Fast Solution-Phase and Liquid-Phase Peptide Syntheses (SolPSS and LPPS) Mediated by Biomimetic Cyclic Propylphosphonic Anhydride (T3P®).

The growing applications of peptide-based therapeutics require the development of efficient protocols from the perspective of an industrial scale-up. T3P® (cyclic propylphosphonic anhydride) promotes amidation in the solution-phase through a biomimetic approach, similar to the activation of carboxylic moiety catalyzed by ATP-grasp enzymes in metabolic pathways. The T3P® induced coupling reaction was applied in this study to the solution-phase peptide synthesis (SolPPS). Peptide bond formation occurred in a few minutes with high efficiency and no epimerization, generating water-soluble by-products, both using N-Boc or N-Fmoc amino acids. The optimized protocol, which was successfully applied to the iterative synthesis of a pentapeptide, also allowed for a decrease in the solvent volume, thus improving process sustainability. The protocol was finally extended to the liquid-phase peptide synthesis (LPPS), where the isolation of the peptide was performed using precipitation, thus also showing the suitability of this coupling reagent to this emerging technique.

Carbodiimide-Mediated Beckmann Rearrangement of Oxyma-B as a Side Reaction in Peptide Synthesis.

The suppression of side reactions is one of the most important objectives in peptide synthesis, where highly reactive compounds are involved. Recently, the violuric acid derivative Oxyma-B was introduced into peptide synthesis protocols as a promising additive to efficiently control the optical purity of the amino acids prone to racemization. However, we discovered a side reaction involving the Beckmann rearrangement of Oxyma-B during the coupling reaction, which compromises the yield and purity of the target peptides. Here, we present the investigation of the mechanism of this rearrangement and the optimization of the coupling reaction conditions to control it. These results can be taken into account for the design of novel efficient oxime-based coupling reagents.

Application of Af4-Multidetection to Liraglutide in Its Formulation: Preserving and Representing Native Aggregation.

Aggregation is among the most critical parameters affecting the pharmacological and safety profile of peptide Active Pharmaceutical Ingredients (APIs). For this reason, it is of utmost importance to define the exact aggregation state of peptide drugs, particularly when the API is marketed as a ready-to-use solution. Consequently, appropriate non-destructive techniques able to replicate the peptide environment must be employed. In our work, we exploited Asymmetrical Flow Field-Flow Fractionation (AF4), connected to UV, dRI, fluorescence, and MALS detectors, to fully characterize the aggregation state of Liraglutide, a peptide API used for the treatment of diabetes type 2 and chronic obesity. In previous studies, Liraglutide was hypothesized to assemble into hexa-octamers in phosphate buffer, but no information on its behavior in the formulation medium was provided up to now. The method used allowed researchers to work using formulation as the mobile phase with excellent recoveries and LoQ/LoD, discerning between stable and degraded samples, and detecting, when present, aggregates up to 108 Da. The native state of Liraglutide was assessed and found to be an association into pentamers, with a non-spherical conformation. Combined to benchmark analyses, the sameness study was complete and descriptive, also giving insight on the aggregation process and covalent/non-covalent aggregate types.

Expanding the Use of Dynamic Electrostatic Repulsion Reversed-Phase Chromatography: An Effective Elution Mode for Peptides Control and Analysis.

Bioactive peptides are increasingly used in clinical practice. Reversed-phase chromatography using formic or trifluoroacetic acid in the mobile phase is the most widely used technique for their analytical control. However, sometimes it does not prove sufficient to solve challenging chromatographic problems. In the search for alternative elution modes, the dynamic electrostatic repulsion reversed-phase was evaluated to separate eight probe peptides characterised by different molecular weights and isoelectric points. This technique, which involves TBAHSO4 in the mobile phase, provided the lowest asymmetry and peak width at half height values and the highest in peak capacity (about 200 for a gradient of 30 min) and resolution concerning the classic reversed-phase. All analyses were performed using cutting-edge columns developed for peptide separation, and the comparison of the chromatograms obtained shows how the dynamic electrostatic repulsion reversed-phase is an attractive alternative to the classic reversed-phase.

Downstream Processing of Therapeutic Peptides by Means of Preparative Liquid Chromatography.

