CC-1065 (NSC-298223), a new antitumor antibiotic. Production, in vitro biological activity, microbiological assays and taxonomy of the producing microorganism

Comprehensive review on the elaboration of payloads derived from natural products for antibody-drug conjugates

Antibody-drug conjugates (ADCs) have arisen as a promising class of biotherapeutics for targeted cancer treatment, combining the specificity of monoclonal antibodies with the cytotoxicity of small-molecule drugs. The choice of an appropriate payload is crucial for the success development of ADCs, as it determines the therapeutic efficacy and safety profile. This review focuses on payloads derived from natural products, including cytotoxic agents, DNA-damaging agents, and immunomodulators. These offer several advantages such as diverse chemical structures, unique mechanism of actions, and potential for improved therapeutic index. Challenges and opportunities associated with their development were highlighted. This review underscores the significance of natural product payloads in the elaboration of ADCs, which serves as a valuable resource for researchers involved in developing and optimizing next-generation ADCs for cancer treatment.

Radiation therapy, tissue radiosensitization, and potential synergism in the era of novel antibody-drug conjugates

Antibody-drug conjugates (ADCs) represent a therapeutic class of agents designed to selectively deliver cytotoxic payloads to cancer cells. With the increasingly positioning of ADCs in the clinical practice, combinations with other treatment modalities, including radiation therapy (RT), will open new opportunities but also challenges. This review evaluates ADC-RT interactions, examining therapeutic synergies and potential caveats. ADC payloads can be radiosensitizing, enhancing cytotoxicity when used in combination with RT. Antigens targeted by ADCs can have various tissue expressions, resulting in possible off-target toxicities by tissue radiosensitization. Notably, the HER-2-directed ADC trastuzumab emtansine has appeared to increase the risk of radionecrosis when used concomitantly with brain RT, as glial cells can express HER2, too. Other possible organ-specific effects are discussed, such as pulmonary and cardiac toxicities. The lack of robust clinical data on the ADC-RT combination raises concerns regarding specific side effects and the ultimate trade-off of toxicity and safety of some combined approaches. Clinical studies are needed to assess ADC-RT combination safety and efficacy.

40 Years of Duocarmycins: A Graphical Structure/Function Review of Their Chemical Evolution, from SAR to Prodrugs and ADCs

Synthetic analogues of the DNA-alkylating cytotoxins of the duocarmycin class have been extensively investigated in the past 40 years, driven by their high potency, their unusual mechanism of bioactivity, and the beautiful modularity of their structure-activity relationship (SAR). This Perspective analyzes how the molecular designs of synthetic duocarmycins have evolved: from (1) early SAR studies, through to modern applications for directed cancer therapy as (2) prodrugs and (3) antibody-drug conjugates in late-stage clinical development. Analyzing 583 primary research articles and patents from 1978 to 2022, we distill out a searchable A0-format "Minard map" poster of ca. 200 key structure/function-tuning steps tracing chemical developments across these three key areas. This structure-based overview showcases the ingenious approaches to tune and target bioactivity, that continue to drive development of the elegant and powerful duocarmycin platform.

Update Breast Cancer 2021 Part 5 – Advanced Breast Cancer

Despite the COVID 19 pandemic and mostly virtual congresses, innovation in the treatment of breast cancer patients continues at an unabated pace. This review summarises the current developments. Initial overall survival data for CDK4/6 inhibitor treatment in combination with an aromatase inhibitor as the first advanced line of therapy in treatment-naive postmenopausal patients have been published. Similarly, a trial comparing trastuzumab-deruxtecan versus trastuzumab-emtansine revealed a clear benefit regarding progression-free survival. Understanding of biomarkers making checkpoint inhibitor therapy particularly effective is increasing, and new compounds such as oral selective estrogen receptor destabilisers (SERDs) are entering clinical development and completing the first phase III trials.

