Daunomycin. I. The Structure of Daunomycinone

Molecular mechanisms of anthracycline induced cardiotoxicity: Zebrafish come into play

Anthracyclines are among the most potent chemotherapeutics; however, cardiotoxicity significantly restricts their use. Indeed, anthracycline-induced cardiotoxicity (AIC) fares among the worst types of cardiomyopathy, and may only slowly and partially respond to standard heart failure therapies including β-blockers and ACE inhibitors. No therapy specifically designed to treat anthracycline cardiomyopathy at present, and neither is it known if any such strategy could be developed. To address this gap and to elucidate the molecular basis of AIC with a therapeutic goal in mind, zebrafish has been introduced as an in vivo vertebrate model about a decade ago. Here, we first review our current understanding of the basic molecular and biochemical mechanisms of AIC, and then the contribution of zebrafish to the AIC field. We summarize the generation of embryonic zebrafish AIC models (eAIC) and their use for chemical screening and assessment of genetic modifiers, and then the generation of adult zebrafish AIC models (aAIC) and their use for discovering genetic modifiers via forward mutagenesis screening, deciphering spatial-temporal-specific mechanisms of modifier genes, and prioritizing therapeutic compounds via chemical genetic tools. Several therapeutic target genes and related therapies have emerged, including a retinoic acid (RA)-based therapy for the early phase of AIC and an autophagy-based therapy that, for the first time, is able to reverse cardiac dysfunction in the late phase of AIC. We conclude that zebrafish is becoming an important in vivo model that would accelerate both mechanistic studies and therapeutic development of AIC.

Upcycling the anthracyclines: New mechanisms of action, toxicology, and pharmacology

The anthracyclines are a family of natural products isolated from soil bacteria with over 2000 chemical representatives. Since their discovery seventy years ago by Waksman and co-workers, anthracyclines have become one of the best-characterized anticancer chemotherapies in clinical use. The anthracyclines exhibit broad-spectrum antineoplastic activity for the treatment of a variety of solid and liquid tumors, however, their clinical use is limited by their dose-limiting cardiotoxicity. In this review article, we discuss the toxicity of the anthracyclines on several organ systems, including new insights into doxorubicin-induced cardiotoxicity. In addition, we discuss new medicinal chemistry developments in the biosynthesis of new anthracycline analogs and the synthesis of new anthracycline analogs with diminished cardiotoxicity. Lastly, we review new studies that describe the repurposing of the anthracyclines, or "upcycling" of the anthracyclines, as anti-infective agents, or drugs for niche indications. Altogether, the anthracyclines remain a mainstay in the clinic with a potential new "lease on life" due to deeper insight into the mechanism underlying their cardiotoxicity and new developments into potential new clinical indications for their use. Keywords: Anthracycline, chemotherapy, toxicology, medicinal chemistry, biosynthesis.

Selective Reduction Leading to 3,5-cis-3-Aminosugars: Synthesis and Stereoselective Glycosylation

Synthesis of 3,5-cis-3-amino glycals with a cis-fused cyclic sulfamidate group has been achieved by selective reduction of sulfamidate ketimine groups. The efficient access to the structurally unique glycals allowed the subsequent divergent synthesis of various naturally occurring 3-amino-2,3,6-trideoxysugars. In addition, Lewis acid-promoted glycosylation of the glycals provided a simple solution for the stereoselective installation of O- and C-linked aglycons on the amino sugar scaffolds.

Synthesis and Cytotoxic Evaluation of Arimetamycin A and Its Daunorubicin and Doxorubicin Hybrids

The arimetamycin A glycan governs the compound's cytotoxicity (IC50). To study this branched, deoxy-amino disaccharide, we designed and synthesized a modified acyl donor that underwent glycosylation with three anthracycline aglycones: steffimycinone, daunorubicinone, and doxorubicinone. The result of the approach was a synthesis of arimetamycin A and two novel hybrid anthracyclines. Each molecule exhibited enhanced cytotoxicity in comparison to the parent anthracyclines, steffimycin B, daunorubicin, and doxorubicin. An orienting mechanistic evaluation revealed that the daunorubicin hybrid inhibits the ability of human topoisomerase IIα to relax negatively and positively supercoiled DNA.

Pathway Engineering of Anthracyclines: Blazing Trails in Natural Product Glycodiversification

The anthracyclines are structurally diverse anticancer natural products that bind to DNA and poison the topoisomerase II-DNA complex in cancer cells. Rational modifications in the deoxysugar functionality are especially advantageous for synthesizing drugs with improved potency. Combinatorial biosynthesis of glycosyltransferases and deoxysugar synthesis enzymes is indispensable for the generation of glycodiversified anthracyclines. This Synopsis considers recent advances in glycosyltransferase structural biology and site-directed mutagenesis, pathway engineering, and deoxysugar combinatorial biosynthesis with a focus on the generation of "new-to-nature" anthracycline analogues.

