A stability-indicating method development and validation for the determination of related substances in novel synthetic decapeptide by HPLC

In the present scenario, peptide is an emerging field of research having vast therapeutic applications. Diverse impurities may rise from various stages of the synthesis process and storage of the peptides. Because these contaminants may have an impact on the therapeutic safety and effectiveness of peptides in their approaching applications, they must be identified and carefully monitored. Considering the pharmaceutical importance of the extent of peptides, we were motivated to synthesize a decapeptide and establish a novel gradient reversed-phase high-performance liquid chromatography (RP-HPLC) method for its analysis along with efficient separation of its six related impurities. Different buffers, organic modifiers, and columns were used in the tests for good separation of these impurities. To establish a stability-indicating method, a stress study was also conducted. The International Conference on Harmonization (ICH) guidelines have been followed for validation of the developed analytical method. The validated method revealed sufficient accuracy, specificity, linearity, robustness, precision, and high sensitivity for its intended use. The proposed method could be appropriate for routine analysis and stability assessment of the decapeptide, which might be useful for further scientific investigation.

On-resin synthesis of Lanreotide epimers and studies of their structure-activity relationships

Peptide drugs often accompany epimeric impurities (isomers). Therefore, efficient chemical synthesis of epimers is critical to identify them correctly and investigate their biological activities. Here, we report the rapid synthesis and structure-activity relationship (SAR) studies of eight possible epimers of a somatostatin synthetic analog (SSA), lanreotide (LAN). SPPS and the subsequent on-resin rapid disulfide closure method offered >90% conversion yield for all epimers (P1-P8). Further, we developed an analytical method to separate these epimers, which enabled the profiling of five epimeric impurities in the API, purchased for Somatuline generic formulations. In SAR studies, most LAN epimers revealed compromised antiproliferative activity, while the P7 epimer retained antiproliferative activity similar to LAN API, as supported by in silico SAR studies in detail. Additionally, P7 showed serum stability nearly identical to LAN, suggesting that drug epimers could be a potential API. Current studies will further encourage the development of novel SSA scaffolds.

Identification, synthesis, and characterization of an unprecedented N-(2-carboxyethyl) adduct impurity in an injectable ganirelix formulation

Ganirelix, a peptide-based drug used to treat female infertility, has been in high market demand, which attracted generic formulation. A hitherto unknown impurity of ganirelix was observed in our formulation process, which reached ~0.3% in 6 months and led to a detailed investigation of its structure. In-depth analysis of ESI-MS/MS data of this impurity coupled with an artificial intelligence prediction tool led to a highly unusual putative structure, that is, N-(2-carboxyethyl)-ganirelix (NCE-GA), which was authenticated by chemical synthesis from ganirelix and NMR analysis and via corroborated HPLC and MS/MS data with the formulation-derived impurity.

An Overview of Peptides and Peptide Pools for Antigen-Specific Stimulation in T-Cell Assays

The analysis of antigen-specific T-cell responses has become routine in many laboratories. Functional T-cell assays like enzyme-linked-immuno-spot (ELISPOT), which depend on antigen-specific stimulation, increasingly use peptides to represent the antigen of interest. Besides single peptides, mixtures of peptides (peptide pools) are very frequently applied. Such peptide pools may, for example, represent entire proteins (with overlapping peptides covering a protein sequence) or include noncontiguous peptides such as a collection of T-cell-stimulating peptides. The optimum specification of single peptides or peptide pools for T-cell stimulation assays will depend on the purpose of the test, the target T-cell population, the availability of sample, requirements regarding reproducibility, and, last but not least, the available budget, to mention only the most important factors. Because of the way peptides are produced, they will always contain certain amounts of impurities such as peptides with deletions or truncated peptides, and there may be additional by-products of peptide synthesis. Optimized synthesis protocols as well as purification help reduce impurities that might otherwise cause false-positive assay results. However, specific requirements with respect to purity will vary depending on the purpose of an assay. Finally, storage conditions significantly affect the shelf life of peptides, which is relevant especially for longitudinal studies. The present book chapter addresses all of these aspects in detail. It should provide the researcher with all necessary background knowledge for making the right decisions when it comes to choosing, using, and storing peptides for ELISPOT and other T-cell stimulation assays.

