Engineering of a Biologically Active Glycosylated Glucagon-Like Peptide-1 Analogue.

Glucagon-like peptide receptor (GLP-1R) agonists (e.g., semaglutide, liraglutide, etc.) are efficient treatment options for people with type 2 diabetes and obesity. The manufacturing method to produce semaglutide, a blockbuster GLP-1 drug on the market, involves multistep synthesis. The large peptide has a hydrophobic fatty acid side chain that makes it sparingly soluble, and its handling, purification, and large-scale production difficult. The growing demand for semaglutide that the manufacturer is not capable of addressing immediately triggered a worldwide shortage. Thus, we have developed a potential alternative analogue to semaglutide by replacing the hydrophobic fatty acid with a hydrophilic human complex-type biantennary oligosaccharide. Our novel glycoGLP-1 analogue was isolated in an ∼10-fold higher yield compared with semaglutide. Importantly, our glycoGLP-1 analogue possessed a similar GLP-1R activation potency to semaglutide and was biologically active in vivo in reducing glucose levels to a similar degree as semaglutide.

Process Mass Intensity (PMI): A Holistic Analysis of Current Peptide Manufacturing Processes Informs Sustainability in Peptide Synthesis.

Small molecule therapeutics represent the majority of the FDA-approved drugs. Yet, many attractive targets are poorly tractable by small molecules, generating a need for new therapeutic modalities. Due to their biocompatibility profile and structural versatility, peptide-based therapeutics are a possible solution. Additionally, in the past two decades, advances in peptide design, delivery, formulation, and devices have occurred, making therapeutic peptides an attractive modality. However, peptide manufacturing is often limited to solid-phase peptide synthesis (SPPS), liquid phase peptide synthesis (LPPS), and to a lesser extent hybrid SPPS/LPPS, with SPPS emerging as a predominant platform technology for peptide synthesis. SPPS involves the use of excess solvents and reagents which negatively impact the environment, thus highlighting the need for newer technologies to reduce the environmental footprint. Herein, fourteen American Chemical Society Green Chemistry Institute Pharmaceutical Roundtable (ACS GCIPR) member companies with peptide-based therapeutics in their portfolio have compiled Process Mass Intensity (PMI) metrics to help inform the sustainability efforts in peptide synthesis. This includes PMI assessment on 40 synthetic peptide processes at various development stages in pharma, classified according to the development phase. This is the most comprehensive assessment of synthetic peptide environmental metrics to date. The synthetic peptide manufacturing process was divided into stages (synthesis, purification, isolation) to determine their respective PMI. On average, solid-phase peptide synthesis (SPPS) (PMI ≈ 13,000) does not compare favorably with other modalities such as small molecules (PMI median 168-308) and biopharmaceuticals (PMI ≈ 8300). Thus, the high PMI for peptide synthesis warrants more environmentally friendly processes in peptide manufacturing.

Glycosylation Improves the Proteolytic Stability of Exenatide.

Exenatide was the first marketed GLP-1 receptor agonist for the treatment of type 2 diabetes. Modification to the chemical structure or the formulation has the potential to increase the stability of exenatide. We introduced human complex-type sialyloligosaccharide to exenatide at the native Asn28 position. The synthesis was achieved using both solid phase peptide synthesis (SPPS) and Omniligase-1-mediated chemoenzymatic ligation. The results demonstrate that glycosylation increases the proteolytic stability of exenatide while retaining its full biological activity.

Biologic Evaluation of a Heterodimeric HER2-Albumin Targeted Affibody Molecule Produced by Chemo-Enzymatic Peptide Synthesis.