Functional Diversity of HemN-like Proteins

HemN is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the anaerobic oxidative decarboxylation of coproporphyrinogen III to produce protoporphyrinogen IX, a key intermediate in heme biosynthesis. Proteins homologous to HemN (HemN-like proteins) are widespread in both prokaryotes and eukaryotes. Although these proteins are in most cases annotated as anaerobic coproporphyrinogen III oxidases (CPOs) in the public database, many of them are actually not CPOs but have diverse functions such as methyltransferases, cyclopropanases, heme chaperones, to name a few. This Perspective discusses the recent advances in the understanding of HemN-like proteins, and particular focus is placed on the diverse chemistries and functions of this growing protein family.

[Synthetic Studies on Complex Natural Products Based on Development of a Novel Synthetic Method for Heteroaromatic Skeleton]

Among my recent work on the syntheses of complex natural products based on the development of a novel synthetic method for the heteroaromatic skeleton, this article primarily deals with the total syntheses of (+)-CC-1065, isobatzeline A/B, and batzeline A. These syntheses were accomplished via a novel indole synthesis utilizing a ring expansion reaction of benzocyclobutenone oxime sulfonate as the key step. The 1,2-dihydro-3H-pyrrolo[3,2-e]indole segments of (+)-CC-1065 were rapidly constructed via a two-directional double-ring expansion strategy. Highly substituted pyrrolidine-fused common 5-chloro-2-methylthioindoles of isobatzeline A/B and batzeline A were constructed using a ring expansion reaction of benzocyclobutenone oxime sulfonate with NaSMe and a benzyne-mediated cyclization/functionalization reaction.

Biosynthesis of cyclopropane in natural products

Covering: 2012 to 2021Cyclopropane attracts wide interests in the fields of synthetic and pharmaceutical chemistry, and chemical biology because of its unique structural and chemical properties. This structural motif is widespread in natural products, and is usually essential for biological activities. Nature has evolved diverse strategies to access this structural motif, and increasing knowledge of the enzymes forming cyclopropane (i.e., cyclopropanases) has been revealed over the last two decades. Here, the scientific literature from the last two decades relating to cyclopropane biosynthesis is summarized, and the enzymatic cyclopropanations, according to reaction mechanism, which can be grouped into two major pathways according to whether the reaction involves an exogenous C1 unit from S-adenosylmethionine (SAM) or not, is discussed. The reactions can further be classified based on the key intermediates required prior to cyclopropane formation, which can be carbocations, carbanions, or carbon radicals. Besides the general biosynthetic pathways of the cyclopropane-containing natural products, particular emphasis is placed on the mechanism and engineering of the enzymes required for forming this unique structure motif.

Structural evolution of a DNA repair self-resistance mechanism targeting genotoxic secondary metabolites

Microbes produce a broad spectrum of antibiotic natural products, including many DNA-damaging genotoxins. Among the most potent of these are DNA alkylating agents in the spirocyclopropylcyclohexadienone (SCPCHD) family, which includes the duocarmycins, CC-1065, gilvusmycin, and yatakemycin. The yatakemycin biosynthesis cluster in Streptomyces sp. TP-A0356 contains an AlkD-related DNA glycosylase, YtkR2, that serves as a self-resistance mechanism against yatakemycin toxicity. We previously reported that AlkD, which is not present in an SCPCHD producer, provides only limited resistance against yatakemycin. We now show that YtkR2 and C10R5, a previously uncharacterized homolog found in the CC-1065 biosynthetic gene cluster of Streptomyces zelensis, confer far greater resistance against their respective SCPCHD natural products. We identify a structural basis for substrate specificity across gene clusters and show a correlation between in vivo resistance and in vitro enzymatic activity indicating that reduced product affinity-not enhanced substrate recognition-is the evolutionary outcome of selective pressure to provide self-resistance against yatakemycin and CC-1065.