Peptiligase, an enzyme for efficient chemo-enzymatic synthesis of aviptadil

Increasing attention to peptides as prospective therapeutics has created a renaissance in searching for new alternatives to the current peptide synthetic approaches as well as their modification. In this context, it is necessary to develop different approaches for peptide ligation. Using enzymes as a novel strategy and powerful tool for the peptide and protein ligation has recently received a lot of attention. We here designed a fully convergent chemo-enzymatic peptide synthesis (CEPS) process for the synthesis of aviptadil a 28-mer therapeutic peptide with potential therapeutic effects in various medical contexts specially in the treatment of acute respiratory distress syndrome (ARDS) by coupling two peptide segments with four different peptiligase variants in aqueous environments. Our study reveals that peptiligase variants are capable of ligation reaction in 15 min. The overall time of ligation is shorter than those peptides with similar lengths and hinderance to aviptadil which reported for conventional synthesis by full solid-phase peptide synthesis. Yields ranged from 54 % to 76 %.

Synthesis and characterization of two potential impurities (des-ethyl-Ganirelix) generated in the Ganirelix manufacturing process

Controlling certain diseases using peptide drugs has remarkably increased in the past two decades. In this regard, a generic formulation is an upfront solution to fulfill market demands. Ganirelix, a leading peptide active pharmaceutical ingredient (API) primarily used as a gonadotropin-releasing hormone antagonist (GnRH), has established a potential market value worldwide. But its generic formulation mandates detailed impurity profiles from a synthetic source and contemplates the sameness of a reference-listed drug (RLD). Post-chemical synthesis and processing of Ganirelix, some commercial sources have revealed two new potential impurities among many known, which show the deletion of an ethyl group from the hArg(Et)2 residue at the sixth and eighth positions, named des-ethyl-Ganirelix. These impurities are unprecedented in traditional peptide chemistry, and such monoethylated-hArg building blocks are not easily accessible commercially to synthesize these two impurities. Here, we have outlined the synthesis, purification, and enantiomeric purity characterization of the amino acids and their incorporation in the Ganirelix peptide sequence to synthesize these potential peptide impurities. This methodology will enable the convenient synthesis of side-chain substituted Arg and hArg derivatives in peptide drug discovery platforms.

High-throughput infrared spectroscopy for quantification of peptides in drug discovery

Peptides have gained an increasing importance in drug discovery as potential therapeutics. Discovery efforts toward finding new, efficacious peptide-based therapeutics have increased the throughput of peptide development, allowing the rapid generation of unique and pure peptide samples. However, high-throughput analysis of peptides may be still challenging and can encumber a high-throughput drug discovery campaign. We report herein a fit-for-purpose method to quantify peptide concentrations using high-throughput infrared spectroscopy (HT-IR). Through the development of this method, multiple critical method parameters were optimized including solvent composition, droplet deposition size, plate drying procedures, sample concentration, and internal standard. The relative absorbance of the amide region (1600-1750 cm^-1) to the internal standard, K₃Fe(CN)₆ (2140 cm^-1), was determined to be most effective at providing lowest interference for measuring peptide concentration. The best sample deposition was achieved by dissolving samples in a 50:50 v/v allyl alcohol/water mixture. The developed method was used on 96-well plates and analyzed at a rate of 22 min per plate. Calibration curves to measure sample concentration versus response relationship displayed sufficient linearity (R² > 0.95). The repeatability and scope of detection was demonstrated with eighteen peptide samples that were measured with most values below 20% relative standard deviation. The linear dynamic range of the method was determined to be between 1 and 5 mg/mL. This developed HT-IR methodology could be a useful tool in peptide drug candidate lead identification and optimization processes.