Antitumour Anthracyclines: Progress and Perspectives

Anthracyclines are ranked among the most effective chemotherapeutics against cancer. They are glycoside drugs comprising the amino sugar daunosamine linked to a hydroxy anthraquinone aglycone, and act by DNA intercalation, oxidative stress generation and topoisomerase II poisoning. Regardless of their therapeutic value, multidrug resistance and severe cardiotoxicity are important limitations of anthracycline treatment that have prompted the discovery of novel analogues. This review covers the most clinically relevant anthracyclines and their development over decades, since the first discovered natural prototypes to recent semisynthetic and synthetic derivatives. These include registered drugs, drug candidates undergoing clinical trials, and compounds under pre-clinical investigation. The impact of the structural modifications on antitumour activity, toxicity and resistance profile is addressed.

Biological Activity and Therapeutic Usefulness of Daunomycin

Daunomycin is a new antibiotic of the anthracycline group obtained from Streptomyces peucetius; it consists of a pigmented aglycone (daunomycinone) in glycoside linkage with an aminosugar (daunosamine), Strictly related substances are Rubidomicine and Rubomycin C. Daunomycin has a strong cytotoxic and antimitotic effect on the «in vitro» growth of mammalian normal and neoplastic cells. Its most important metabolic effect is the inhibition of the synthesis of RNA and DNA. This effect can be considered as a result of the binding of Daunomycin to DNA. The antimitotic activity of Daunomycin however is only in part dependent on this metabolic effect. Daunomycin has a strong inhibiting effect on the growth of transplanted tumors, both in the ascitic and solid forms with a remarkable prolongation of survival time in animals. In experimental leukemia this antibiotic shows a significant therapeutic effect also on advanced systemic L 1210, on the leukemia transplantable linea resistant to methotrexate, 6MP, and cyclophosphamide. The most pronounced toxic effects of Daunomycin are bone marrow depression and marked reduction in lymphoid tissues; histological studies in the lethal dose range showed also degenerative changes in liver, kidney, intestinal tract and testis. Daunomycin is not effective by mouth probably because it is inactivated in the gastro-intestinal tract; in fact the antibiotic is quickly transformed by liver extracts in inactive products. The observed toxic effects in man are: severe local reactions if the drug extravasates, bone marrow depression, leucopenia, anemia, thrombocytopenia, bleeding, fever, oral ulcers and alopecia. Liver disturbances were observed in some patients treated with Daunomycin. In patients receiving a total dosage of Daunomycin of 25 mg/or more, cardiac symptoms were observed, such as tachycardia, pulmonary insufficiency, heart failure and hypotension, possibly associated with the drug. Similar and more frequent effects were observed in patients treated with Rubidomicine. A relatively high remission rate was observed in acute lymphoid leukemia; the remission could be prolonged by maintenance therapy. Daunomycin was also temporarily effective in some cases of neuroblastoma, reticular cell sarcoma and rhabdomyosarcoma. A more extensive evaluation of this drug, on different neoplasias is under way at several hospitals.

The roots of modern oncology: from discovery of new antitumor anthracyclines to their clinical use

In May 1960, the Farmitalia CEO Dr. Bertini and the director of the Istituto Nazionale dei Tumori of Milan Prof. Bucalossi (talent scout and city's Mayor) signed a research agreement for the discovery and development up to clinical trials of new natural antitumor agents. This agreement can be considered as a pioneering and fruitful example of a translational discovery program with relevant transatlantic connections. Owing to an eclectic Streptomyces, found near Castel del Monte (Apulia), and to the skilled and motivated participants of both institutions, a new natural antitumor drug, daunomycin, was ready for clinical trials within 3 years. Patent interference by the Farmitalia French partner was overcome by the good quality of the Italian drug and by the cooperation between Prof. Di Marco, director of the Istituto Ricerche Farmitalia Research Laboratories for Microbiology and Chemotherapy, and Prof. Karnofsky, head of the Sloan-Kettering Cancer Institute of New York, leading to the first transatlantic clinical trials. The search for daunomycin's sister anthracyclines led to the discovery and development of adriamycin, one of the best drugs born in Milan. This was the second act prologue of the history of Italian antitumor discovery and clinical oncology, which started in July 1969 when Prof. Di Marco sent Prof. Bonadonna the first vials of adriamycin (doxorubicin) to be tested in clinical trials. This article reviews the Milan scene in the 1960s, a city admired and noted for the outstanding scientific achievements of its private and public institutions in drugs and industrial product discovery.

Nemorubicin and doxorubicin bind the G-quadruplex sequences of the human telomeres and of the c-MYC promoter element Pu22

BACKGROUND

Intra-molecular G-quadruplex structures are present in the guanine rich regions of human telomeres and were found to be prevalent in gene promoters. More recently, the targeting of c-MYC transcriptional control has been suggested, because the over expression of the c-MYC oncogene is one of the most common aberration found in a wide range of human tumors.