Duocarmycin-based antibody-drug conjugates as an emerging biotherapeutic entity for targeted cancer therapy: Pharmaceutical strategy and clinical progress

Duocarmycins are a class of DNA minor-groove-binding alkylating molecules. For the past decade, various duocarmycin analogues have been used as payloads in the development of antibody-drug conjugates (ADCs). Currently, more than 15 duocarmycin-based ADCs have been studied preclinically, and some of them such as SYD985 have been granted Fast-Track Designation status. Nevertheless, progress in duocarmycin-based ADCs also faces challenges, with setbacks including the termination of BMS-936561/MDX-1203. In this review, we discuss issues associated with the efficacy, pharmacokinetic profile, and toxicological activity of these biotherapeutics. Furthermore, we summarize the latest advances in duocarmycin-based ADCs that have different target specificities and linker chemistries. Evidence from preclinical and clinical studies has indicated that duocarmycin-based ADCs are promising biotherapeutics for oncological application in the future.

Natural Product Based Antibody Drug Conjugates: Clinical Status as of November 9, 2020

As of early November 2020, there are 10 approved antibody drug conjugates (ADCs) plus two others that are not usually listed. In addition, there are 70 ADCs at stages from phase I to phase III and 23 that are at the preclinical stage. The warheads of all of these drugs and drug candidates have their origins in natural product structures. The sources and modifications are discussed in general and then specifically commented on in each case with either the generic name if known and/or the ADC's ID names. Interestingly, almost all warheads listed are from microbial sources though initially a number were thought to have been from plants. The latest NCT numbers from Clintrials.gov of all phase I to phase III candidates are also given. Three unusual ADCs are also discussed, two of which (an antitumor agent and one directed against autoimmune diseases) are not usually listed as ADCs, with the third being an anti-infective.

Diversity of the reaction mechanisms of SAM-dependent enzymes

S-adenosylmethionine (SAM) is ubiquitous in living organisms and is of great significance in metabolism as a cofactor of various enzymes. Methyltransferases (MTases), a major group of SAM-dependent enzymes, catalyze methyl transfer from SAM to C, O, N, and S atoms in small-molecule secondary metabolites and macromolecules, including proteins and nucleic acids. MTases have long been a hot topic in biomedical research because of their crucial role in epigenetic regulation of macromolecules and biosynthesis of natural products with prolific pharmacological moieties. However, another group of SAM-dependent enzymes, sharing similar core domains with MTases, can catalyze nonmethylation reactions and have multiple functions. Herein, we mainly describe the nonmethylation reactions of SAM-dependent enzymes in biosynthesis. First, we compare the structural and mechanistic similarities and distinctions between SAM-dependent MTases and the non-methylating SAM-dependent enzymes. Second, we summarize the reactions catalyzed by these enzymes and explore the mechanisms. Finally, we discuss the structural conservation and catalytical diversity of class I-like non-methylating SAM-dependent enzymes and propose a possibility in enzymes evolution, suggesting future perspectives for enzyme-mediated chemistry and biotechnology, which will help the development of new methods for drug synthesis.

Evaluation of the DNA Alkylation Properties of a Chlorambucil-Conjugated Cyclic Pyrrole-Imidazole Polyamide

Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as anticancer drugs. Here, we conjugated Chb to a cyclic PIP (cPIP), which is known to have a higher binding affinity than the corresponding hPIP, and investigated the DNA alkylation properties of the resulting cPIP-Chb using the optimized capillary electrophoresis method and conventional HPLC product analysis. cPIP-Chb conjugate 3 showed higher alkylation activity at its binding sites than did hPIP-Chb conjugates 1 and 2. Subsequent HPLC analysis revealed that the alkylation site of conjugate 3, which was identified by capillary electrophoresis, was reliable and that conjugate 3 alkylates the N3 position of adenine as do hPIP-Chbs. Moreover, conjugate 3 showed higher cytotoxicity against LNCaP prostate cancer cells than did conjugate 1 and cytotoxicity comparable to that of conjugate 2. These results suggest that cPIP-Chbs could be novel DNA alkylating anticancer drugs.

