Monomeric RGD peptides show unspecific fluid‐phase uptake in cells, whereas multimeric RGD peptides are thought to be internalized by integrin‐mediated endocytosis. However, a potential correlation between uptake mechanism and molecular mass has been neglected so far. A dual derivatization of peptide c(RGDw(7Br)K) was performed to investigate this. A fluorescent probe was installed by chemoselective Suzuki–Miyaura cross‐coupling of the 7‐bromotryptophan and a poly(ethylene glycol) (PEG) linker was attached to the lysine residue. Flow cytometry and live cell imaging confirmed unspecific uptake of the small, non‐PEGylated peptide, whereas the PEG₅₀₀₀ peptide conjugate unveiled a selective internalization by M21 cells overexpressing α_vβ₃ and no uptake in α_v‐deficient M21L cells.

Recombinant adeno-associated viruses (rAAV) provide outstanding options for customization and superior capabilities for gene therapy. To access their full potential, facile genetic manipulation is pivotal, including capsid loop modifications. Therefore, we assessed capsid tolerance to modifications of the structural VP proteins in terms of stability and plasticity. Flexible glycine-serine linkers of increasing sizes were, at the genetic level, introduced into the 587 loop region of the VP proteins of serotype 2, the best studied AAV representative. Analyses of biological function and thermal stability with respect to genome release of viral particles revealed structural plasticity. In addition, insertion of the 29 kDa enzyme β-lactamase into the loop region was tested with a complete or a mosaic modification setting. For the mosaic approach, investigation of VP2 trans expression revealed that a Kozak sequence was required to prevent leaky scanning. Surprisingly, even the full capsid modification with β-lactamase allowed for the assembly of capsids with a concomitant increase in size. Enzyme activity assays revealed lactamase functionality for both rAAV variants, which demonstrates the structural robustness of this platform technology.

The epidermal growth factor receptor (EGFR) plays a central role in the progression of many solid tumors. We used this validated target to analyze the de novo design of EGFR-binding peptides and their application for the delivery of complex payloads via rational design of a viral vector. Peptides were computationally designed to interact with the EGFR dimerization interface. Two new peptides and a reference (EDA peptide) were chemically synthesized, and their binding ability characterized. Presentation of these peptides in each of the 60 capsid proteins of recombinant adeno-associated viruses (rAAV) via a genetic based loop insertion enabled targeting of EGFR overexpressing tumor cell lines. Furthermore, tissue distribution and tumor xenograft specificity were analyzed with systemic injection in chicken egg chorioallantoic membrane (CAM) assays. Complex correlations between the targeting of the synthetic peptides and the viral vectors to cells and in ovo were observed. Overall, these data demonstrate the potential of computational design in combination with rational capsid modification for viral vector targeting opening new avenues for viral vector delivery and specifically suicide gene therapy.

During production, recombinant adeno-associated virus (rAAV) capsids are equipped with heterogeneous genetic payloads including undesired DNA impurities as well as truncated vector genomes. Comprehensive analysis of encapsidated DNA by long-read next-generation sequencing is destined to guide platform optimization and provide crucial insights into safety of gene therapies. We used nanopore sequencing for in-depth profiling of an rAAV9 batch produced using our proprietary split two-plasmid system in a 50-L bioreactor. We compared three methods for single-strand to double-strand DNA conversion and their impact on the sequencing data. We observed a distinct library size profile but comparable impurity distribution. We contrasted recent nanopore sequencing advancements such as the V14 chemistry and dorado basecalling software with the widespread V9 chemistry and detected a markedly increased read quality. Our data highlight a high vector batch quality with low plasmid-derived and host cell DNA impurities of random origin, critical for mitigating associated safety risks. Finally, we compared nanopore data with orthogonal SMRT sequencing data and observed a higher base quality, but largely similar length and impurity profiles. Taken together, nanopore sequencing is a state-of-the-art method for comprehensive, in-depth rAAV vector batch analysis during all stages of gene therapy development.

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.