Targeted molecular radiation therapy is a promising emerging treatment modality in oncology, and peptide synthesis may shorten the time to reach the clinical stage. In this study, we have explored Chemo-Enzymatic Peptide Synthesis, or CEPS, as a new means of producing a therapeutic HER2 targeted Affibody® molecule, comprising a C-terminal albumin binding domain (ABD) for half-life extension and a total length of 108 amino acids. In addition, a DOTA moiety could be incorporated at N-terminus directly during the synthesis step and subsequently utilized for site-specific radiolabeling with the therapeutic radionuclide 177Lu. Retained thermodynamic stability as well as retained binding to both HER2 and albumin was verified. Furthermore, HER2 binding specificity of the radiolabeled Affibody molecule was confirmed by an in vitro saturation assay showing a significantly higher cell-bound activity of SKOV-3 (high HER2 expression) compared with BxPC3 (low HER2 expression), both in the presence and absence of HSA. In vivo evaluation in mice bearing HER2 expressing xenografts also showed specific tumor targeting as well as extended time in circulation and reduced kidney uptake compared with a HER2 targeted Affibody molecule without the ABD moiety. To conclude, we have demonstrated that CEPS can be used for production of Affibody-fusion molecules with retained in vitro and in vivo functionality.

From Farm to Pharma: An Overview of Industrial Heparin Manufacturing Methods.

The purification of heparin from offal is an old industrial process for which commercial recipes date back to 1922. Although chemical, chemoenzymatic, and biotechnological alternatives for this production method have been published in the academic literature, animal-tissue is still the sole source for commercial heparin production in industry. Heparin purification methods are closely guarded industrial secrets which are not available to the general (scientific) public. However by reviewing the academic and patent literature, we aim to provide a comprehensive overview of the general methods used in industry for the extraction of heparin from animal tissue.

Galacturonic acid lactones in the synthesis of all trisaccharide repeating units of the zwitterionic polysaccharide Sp1.

A modular approach toward the synthesis of all possible trimer repeating units of the type 1 capsular polysaccharide of Streptococcus pneumonia, Sp1, is described. This zwitterionic polysaccharide is built up from trisaccharide repeats, which in turn are composed of two galacturonic acid monomers and a 2,4,6-trideoxy-4-amino-2-acetamido-D-galactose moiety. All monomeric constituents are linked through cis-glycosidic bonds. To overcome the difficulty associated with the efficient stereoselective introduction of the α-galacturonic acid bonds, we have employed galacturonic acid-[3,6]-lactone building blocks. Not only did these building blocks perform well when used as donor galactosides, they were also shown to be reactive acceptor glycosides when equipped with a free hydroxyl function. All three frame-shifted trimer repeats were constructed via highly stereoselective glycosylation reactions, with one exception. The epimeric mixture of trisaccharides, formed in the nonselective glycosylation event, could be readily separated after global deprotection using high performance anion exchange chromatography (HPEAC).

The impact of oxacarbenium ion conformers on the stereochemical outcome of glycosylations.

The search for stereoselective glycosylation reactions has occupied synthetic carbohydrate chemists for decades. Traditionally, most attention has been focused on controlling the S(N)2-like substitution of anomeric leaving groups as highlighted by Lemieux's in situ anomerization protocol and by the discovery of anomeric triflates as reactive intermediates in the stereoselective formation of beta-mannosides. Recently, it has become clear that also S(N)1-like reaction pathways can lead to highly selective glycosylation reactions. This review describes some recent examples of stereoselective glycosylations in which oxacarbenium ions are believed to be at the basis of the selectivity. Special attention is paid to the stereodirecting effect of substituents on a pyranosyl ring with an emphasis on the role of the C-5 carboxylate ester in the condensations of mannuronate ester donors.

The stereodirecting effect of the glycosyl C5-carboxylate ester: stereoselective synthesis of beta-mannuronic acid alginates.

Glycosylations of mannuronate ester donors proceed highly selectively to produce the 1,2-cis-linked products. We here forward a mechanistic rationale for this counterintuitive selectivity, based on the remote stereodirecting effect of the C5-carboxylate ester, which has been demonstrated using pyranosyl uronate ester devoid of ring substituents other than the C5- carboxylate ester. It is postulated that the C5-carboxylate ester prefers to occupy an axial position in the oxacarbenium intermediate, thereby favoring the formation of the (3)H4 half-chair over the (4)H3 conformer. Nucleophilic attack on the (3)H4 half-chair intermediate occurs in a beta-fashion, providing the 1,2-cis-mannuronates with excellent stereoselectivity. The potential of the mannuronate ester donors in the formation of the beta-mannosidic linkage has been capitalized upon in the construction of a mannuronic acid alginate pentamer using a convergent orthogonal glycosylation strategy.