How can the potential of the duocarmycins be unlocked for cancer therapy?

The duocarmycins belong to a class of agent that has fascinated scientists for over four decades. Their exquisite potency, unique mechanism of action, and efficacy in multidrug-resistant tumour models makes them attractive to medicinal chemists and drug hunters. However, despite great advances in fine-tuning biological activity through structure-activity relationship studies (SARS), no duocarmycin-based therapeutic has reached clinical approval. In this review, we provide an overview of the most promising strategies currently used and include both tumour-targeted prodrug approaches and antibody-directed technologies.

Recent advances in HemN-like radical S-adenosyl-l-methionine enzyme-catalyzed reactions

HemN-like radical S-adenosyl-l-methionine (SAM) enzymes have been recently disclosed to catalyze diverse chemically challenging reactions from primary to secondary metabolic pathways.

Total Synthesis of (+)-CC-1065 Utilizing Ring Expansion Reaction of Benzocyclobutenone Oxime Sulfonate

An indole synthesis via ring expansion of benzocyclobutenone oxime sulfonate was developed. Utility of the indole synthesis was demonstrated by the total synthesis of (+)-CC-1065. The middle and right segments were constructed by a sequential ring expansion of the symmetrical benzo-bis-cyclobutenone. The left segment was also constructed via ring expansion of the methyl-substituted benzocyclobutenone oxime sulfonates. After condensation of these three segments, the dienone cyclopropane structure was formed to complete the total synthesis.

Covalent binders in drug discovery

Covalent modulation of protein function can have multiple utilities including therapeutics, and probes to interrogate biology. While this field is still viewed with scepticism due to the potential for (idiosyncratic) toxicities, significant strides have been made in terms of understanding how to tune electrophilicity to selectively target specific residues. Progress has also been made in harnessing the potential of covalent binders to uncover novel biology and to provide an enhanced utility as payloads for Antibody Drug Conjugates. This perspective covers the tenets and applications of covalent binders.

Synthesis of DNA interactive C3-trans-cinnamide linked β-carboline conjugates as potential cytotoxic and DNA topoisomerase I inhibitors

A series of new C3-trans-cinnamide linked β-carboline conjugates has been synthesized by coupling between various β-carboline amines and substituted cinnamic acids. Evaluation of their anti-proliferative activity against a panel of selected human cancer cell lines such as A549 (lung cancer), MCF-7 (breast cancer), B16 (melanoma), HeLa (cervical cancer) and a normal cell line NIH3T3 (mouse embryonic fibroblast cell line), suggested that the newly designed conjugates are considerably active against all the tested cancer cell lines with IC₅₀ values 13-45 nM. Moreover, the conjugates 8v and 8x were the most active against MCF-7 cells (14.05 nM and 13.84 nM respectively) and also even potent on other cell lines tested. Further, detailed investigations such as cell cycle analysis, apoptosis induction study, topoisomerase I inhibition assay, DNA binding affinity and docking studies revealed that these new conjugates are DNA interactive topoisomerase I inhibitors.

A radical S-adenosyl-L-methionine enzyme and a methyltransferase catalyze cyclopropane formation in natural product biosynthesis

Cyclopropanation of unactivated olefinic bonds via addition of a reactive one-carbon species is well developed in synthetic chemistry, whereas natural cyclopropane biosynthesis employing this strategy is very limited. Here, we identify a two-component cyclopropanase system, composed of a HemN-like radical S-adenosyl-L-methionine (SAM) enzyme C10P and a methyltransferase C10Q, catalyzes chemically challenging cyclopropanation in the antitumor antibiotic CC-1065 biosynthesis. C10P uses its [4Fe-4S] cluster for reductive cleavage of the first SAM to yield a highly reactive 5'-deoxyadenosyl radical, which abstracts a hydrogen from the second SAM to produce a SAM methylene radical that adds to an sp²-hybridized carbon of substrate to form a SAM-substrate adduct. C10Q converts this adduct to CC-1065 via an intramolecular S_N2 cyclization mechanism with elimination of S-adenosylhomocysteine. This cyclopropanation strategy not only expands the enzymatic reactions catalyzed by the radical SAM enzymes and methyltransferases, but also sheds light on previously unnoticed aspects of the versatile SAM-based biochemistry.

