Lipoamino bundle LNPs for efficient mRNA transfection of dendritic cells and macrophages show high spleen selectivity

Messenger RNA (mRNA) is a powerful tool for nucleic acid-based therapies and vaccination, but efficient and specific delivery to target tissues remains a significant challenge. In this study, we demonstrate lipoamino xenopeptide carriers as components of highly efficient mRNA LNPs. These lipo-xenopeptides are defined as 2D sequences in different 3D topologies (bundles or different U-shapes). The polar artificial amino acid tetraethylene pentamino succinic acid (Stp) and various lipophilic tertiary lipoamino fatty acids (LAFs) act as ionizable amphiphilic units, connected in different ratios via bisamidated lysines as branching units. A series of more lipophilic LAF4-Stp1 carriers with bundle topology is especially well suited for efficient encapsulation of mRNA into LNPs, facilitated cellular uptake and strongly enhanced endosomal escape. These LNPs display improved, faster transfection kinetics compared to standard LNP formulations, with high potency in a variety of tumor cell lines (including N2a neuroblastoma, HepG2 and Huh7 hepatocellular, and HeLa cervical carcinoma cells), J774A.1 macrophages, and DC2.4 dendritic cells. High transfection levels were obtained even in the presence of serum at very low sub-microgram mRNA doses. Upon intravenous application of only 3 µg mRNA per mouse, in vivo mRNA expression is found with a high selectivity for dendritic cells and macrophages, resulting in a particularly high overall preferred expression in the spleen.

mCherry on Top: A Positive Read-Out Cellular Platform for Screening DMD Exon Skipping Xenopeptide-PMO Conjugates

Phosphorodiamidate morpholino oligomers (PMOs) are a special type of antisense oligonucleotides (ASOs) that can be used as therapeutic modulators of pre-mRNA splicing. Application of nucleic-acid-based therapeutics generally requires suitable delivery systems to enable efficient transport to intended tissues and intracellular targets. To identify potent formulations of PMOs, we established a new in vitro-in vivo screening platform based on mdx exon 23 skipping. Here, a new in vitro positive read-out system (mCherry-DMDEx23) is presented that is sensitive toward the PMO(Ex23) sequence mediating DMD exon 23 skipping and, in this model, functional mCherry expression. After establishment of the reporter system in HeLa cells, a set of amphiphilic, ionizable xenopeptides (XPs) was screened in order to identify potent carriers for PMO delivery. The identified best-performing PMO formulation with high splice-switching activity at nanomolar concentrations in vitro was then translated to in vivo trials, where exon 23 skipping in different organs of healthy BALB/c mice was confirmed. The predesigned in vitro-in vivo workflow enables evaluation of PMO(Ex23) carriers without change of the PMO sequence and formulation composition. Furthermore, the identified PMO-XP conjugate formulation was found to induce highly potent exon skipping in vitro and redistributed PMO activity in different organs in vivo.

Transcriptional Targeting of Dendritic Cells Using an Optimized Human Fascin1 Gene Promoter

Deeper knowledge about the role of the tumor microenvironment (TME) in cancer development and progression has resulted in new strategies such as gene-based cancer immunotherapy. Whereas some approaches focus on the expression of tumoricidal genes within the TME, DNA-based vaccines are intended to be expressed in antigen-presenting cells (e.g., dendritic cells, DCs) in secondary lymphoid organs, which in turn induce anti-tumor T cell responses. Besides effective delivery systems and the requirement of appropriate adjuvants, DNA vaccines themselves need to be optimized regarding efficacy and selectivity. In this work, the concept of DC-focused transcriptional targeting was tested by applying a plasmid encoding for the luciferase reporter gene under the control of a derivative of the human fascin1 gene promoter (pFscnLuc), comprising the proximal core promoter fused to the normally more distantly located DC enhancer region. DC-focused activity of this reporter construct was confirmed in cell culture in comparison to a standard reporter vector encoding for luciferase under the control of the strong ubiquitously active cytomegalovirus promoter and enhancer (pCMVLuc). Both plasmids were also compared upon intravenous administration in mice. The organ- and cell type-specific expression profile of pFscnLuc versus pCMVLuc demonstrated favorable activity especially in the spleen as a central immune organ and within the spleen in DCs.

Molecular Chameleon Carriers for Nucleic Acid Delivery: The Sweet Spot between Lipoplexes and Polyplexes

Taking advantage of effective intracellular delivery mechanisms of both cationizable lipids and polymers, highly potent double pH-responsive nucleic acid carriers are generated by combining at least two lipo amino fatty acids (LAFs) as hydrophobic cationizable motifs with hydrophilic cationizable aminoethylene units into novel sequence-defined molecules. The pH-dependent tunable polarity of the LAF is successfully implemented by inserting a central tertiary amine, which disrupts the hydrophobic character once protonated, resulting in pH-dependent structural and physical changes. This "molecular chameleon character" turns out to be advantageous for dynamic nucleic acid delivery via lipopolyplexes. By screening different topologies (blocks, bundles, T-shapes, U-shapes), LAF types, and LAF/aminoethylene ratios, highly potent pDNA, mRNA, and siRNA carriers are identified, which are up to several 100-fold more efficient than previous carrier generations and characterized by very fast transfection kinetics. mRNA lipopolyplexes maintain high transfection activity in cell culture even in the presence of ≥90% serum at an ultra-low mRNA dose of 3 picogram (≈2 nanoparticles/cell), and thus are comparable in potency to viral nanoparticles. Importantly, they show great in vivo performance with high expression levels especially in spleen, tumor, lungs, and liver upon intravenous administration of 1-3 µg luciferase-encoding mRNA in mice.