Characterization of low-level D-amino acid isomeric impurities of Semaglutide using liquid chromatography-high resolution tandem mass spectrometry

Under the guideline issued by Food and Drug Administration (FDA), ANDAs for Certain Highly Purified Synthetic Peptide Drug Products That Refer to Listed Drugs of rDNA Origin Guidance for Industry, a synthetic Semaglutide that is intended to be a "generic" of the approved rDNA origin Semaglutide is under exploring. Thus, each peptide-related impurity that is 0.10% of the drug substance or greater need to be identified for Semaglutide covered by this guidance. Among others, characterization of the low-level D-amino acid (D form) isomeric impurities are always the most challenging ones. Reverse-phase high-performance liquid chromatography (RP-UPLC) was used to separate the impurities, followed by high resolution mass spectrometry (HRMS) to determine the molecular weight of the impurities that existed in both formulations. Following the targeted D form isomers off-line collection, the samples went through lyophilization, deuterated hydrochloric acid (D-HCl) hydrolyzation with low level D/L form shifting suppression substrates, chiral derivatization and RP-UPLC tandem mass spectrometry analysis of different amino acids by comparing with standards. Herein, we reported an accurate, straightforward characterization method with low limit of detection for the low-level D-Ser⁸, D-His¹ and D-Asp⁹ Semaglutide impurities in Semaglutide formulations. The developed UPLC tandem HRMS method entails a valuable step forward in the detection of trace levels of the D-isomers of Semaglutide and other peptide products.

Separation, identification and quantification of associated impurities in cobratide using sheathless CE-MS and CE-UV

Cobratide is a peptide drug extracted from the venom of Chinese cobra, and has been widely used in the clinical treatment of chronic, intractable and persistent pain. In a recent study, it was reported that it has the potential to treat COVID-19. In order to control the quality of commercial cobratide drugs, a protocol was established for the separation, identification and quantification of cobratide and its associated impurities, in which sheathless capillary electrophoresis-mass spectrometry (CE-MS) was used for identification and a rapid capillary electrophoresis-ultraviolet-visible detector (CE-UV) method was developed for accurate quantification. Separation conditions that affect the resolution and MS intensities of cobratide and its associated impurities were investigated, including pH value, concentration of background electrolyte (BGE), ratio of organic additive and sample solution. The optimized CE conditions (BGE: 50 mM NH₄Ac, pH 4.0; sample solution: deionized water) were used for both sheathless CE-MS and CE-UV methods. Three associated impurities were separated and identified for the first time by sheathless CE-MS. Then, a rapid CE-UV method was validated and used for accurate quantification of cobratide and its associated impurities. The CE-UV method showed good linearity between concentration and corrected peak area of cobratide in the concentration range of 5.36-536.30 μg mL^-1. The limit of quantification of the CE-UV method was 4.16 μg mL^-1. The relative standard deviations of migration time were less than 1% for both intra-day and inter-day experiments, and those of corrected peak area were less than 5%. Finally, different cobratide drugs were analyzed to evaluate the batch-to-batch consistency. This established protocol combining sheathless CE-MS and CE-UV methods would provide useful information for both quality control and process analysis of peptide drugs.

Characterization of Synthetic Peptide Therapeutics Using Liquid Chromatography-Mass Spectrometry: Challenges, Solutions, Pitfalls, and Future Perspectives