The market of biomolecules with therapeutic scopes, including peptides, is continuously expanding. The interest towards this class of pharmaceuticals is stimulated by the broad range of bioactivities that peptides can trigger in the human body. The main production methods to obtain peptides are enzymatic hydrolysis, microbial fermentation, recombinant approach and, especially, chemical synthesis. None of these methods, however, produce exclusively the target product. Other species represent impurities that, for safety and pharmaceutical quality reasons, must be removed. The remarkable production volumes of peptide mixtures have generated a strong interest towards the purification procedures, particularly due to their relevant impact on the manufacturing costs. The purification method of choice is mainly preparative liquid chromatography, because of its flexibility, which allows one to choose case-by-case the experimental conditions that most suitably fit that particular purification problem. Different modes of chromatography that can cover almost every separation case are reviewed in this article. Additionally, an outlook to a very recent continuous chromatographic process (namely Multicolumn Countercurrent Solvent Gradient Purification, MCSGP) and future perspectives regarding purification strategies will be considered at the end of this review.

Innovative chemical synthesis and conformational hints on the lipopeptide liraglutide.

Liraglutide is a new generation lipopeptide drug used for the treatment of type II diabetes. In this work, we describe new approaches for its preparation fully by chemical methods. The key step of these strategies is the synthesis in solution of the Lys/γ-Glu building block, Fmoc-Lys-(Pal-γ-Glu-OtBu)-OH, in which Lys and Glu residues are linked through their side chains and γ-Glu is N(α) -palmitoylated. This dipeptide derivative is then inserted into the peptide sequence on solid phase. As liraglutide is obtained with great purity and high yield, our approach can be particularly attractive for an industrial production. We also report here the results of a circular dichroism conformational analysis in a membrane mimetic environment that offers new insights into the mechanism of action of liraglutide. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Lactam based 7-amino suberoylamide hydroxamic acids as potent HDAC inhibitors.

A series of SAHA-like molecules were prepared introducing different lactam-carboxyamides in position 7 of the suberoylanilide skeleton. The activity against different HDAC isoforms was tested and the data compared with the corresponding linear products, without substituent in position 7. In general, this modification provided an effective reinforcement of in vitro activity. While the lactam size or the CO/NH group orientation did not strongly influence the inhibition, the contemporary modification of the suberoylamide fragment gave vary active variants in the lactam series, with compound 28 (ST8078AA1) that showed IC50 values between 2 and 10nM against all Class I HDAC isoforms, demonstrating it to be a large spectrum pan-inhibitor. This strong affinity with HDAC was also confirmed by the value of IC50=0.5µM against H460 cells, ranking 28 as one of the most potent HDAC inhibitors described so far.

Protective effect of Panax ginseng in cisplatin-induced cachexia in rats.

AIM: This study investigated the protective effect of a standardized extract of Panax ginseng on multiple cisplatin-induced 'sickness behaviors' (model of cancer-induced cachexia) in rats. MATERIALS & METHODS: Cisplatin was administered twice weekly (1-2 mg/kg, intraperitoneal) for 5 consecutive weeks. Panax ginseng extract (0, 25 and 50 mg/kg, intragastric) was administered daily over the 5-week period of cisplatin exposure. Malaise, bodyweight and temperature, pain sensitivity, and endurance running were recorded at baseline and at 5 weekly intervals. RESULTS: Treatment with cisplatin produced severe signs of malaise, marked loss of bodyweight, hypothermia, hyperalgesia and reduction in running time. Treatment with Panax ginseng extract completely prevented all cisplatin-induced alterations. CONCLUSION: These data indicate that treatment with Panax ginseng extract exerted a protective effect in a rat model of cachexia and suggest that Panax ginseng extract may be a therapeutic promising tool for supportive care in oncology.

Assessing the performance of new chromatographic technologies for the separation of peptide epimeric impurities: the case of Icatibant.

The biopharmaceutical industry faces the challenge of efficiently characterising impurity profiles of therapeutical peptides, also due to their complex polar and ionisable attributes. This research explores the potential of advanced chromatographic techniques to address this challenge. The study compares dynamic electrostatic repulsion reversed phase (d-ERRP) to its counterparts (static ERRP and ion pair reversed phase IP-RP) in analysing Icatibant and its elusive epimeric impurity, [L-Arg]1-Icatibant and highlights its exceptional capabilities in generating symmetric peaks, mitigating the common tailing phenomenon, and serving as a steadfast guardian of column longevity. The result highlights d-ERRP as a pioneering tool in the domain of liquid chromatography, fostering its role as a reference technique for the analysis of therapeutic peptides.