Stereoselective synthesis of L-guluronic acid alginates.

The glycosylation properties of gulopyranosides have been mapped out, and it is shown that gulose has an intrinsic preference for the formation of 1,2-cis-glycosidic bonds. It is postulated that this glycosylation behaviour originates from nucleophilic attack at the oxacarbenium ion, which adopts the most favourable 3H4 conformation. Building on the stereoselectivity of gulose, a guluronic acid alginate trisaccharide was assembled for the first time by using gulopyranosyl building blocks.

Synthesis of hyaluronic acid oligomers using Ph2SO/Tf2O-mediated glycosylations.

The synthesis of hyaluronic acid (HA) oligomers using a stepwise glycosylation strategy is described. This method employs protected 1-hydroxyuronic acid and 1-phenylthio glucosamine donors, both of which are activated with the Ph2SO/Tf2O activator system.

The use of cyclic bifunctional protecting groups in oligosaccharide synthesis--an overview.

A historical overview is presented on stereo-directing effects of cis- and trans-fused diol protective groups used on both donor and acceptor glycosides. Attention is focused on the use of cyclic carbonates and carbamates, diacetals and acetals and finally the special case of 1,2-O-orthoesters and 1,2-O-cyanoalkylidene functionalised residues.

Stereocontrolled synthesis of beta-D-mannuronic acid esters: synthesis of an alginate trisaccharide.

A facile synthesis route toward beta-linked mannuronic acid oligomers using the corresponding 1-thiomannuronic acid esters in combination with the Ph2SO/Tf2O or NIS/TMSOTf reagent combinations is presented. The presence of the remotely attached carboxylic ester sufficiently influences the electronic environment to allow good to excellent beta-selectivities.

NIS/TFA: a general method for hydrolyzing thioglycosides.

A variety of thioglycosides are chemoselectively hydrolyzed to the corresponding 1-hydroxy glycosides using equimolar amounts of NIS/TFA as promoter systems.

Thioglycosides in sequential glycosylation strategies.

This tutorial review surveys the use of thioglycosides in the development of sequential glycosylation methodologies, with a focus on chemoselective, orthogonal and iterative glycosylation strategies reported since the beginning of this century. Both fundamental aspects of glycosidic bond formation and ingenious state-of-the-art methodologies are presented.

Preparation of 1-thio uronic acid lactones and their use in oligosaccharide synthesis.

The chemo- and regioselective TEMPO/BAIB-mediated oxidation of 2,6- and 3,6-dihydroxy 1-thio glycopyranosides to the corresponding 1-thio uronic acid lactones is described. These locked 1-thio glycuronides can directly be used as donors in glycosidation reactions using the Ph(2)SO/Tf(2)O reagent system. Alternatively, selective opening of the lactone bridge liberates a hydroxyl function for ensuing glycosylations.

Thioglycuronides: synthesis and application in the assembly of acidic oligosaccharides.

[reaction: see text] Partially protected thioglycuronic acids are prepared efficiently by chemo- and regioselective oxidation of the corresponding thioglycosides using the TEMPO/BAIB reagent combination. After esterification, the thioglycuronic acids proved to be useful as both donor and acceptor in sulfonium-mediated condensations toward acidic di- and trisaccharides.

A novel strategy towards the synthesis of orthogonally functionalised 4-aminoglycosides.

A tethered nucleophilic substitution strategy for the stereoselective introduction of axially oriented amino functions on suitably protected gluco- and mannopyranosides is presented. The obtained oxazine is a versatile building block, which after some manipulation, could be used in the construction of highly functionalised oligosaccharides.

Sequential one-pot glycosylations using 1-hydroxyl and 1-thiodonors.

[reaction: see text] A novel sequential glycosylation procedure is described that combines the use of 1-hydroxyl and thiodonors. The Ph(2)SO/Tf(2)O-mediated dehydrative condensation of 1-hydroxyl donors with thioglycosides affords in good yield the thiodisaccharides, which in turn can be activated by the same activator system to furnish trisaccharides. The alpha-Gal epitope and a hyaluronan trisaccharide were efficiently assembled in a one-pot procedure.