Synthetic peptides represent an important and expanding class of therapeutics. Despite having a relatively small size as compared to monoclonal antibodies and other proteins, synthetic peptides are subject to many complex structural modifications originating from the starting materials, manufacturing process, and storage conditions. Although mass spectrometry has been increasingly used to characterize impurities of synthetic peptides, systematic review of this field is scarce. In this paper, an overview of the impurities in synthetic peptide therapeutics is provided in the context of how the knowledge from detailed characterization of the impurities using liquid chromatography-mass spectrometry (LC-MS) can be used to develop the manufacturing process and control strategy for synthetic peptide therapeutics following the critical quality attribute (CQA)-driven and risk-based approach. The thresholds for identifying and controlling the impurities are discussed based on currently available regulatory guidance. Specific LC-MS techniques for identification of various types of impurities based on their structural characteristics are discussed with the focus on structural isomers and stereoisomers (i.e., peptide epimers). Absolute and relative quantitation methods for the peptide impurities are critiqued. Potential pitfalls in characterization of synthetic peptide therapeutics using LC-MS are discussed. Finally, a systematic LC-MS workflow for characterizing the impurities in synthetic peptide therapeutics is proposed, and future perspectives on applying emerging LC-MS techniques to address the remaining challenges in the development of synthetic peptide therapeutics are presented.

Cell-penetrating peptides containing 2,5-diketopiperazine (DKP) scaffolds as shuttles for anti-cancer drugs: conformational studies and biological activity

A series of linear and cyclic peptidomimetics composed of a cell-penetrating peptide and a non-natural, bifunctional 2,5-diketopiperazine scaffold is reported. Conformational studies revealed well-defined helical structures in micellar medium for linear structures, while cyclic peptidomimetics were more flexible. Biological investigations showed higher membrane-activity of cyclic derivatives allowing their use as shuttles for anti-cancer drugs.

The Role of Counter-Ions in Peptides-An Overview

Peptides and proteins constitute a large group of molecules that play multiple functions in living organisms. In conjunction with their important role in biological processes and advances in chemical approaches of synthesis, the interest in peptide-based drugs is still growing. As the side chains of amino acids can be basic, acidic, or neutral, the peptide drugs often occur in the form of salts with different counter-ions. This review focuses on the role of counter-ions in peptides. To date, over 60 peptide-based drugs have been approved by the FDA. Based on their area of application, biological activity, and results of preliminary tests they are characterized by different counter-ions. Moreover, the impact of counter-ions on structure, physicochemical properties, and drug formulation is analyzed. Additionally, the application of salts as mobile phase additives in chromatographic analyses and analytical techniques is highlighted.

Evaluation of Heavy Metal and Microbial Contamination in Green Tea and Herbal Tea Used for Weight Loss in the Palestinian Market

The use of green tea and herbal tea for weight loss is increasing worldwide owing to the rising rates of obesity. There are concerns about the safety and quality of these herbal products owing to their increased consumption worldwide. In this study, we evaluated randomly collected samples of green tea and herbal tea and tested them for heavy metal and microbial contamination. Eighteen samples of green tea or herbal tea of widely used brands in Palestine were tested for heavy metal and microbial contamination. The results showed that 7 of the samples had toxic heavy metals such as chromium (Cr) and lead (Pb), and their concentrations were above the allowable limits set by the World Health Organization (WHO). Moreover, 6 of the samples that were tested had microbial contamination with high total aerobic microbial count (TAMC) and total yeast and mold count (TYMC). This could be due to improper handling and storage conditions of these herbal products. This study is the first of its kind in Palestine, and its results are forewarning to all the responsible authorities, including the Ministry of Health (MoH), to take immediate corrective actions such as quality control testing, auditing, and registration of marketed tea products.

