 7-OMEN was the predominant fluorescent compound in urine, but four metabolites were also seen. In bile, 7-OMEN represented only 9.6% of the cumulative excretion and six metabolites were observed. Among the organs, lungs contained the highest concentrations of parent drug. Substantial concentrations of metabolites were observed in the kidneys, liver, duodenum, and small intestine. Three of the observed metabolites of 7-OMEN have been tentatively identified as N-demethylmenogaril, 7-deoxynogarol, and N-demethyl-7-deoxynogarol.

Template specificity of DNA binding by nogalamycin and its analogs utilizing competitive fluorescence polarization.

Nogalamycin, an anthracycline antibiotic, interacts with DNA. This interaction is measured by a competitive fluorescence polarization assay in which nogalamycin displaces acridine orange. The amount of acridine orange displaced is dependent upon the concentration and DNA-binding capability of the drug. The relative DNA-binding capacities of several nogalamycin analogs are also determined by this method. A comparison of these results with circular dichroism and thermal denaturation yields a positive correlation. The base-pair specificities of these compounds are also evaluated by competitive fluorescence polarization using DNA's of differing base composition. These results indicate that compounds containing the nogalose moiety generally prefer adenine and thymine. On the other hand, some of the 7-O-alkyl analogs appear to interact similarly with DNA's of differing base composition, and others show a preference for DNA's with high guanine and cytosine content. Specificities obtained with this method are compared with DNA thermal denaturation and polymerase inhibition studies. The potential value of this relatively new competitive method for the study of DNA-reactive antitumor compounds is discussed.

Pharmacokinetics and systemic bioavailability of menogaril, an anthracycline antitumor agent, in the mouse, dog, and monkey.

Menogaril is an antitumor agent of the anthracycline type which is less cardiotoxic than doxorubicin in a chronic rabbit model and is active in experimental tumor systems when given by p.o. or parenteral routes. It is currently undergoing i.v. and p.o. Phase II clinical evaluation. We report here the results of pharmacokinetic and systemic bioavailability studies of menogaril in three species (mouse, dog, and monkey). Upon i.v. administration, menogaril plasma concentration-time curves declined in a biexponential (dog) or triexponential (mouse and monkey) manner, with the terminal disposition half-life (t1/2) being considerably shorter in the dog (2.86 +/- 0.47 h) than in the mouse and monkey (21.6 and 19.0 +/- 3.7 h, respectively). The systemic clearance (CL, in liters/h/kg) was highest in mouse (6.2), followed by dog (2.9) and then monkey (1.4). The drug was extensively distributed in all three species, with steady state volumes of distribution being 88.5, 9.8, and 27.9 liters/kg in the mouse, dog, and monkey, respectively. One, two, and three metabolites were detected in the plasma of mice, monkeys, and dogs, respectively, using reverse phase high performance liquid chromatography. The major fluorescent metabolite in all species coeluted with authentic N-demethyl-menogaril; the other two metabolites were present at low concentrations relative to unchanged menogaril and its putative N-demethylated metabolite. One of these metabolites, which was found in both the dog and monkey, eluted with authentic (7R)-nogarol. Mean maximum plasma concentrations of the putative N-demethylmenogaril metabolite were approximately one-tenth those of menogaril in all three species following i.v. drug administration. Upon p.o. treatment, first-pass metabolism or incomplete absorption reduced the systemic bioavailability to 12% in the dog and 33% in the mouse and monkey. N-Demethylmenogaril was the major fluorescent metabolite observed in the plasma of p.o. treated animals. Interspecies comparison of menogaril pharmacokinetic parameters in mice, dogs, monkeys, and humans using allometric techniques indicated that the parameters for mice, monkeys, and humans were highly correlated; in each of these species presystemic metabolism of p.o. administered menogaril reduced its systemic bioavailability to an equivalent extent (30-35%). To determine if metabolically formed N-demethylmenogaril might contribute to the overall antitumor activity of menogaril, we determined the effect of synthetic N-demethylmenogaril on the life span of mice bearing P388 leukemia. Results indicated that the metabolite is marginally active compared to menogaril itself.

Laser flow cytometric studies on the intracellular fluorescence of anthracyclines.

