Engineered Microencapsulated Lactoferrin Nanoconjugates for Oral Targeted Treatment of Colon Cancer.

Despite current progress in the development of targeted therapies for cancer treatment, there is a lack in convenient therapeutics for colorectal cancer (CRC). Lactoferrin nanoparticles (Lf NPs) are a promising drug delivery system in cancer therapy. However, numerous obstacles impede their oral delivery, including instability against stomach enzymes and premature uptake during passage through the small intestine. Microencapsulation of Lf NPs offer a great solution for these obstacles. It can protect Lf NPs and their drug payloads from degradation in the upper gastrointestinal tract (GIT), reduce burst drug release, and improve the release profile of the encapsulated NPs triggered by stimuli in the colon. Here, we developed nanoparticle-in-microparticle delivery systems (NIMDs) for the oral delivery of docetaxel (DTX) and atorvastatin (ATR). The NPs were obtained by dual conjugation of DTX and ATR into the Lf backbone, which was further microencapsulated into calcium-crosslinked microparticles using polysaccharide-protein hybrid copolymers. The NIMDs showed no detectable drug release in the upper GIT compared to NPs. Furthermore, sustained release of the NPs from the NIMDs in rat cecal content was observed. Moreover, the in vivo study demonstrated the superiority of the NIMDs over NPs in CRC treatment by suppressing p-AKT, p-ERK1/2, and NF-κB. This study provides the proof of concept for using NIMDs to enhance the effect of protein NPs in CRC treatment.

N-methylation in amino acids and peptides: Scope and limitations.

Active pharmaceutical ingredients (APIs) can be divided into two types, namely chemical and biological entities. Traditionally, the former has been associated with the so-called small molecules. The revival of peptides in pharmaceutical industry results from their importance in many biological roles. However, low metabolic stability and the lack of oral availability of most peptides is the main drawback for peptide to fulfill that paradigmatic situation. In this regard, efforts are being channeled into addressing this issue by introducing restrictions into the flexible peptide backbone, mainly through N-methyl amino acids (NMAAs) or development of small cyclic peptides. In many cases, both the above restrictions are combined with the aim to enhance oral availability. The synthesis of NMAAs is complex and their introduction into the peptide chain brings additional synthetic challenges and also sometimes leads to side-reactions. Here we discuss the most efficient methods for the synthesis of NMAAs (either in solution or in solid phase) and also their introduction into peptide sequences. Special attention is also given to the detection of side reactions and the most efficient way to prevent them.

Formation of Nα-terminal 2-dialkyl amino oxazoles from guanidinated derivatives under mild conditions.

Oxazole-containing peptides are an important class of molecules in medicinal chemistry programs. Here we describe a convenient solid-phase synthesis of Nα-terminal oxazole peptides. The strategy took advantage of an intramolecular rearrangement side reaction that occurred during the guanidination of the Nα-amino function of a peptide still anchored on the solid-support. The substitution map of the N,N-dialkylamino oxazole obtained using this strategy differed completely from the one achieved through the heterocyclization of the Ser or Thr side chain with the preceding carbonyl group, which is a common approach for the preparation of these compounds. This unexpected reaction was observed with N-terminal aromatic and aliphatic amino acids that have a Gly as the last before residue in both short as well as long peptides; however, it does not form the oxazole ring if Gly was substituted with other amino acids.

Teixobactin as a scaffold for unlimited new antimicrobial peptides: SAR study.

It looks that a new era of antimicrobial peptides (AMPs) started with the discovery of teixobactin, which is a "head to side-chain" cyclodepsipeptide. It was isolated from a soil gram-negative b-proteobacteria by means of a revolutionary technique. Since there, several groups have developed synthetic strategies for efficient synthesis of this peptide and its analogues as well. Herein, all chemistries reported as well as the biological activity of the analogues are analyzed. Finally, some inputs regarding new trends for the next generation of analogues are discussed.

Bacteria Hunt Bacteria through an Intriguing Cyclic Peptide.

