Characterization of a 21 amino acid peptide sequence of the laminin G2 domain that is involved in HNK-1 carbohydrate binding and cell adhesion

The N-linked HNK-1 carbohydrate expressed by several recognition molecules mediates the adhesion of early postnatal cerebellar neurons to the G2 domain of the terminal globular domain of the laminin α1 chain (H.Hall et al., submitted). To define this binding site more precisely, G2-derived synthetic peptides were used for binding and competition studies. Peptide 5-G2, comprising the amino acid residues 3431-3451 of G2, inhibited the interaction between the HNK-1-carrying glycolipid and laminin in a concentrationdependent and saturable manner. Peptides which overlap only partially with this sequence interfered less. Peptides comprising other amino acid sequences from G2, and peptides derived from G1 and G3 or a scrambled version of peptide 5-G2, did not show significant effects. Direct binding of peptide 5-G2 to the HNK-1 glycolipid was also demonstrated. Furthermore, peptide 5-G2 interfered in a concentration-dependent and saturable manner with the adhesion of early postnatal cerebellar neurons to laminin. These observations indicate that amino acid residues 3431-3451 of the laimnin G2 domain are involved in HNK-1 carbohydratemediated cell adhesio

Modifying peptides to enhance permeability

Recently, peptides have been validated to address intracellular targets and/or to be orally bioavailable. This review describes some of these scaffolds, offers insight in new cyclization methodologies thought to be beneficial to enhance permeability and highlights modification on peptides thought to improve oral bioavailability. In this context, side chains and back-bone derivatization beneficial to encourage cellular uptake are presented. In addition, new methodologies supporting the assessment of permeability are discussed

Peptide Therapeutics

Contributions highlighted in this Symposium-in-Print provide a snapshot of topics relevant for the various aspects of peptide therapeutics, and by no means, this assembly of manuscripts can achieve complete coverage of the field. Nevertheless, this collection clearly indicates the various opportunities for peptides in drug discovery. Similarly, this is exemplified in the first contribution of M. Dunn and J. Lau regarding the trends for the therapeutic peptide landscape. The market for peptide therapeutics experiences a strong and steady growth across a wide range of disease areas. Thus, companies investing in this area are supposed to profit, if indications and projects are chosen wisely. In the first instance, the sequence of articles follows more or less the drug discovery track. In most cases, projects start with more theoretical considerations. Artificial intelligence and in-silico design, in particular to permit structure and property prediction, are becoming more and more important during the early drug discovery process and even up to the analyses of clinical results. The contribution on machine-learning is regarded as a showcase in this context. As a next step, dependent on the project, hits may be generated from natural products (animals, humans, plants etc), synthetic libraries, and/or by display technologies. In particular, the latter two topics have not really been covered separately, however excellent reviews are available.1, 2 Optimization of hits is often required to manipulate the properties, e.g. permeability and stability. For this reason, an overview of the peptide chemical toolbox indicates the various options. Cyclic peptides and modifications thereof to achieve membrane penetration have received special attention, which bridge the gap to classical medicinal chemistry. In addition, particular sequence motifs and scaffolds able to be taken up into cells, so called cell penetrating peptides are of interest. By contrast to most of the publications in this area, the corresponding summary by R. Brock provides a realistic picture what can be expected. Furthermore, targeting cells, organs, microbes (e.g. with Teixobactin), or tumors represents another route to innovative medicines based on peptides. The combination of medical imaging with immediate next steps for therapy represents another interesting approach for peptides. Following a description on modifications with respect to insulin-like peptides, articles exemplifying the use for application as vaccines in the context of cancer immunotherapy, as antibiotics, to treat CNS-diseases, to overcome GI-disorders, and for the treatment of diabetes and obesity clearly show the impact of peptides across disease areas. The final series of mini-reviews nicely complements this collection by offering insights into options for half-life extension, considerations regarding formulation and adaptations required for manufacturing the latest generation of peptide APIs. For more chemical options regarding half-life extension, the recent review by K. Jensen is recommended.3 I would like to express my gratitude to the authors regarding their valuable contributions, which helped to achieve an excellent coverage of the field of Peptide Therapeutics. In addition, I am grateful to Prof. Herbert Waldmann, who provided me with the opportunity to serve as a Guest Editor, and Birgit Apprecht for her expert help to assemble this SiP issue. References 1 B. P. Gray, K. Brown, Combinatorial peptide libraries: mining for cell-binding peptides, Chem. Rev. 114 (2014) 1020-1081 2 N. K. Bashiruddin, H. Suga, Construction and screening of vast libraries of natural product-like macrocyclic peptides using in vitro display technologies, Curr. Opin. Chem. Biol. 24 (2015) 131-138 3 S. B. van Witteloostuijn, S. L. Pedersen, K. J. Jensen, Half-Life Extension of Biopharmaceuticals using Chemical Methods: Alternatives to PEGylation, ChemMedChem 11 (2016) 2474-249

