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Die Pyrrolo[2,1 ‐ c][1,4]benzodiazepine (PBDs) sind eine Familie sequenzselektiver Wirkstoffe, die an die kleine Furche der DNA binden und eine kovalente Aminalbindung zwischen der C11 ‐ Position und den C2 ‐ NH2 ‐ Gruppen der Guaninbasen bilden. Anthramycin ist das erste Beispiel eines PBD ‐ Monomers und wurde in den 1960er Jahren entdeckt. In den 1990er Jahren wurde das bekannteste PBD ‐ Dimer SJG ‐ 136 entwickelt und hat jetzt bereits die klinischen Studien der Phase II in Patienten mit Leukämie und Eierstockkrebs durchlaufen. Seit kurzem werden aus PBD ‐ Dimeranaloga und spezifisch an Tumorzellen bindenden Antikörpern Antikörper ‐ Wirkstoff ‐ Konjugate (ADCs) hergestellt. Von diesen befinden sich derzeit mehrere in klinischen Studien und viele andere in der präklinischen Entwicklung. Dieser Aufsatz zeigt die Entwicklung der PBDs ausgehend von Anthramycin über die ersten PBD ‐ Dimere bis hin zu PBD ‐ haltigen ADCs und behandelt sowohl die Struktur ‐ Wirkungs ‐ Beziehungen und die Biologie der PBDs als auch die Strategien für ihre Verwendung als Wirkstoffkomponente in ADCs. PBDs in ADCs: Pyrrolobenzodiazepine (PBDs; Beispiel siehe Bild) sind DNA ‐ interaktive Tumortherapeutika, die sequenzselektiv an die Guaninbasen der kleinen Furche der DNA binden. Sie sind stark zytotoxisch und werden als Wirkstoffkomponente in Antikörper ‐ Wirkstoff ‐ Konjugaten (ADCs) verwendet. Dieser Aufsatz beschreibt ihre Entwicklung, ausgehend von der Entdeckung des Naturstoffs Anthramycin bis hin zur Verwendung von PBD ‐ Dimer ‐ Wirkstoffen in ADCs. [ABSTRACT FROM AUTHOR]

The pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are a family of sequence-selective DNA minor-groove binding agents that form a covalent aminal bond between their C11-position and the C2-NH2 groups of guanine bases. The first example of a PBD monomer, the natural product anthramycin, was discovered in the 1960s, and the best known PBD dimer, SJG-136 (also known as SG2000, NSC 694501 or BN2629), was synthesized in the 1990s and has recently completed Phase II clinical trials in patients with leukaemia and ovarian cancer. More recently, PBD dimer analogues are being attached to tumor-targeting antibodies to create antibody-drug conjugates (ADCs), a number of which are now in clinical trials, with many others in pre-clinical development. This Review maps the development from anthramycin to the first PBD dimers, and then to PBD-containing ADCs, and explores both structure-activity relationships (SARs) and the biology of PBDs, and the strategies for their use as payloads for ADCs. [ABSTRACT FROM AUTHOR]

The pyrrolobenzodiazepine (PBD) and duocarmycin families are DNA-interactive agents that covalently bond to guanine (G) and adenine (A) bases, respectively, and that have been joined together to create synthetic dimers capable of cross-linking G-G, A-A, and G-A bases. Three G-A alkylating dimers have been reported in publications to date, with defined DNA-binding sites proposed for two of them. In this study we have used molecular dynamics simulations to elucidate preferred DNA-binding sites for the three published molecular types. For the PBD-CPI dimer UTA-6026 (1), our simulations correctly predicted its favoured binding site (i.e., 50-C(G)AATTA-30) as identified by DNA cleavage studies. However, for the PBD-CI molecule ('Compound 11', 3), we were unable to reconcile the results of our simulations with the reported preferred cross-linking sequence (50-ATTTTCC(G)-30). We found that the molecule is too short to span the five base pairs between the A and G bases as claimed, but should target instead a sequence such as 50-ATTTC(G)-30 with two less base pairs between the reacting G and A residues. Our simulation results for this hybrid dimer are also in accord with the very low interstrand cross-linking and in vitro cytotoxicity activities reported for it. Although a preferred cross-linking sequence was not reported for the third hybrid dimer ('27eS', 2), our simulations predict that it should span two base pairs between covalently reacting G and A bases (e.g., 50-GTAT(A)-30). [ABSTRACT FROM AUTHOR]