In the last few decades, peptides have been victorious over small molecules as therapeutics due to their broad range of applications, high biological activity, and high specificity. However, the main challenges to overcome if peptides are to become effective drugs is their low oral bioavailability and instability under physiological conditions. Cyclic peptides play a vital role in this context because they show higher stability under physiological conditions, higher membrane permeability, and greater oral bioavailability than that of their corresponding linear analogues. In this regard, cyclic antimicrobial peptides (AMPs) have gained considerable attention in the field of novel antibiotic development. Bacterial strains produce cyclic AMPs through two pathways: ribosomal and nonribosomal. This review provides an overview of the chemical classification of cyclic AMPs isolated from bacteria, and provides a description of their biological activity and mode of action.

In Vitro Antibacterial Activity of Teixobactin Derivatives on Clinically Relevant Bacterial Isolates.

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE) are included on the WHO high priority list of pathogens that require urgent intervention. Hence emphasis needs to be placed on developing novel class of molecules to tackle these pathogens. Teixobactin is a new class of antibiotic that has demonstrated antimicrobial activity against common bacteria. Here we examined the antimicrobial properties of three Teixobactin derivatives against clinically relevant bacterial isolates taken from South African patients. The minimum inhibitory concentration (MIC), the minimal bactericidal concentration (MBC), the effect of serum on MICs and the time-kill kinetics studies of our synthesized Teixobactin derivatives (3, 4, and 5) were ascertained following the CLSI 2017 guidelines and using the broth microdilution method. Haemolysis on red blood cells (RBCs) and cytotoxicity on peripheral blood mononuclear cells (PBMCs) were performed to determine the safety of these compounds. The MICs of 3, 4, and 5 against reference strains were 4-64 µg/ml, 2-64 µg/ml, and 0.5-64 µg/ml, respectively. The MICs observed for MRSA were (3) 32 µg/ml, (4) 2-4 µg/ml and (5) 2-4 µg/ml whilst those for VRE were (3) 8-16 µg/ml, (4) 4 µg/ml and (5) 2-16 µg/ml, respectively. In the presence of 50% human serum, there was no significant effect on the MICs. The compounds did not exhibit any effect on cell viability at their effective concentrations. Teixobactin derivatives (3, 4, and 5) inhibited bacterial growth in drug-resistant bacteria and hence emerge as potential antimicrobial agents. Molecular dynamic simulations suggested that the most dominant binding mode of Lys10-teixobactin (4) to lipid II is through the amide protons of the cycle, which is identical to data described in the literature for the natural teixobactin hence predicting the possibility of a similar mechanism of action.

Converting Teixobactin into a Cationic Antimicrobial Peptide (AMP).

Teixobactin is a head to side chain cyclodepsipeptide that contains two positive charges. One is found in the cycle, as a result of the presence of the guanidino-unusual amino acid L-allo-End, while the other is at the N-terminal. Here we introduce 26 new Teixobactin analogues with an increasing number of positive charges. In an attempt to fine-tune the biological activity of Teixobactin, we examined the effect of cationicity on the SAR of these analogues. The maximum number of positive charges to maintain the activity are three to four. Analogues with five positive charges show the lowest activity.

Lysine Scanning of Arg10-Teixobactin: Deciphering the Role of Hydrophobic and Hydrophilic Residues.

Teixobactin is a recently discovered antimicrobial cyclodepsipeptide with good activity against Gram positive bacteria. Taking Arg10-teixobactin as a reference, where the nonproteinogenic residue l-allo-enduracididine was substituted by arginine, a lysine scan was performed to identify the importance of keeping the balance between hydrophilic and hydrophobic amino acids for the antimicrobial activities of this peptide family. Thus, the substitution of four isoleucine residues present in the natural sequence by lysine led to a total loss of activity. On the other hand, the substitution of the polar noncharged residues and alanine by lysine allowed us to keep and in some cases to improve the antimicrobial activity.