Methods for engineering therapeutic peptides

Discovery and Biosynthesis of Persiathiacins: Unusual Polyglycosylated Thiopeptides Active Against Multidrug Resistant Tuberculosis

Thiopeptides are ribosomally biosynthesized and post-translationally modified peptides (RiPPs) that potently inhibit the growth of Gram-positive bacteria by targeting multiple steps in protein biosynthesis. The poor pharmacological properties of thiopeptides, particularly their low aqueous solubility, has hindered their development into clinically useful antibiotics. Antimicrobial activity screens of a library of Actinomycetota extracts led to discovery of the novel polyglycosylated thiopeptides persiathiacins A and B from Actinokineospora sp. UTMC 2448. Persiathiacin A is active against methicillin-resistant Staphylococcus aureus and several Mycobacterium tuberculosis strains, including drug-resistant and multidrug-resistant clinical isolates, and does not significantly affect the growth of ovarian cancer cells at concentrations up to 400 μM. Polyglycosylated thiopeptides are extremely rare and nothing is known about their biosynthesis. Sequencing and analysis of the Actinokineospora sp. UTMC 2448 genome enabled identification of the putative persiathiacin biosynthetic gene cluster (BGC). A cytochrome P450 encoded by this gene cluster catalyzes the hydroxylation of nosiheptide in vitro and in vivo, consistent with the proposal that the cluster directs persiathiacin biosynthesis. Several genes in the cluster encode homologues of enzymes known to catalyze the assembly and attachment of deoxysugars during the biosynthesis of other classes of glycosylated natural products. One of these encodes a glycosyl transferase that was shown to catalyze attachment of a D-glucose residue to nosiheptide in vitro. The discovery of the persiathiacins and their BGC thus provides the basis for the development of biosynthetic engineering approaches to the creation of novel (poly)glycosylated thiopeptide derivatives with enhanced pharmacological properties.

Capillary electrophoresis in the analysis of therapeutic peptides-A review

Therapeutic peptides are a growing class of innovative drugs with high efficiency and a low risk of adverse effects. These biomolecules fall within the molecular mass range between that of small molecules and proteins. However, their inherent instability and potential for degradation underscore the importance of reliable and effective analytical methods for pharmaceutical quality control, therapeutic drug monitoring, and compliance testing. Liquid chromatography-mass spectrometry (LC-MS) has long time been the "gold standard" conventional method for peptide analysis, but capillary electrophoresis (CE) is increasingly being recognized as a complementary and, in some cases, superior, highly efficient, green, and cost-effective alternative technique. CE can separate peptides composed of different amino acids owing to differences in their net charge and size, determining their migration behavior in an electric field. This review provides a comprehensive overview of therapeutic peptides that have been used in the clinical environment for the last 25 years. It describes the properties, classification, current trends in development, and clinical use of therapeutic peptides. From the analytical point of view, it discusses the challenges associated with the analysis of therapeutic peptides in pharmaceutical and biological matrices, as well as the evaluation of CE as a whole and the comparison with LC methods. The article also highlights the use of microchip electrophoresis, nonaqueous CE, and nonconventional hydrodynamically closed CE systems and their applications. Overall, the article emphasizes the importance of developing new CE-based analytical methods to ensure the high quality, safety, and efficacy of therapeutic peptides in clinical practice.

Sulfur-containing peptides: Synthesis and application in the discovery of potential drug candidates

Peptides act as biological mediators and play a key role of various physiological activities. Sulfur-containing peptides are widely used in natural products and drug molecules due to their unique biological activity and chemical reactivity of sulfur. Disulfides, thioethers, and thioamides are the most common motifs of sulfur-containing peptides, and they have been extensively studied and developed for synthetic methodology as well as pharmaceutical applications. This review focuses on the illustration of these three motifs in natural products and drugs, as well as the recent advancements in the synthesis of the corresponding core scaffolds.