We have used a laser flow cytometer to excite and quantitate the intracellular fluorescence of cells exposed in vitro and in vivo to various anthracyclines. In cells exposed to Adriamycin (ADR), intracellular drug fluorescence appeared slowly and reached a peak after 4 hr of incubation. Cells incubated with 10 micrograms/ml were 5 times more fluorescent than were cells incubated with 1 microgram/ml. Cells exposed to daunomycin were 2 to 4 times more fluorescent than were cells similarly exposed to ADR, and the intracellular appearance of daunomycin fluorescence was much more rapid. Cells exposed to N-trifluoroacetyladriamycin and carminomycin had higher amounts of intracellular fluorescence (2 to 4 times), and peak values were reached much more rapidly than in cells exposed to ADR. In cells exposed to rubidazone, fluorescence increased 2- to 4-fold with increased drug concentration and length of exposure. In contrast, nogalamycin fluorescence reached a peak after 60 min of incubation, and a 10-fold increase in drug concentration increased fluorescence only 2-fold. In animals given injections of ADR (4 mg/kg) and sacrificed after 3 hr, drug fluorescence could be detected in tumor and spleen cells. In contrast, fluorescence in heart nuclei was barely recognizable. However, incubation of isolated nuclei in ADR (1 microgram/ml) showed that bone marrow and heart nuclei had greater amounts of ADR fluorescence (2- to 3-fold) than did spleen or liver nuclei similarly treated. The use of laser flow cytometry for monitoring intracellular anthracycline transport, binding, and efflux is demonstrated.

Effects of 7-R-O-methylnogarol (menogaril) on L1210 cell progression in vitro and in vivo.

Menogaril (7-R-O-methylnogarol) is an anthracycline which has significant antitumor activity in vivo and is in Phase II clinical trial. We report here the drug effect on growth and cell cycle progression of L1210 mouse leukemia cells in vitro and in vivo. At doses which inhibited the growth of L1210 cells in vitro, menogaril slowed the progression of cells through S phase and blocked cells in G2 + M. 7-R-O-Methyl-N-demethylnogarol, the major metabolite of menogaril had the same effects on cell progression in vitro. Menogaril effect on cell progression in vivo was studied with peritoneal L1210 ascites growing in CD2F1 mice. Early in infection, i.e., 3 days after inoculation of 10(5) L1210 cells, DNA histograms of cells from control and drug-treated mice showed only a G1 peak. This presumably represented host diploid G0-G1 cells which predominated in the peritoneal cavity and masked the histogram of L1210 cells. Later in infection, when about 10(8) or more cells were present in the ascites, L1210 cells predominated and DNA histograms were representative of L1210 cells. When menogaril was injected at this time, the cell cycle effects were similar to those seen in vitro. Therefore, the L1210 in vivo model can be used to study cell progression effects only late in infection (when L1210 cells predominate), and due consideration should be given to contamination of the L1210 cells with host G0-G1 cells.

The use of micrococcal nuclease as a probe for drug-binding sites on DNA.

The cutting pattern produced by micrococcal nuclease on three DNA fragments has been determined in the absence and presence of various DNA-binding drugs. The enzyme itself cuts almost exclusively at pA and pT bonds, showing a greater activity at (A-T)n than in homopolymeric runs of A and T. Each drug produces distinct changes in the cleavage pattern. The protected regions can not be pinpointed with sufficient precision to assess the exact drug-binding sites on account of the sequence selectivity of the enzyme, although where a direct comparison is possible these include most of those seen as DNAase I footprints. The enzyme is most useful for assessing the selectivity of drugs which bind to AT-rich regions. Several drugs protect the DNA from micrococcal nuclease attack in regions which do not contain their acknowledged best binding sites. It appears that micrococcal nuclease is sensitive to the existence of secondary drug-binding sites which are not evident with other footprinting techniques.

Evidence of different binding sites for nogalamycin in DNA revealed by association kinetics.

The kinetics of association between nogalamycin and DNA have been measured by stopped-flow spectrometry. With a naturally occurring DNA (calf thymus) the reaction profile requires not less than three exponentials for its complete description. By contrast, binding to poly(dA-dT) is fully described by two exponentials which correspond to the two faster components seen with the natural DNA, whereas binding to poly(dG-dC) is a single exponential process whose time constant is about the same as the slowest component measured with calf thymus DNA. In all cases the amplitude of each component in the decay varies considerably with polynucleotide concentration. The results are consistent with a model in which the antibiotic is only able to bind directly to regions of the DNA which are transiently perturbed, probably non-basepaired. As a result, the antibiotic interacts much faster with AT-rich rather than GC-rich DNA sequences, which may provide a basis for its apparent sequence selectivity.