Success stories of natural product-based hybrid molecules for multi-factorial diseases

Complex diseases comprises of highly complicated etiology resulting in limited applicability of conventional targeted therapies. Consequently, conventional medicinal compounds suffer major failure when used for such disease conditions. Additionally, development of multidrug resistance (MDR), adverse drug reactions and clinical specificity of single targeted drug therapy has increased thrust for novel drug therapy. In this rapidly evolving era, natural product-based discovery of hybrid molecules or multi-targeted drug therapies have shown promising results and are trending now a days. Historically, nature has blessed human with different sources viz. plant, animal, microbial, marine and ethnopharmaceutical sources which has given a wide variety of medicinally active compounds. These compounds from natural origin are always choice of interest of medicinal chemists because of their minimum side effects. Hybrid molecules synthesized by fusing or conjugating different active molecules obtained from these sources are reported to synergistically block different pathways which contribute in the pathogenesis of complex diseases. This review strives to encompass all natural product-derived hybrid molecules which act as multi-targeting agents striking various targets involved in different pathways of complex diseased conditions reported in literature.

Toxicity and repair of DNA adducts produced by the natural product yatakemycin

Yatakemycin (YTM) is an extraordinarily toxic DNA alkylating agent with potent antimicrobial and antitumor properties and the most recent addition to the CC-1065 and duocarmycin family of natural products. While bulky DNA lesions the size of those produced by YTM are normally removed from the genome by the nucleotide excision repair (NER) pathway, YTM adducts are also a substrate for the bacterial DNA glycosylases AlkD and YtkR2, unexpectedly implicating base excision repair (BER) in their elimination. The reason for the extreme toxicity of these lesions and the molecular basis for how they are eliminated by BER have been unclear. Here, we describe the structural and biochemical properties of YTM adducts responsible for their toxicity, and define the mechanism by which they are excised by AlkD. These findings delineate an alternative strategy for repair of bulky DNA damage and establish the cellular utility of this pathway relative to that of NER.

Unified Biosynthetic Origin of the Benzodipyrrole Subunits in CC-1065

CC-1065 is the first characterized member of a family of naturally occurring antibiotics including yatakemycin and duocarmycins with exceptionally potent antitumor activity. CC-1065 contains three benzodipyrroles (1a-, 1b-, and 1c-) of which the 1a-subunit is remarkable by being composed of a cyclopropane ring, and the mechanism for the biological formation of benzodipyrrole rings remains elusive. Previously, biosynthetic studies of CC-1065 were limited to radioactively labeled precursor feeding experiments, which showed that tyrosine (Tyr) and serine (Ser) were incorporated into the two benzodipyrrole (1b- and 1c-) subunits via the same mode but that this was different from the key cyclopropabenzodipyrrole (1a-) subunit with N1-C2-C3 derived from Ser. Herein, the biosynthetic gene cluster of CC-1065 has been cloned, analyzed, and characterized by a series of gene inactivations. Significantly, a key intermediate bearing a C7-OH group derived from a Δc10C mutant exhibited improved cytotoxicity. Moreover, this data inspired us to suspect that the 1a-subunit might employ the same precursor incorporation mode as the 1b- and 1c-subunits. Subsequently, ¹³C-labeled Tyr feeding experiments confirmed that the N1-C2-C3 is originated from Tyr via DOPA as an intermediate. Collectively, a biosynthetic pathway of benzodipyrrole is proposed featuring a revised and unified precursor incorporation mode, which implicates an oxidative cyclization strategy for the assembly of benzodipyrrole. This work sets the stage for further study of enzymatic mechanisms and combinatorial biosynthesis for new DNA alkylating analogues.