Recent advances in peptide-based therapeutic strategies for breast cancer treatment

Breast cancer is the leading cause of cancer-related fatalities in female worldwide. Effective therapies with low side effects for breast cancer treatment and prevention are, accordingly, urgently required. Targeting anticancer materials, breast cancer vaccines and anticancer drugs have been studied for many years to decrease side effects, prevent breast cancer and suppress tumors, respectively. There are abundant evidences to demonstrate that peptide-based therapeutic strategies, coupling of good safety and adaptive functionalities are promising for breast cancer therapy. In recent years, peptide-based vectors have been paid attention in targeting breast cancer due to their specific binding to corresponding receptors overexpressed in cell. To overcome the low internalization, cell penetrating peptides (CPPs) could be selected to increase the penetration due to the electrostatic and hydrophobic interactions between CPPs and cell membranes. Peptide-based vaccines are at the forefront of medical development and presently, 13 types of main peptide vaccines for breast cancer are being studied on phase III, phase II, phase I/II and phase I clinical trials. In addition, peptide-based vaccines including delivery vectors and adjuvants have been implemented. Many peptides have recently been used in clinical treatments for breast cancer. These peptides show different anticancer mechanisms and some novel peptides could reverse the resistance of breast cancer to susceptibility. In this review, we will focus on current studies of peptide-based targeting vectors, CPPs, peptide-based vaccines and anticancer peptides for breast cancer therapy and prevention.

Strategies employed in the design of antimicrobial peptides with enhanced proteolytic stability

Due to the alarming developing rate of multidrug-resistant bacterial pathogens, the development and modification of antimicrobial peptides (AMPs) are unprecedentedly active. Despite the fact that considerable efforts have been expended on the discovery and design strategies of AMPs, the clinical translation of peptide antibiotics remains inadequate. A large number of articles and reviews credited the limited success of AMPs to their poor stability in the biological environment, particularly their poor proteolytic stability. In the past forty years, various design strategies have been used to improve the proteolytic stability of AMPs, such as sequence modification, cyclization, peptidomimetics, and nanotechnology. Herein, we focus our discussion on the progress made in improving the proteolytic stability of AMPs and the principle, successes, and limitations of various anti-proteolytic design strategies. It is of prospective significance to extend current insights into the degradation-related inactivation of AMPs and also alleviate/overcome the problem.

Advances on chemically modified antimicrobial peptides for generating peptide antibiotics

Antimicrobial peptides (AMPs) are pinpointed as promising molecules against antibiotic-resistant bacterial infections. Nevertheless, there is a discrepancy between the AMP sequences generated and the tangible outcomes in clinical trials. AMPs' limitations include enzymatic degradation, chemical/physical instability and toxicity toward healthy human cells. These factors compromise AMPs' bioavailability, resulting in limited therapeutic potential. To overcome such obstacles, peptidomimetic approaches, including glycosylation, PEGylation, lipidation, cyclization, grafting, D-amino acid insertion, stapling and dendrimers are promising strategies to fine-tune AMPs. Here we focused on chemical modifications applied for AMP optimization and how they have helped these peptide-based antibiotic candidates' design and translational potential.

Deimmunization of protein therapeutics - Recent advances in experimental and computational epitope prediction and deletion

Biotherapeutics, and antimicrobial proteins in particular, are of increasing interest for human medicine. An important challenge in the development of such therapeutics is their potential immunogenicity, which can induce production of anti-drug-antibodies, resulting in altered pharmacokinetics, reduced efficacy, and potentially severe anaphylactic or hypersensitivity reactions. For this reason, the development and application of effective deimmunization methods for protein drugs is of utmost importance. Deimmunization may be achieved by unspecific shielding approaches, which include PEGylation, fusion to polypeptides (e.g., XTEN or PAS), reductive methylation, glycosylation, and polysialylation. Alternatively, the identification of epitopes for T cells or B cells and their subsequent deletion through site-directed mutagenesis represent promising deimmunization strategies and can be accomplished through either experimental or computational approaches. This review highlights the most recent advances and current challenges in the deimmunization of protein therapeutics, with a special focus on computational epitope prediction and deletion tools.

PLA-PEG nanospheres decorated with phage display selected peptides as biomarkers for detection of human colorectal adenocarcinoma

Peptide-mediated targeting to colorectal cancer can increase selectivity and specificity of this cancer diagnosis acting as biomarkers. The present work aimed to select peptides using the phage display technique and associate the peptides with polymeric nanospheres in order to evaluate their cytotoxicity and selectivity during cell interaction with Caco-2 human colon tumor cell line. Two peptides identified by phage display (peptide-1 and peptide-2) were synthesized and exhibited purity higher than 84%. Poly(lactic acid)-block-polyethylene glycol nanospheres were prepared by nanoprecipitation and double emulsion methods in order to load the two peptides. Nanoparticles ranged in size from 114 to 150 nm and peptide encapsulation efficiency varied from 16 to 32%, depending on the methodology. No cytotoxic activity was observed towards Caco-2 tumor cell line, either free or loaded peptides in concentrations up to 3 μM at incubation times of 6 and 24 h, indicating safety as biomarkers. Fluorescein isothiocyanate-labeled peptides allowed evaluating selective interactions with Caco-2 cells, where peptide-1 entrapped in nanospheres showed greater intensity of co-localized cell fluorescence, in comparison to peptide-2. Peptide-1 loaded in nanospheres revealed promising to be investigated in further studies of selectivity with other human colon rectal cells as a potential biomarker.Graphical abstract.