METHODS

The interaction of nemorubicin and doxorubicin with DNA G-quadruplex structures has been studied by NMR, ESI-MS and molecular modelling, in order to obtain further information about the complex and the multiple mechanisms of action of these drugs.

RESULTS AND CONCLUSIONS

Nemorubicin intercalates between A3 and G4 of d(TTAGGGT)4 and form cap-complex at the G6pT7 site. The presence of the adenine in this sequence is important for the stabilization of the complex, as was shown by the interaction with d(TTGGGTT)4 and d(TTTGGGT)4, which form only a 1:1 complex. The interaction of doxorubicin with d(TTAGGGT)4 is similar, but the complex appears less stable. Nemorubicin also binds with high efficiency the c-MYC G-quadruplex sequence Pu22, to form a very well defined complex. Two nemorubicin molecules bind to the 3'-end and to the 5'-end, forming an additional plane of stacking over each external G-tetrad. The wild type c-MYCPu22 sequence forms with nemorubicin the same complex.

GENERAL SIGNIFICANCE

Nemorubicin and doxorubicin, not only intercalate into the duplex DNA, but also result in significant ligands for G-quadruplex DNA segments, stabilizing their structure; this may in part explain the multiple mechanisms of action of their antitumor activity.

Fifty years of chemical research at Farmitalia

This review contains a brief description of the chemistry developed in Farmitalia and, after 1978, Farmitalia-Carlo Erba Research Laboratories, during the second half of the last century. It gives an overview of work that represents a significant part of the chemistry carried out in Italy during this period in the field of medicinal and natural product chemistry. This is particularly true when we consider in addition to the work done intramurally in the said laboratories, the work done by academic scientists in the frame of the various extramural collaborations. Only a fraction of the chemical research actually carried out is reported here as time and space dictated a selection. Subjects typically associated with Farmitalia and which gave rise to important scientific or therapeutic outcomes are given preference in this review.

2,3-Anhydrosugars in glycoside bond synthesis. Application to 2,6-dideoxypyranosides

We describe here the first use of 2,3-anhydrosugars as glycosylating agents for the preparation of 2-deoxypyranosides. In particular, the methodology was used to assemble 2,6-dideoxysugar glycosides. Glycosylation of a panel of alcohols with one of two 6-deoxy-2,3-anhydrosugar thioglycosides (8 and 9) in the presence of a Lewis acid afforded 2,6-dideoxy-2-thiotolyl glycoside products in generally excellent yields with an exclusively syn relationship between the aglycon and the C-3 hydroxyl group. Removal of the 2-thiotolyl group can be achieved upon reaction with tri-n-butyltin hydride and AIBN to give the corresponding 2,6-dideoxy pyranosides. Once developed, the method was applied to the synthesis of oligosaccharide moieties in the natural products apoptolidin and olivomycin A.

Asymmetric synthesis of 1,2-amino alcohols using (S)-indoline chiral auxiliary

Chiral hydrazones 1 reacted with aryl- or alkyl-lithiums at -78 degrees C in a short reaction time, within 10 min, to afford arylated or alkylated chiral hydrazines 3 with extremely high diastereoselectivity (up to >99% de) and high chemical yields. The hydrazines are readily converted to chiral amino alcohols 4.

Adriamycin, 14-hydroxydaunomycin, a new antitumor antibiotic from S. peucetius var. caesius. Reprinted from Biotechnology and Bioengineering, Vol. XI, Issue 6, Pages 1101-1110 (1969)

Streptomyces peucetius var. caesius, obtained from S. peucetius, the daunomycin producing microorganism, by mutagenic treatment, differs from the parent culture by the color of the vegetative and aerial mycelia and by its antibiotic producing ability. S. peucetius var. caesius accumulates adriamycin in submerged and aerated culture on a medium containing glucose, brewer's yeast, and inorganic salts both in shake flasks and in stirred fermenters. Isolation of the product is performed by solvent extraction, chromatography on buffered cellulose columns, and crystallization as the hydrochloride. The new antitumor agent, adriamycin, is the 14-hydroxy derivative of daunomycin.

From the pigments of the actinomycetes to third generation antitumor anthracyclines

After the assessment of the antitumor activity of the anthracycline pigments, the S peucetius group of metabolites was discovered and eventually doxorubicin, a major anticancer agent of established clinical usefulness was developed in the early seventies. A second generation of compounds followed, represented mainly by the better tolerated epirubicin and by the highly potent antileukemic drug, idarubicin. This was the result of a wide program of analog development that provided the basis for further investigations concerning both the study of structure-activity relationships and the synthesis of novel promising derivatives including the 8- and 10-fluoro compounds and the disaccharides. A member of the latter group, namely 7-O-(4'-O-alpha-L-daunosaminyl-2'-deoxy- alpha-L-fucosyl)-4-demethoxyadriamycinone, is undergoing clinical trials as a third generation antitumor anthracycline.