Solid-Phase Synthesis of Duocarmycin Analogues and the Effect of C-Terminal Substitution on Biological Activity

The duocarmycins are potent antitumor agents with potential for use in the development of antibody-drug conjugates (ADCs) as well as being clinical candidates in their own right. In this article, we describe the synthesis of a duocarmycin monomer (DSA) that is suitably protected for utilization in solid-phase synthesis. The synthesis was performed on a large scale, and the resulting racemic protected Fmoc-DSA subunit was separated by supercritical fluid chromatography (SFC) into the single enantiomers; its application to solid-phase synthesis methodology gave a series of monomeric and extended duocarmycin analogues with amino acid substituents. The DNA sequence selectivity was similar to that in previous reports for both the monomeric and extended compounds. Substitution at the C-terminus of duocarmycin caused a decrease in antiproliferative activity for all of the compounds studied. An extended compound containing an alanine at the C-terminus was converted to the primary amide or to an extended structure containing a terminal tertiary amine, but this had no beneficial effects on biological activity.

Rational approaches, design strategies, structure activity relationship and mechanistic insights for anticancer hybrids

A Hybrid drug which comprises the incorporation of two drug pharmacophores in one single molecule are basically designed to interact with multiple targets or to amplify its effect through action on another bio target as one single molecule or to counterbalance the known side effects associated with the other hybrid part(.) The present review article offers a detailed account of the design strategies employed for the synthesis of anticancer agents via molecular hybridization techniques. Over the years, the researchers have employed this technique to discover some promising chemical architectures displaying significant anticancer profiles. Molecular hybridization as a tool has been particularly utilized for targeting tubulin protein as exemplified through the number of research papers. The microtubule inhibitors such as taxol, colchicine, chalcones, combretasatin, phenstatins and vinca alkaloids have been utilized as one of the functionality of the hybrids and promising results have been obtained in most of the cases with some of the tubulin based hybrids exhibiting anticancer activity at nanomolar level. Linkage with steroids as biological carrier vector for anticancer drugs and the inclusion of pyrrolo [2,1-c] [1,4]benzodiazepines (PBDs), a family of DNA interactive antitumor antibiotics derived from Streptomyces species in hybrid structure based drug design has also emerged as a potential strategy. Various heteroaryl based hybrids in particular isatin and coumarins have also been designed and reported to posses' remarkable inhibitory potential. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the hybrids.

Antibody-drug conjugates: an emerging concept in cancer therapy

Traditional cancer chemotherapy is often accompanied by systemic toxicity to the patient. Monoclonal antibodies against antigens on cancer cells offer an alternative tumor-selective treatment approach. However, most monoclonal antibodies are not sufficiently potent to be therapeutically active on their own. Antibody-drug conjugates (ADCs) use antibodies to deliver a potent cytotoxic compound selectively to tumor cells, thus improving the therapeutic index of chemotherapeutic agents. The recent approval of two ADCs, brentuximab vedotin and ado-trastuzumab emtansine, for cancer treatment has spurred tremendous research interest in this field. This Review touches upon the early efforts in the field, and describes how the lessons learned from the first-generation ADCs have led to improvements in every aspect of this technology, i.e., the antibody, the cytotoxic compound, and the linker connecting them, leading to the current successes. The design of ADCs currently in clinical development, and results from mechanistic studies and preclinical and clinical evaluation are discussed. Emerging technologies that seek to further advance this exciting area of research are also discussed.