Optimization of the Red Tilapia (Oreochromis spp.) Viscera Hydrolysis for Obtaining Iron-Binding Peptides and Evaluation of In Vitro Iron Bioavailability

Iron deficiencies continue to cause significant health problems in vulnerable populations. A good strategy to combat mineral deficiency includes fortification with iron-binding peptides. This research aims to determine the optimal conditions to hydrolyze red tilapia viscera (RTV) using Alcalase 2.4 L and recovery of iron-binding protein hydrolysate. The result showed that under the optimal hydrolysis condition including pH 10, 60 °C, E/S ratio of 0.306 U/g protein, and substrate concentration of 8 g protein/L, the obtained hydrolysate with 42.5% degree of hydrolysis (RTVH-B), displayed the maximal iron-binding capacity of 67.1 ± 1.9%. Peptide fractionation was performed using ultrafiltration and the <1 kDa fraction (FRTVH-V) expressed the highest iron-binding capacity of 95.8 ± 1.5%. Iron content of RTVH-B and its fraction was assessed, whereas iron uptake was measured indirectly as ferritin synthesis in a Caco-2 cell model and the result showed that bioavailability of bound minerals from protein complexes was significantly higher (p < 0.05) than iron salt in its free form, increased 4.7 times for the Fe2+-RTVH-B complex. This research suggests a potential application of RTVH-B as dietary supplements to improve iron absorption.

Development of a hybrid nanocarrier-recognizing tumor vasculature and penetrating the BBB for glioblastoma multi-targeting therapy

The success of glioma chemotherapy is hampered by poor drug penetration ability across the blood-brain barrier (BBB) and low intratumoral drug concentration. Novel tumor-targeted delivery systems are useful in specifically accumulating in the tumor foci and penetrating into the glioma core after entering into the brain. Here we show that a multi-targeting hybrid nanocarrier (Pep-MLHA HNPs) system based on hyaluronic acid (HA)-modified polymer and a functional peptide possesses multi-target capability and stronger penetration ability into the core of three-dimensional tumor spheroids, could migrate efficiently across the BBB in vitro. The intensity of the Pep-MLHA HNPs after transporting across the BBB was 5.2-fold and 5.6-fold higher than that of ML NPs in C6 and U87 cells, respectively. More interestingly, this multi-targeting hybrid system displayed high colloidal stability in PBS solution, and weak negative zeta potential (-1.99 ± 0.655 mV) minimizing nonspecific interactions with plasma proteins and promoting long-term circulation in vivo. Additionally, the multi-targeting hybrid system induced enhanced tumor localization in U87 in situ-bearing nude mice and xenograft-bearing nude mice after systemic administration. Furthermore, docetaxel (DTX)-loaded Pep-MLHA HNPs showed negligible systemic toxicity and enhanced therapeutic efficacy, with significantly improved survival rates in intracranial C6 glioma-bearing rats. The 50% survival rate of DTX/Pep-MLHA HNPs-treated rats (40 days) was significantly longer than that of rats treated with NS (22 days), Taxotere® (25 days), DTX/ML NPs (25 days), DTX/Pep NPs (32 days) and DTX/MLHA NPs (29 days). All the results suggested that the multi-targeting hybrid nanocarrier system is promising for glioma treatment.

Chemical biology of glycoproteins: From chemical synthesis to biological impact

Recent advances have demonstrated the feasibility and robustness of chemical synthesis for the production of homogeneously glycosylated protein forms (glycoforms). By taking advantage of the unmatchable flexibility and precision provided by chemical synthesis, the quantitative effects of glycosylation were obtained using chemical glycobiology approaches. These findings greatly advanced our fundamental knowledge of glycosylation. More importantly, analysis of these findings has led to the development of glycoengineering guidelines for rationally improving the properties of peptides and proteins. In this chapter, we present the key experimental steps for chemical biology studies of protein glycosylation, with the aim of facilitating and promoting research in this important but significantly underexplored area of biology.