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part II: Purification of a therapeutic peptide.

Preparative liquid chromatography in reversed phase conditions (RPLC) is the most common approach adopted in the downstream processing for the purification of therapeutic peptides at industrial level. Due to the strict requirements on the quality imposed by the Regulatory Agencies, routinary methods based on the use of aqueous buffers and acetonitrile (ACN) as organic modifier are commonly used, where ACN is practically the only available choice for the purification of peptide derivatives. However, ACN is known to suffers of many shortcomings, such as drastic shortage in the market, high costs and, most importantly, it shows unwanted toxicity for human health and environment, which led it among the less environmentally friendly ones. For this reason, the selection of a suitable alternative becomes crucial for the sustainable downstream processing of peptides and biopharmaceuticals in general. In this paper, a promising green solvent, namely dimethyl carbonate (DMC) has been used for the separation of a peptide not only in linear conditions but also for its purification through non-linear overloaded chromatography. The performance of the process has been compared to that achievable with the common method where ACN is used as organic modifier and to that obtained with two additional solvents (namely ethanol and isopropanol), already used as greener alternatives to ACN. This proof-of-concept study showed that, thanks to its higher elution strength, DMC can be considered a green alternative to ACN, since it allows to reduce method duration while reaching good purities and recoveries. Indeed, at a target purity fixed to 98.5 %, DMC led to the best productivity with respect to all the other solvents tested, confirming its suitability as a sustainable alternative to ACN for the purification of complex biopharmaceutical products.

Identification of a novel arylpiperazine scaffold for fatty acid amide hydrolase inhibition with improved drug disposition properties.

We herein describe the systematic approach used to develop new analogues of compound 2, recently identified as a potent and selective fatty acid amide hydrolase (FAAH) inhibitor. Aiming at identifying new scaffolds endowed with improved drug disposition properties with respect to the phenylpyrrole-based lead, we subjected it to two different structural modification strategies. This process allowed the identification of derivatives 4b and 5c as potent, reversible and non-competitive FAAH inhibitors.

SAMITAL®: a new botanical drug for the treatment of mucositis induced by oncological therapies.

SAMITAL(®) (Indena SpA, Milan, Italy) is a new multicomponent and multiacting botanical formulation rationally designed for the relief of oral mucositis induced by chemotherapy and/or radiotherapy in oncological patients. Each of the individual botanical constituents of SAMITAL-standardized extracts of Vaccinium myrtillus, Macleaya cordata and Echinacea angustifolia have a long history of clinical use that corroborates their safety and activity in SAMITAL. A number of pilot trials in oncological patients demonstrated that SAMITAL has good clinical efficacy and tolerability as evidenced by its significant effects in terms of reduction of mucositis, pain and a general improvement in patient quality of life. Importantly, the use of this botanical formulation had the added benefit that patients were able to complete their chemotherapy/radiotherapy regimen. Phase II trials with SAMITAL as part of an overall clinical development program are currently ongoing in Italy and are planned in the USA.

Effect of SAMITAL® in the treatment of chemotherapy-induced mucositis in adult oncohematological patients.

AIM: We sought to evaluate the efficacy and safety of SAMITAL(®) (Indena SpA, Milan, Italy), a highly standardized botanical formulation, in reducing mucositis in patients undergoing treatment for hematological malignancies. PATIENTS & METHODS: In this observational, uncontrolled study, a total of 25 consecutively enrolled patients (19 males, aged 18-74 years) with chemotherapy-induced mucositis were compassionately treated orally with SAMITAL (three to four times per day) for 4-22 days per cycle. RESULTS: Patients demonstrated clinically relevant reductions in WHO mucositis grade with a reduction in pain, mucosal erosions, bleeding, dysphagia/feeding impairment and improvements in quality of life. SAMITAL was well tolerated and no local or systemic pharmacological, allergic, toxic or synergistic/antagonistic side effects were reported. Of note, SAMITAL also showed efficacy when administered prophylactically. CONCLUSION: These results add weight to previous experiences with SAMITAL. However, randomized, placebo-controlled clinical trials will need to confirm the suitability of SAMITAL for use in the treatment of mucositis.

Investigation of the GnRH antagonist degarelix isomerization in biological matrices.