DNA binding 4-(1-methyl-1H-pyrrol-3-yl)benzenamine(MPB) building blocks have been developed that span two DNA base pairswith a strong preference for GC-rich DNA. They have been conjugatedto a pyrrolo[2,1-c][1,4]benzodiazepine (PBD) moleculeto produce C8-linked PBD–MPB hybrids that can stabilize GC-richDNA by up to 13-fold compared to AT-rich DNA. Some have subpicomolarIC50values in human tumor cell lines and in primary chroniclymphocytic leukemia cells, while being up to 6 orders less cytotoxicin the non-tumor cell line WI38, suggesting that key DNA sequencesmay be relevant targets in these ultrasensitive cancer cell lines.One conjugate, 7h(KMR-28-39), which has femtomolar activityin the breast cancer cell line MDA-MB-231, has significant dose-dependentantitumor activity in MDA-MB-231 (breast) and MIA PaCa-2 (pancreatic)human tumor xenograft mouse models with insignificant toxicity attherapeutic doses. Preliminary studies suggest that 7hmay sterically inhibit interaction of the transcription factor NF-κBwith its cognate DNA binding sequence. [ABSTRACT FROM AUTHOR]

Antibody-Drug Conjugates (ADCs) consist of antibodies attached to cytotoxic small molecules or biological agents (i.e., payloads) through chemical linkers which may be cleavable or non-cleavable. The development of new ADCs is challenging, particularly the process of attaching the linker-payload construct to the antibody (i.e., the conjugation process). One of the major problems associated with conjugation is high hydrophobicity of the payload which can lead to low yields of the ADC through aggregation and/or lower than desired Drug-Antibody Ratios (DARs). We report here a UPLC-based assay that can be used to study the physicochemical properties of ADC payloads at an early stage of development, and to provide information on whether the hydrophilic-hydrophobic balance is suitable for conjugation or further physicochemical optimization is required. The assay is relatively simple to establish and should be of use to those working in the ADC area., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: IP has share options and PJMJ, KMR and DET have founding stock in Femtogenix Ltd, the company supplying one of the experimental ADC payloads evaluated in this study. IP and PJMJ are fully employed by Femtogenix Ltd, and KMR and DET have consultancies with the company. PJMJ, KMR and DET are named inventors on patents filed and owned by the company., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Antibody-drug conjugates (ADCs) consist of monoclonal antibodies (mAbs) or antibody fragments conjugated to biologically active molecules (usually highly cytotoxic small molecules) through chemical linkers. Although no ADCs containing covalent-binding DNA-interactive payloads have yet been approved (although two containing the DNA-cleaving payload calicheamicin have), of those in clinical trials systemic toxicities are beginning to emerge. This article discusses the observed toxicities in relation to the structures and mechanisms of action of payload type., (Copyright © 2018. Published by Elsevier Ltd.)

DNA footprinting and melting experiments have been used to examine the sequence-specific binding of C8-conjugates of pyrrolobenzodiazepines (PBDs) and benzofused rings including benzothiophene and benzofuran, which are attached using pyrrole- or imidazole-containing linkers. The conjugates modulate the covalent attachment points of the PBDs, so that they bind best to guanines flanked by A/T-rich sequences on either the 5'- or 3'-side. The linker affects the binding, and pyrrole produces larger changes than imidazole. Melting studies with 14-mer oligonucleotide duplexes confirm covalent attachment of the conjugates, which show a different selectivity to anthramycin and reveal that more than one ligand molecule can bind to each duplex., (Copyright © 2017 Elsevier B.V. All rights reserved.)

STAT3 (Signal Transducer and Activator of Transcription factor 3) is constitutively active in a wide range of human tumours. Stattic is one of the first non-peptidic small molecules reported to inhibit formation of the STAT3:STAT3 protein dimer complex. A mass spectrometry method has been developed to investigate the binding of Stattic to the un-phosphorylated STAT3βtc (U-STAT3) protein. Alkylation of four cysteine residues has been observed with possible reaction at a fifth which could account for the mechanism of action., (Copyright © 2013. Published by Elsevier Ltd.)