Important considerations related to permeability of peptides

This review on intracellular delivery and oral bioavailability of peptides reflects a number of principal investigations at Novartis. Our studies were aiming at either to understand features enabling peptides to interfere with intracellular protein-protein interactions, or to achieve a more patient-friendly delivery by the oral route. In the light of these objectives, we have also spent some effort on assay development to come up with alternative methods for monitoring cellular peptide uptake. This summary of our insights is thought to help in the assessment and development of peptide therapeutics requiring membrane transitio

Towards intracellular delivery of peptides

In view of our more comprehensive understanding with respect to intracellular pathways and their regulation, a vast number of interesting drug targets appear to be in a space that can neither be addressed by small molecules nor by biologics. Especially, interference with intracellular protein-protein interactions, if successful, seems to offer considerable opportunities to expand the application of peptides as therapeutics, e.g. in particular in the field of oncology. Thus, this review focuses on requirements for the development of peptide therapeutics aiming at intracellular targets. In addition, an outlook for developments in this field based on recent examples for peptides active in cellular assays, highlighting key requirement to assess permeability, is provided

Discovery and Development of therapeutic Peptides

This mini-review summarizes the content of lectures held during the “Peptide Therapeutics Forum” in the framework of MipTec 2013. The first session was dedicated to various technologies to support hit finding of peptide therapeutics. In the second part the development of clinical and commercial peptide candidates was introduced, and in addition, an overview in the field of formulations relevant for peptides was provided

Future perspectives of venoms for drug discovery

Venoms have been regarded as an interesting source for screening difficult-to-address pharmaceutical targets like ion channels, transmembrane or circulating proteins for quite some time. Moreover, recent developments open up new opportunities to better exploit well-structured toxins - so called “mini-proteins” that we also like to refer to as “picologics” - in a more general way for lead discovery and drug development. In particular, progress in throughput and the first results from the next generation of genome/transcriptome analyses and systems biology investigations widen the scope of an integrated understanding of global transcriptional activity in venom glands. As a result, natural products from venoms are thought to represent a sustainable source of molecules for addressing a wider range of targets, and thus enable a more systematic approach to the identification of new peptide therapeutic candidates

Evaluating Cellular Uptake of Drugs with Fluorescent Sensor Proteins

Here we introduce a qualitative approach to evaluate cellular uptake of inhibitors with spatiotemporal resolution in living cells. The approach is based on con-verting the protein target of a given class of inhibitors into a fluorescent biosensor. By measuring the affinity and kinetics of binding of different inhibitors to their cognate biosensor in live cells and comparing these values to those measured in vitro, the cellular uptake and concentrations of the inhibitors can be ranked. The approach is label-free and does not require the measurement of a biological read-out of the inhibition. We demonstrate the feasibility of the approach by evaluating cellular uptake of two different classes of inhibitors into the cytosol of living cells: inhibitors of the enzyme human carbonic anhydrase II and inhibitors of the protein-protein interaction between p53 and HDM2

Late-stage Functionalization of Peptides and Cyclopeptides using Organozinc reagents

We have reported a new late-stage functionalization of small peptides and cyclopeptides using readily prepared iodotyrosine or iodophenylalanine containing peptides and performing Negishi cross-couplings with aryl-, heteroaryl- and alkyl-zinc pivalates or halides. In-silico and in-vitro determinations of membrane permeability data of the modified cyclopeptides showed that in most cases, the solubility was improved while the cell-membrane permeability was maintained by the introduction of polar pyridyl units