Newly Identified HNP-F from Human Neutrophil Peptide-1 Promotes Hemostasis

Active hemostatic agents can play a crucial role in saving patients' lives during surgery. Active hemostats have several advantages including utilization of natural blood coagulation and biocompatibility. Among them, although human neutrophil peptide-1 (HNP-1) has been previously reported with the hemostatic mechanism, which part of HNP-1 facilitates the hemostatic activity is not known. Here, a partial peptide (HNP-F) promoting hemostasis, originating from HNP-1, has been newly identified by the blood coagulation ability test. HNP-F shows the best hemostatic effect between the anterior half and posterior half of peptides. Moreover, microscopic images show platelet aggregation and an increase in the concentration of platelet factor 4, and the scanning electron microscope image of platelets support platelet activation by HNP-F. Thromboelastography indicates decreased clotting time and increased physical properties of blood clotting. Mouse liver experiments demonstrate improved hemostatic effect by treatment of peptide solution. Cell viability and hemolysis assays confirm the HNP-F's biosafety. It is hypothesized that the surface charge and structure of HNP-F could be favorable to interact with fibrinogen or thrombospondin-1. Collectively, because HNP-F as an active peptide hemostat has many advantages, it could be expected to become a potent hemostatic biomaterial, additive or pharmaceutical candidate for various hemostatic applications.

Peptide-based therapeutics: quality specifications, regulatory considerations, and prospects

Exquisite selectivity, remarkable efficacy, and minimal toxicity are key attributes inherently assigned to peptides, resulting in increased research interest from the pharmaceutical industry in peptide-based therapeutics (PbTs). Pharmacopoeias develop authoritative standards for PbT by providing standard specifications and test methods. Nevertheless, a lack of harmonization in test procedures adopted for PbT in the latest editions of Pharmacopoeias has been observed. Adoption of a harmonized monograph could increase further the interest of the global pharmaceutical industry in PbTs. Here, we provide an overview of pharmacopoeial methodologies and specifications commonly observed in PbT monographs and highlight the main differences among the pharmacopoeias in terms of the active pharmaceutical ingredients that they focus on. We also address the prospects for PbTs to mature as a new therapeutic niche.

Investigations of the Copper Peptide Hepcidin-25 by LC-MS/MS and NMR

Hepcidin-25 was identified as the main iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II)-binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandem mass spectrometry (MS/MS), high-resolution mass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D) model of hepcidin-25 with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or reference material comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.

The next generation of antimicrobial peptides (AMPs) as molecular therapeutic tools for the treatment of diseases with social and economic impacts

Anti-infective drugs have had a key role in the contemporary world, contributing to dramatically decrease mortality rates caused by infectious diseases worldwide. Antimicrobial peptides (AMPs) are multifunctional effectors of the innate immune system of mucosal surfaces and present antimicrobial activity against a range of pathogenic viruses, bacteria, and fungi. However, the discovery and development of new antibacterial drugs is a crucial step to overcome the great challenge posed by the emergence of antibiotic resistance. In this review, we outline recent advances in the development of novel AMPs with improved antimicrobial activities that were achieved through characteristic structural design. In addition, we describe recent progress made to overcome some of the major limitations that have hindered peptide biosynthesis.

Identification of site-specific heterogeneity in peptide drugs using intact mass spectrometry with electron transfer dissociation

RATIONALE

Protamine sulfate is a peptide drug product consisting of multiple basic peptides. As traditional high-performance liquid chromatography (HPLC) separation methods may not resolve these peptides, as well as any possible peptide-related impurities, a method utilizing top-down mass spectrometry was developed for the characterization of complex peptide drug products, including any low-level impurities, which is described in this study.

METHODS

Herring protamine sulfate was used as a model system to demonstrate the applicability of the method. Direct infusion mass spectrometry and tandem mass spectrometry (MS/MS) on a high-resolution, mass accurate instrument with electron transfer dissociation (ETD) were used to identify all the species present in the herring protamine sulfate sample. Identifications were made based on mass accuracy analysis as well as MS/MS fragmentation patterns.

RESULTS

Complete sequence coverage of the three abundant herring protamine peptides was obtained using the top-down ETD-MS/MS method, which also identified a discrepancy with the published herring protamine peptide sequences. Additionally, three low-abundance related peptide species were also identified and fully characterized. These three peptides had not previously been reported as herring protamine peptides, but could be related to the published sequences through amino acid additions and/or substitutions.

