Peptide therapeutics have played a notable role in medical practice since the advent of insulin therapy in the 1920s. Over 60 peptide drugs are approved in the United States and other major markets, and peptides continue to enter clinical development at a steady pace. Peptide drug discovery has diversified beyond its traditional focus on endogenous human peptides to include a broader range of structures identified from other natural sources or through medicinal chemistry efforts. We maintain a comprehensive dataset on peptides that have entered human clinical studies that includes over 150 peptides in active development today. Here we provide an overview of the peptide therapeutic landscape, including historical perspectives, molecular characteristics, regulatory benchmarks, and a therapeutic area breakdown.

Packaged molecular machines are available in large amounts using dual expression vectors that guide the preparation of Qβ virus-like particles encapsulating multiple copies of functional enzymes. Packaging is promoted by RNA aptamer sequences that bridge between the coat protein and a peptide tag fused to the desired cargo. Peptidase E and luciferase were thus encapsulated and shown to be catalytically active inside the particle. The encapsulated enzymes are less sensitive to inactivation by heating and surface adsorption than the corresponding free enzymes. This system represents a modular way to marry catalytic activity with robust scaffolding for the development of multifunctional materials. Keywordsvirus-like particles; Qβ bacteriophage; enzyme catalysis; enzyme protection; RNA-protein interactions; encapsulationThe sequestration of functional units from the environment is a hallmark of biological organization. In addition to encapsulation within lipid membrane-bound organelles, proteinaceous cages serve this purpose for many prokaryotes.[1] From a chemical perspective, the outstanding advantages of such packages are their capabilities for high selectivity and activity, both achieved by encapsulating only those catalysts required for the desired task in confined space, and the potential for the container to control its position in a complex environment. Artificial encapsulation or immobilization on solid supports has been shown to confer stability as well as facilitate purification and reuse.[2] While chemists have sequestered enzymes in or on a wide variety of non-biological compartments, Nature remains the undisputed master of the art.Protein nanoparticles represent a uniquely useful bridge between chemistry, materials science, and biology because they combine robust self-assembly properties with geneticallyenabled atomic control of chemical reactivity. The synthetic biomimetic packaging of functional proteins has been accomplished with several different types of protein nanoparticles. Two general strategies have been employed: genetic fusion of the cargo to a component that directs localization to the particle interior,[3] and non-specific packaging by in vitro assembly.[4] However, yields of the encapsulated protein products have been low, and, while examples of increased stability towards a variety of treatments have been noted, [3b, 3e, 4b] no quantitative kinetic comparisons of enzymes in free vs. protein-encapsulated forms have been described. We report here the use of a virus-like particle for this purpose, providing a general and robust method for the encapsulation of highly active enzymes. [8] The infectious phage particle packages its singlestranded RNA genome by virtue of a high-affinity interaction between a hairpin structure and interior-facing residues of the CP.[9] This interaction is preserved when the CP is expressed recombinantly to form VLPs[10] and we used this to direct the packaging of cargo materials (Figure 1). A related approach has been reported by Franzen and coworkers t...

Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA.

Manipulation of inorganic materials with organic macromolecules enables organisms to create biominerals such as bones and seashells, where occlusion of biomacromolecules within individual crystals generates superior mechanical properties. Current understanding of this process largely comes from studying the entrapment of micron-size particles in cooling melts. Here, by investigating micelle incorporation in calcite with atomic force microscopy and micromechanical simulations, we show that different mechanisms govern nanoscale occlusion. By simultaneously visualizing the micelles and propagating step edges, we demonstrate that the micelles experience significant compression during occlusion, which is accompanied by cavity formation. This generates local lattice strain, leading to enhanced mechanical properties. These results give new insight into the formation of occlusions in natural and synthetic crystals, and will facilitate the synthesis of multifunctional nanocomposite crystals.

The simultaneous expression in Escherichia coli cells of the Qβ virus-like particle (VLP) capsid protein and protein "cargo" tagged with a positively charged Rev peptide sequence leads to the spontaneous self-assembly of VLPs with multiple copies of the cargo inside. We report the packaging of four new enzymes with potential applications in medicine and chemical manufacturing. The captured enzymes are active while inside the nanoparticle shell and are protected from environmental conditions that lead to free-enzyme destruction. We also describe genetic modifications to the packaging scheme that shed light on the self-assembly mechanism of this system and allow indirect control over the internal packaging density of cargo. The technology was extended to create, via self-assembly, VLPs that simultaneously display protein ligands on the exterior and contain enzymes within. Inverse relationships were observed between the size of both the packaged and externally displayed protein or domains and nanoparticle yield. These results provide a general method for the rapid creation of robust protein nanoparticles with desired catalytic and targeting functionalities.