One of the main objectives of peptide drug design is the improvement of peptide pharmacokinetics with maintaining biological activity, which can be achieved by the complex modifications of the primary structure of the peptides. However, these changes often lead to the formation of peculiar impurities in the peptide drugs and their metabolites, which require the development of advanced analytical methods to properly assess their content. Here, we investigated the degradation of the potent long-acting GnRH antagonist degarelix in various biologic media by the tailor-made HPLC method, which allows precise determination of 5-Aph(Hyd)-degarelix isomer, an impurity found in the degarelix active pharmaceutical ingredient (API) during its manufacturing. Unexpectedly, we discovered a rapid and irreversible conversion of degarelix API into the corresponding hydantoin isomer in serum, suggesting that this impurity can be also a potential drug metabolite in vivo. This finding underlines the importance of the development of more accurate and performing analytical techniques to correctly characterize the chemical composition of the manufactured drugs and their behavior under physiological conditions.

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part I: Separation of small molecules.

Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols. In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7 % v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18 % v/v), and larger efficiency than alcohols. This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions.

Camptothecins in tumor homing via an RGD sequence mimetic.

A RGD peptide mimetic was conjugated to four camptothecins, with the purpose to improve their therapeutic index. The conjugate derivatives were evaluated against two tumor cell lines, one overexpressing integrins (human ovarian carcinoma, A2780) and a second one with a low integrin expression (human prostate cancer, PC3). The in vitro screening was completed with the adhesion behavior to vitronectin. Compound 8 (ST7456CL1) was selected for the in vivo investigation after stability tests over 24h, in PBS solution and in rat plasma, and compared to irinotecan. The former showed a prolonged half-life.

Divergent synthesis of novel 9-deazaxanthine derivatives via late-stage cross-coupling reactions.

A small library of 8-substituted 9-deazaxanthines has been prepared by late-stage diversification of an 8-bromo-9-deazaxanthine. By utilizing palladium-catalyzed cross-coupling reactions a single key precursor can be transformed into a variety of 8-substituted-9-deazaxanthine compounds. Three key 8-bromo-9-deazaxanthine intermediates were efficiently prepared from commercially available 6-chlorouracil in six steps.

New retinoid derivatives as back-ups of Adarotene.

Adarotene belongs to the so-called class of atypical retinoids. The presence of the phenolic hydroxyl group on Adarotene structure allows a rapid O-glucuronidation as a major mechanism of elimination of the drug, favoring a fast excretion of its glucuronide metabolite in the urines. A series of ether, carbamate and ester derivatives was synthesized. All of them were studied and evaluated for their stability at different pH. The cytotoxic activity in vitro on NCI-H460 non-small cell lung carcinoma and A2780 ovarian tumor cell lines was also tested. A potential back-up of Adarotene has been selected to be evaluated in tumor models.

Fast MacMillan's Imidazolidinone-Catalyzed Enantioselective Synthesis of Polyfunctionalized 4-Isoxazoline Scaffolds.

The enantioselective 1,3-dipolar cycloaddition of nitrones and arylpropionaldehydes to generate highly functionalized scaffolds for application in drug discovery was herein investigated. The use of a second-generation MacMillan catalyst as hydrochloride salt consistently accelerated the reaction speed, allowing a decrease in the reaction time up to >100 times, still affording 4-isoxazolines with good to excellent enantiomeric ratios at room temperature. As a proof of concept, further functionalization of the isoxazoline core through Pd-catalyzed cross-coupling was performed, generating differently functionalized chemical architectures in high yield.

A New Approach to Supramolecular Structure Determination in Pharmaceutical Preparation of Self-Assembling Peptides: A Case Study of Lanreotide Autogel.

The supramolecular structure in peptides' prolonged-released gel formulations is the most critical parameter for the determination of the pharmaceutical profile of the drug. Here, we report our investigation on lanreotide Autogel as a case study. For the first time, we describe the use of the pulsed field gradient (PFG) diffusion-ordered spectroscopy (DOSY) magic-angle spinning NMR to characterize the supramolecular self-assembly and molecular mobility of different samples of lanreotide Autogel formulations prepared according to different formulation protocols. The diffusion coefficient was used to calculate the hydrodynamic radii of supramolecular assemblies and build relative molecular models. DOSY data were integrated with NMR imaging (MRI) measurements and atomic force microscopy (AFM) imaging.