CONCLUSIONS

A method for the characterization of protamine, a complex peptide drug product, was developed that can be extended to other complex peptide or protein drug products. The selectivity and sensitivity of this method improves a regulator's ability to identify peptide impurities not previously observed using the established methods and presents an opportunity to better understand the composition of complex peptide drug products.

Patchwork protein chemistry: a practitioner's treatise on the advances in synthetic peptide stitchery

With the study of peptides and proteins at the heart of many scientific endeavors, the omics era heralded a multitude of opportunities for chemists and biologists alike. Across the interface with life sciences, peptide chemistry plays an indispensable role, and progress made over the past decades now allows proteins to be treated as molecular patchworks stitched together through synthetic tailoring. The continuous elaboration of sophisticated strategies notwithstanding, Merrifield's solid-phase methodology remains a cornerstone of chemical protein design. Although the non-practitioner might misjudge peptide synthesis as trivial, routine, or dull given its long history, we comment here on its many advances, obstacles, and prospects from a practitioner's point of view. While sharing our perspectives through thematic highlights across the literature, this treatise provides an interpretive overview as a guide to novices, and a recap for specialists.

Phage display as a technology delivering on the promise of peptide drug discovery

Phage display represents an important approach in the development pipeline for producing peptides and peptidomimetics therapeutics. Using randomly generated DNA sequences and molecular biology techniques, large diverse peptide libraries can be displayed on the phage surface. The phage library can be incubated with a target of interest and the phage which bind can be isolated and sequenced to reveal the displayed peptides' primary structure. In this review, we focus on the 'mechanics' of the phage display process, whilst highlighting many diverse and subtle ways it has been used to further the drug-development process, including the potential for the phage particle itself to be used as a drug carrier targeted to a particular pathogen or cell type in the body.

Chemical-functional diversity in cell-penetrating peptides

Cell-penetrating peptides (CPPs) are a promising tool to overcome cell membrane barriers. They have already been successfully applied as carriers for several problematic cargoes, like e.g. plasmid DNA and (si)RNA, opening doors for new therapeutics. Although several hundreds of CPPs are already described in the literature, only a few commercial applications of CPPs are currently available. Cellular uptake studies of these peptides suffer from inconsistencies in used techniques and other experimental conditions, leading to uncertainties about their uptake mechanisms and structural properties. To clarify the structural characteristics influencing the cell-penetrating properties of peptides, the chemical-functional space of peptides, already investigated for cellular uptake, was explored. For 186 peptides, a new cell-penetrating (CP)-response was proposed, based upon the scattered quantitative results for cellular influx available in the literature. Principal component analysis (PCA) and a quantitative structure-property relationship study (QSPR), using chemo-molecular descriptors and our newly defined CP-response, learned that besides typical well-known properties of CPPs, i.e. positive charge and amphipathicity, the shape, structure complexity and the 3D-pattern of constituting atoms influence the cellular uptake capacity of peptides.

Peptides as the next generation of anti-infectives

Synthesis and large-scale manufacturing technologies are now available for the commercial production of even the most complex peptide anti-infectives. Married with the potential of this class of molecule as the next generation of effective, resistance-free and safe antimicrobials, and a much better understanding of their biology, pharmacology and pharmacodynamics, the first regulatory approvals and introduction into clinical practice of these promising drug candidates will likely be soon. This is a key juncture in the history/life cycle of peptide anti-infectives and, perhaps, their commercial and therapeutic potential is about to be realized. This review highlights the promise of these agents as the next generation of therapeutics and summarizes the challenges faced in, and lessons learned from, the past.