Minor groove binders as anti-infective agents

Minor groove binders are small molecules that form strong complexes with the minor groove of DNA. There are several structural types of which distamycin and netropsin analogues, oligoamides built from heterocyclic and aromatic amino acids, and bis-amidines separated by aromatic and heterocyclic rings are of particular pharmaceutical interest. These molecules have helical topology that approximately matches the curvature of DNA in the minor groove. Depending upon the precise structure of the minor groove binder, selectivity can be obtained with respect to the DNA base sequence to which the compound binds. Minor groove binders have found substantial applications in anti-cancer therapy but their significance in anti-infective therapy has also been significant and is growing. For example, compounds of the bis-amidine class have been notable contributors to antiparasitic therapy for many years with examples such as berenil and pentamidine being well-known. A recent growth area has been inreased sophistication in the oligoamide class. High sequence selectivity is now possible and compounds with distinct antibacterial, antifungal, antiviral, and antiparasitic activity have all been identified. Importantly, the structures of the most active compounds attacking the various infective organisms differ significantly but not necessarily predictively. This poses interesting questions of mechanism of action with many different targets involved in DNA processing being candidates. Access of compounds to specific cell types also plays a role and in some cases, can be decisive. Prospects for a range of selective therapeutic agents from this class of compounds are higher now than for some considerable time.

Synthesis, biological evaluation, and live cell imaging of novel fluorescent duocarmycin analogs

For a better understanding of the mode of action of duocarmycin and its analogs, the novel fluorescent duocarmycin derivatives 13-15 and 17b-19b were synthesized, and their bioactivity as well as their cellular uptake investigated using confocal laser scanning microscopy (CLSM) in live-cell imaging experiments.

From multiply active natural product to candidate drug? Antibacterial (and other) minor groove binders for DNA

Natural products that bind to DNA in the minor groove are valuable templates for drug design. Examples include distamycin, netropsin, duocarmycin and anthramycin. Anticancer and anti-infective drugs feature strongly amongst their derivatives. The structures and activities of chemotypes with various therapeutic actions are discussed in the context of the broader field of therapeutically active minor groove binders. The evolution of a series of exceptionally potent and nontoxic antibacterial compounds is discussed using the general design principle of introducing additional hydrophobicity into the distamycin template to increase the strength of binding to DNA. As well as potent antibacterial compounds, antifungal and antiparasitic compounds with exceptional cellular activity against trypanosomes have been identified. Possible mechanisms of action including gene regulation and topoisomerase inhibition are discussed with the need in mind to understand selective toxicity in the series to support future drug discovery.

Mutation spectra induced by adozelesin in the supF gene of human XP-A fibroblasts

Adozelesin is a synthetic analog of the antitumor antibiotic, CC-1065, which alkylates N3 of adenine in the minor DNA groove in a sequence-specific manner. Here we tested the mutation spectra induced by adozelesin in the supF gene of human XP-A fibroblasts using a shuttle vector assay. Adozelesin primarily induces mutations via an A --> T transversion and a single base insertion. The A --> T transversion (43/59) was observed at the adenine alkylation site in the 5'-ATTTA* sequence (A* is the site of alkylation). The single base insertion (5/59) was observed at the 3'-side of the covalently modified adenine in the 5'-CTAAA* sequence. The results of this study suggest that the DNA alkylating sequence of adozelesin influences the type of DNA mutation.

DNA minor groove binders: back in the groove

With recent approval of the minor groove binding agent trabectidin in Europe for the treatment of patients with soft tissue sarcomas, there has been renewed interest in minor groove binders. Though previously considered to be without clinical value due to their initial significant toxicities, new minor groove binders are emerging which are challenging that perception. Toxicities in the most recently completed and ongoing trials have been easily manageable. These agents have demonstrable anti-tumor activity against a wide variety of tumor types including leukemias, sarcomas, melanomas, breast and ovarian cancers. Applying these agents according to a particular tumor's context of vulnerability might reveal previously unconsidered applications for this diverse class of agents. This review provides a look at how minor groove binding agents have progressed from the lab through the clinic with particular emphasis on identifying the contexts of vulnerabilities of patient tumors which increase the effectiveness of these drugs.