Folate Receptor-Mediated Delivery of Cas9 RNP for Enhanced Immune Checkpoint Disruption in Cancer Cells

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system offers great opportunities for the treatment of numerous diseases by precise modification of the genome. The functional unit of the system is represented by Cas9/sgRNA ribonucleoproteins (RNP), which mediate sequence-specific cleavage of DNA. For therapeutic applications, efficient and cell-specific transport into target cells is essential. Here, Cas9 RNP nanocarriers are described, which are based on lipid-modified oligoamino amides and folic acid (FolA)-PEG to realize receptor-mediated uptake and gene editing in cancer cells. In vitro studies confirm strongly enhanced potency of receptor-mediated delivery, and the nanocarriers enable efficient knockout of GFP and two immune checkpoint genes, PD-L1 and PVR, at low nanomolar concentrations. Compared with non-targeted nanoparticles, FolA-modified nanocarriers achieve substantially higher gene editing including dual PD-L1/PVR gene disruption after injection into CT26 tumors in vivo. In the syngeneic mouse model, dual disruption of PD-L1 and PVR leads to CD8+ T cell recruitment and distinct CT26 tumor growth inhibition, clearly superior to the individual knockouts alone. The reported Cas9 RNP nanocarriers represent a versatile platform for potent and receptor-specific gene editing. In addition, the study demonstrates a promising strategy for cancer immunotherapy by permanent and combined immune checkpoint disruption.

Combating Drug Resistance by Exploiting miRNA-200c-Controlled Phase II Detoxification

Acquired drug resistance constitutes a serious obstacle to the successful therapy of cancer. In the process of therapy resistance, microRNAs can play important roles. In order to combat resistance formation and to improve the efficacy of chemotherapeutics, the mechanisms of the multifaceted hsa-miR-200c on drug resistance were elucidated. Upon knockout of hsa-miR-200c in breast carcinoma cells, a proteomic approach identified altered expression of glutathione S-transferases (GSTs) when cells were treated with the chemotherapeutic drug doxorubicin. In different hsa-miR-200c expression systems, such as knockout, inducible sponge and inducible overexpression, the differential expression of all members of the GST family was evaluated. Expression of hsa-miR-200c in cancer cells led to the repression of a multitude of these GSTs and as consequence, enhanced drug-induced tumor cell death which was evaluated for two chemotherapeutic drugs. Additionally, the influence of hsa-miR-200c on the glutathione pathway, which is part of the phase II detoxification mechanism, was investigated. Finally, the long-term effects of hsa-miR-200c on drug efficacy were studied in vitro and in vivo. Upon doxycycline induction of hsa-miR-200c, MDA-MB 231 xenograft mouse models revealed a strongly reduced tumor growth and an enhanced treatment response to doxorubicin. A combined treatment of these tumors with hsa-miR-200c and doxorubicin resulted in complete regression of the tumor in 60% of the animals. These results identify hsa-miR-200c as an important player regulating the cellular phase II detoxification, thus sensitizing cancer cells not expressing this microRNA to chemotherapeutics and reversing drug resistance through suppression of GSTs.

Optimizing pDNA Lipo-polyplexes: A Balancing Act between Stability and Cargo Release

When optimizing nanocarriers, structural motifs that are beneficial for the respective type of cargo need to be identified. Here, succinoyl tetraethylene pentamine (Stp)-based lipo-oligoaminoamides (OAAs) were optimized for the delivery of plasmid DNA (pDNA). Structural variations comprised saturated fatty acids with chain lengths between C2 and C18 and terminal cysteines as units promoting nanoparticle stabilization, histidines for endosomal buffering, and disulfide building blocks for redox-sensitive release. Biophysical and tumor cell culture screening established clear-cut relationships between lipo-OAAs and characteristics of the formed pDNA complexes. Based on the optimized alternating Stp-histidine backbones, lipo-OAAs containing fatty acids with chain lengths around C6 to C10 displayed maximum gene transfer with around 500-fold higher gene expression than that of C18 lipo-OAA analogues. Promising lipo-OAAs, however, showed only moderate in vivo efficiency. In vitro testing in 90% full serum, revealing considerable inhibition of lytic and gene-transfer activity, was found as a new screening model predictive for intravenous applications in vivo.

Hyaluronate siRNA nanoparticles with positive charge display rapid attachment to tumor endothelium and penetration into tumors

A cationizable sequence-defined lipo-oligoaminoamide (lipo-OAA) conferring stable assembly of siRNA into ~200 nm sized complexes contains an N-terminal azidolysine for covalent coating of formed nanoparticles with dibenzocyclooctyne-amine (DBCO)-modified hyaluronic acid (HA). Depending on the applied equivalents of DBCO-HA, stable nanoparticles with either cationic or anionic surface charge can be formed. The unmodified and two types of covalent HA-modified siRNA nanoparticles differ in their biological characteristics. Both types of HA coated siRNA complexes show an enhanced cellular uptake over uncoated complexes and facilitate efficient gene silencing, but differ in intracellular uptake pathways and distribution. Upon intravenous administration in mice, beyond our expectation and in contrast to the in vitro findings, only the cationic HA nanoparticles but neither the non-coated cationic nor the anionic HA complexes were able to target subcutaneous Huh 7 tumors and exert potent (78%) gene silencing. The favorable and very fast accumulation of cationic HA nanoparticles was confirmed in another subcutaneous tumor model. As evidenced by 3D nanoparticle distribution within Huh 7 tumors evaluated at early time points of 5 min and 45 min, only the cationic HA-based nanoparticles rapidly attach to the tumor endothelium and subsequently penetrate into tumor, in contrast to the analogous anionic HA coated or the cationic non-coated formulation.