Kinetics of dissociation of nogalamycin from DNA: comparison with other anthracycline antibiotics.

Stopped-flow spectrometry and simple mixing techniques have been employed to investigate the detergent-induced dissociation of anthracycline antibiotics from natural and synthetic DNAs. Both daunomycin and nogalamycin dissociate more slowly from poly(dG-dC) than from poly(dA-dT) but the difference is much more marked for nogalamycin. With an equimolar mixture of poly(dG-dC) and poly(dA-dT), or with poly(dA-dC).poly(dG-dT), dissociation of nogalamycin occurs very slowly. In all cases the release of antibiotic from a synthetic polynucleotide is a one-step process following a single exponential. Dissociation of daunomycin, adriamycin and iremycin from calf thymus DNA is a more complex reaction which requires a two-exponential fit, in contrast to earlier reports, but differences between the behaviour of the three antibiotics are minor. Dissociation of nogalamycin from natural DNA requires a three-exponential fit, is in general far slower, and depends upon the base composition, the level of binding and the time allowed for the complex to equilibrate. It is concluded that sequence selectivity is minimal or lacking for daunomycin, whereas nogalamycin binding is sequence dependent and probably involves migration of the antibiotic between DNA binding sites. There is an inverse correlation between dissociation rate constants and antibacterial potency in simple tests.

Phase I study of intravenous menogaril administered intermittently.

Thirty-three adult patients with solid tumors were treated with menogaril, a new anthracycline antibiotic. The drug was given as a two-hour infusion every 4 to 5 weeks at doses ranging from 17 to 250 mg/m2. The maximum tolerated dose was 250 mg/m2. Reversible and dose-related leukopenia was the dose-limiting toxicity. Thrombocytopenia was less frequent. Hematologic toxicity was maximal 2 weeks after treatment, and recovery usually occurred within 4 weeks. There was no dissociation between WBC and neutrophil counts, and myelosuppression did not appear to be cumulative up to 200 mg/m2. Myelosuppression was more severe for patients with heavy pretreatment and/or bone marrow involvement. Local toxicity consisting of phlebitis and/or erythema was the most common nonhematologic toxicity, especially at 250 mg/m2 (eight out of nine patients). Usually, erythema appeared within 24 hours after treatment at or near the infusion site and resolved within a few days. Occasionally, a more persistent (several weeks) orange discoloration suggesting cutaneous deposits of menogaril was observed. Nausea and vomiting were uncommon and never severe. Alopecia and mucositis were rare. Minor arrhythmias were seen in several patients during treatment, but their relationship with menogaril therapy was unclear, and in no patient did heart failure develop. Plasma concentrations were best described by a tricompartmental model with a mean terminal half-life of 29.5 hours and a mean total-body clearance of 20.2 L/h/m2. Doses of 160 and 200 mg/m2 are recommended for phase II trials in poor- and good-risk patients, respectively.

A phase I study of menogaril in patients with advanced cancer.

Menogaril (7-con-O-methylnogarol) is a semisynthetic anthracycline analogue of nogalamycin that has shown good activity against a variety of experimental tumor systems as well as decreased cardiac toxicity when compared with doxorubicin in preclinical studies. Forty-one patients with refractory solid tumors received menogaril during a phase I trial at The Johns Hopkins Oncology Center (Baltimore). Menogaril was administered as an intravenous (IV) infusion on days 1 and 8 of a 28-day cycle in doses of 8 to 140 mg/m2. Eastern Cooperative Oncology Group (ECOG) grade 3 and 4 leukopenia was the principle dose-limiting toxicity and was occasionally accompanied by thrombocytopenia. Both WBC and platelet nadirs occurred between days 15 and 22. Anemia requiring transfusion was occasionally seen. Nonhematologic toxicities observed included frequent anorexia and malaise that was not dose related and postinfusion phlebitis that was dose related and occasionally dose limiting. Gastrointestinal toxicity and alopecia were infrequent and mild in severity. Three patients with cumulative doses of menogaril greater than 1,400 mg/m2 had no significant changes in ejection fractions as determined by serial gated blood pool scans. Two patients had greater than 10% decrements in ejection fractions without clinical changes at total doses of 128 and 288 mg/m2. One patient with prior anthracycline therapy and chest irradiation decreased her left ventricular ejection fraction from 52% to 30% and developed respiratory failure after two cycles of therapy in the setting of disease progression. No responses to menogaril therapy were observed. The recommended phase II dose for menogaril on this day 1 and 8 schedule is 140 mg/m2. A starting dose of 90 mg/m2 should be considered for heavily pretreated patients. In comparing results of this phase I schedule with those of other schedules, evidence for schedule-dependent toxicity differences should be sought.

