Phenothiazine-Biaryl-Containing Fluorescent RGD Peptides

Tumor-Homing Peptides as Crucial Component of Magnetic-Based Delivery Systems: Recent Developments and Pharmacoeconomical Perspective

According to data from the World Health Organization (WHO), cancer is considered to be one of the leading causes of death worldwide, and new therapeutic approaches, especially improved novel cancer treatment regimens, are in high demand. Considering that many chemotherapeutic drugs tend to have poor pharmacokinetic profiles, including rapid clearance and limited on-site accumulation, a combined approach with tumor-homing peptide (THP)-functionalized magnetic nanoparticles could lead to remarkable improvements. This is confirmed by an increasing number of papers in this field, showing that the on-target peptide functionalization of magnetic nanoparticles improves their penetration properties and ensures tumor-specific binding, which results in an increased clinical response. This review aims to highlight the potential applications of THPs in combination with magnetic carriers across various fields, including a pharmacoeconomic perspective.

Biomaterials-Mediated Tumor Infarction Therapy

Agents for tumor vascular infarction are recently developed therapeutic agents for the vascular destruction of tumors. They can suppress the progression of the tumor by preventing the flow of nutrition and oxygen to its tissues. Agents of tumor vascular infarction can be divided into three categories according to the differences in their pathways of action: those that use the thrombin-activating pathway, fibrin-activating pathway, and platelet-activating pathway. However, poor targeting ability, low permeation, and potential side-effects restrict the development of the corresponding drugs. Biomaterials can subtly avoid these drawbacks to suppress the tumor. In this article, the authors summarize currently used biomaterials for tumor infarction therapy with the goal of identifying its mechanism, and discuss outstanding deficiencies in methods of this kind.

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

The development of peptide stapling techniques to stabilise α-helical secondary structure motifs of peptides led to the design of modulators of protein–protein interactions, which had been considered undruggable for a long time. We disclose a novel approach towards peptide stapling utilising macrocyclisation by late-stage Suzuki–Miyaura cross-coupling of bromotryptophan-containing peptides of the catenin-binding domain of axin. Optimisation of the linker length in order to find a compromise between both sufficient linker rigidity and flexibility resulted in a peptide with an increased α-helicity and enhanced binding affinity to its native binding partner β-catenin. An increased proteolytic stability against proteinase K has been demonstrated.

Late-stage construction of stapled peptides through Fujiwara-Moritani reaction between tryptophan and olefins

Herein, the first example of a palladium-catalyzed Fujiwara-Moritani reaction for olefination of tryptophan (Trp) residues, free from directing groups, was presented. The developed reaction proceeds efficiently for peptide modification, ligation and peptide stapling.

Recent Advances in Late-Stage Construction of Stapled Peptides via C-H Activation

Stapled peptides have been widely applied in many fields, including pharmaceutical chemistry, diagnostic reagents, and materials science. However, most traditional stapled peptide preparation methods rely on prefunctionalizations, which limit the diversity of stapled peptides. Recently, the emergence of late-stage transition metal-catalyzed C-H activation in amino acids and peptides has attracted wide interest due to its robustness and applicability for peptide stapling. In this review, we summarize the methods for late-stage construction of stapled peptides via transition metal-catalyzed C-H activation.

Tuning the Biological Activity of RGD Peptides with Halotryptophans†

An array of l- and d-halotryptophans with different substituents at the indole moiety was synthesized employing either enzymatic halogenation by halogenases or incorporation of haloindoles using tryptophan synthase. Introduction of these Trp derivatives into RGD peptides as a benchmark system was performed to investigate their influence on bioactivity. Halotryptophan-containing RGD peptides display increased affinity toward integrin α_vβ₃ and enhanced selectivity over integrin α₅β₁. In addition, bromotryptophan was exploited as a platform for late-stage diversification by Suzuki-Miyaura cross-coupling (SMC), resulting in new-to-nature biaryl motifs. These peptides show enhanced affinity toward α_vβ₃, good affinity to α_vβ₈, and remarkable selectivity over α₅β₁ and α_IIbβ₃ while featuring fluorogenic properties. Their feasibility as a probe was demonstrated in vitro. Extensive molecular dynamics simulations were undertaken to elucidate NMR and high-performance liquid chromatography (HPLC) data for these late-stage diversified cyclic RGD peptides and to further characterize their conformational preferences.