The influence of peptide impurity profiles on functional tissue-organ bath response: the 11-mer peptide INSL6[151-161] case

Bioactive peptides have great pharmaceutical potential as nutraceuticals, diagnostics, and therapeutic drugs in several clinical areas. Thus, the search for novel lead peptides with a biological function has attracted renewed interest. Crude peptide material (i.e., ~70% purity) of INSL6[151-161] (NH₂-FRSLFWGNHSQ-COOH) was found to trigger a contractile response in guinea pig ileum longitudinal smooth muscle preparations using tissue-organ baths. However, the purified peptide (i.e., ≥ 95% purity) had no effect on this model. Further investigation with crude materials from other suppliers, with purities ranging between 50% and 80%, indicated that the crude products gave a false-positive functional tissue-organ bath conclusion. These observations question the functionality conclusions when using crude-purity peptide materials; during the initial research or discovery phase, peptide quality is generally neglected, possibly leading to misinterpretation of biological results due to by-products from peptide synthesis and, thus, wrong fail/pass decisions. Therefore, we strongly recommend appropriate quality control testing before using any peptides for initial biomedical research or discovery purposes.

Stability-indicating HPLC-DAD/UV-ESI/MS impurity profiling of the anti-malarial drug lumefantrine

BACKGROUND

Lumefantrine (benflumetol) is a fluorene derivative belonging to the aryl amino alcohol class of anti-malarial drugs and is commercially available in fixed combination products with β-artemether. Impurity characterization of such drugs, which are widely consumed in tropical countries for malaria control programmes, is of paramount importance. However, until now, no exhaustive impurity profile of lumefantrine has been established, encompassing process-related and degradation impurities in active pharmaceutical ingredients (APIs) and finished pharmaceutical products (FPPs).

METHODS

Using HPLC-DAD/UV-ESI/ion trap/MS, a comprehensive impurity profile was established based upon analysis of market samples as well as stress, accelerated and long-term stability results. In-silico toxicological predictions for these lumefantrine related impurities were made using Toxtree® and Derek®.

RESULTS

Several new impurities are identified, of which the desbenzylketo derivative (DBK) is proposed as a new specified degradant. DBK and the remaining unspecified lumefantrine related impurities are predicted, using Toxtree® and Derek®, to have a toxicity risk comparable to the toxicity risk of the API lumefantrine itself.

CONCLUSIONS

From unstressed, stressed and accelerated stability samples of lumefantrine API and FPPs, nine compounds were detected and characterized to be lumefantrine related impurities. One new lumefantrine related compound, DBK, was identified and characterized as a specified degradation impurity of lumefantrine in real market samples (FPPs). The in-silico toxicological investigation (Toxtree® and Derek®) indicated overall a toxicity risk for lumefantrine related impurities comparable to that of the API lumefantrine itself.

Quality analysis of salmon calcitonin in a polymeric bioadhesive pharmaceutical formulation: sample preparation optimization by DOE

A sensitive and selective HPLC method for the assay and degradation of salmon calcitonin, a 32-amino acid peptide drug, formulated at low concentrations (400 ppm m/m) in a bioadhesive nasal powder containing polymers, was developed and validated. The sample preparation step was optimized using Plackett-Burman and Onion experimental designs. The response functions evaluated were calcitonin recovery and analytical stability. The best results were obtained by treating the sample with 0.45% (v/v) trifluoroacetic acid at 60 degrees C for 40 min. These extraction conditions did not yield any observable degradation, while a maximum recovery for salmon calcitonin of 99.6% was obtained. The HPLC-UV/MS methods used a reversed-phase C(18) Vydac Everest column, with a gradient system based on aqueous acid and acetonitrile. UV detection, using trifluoroacetic acid in the mobile phase, was used for the assay of calcitonin and related degradants. Electrospray ionization (ESI) ion trap mass spectrometry, using formic acid in the mobile phase, was implemented for the confirmatory identification of degradation products. Validation results showed that the methodology was fit for the intended use, with accuracy of 97.4+/-4.3% for the assay and detection limits for degradants ranging between 0.5 and 2.4%. Pilot stability tests of the bioadhesive powder under different storage conditions showed a temperature-dependent decrease in salmon calcitonin assay value, with no equivalent increase in degradation products, explained by the chemical interaction between salmon calcitonin and the carbomer polymer.