Factors affecting DNA sequence selectivity of nogalamycin intercalation: the crystal structure of d(TGTACA)2-nogalamycin2.

As part of an investigation into the sequence selectivity of the nogalamycin-DNA interaction, the 1.58 A structure of nogalamycin complexed with d5'(TGTACA)2 has been determined by single-crystal X-ray analysis. The complex crystallised in the orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 26.3 A, b = 52.0 A and c = 67.1 A, incorporating two B-DNA duplexes and four nogalamycin molecules in the asymmetric unit. The final refined structure included 97 water molecules, one spermine molecule, two acetate ions and one sodium ion, yielding an overall R factor of 19.2% (calculated using all 12,358 reflections in the resolution range 10.7 to 1.6 A) and an Rtree of 23.7% (using 1229 test reflections). The d5'(TGTACA)2 sequence was designed to include the d5'(TpG) pyrimidine-purine base step that has been ascertained as a preferential intercalation site. The complexes in the asymmetric unit are globally similar; one nogalamycin molecule intercalates between each d5'(TpG) step in each duplex. The DNA of each complex exists as a distorted B-DNA duplex displaying some Z-DNA character in the form of C3' endo sugars at some residues. Structural comparisons between the d5'(TGTACA)2-nogalamycin2 complex and the complexes of this drug with the sequences d5'(TGATCA)2 and d5'(5MeCGT(pS)A5MeCG)2 highlight differences in binding interactions between nogalamycin and these various triplet DNA binding sites, with regards to the stability of drug intercalation, which in turn is correlated to effective levels of cytotoxicity towards tumour cells. The number of both direct and water-mediated hydrogen bonds and van der Waal's interactions between substituents of nogalamycin and the d5'(TGTACA)2 and d5'(5MeCGT(pS)A5MeCG)2 sequences are significantly greater than those made with the d5'(TGATCA)2 sequence, suggesting that the central d5'(TpA) in the former confers additional stability to the complex once the drug has bound.

31P NMR investigation of the backbone conformation and dynamics of the hexamer duplex d(5'-GCATGC)2 in its complex with the antibiotic nogalamycin.

Heteronuclear chemical shift correlation experiments confirm that the two down-field shifted 31P resonances in the spectrum of the (nogalamycin)2-d(GCATGC)2 complex correspond to the phosphodiesters CpA and TpG at the intercalation sites. 31P relaxation measurements (R1, R2 and [1H]-31P NOE) at 4.7 and 9.4 T permit the correlation time of each phosphate to be determined together with their chemical shift anisotropies. Significant differences in deoxyribose H3'-31P coupling constants and chemical shift anisotropy contributions are observed, consistent with an asymmetric DNA backbone conformation for the phosphate groups at the intercalation sites. Large amplitude internal motions of the phosphates do not appear to contribute significantly to relaxation.

Visualising the dissociation of sequence selective ligands from individual binding sites on DNA.

We have used a modification of the footprinting technique to measure the dissociation of mithramycin, echinomycin and nogalamycin from their binding sites in a natural DNA fragment. Complexes with radiolabelled DNA were dissociated by addition of unlabelled DNA. Samples were removed at various times and subjected to DNase I digestion, and the rate of dissociation from each site was estimated from the time-dependent disappearance of the footprints. For echinomycin the slowest rate of dissociation is from ACGT, while the slowest site for mithramycin contains four contiguous guanines. The dissociation of nogalamycin is extremely slow, even from its weaker sites; the slowest rate was from ACGTA, which took longer than 4 h, even at 37 degrees C.