Semiquinone free radical formation by daunorubicin aglycone incorporated into the cellular membranes of intact Chinese hamster ovary cells

The production of semiquinone free radicals has been measured by electron paramagnetic resonance spectroscopy (EPR) in Chinese hamster ovary cells in which 7-hydroxy daunorubicin aglycone had been incorporated. The highly lipophilic daunorubicin aglycone was incorporated into the cellular membrane by swirling a cell suspension over a thin layer of daunorubicin aglycone. Thus, the observed semiquinone free radical was likely formed directly in the lipophilic environment of the cellular membrane. The linewidth of the observed EPR signal suggested that a neutral protonated semiquinone species was formed. In the presence of the cell-impermeant paramagnetic line broadening agent chromium(III) oxalate, no detectable signal was observed. This result indicates that even though the semiquinone is embedded in the membrane, it is still partly accessible to the external chromium(III) oxalate. Analysis of chloroform extracts of the cells after EPR experiments indicated that daunorubicin aglycone was extensively metabolized. The results of a growth inhibition assay carried out on cells into which daunorubicin aglycone had been incorporated showed almost no effect on cell growth. This result indicates that in spite of significant daunorubicin aglycone-induced radical formation taking place directly in the cell membrane, little cell damage results.

Anthracycline and anthraquinone anticancer agents: current status and recent developments

The clinical treatment of neoplastic diseases relies on the complementary procedures of surgery, radiation treatment, immunotherapy and chemotherapy. The latter technique has matured from its earliest applications of mustard alkylating agents in the 1940s to an increasingly rationally based discipline, which is contributing significantly to the management of human malignancies. As the field of chemotherapy matured, several promising natural anticancer agents were identified. However, a more urgent need soon arose from the common experience of clinically limiting toxicities of most anticancer drugs, i.e. the necessity to develop less toxic clinical drug candidates. Thus, the medicinal chemist turned towards analog development involving certain anthraquinones. Hand-in-hand with this considerable synthetic effort, which uncovered several promising clinical leads, biochemical pharmacology, or study of the mechanisms of action of clinical anticancer agents, afforded deeper insight into drug metabolism and mode of action. More recently, therefore, the field of synthetic organic chemistry, which has been complemented by the methods of microbial chemistry, has been faced with new synthetic challenges, occasioned by the identification of hitherto unrecognized cellular targets for anticancer drugs, such as topoisomerases and helicases. The armementarium of the oncologist currently includes about 40-50 clinically useful chemical agents. The paradigm of cytotoxic anticancer agents is doxorubicin, an anthracycline, which is still amongst the most widely prescribed and effective of anticancer agents. The review attempts to summarize the discovery of anthracyclines and the elucidation of their several mechanisms of action and efforts towards improvement of their therapeutic efficacy.

Marked inter-patient variation in adriamycin biotransformation to 7-deoxyaglycones: evidence from metabolites identified in serum

Several factors are known to modulate the clinical pharmacokinetics of adriamycin (ADR). Biotransformation has not been studied in this context because of problems identifying serum metabolites. We have studied patterns of ADR biotransformation in 25 patients with normal liver and kidney function and in most cases receiving ADR for the first time. Three major serum metabolites were identified by HPLC, TLC and mass spectrometry and their pharmacokinetics were followed over a 24-hr period. The relative amount of each metabolite present in a patient was quantitated by calculating its AUC. Adriamycinol was the major metabolite detected in the majority of patients. Adriamycin 7-deoxyaglycone was detected in the serum of 15 patients where it accounted for a small percentage of the total ADR concentration (1-5%). Its apparent half-life was normally less than 30 min. Adriamycinol 7-deoxyaglycone was detected in the serum of only 13 patients where it accounted for a greater percentage of the total ADR concentration (10-20%). Its pharmacokinetics exhibited marked inter-patient variations, with apparent half-lives ranging from 0.1 to 24 hr. There was a correlation between the AUC of ADR and the relative amount of metabolites present in each patient (r = 0.73). Thus, biotransformation may explain, partly, inter-patient variations in ADR pharmacokinetics. In turn, variations in biotransformation are dictated by whether or not ADR is converted to 7-deoxyaglycones.

Anthracycline antitumour agents. A review of physicochemical, analytical and stability properties

A review of physicochemical and analytical properties of anthracycline antitumour agents is presented. The following subjects are discussed: protolytic equilibria, partition and partition coefficients, self-association, adsorptive properties, metal complexation, spectroscopy and chromatography. Furthermore, the stability of anthracyclines in solutions, in pharmaceutical preparations and in biological media is discussed.