Comparative binding of antitumor drugs to DNA containing the telomere repeat sequence.

Telomeres are the ends of the linear chromosomes of eukaryotes and consist of tandem GT-rich repeats in telomere sequence i.e. 500-3000 repeats of 5'-TTAGGG-3' in human somatic cells, which are shortened gradually with age. The G-rich overhang of telomere sequence can adopt different intramolecular fold-backs and tetra-stranded DNA structures, in vitro, which inhibit telomerase activity. In this report, DNA binding agents to telomere sequence were studied novel therapeutic possibility to destabilize telomeric DNA sequences. Oligonucleotides containing the guanine repeats in human telomere sequence were synthesized and used for screening potential antitumor drugs. Telomeric DNA sequence was characterized using spectral measurements and CD spectroscopy. CD spectrum indicated that the double-stranded telomeric DNA is in a right-handed conformation. Polyacrylamide gel electrophoresis was performed for binding behaviors of antitumor compounds with telomeric DNA sequence. Drugs interacted with DNA sequence caused changes in the electrophoretic mobility and band intensity of the gels. Depending on the binding mode of the anticancer drugs, telomeric DNA sequence was differently recognized and the efficiency of cleavage of DNA varies in the bleomycin-treated samples under different conditions. DNA cleavage occurred at about 1% by the increments of 1 micromM bleomycin-Fe(III). These results imply that the stability of human telomere sequence is important in conjunction with the cancer treatment and aging process.

Phase I and II agents in cancer therapy: I. Anthracyclines and related compounds.

Anthracycline antibiotics remain among the most potent anticancer drugs, but their efficacy is limited by the development of a dose-dependent irreversible cardiomyopathy and by the emergence of clones of tumor cells resistant to the effects of the drug. Modifications of the basic anthracycline structure have resulted in molecules that may share the activity of the parent compound, with amelioration of some toxicities, absence of cross-resistance, or activity against tumors insensitive to the parent drug. Epirubicin has a unique metabolic pathway, glucuronidation, that may result in more rapid plasma clearance and reduced toxicity as compared with doxorubicin. Epirubicin has demonstrated comparable activity to doxorubicin in breast cancer, with possibly reduced toxicity. Idarubicin is of interest because of its cytotoxic activity when given orally. Idarubicin has prolonged retention in the plasma and has equal cytotoxic activity to the parent compound. Idarubicin has demonstrated activity against acute leukemia and breast cancer; in the latter tumor category, some doxorubicin-resistant tumors have responded. Esorubicin is of interest because of its nearly absent cardiac toxicity. This agent has some activity against solid tumors and is currently being clinically tested. Aclacinomycin A is an anthracycline in which a trisaccharide is substituted for the aminosugar. Aclacinomycin A and the related compound marcellomycin are of interest as both cytotoxic and differentiating agents. Menogaril is an anthracycline with the aminosugar on the D ring; it does not exhibit cross-resistance with doxorubicin or cardiotoxicity. Mitoxantrone is a compound that is related to the anthracyclines but has a different mechanism of action. This agent has significant activity against acute leukemia and breast cancer and is currently being compared with doxorubicin. Amsacrine is another compound related to the anthracyclines that possesses major activity against acute leukemias. Minor modifications of the anthracycline molecule have had major impact on the biologic activity of these drugs. New anthracycline analogues with up to 100 times the potency of currently available anthracyclines are being developed for clinical testing, and these complex molecules retain a nearly unlimited potential for structural modification.

Pharmacokinetics of 7-con-O-methylnogarol in patients with solid tumors.

The pharmacokinetics of 7-con-O-methylnogarol were investigated by HPLC assay with fluorometric detection in nine cancer patients with normal hepatic and renal function, after a 2-h infusion of 160 or 200 mg/m2. The drug disappeared from plasma biexponentially with a mean elimination half-life of 38 +/- 3 h; the mean apparent volume of distribution and the plasma clearance were 805 +/- 91 1/m2 and 14 +/- 2 1/h per m2. Within 48 h of administration, urinary excretion of the drug and its metabolite 7-con-O-methyl-N-demethylnogarol accounted for 2%-15% and 0.1%-6% of the dose, respectively. Neither 7-con-O-methylnogarol nor its N-demethyl derivative was conjugated with glucuronic acid or sulfate in detectable amounts.