Lysine-Derived Charge-Altering Releasable Transporters: Targeted Delivery of mRNA and siRNA to the Lungs

Targeted delivery of nucleic acid therapeutics to the lungs could transform treatment options for pulmonary disease. We have previously developed oligomeric charge-altering releasable transporters (CARTs) for in vivo mRNA transfection and demonstrated their efficacy for use in mRNA-based cancer vaccination and local immunomodulatory therapies against murine tumors. While our previously reported glycine-based CART-mRNA complexes (G-CARTs/mRNA) show selective protein expression in the spleen (mouse, >99%), here, we report a new lysine-derived CART-mRNA complex (K-CART/mRNA) that, without additives or targeting ligands, shows selective protein expression in the lungs (mouse, >90%) following systemic IV administration. We further show that by delivering siRNA using the K-CART, we can significantly decrease expression of a lung-localized reporter protein. Blood chemistry and organ pathology studies demonstrate that K-CARTs are safe and well-tolerated. We report on the new step economical, organocatalytic synthesis (two steps) of functionalized polyesters and oligo-carbonate-co-α-aminoester K-CARTs from simple amino acid and lipid-based monomers. The ability to direct protein expression selectively in the spleen or lungs by simple, modular changes to the CART structure opens fundamentally new opportunities in research and gene therapy.

Fingolimod-Conjugated Charge-Altering Releasable Transporters Efficiently and Specifically Deliver mRNA to Lymphocytes In Vivo and In Vitro

Charge-altering releasable transporters (CARTs) are a class of oligonucleotide delivery vehicles shown to be effective for delivery of messenger RNA (mRNA) both in vitro and in vivo. Here, we exploited the chemical versatility of the CART synthesis to generate CARTs containing the small-molecule drug fingolimod (FTY720) as a strategy to increase mRNA delivery and expression in lymphocytes through a specific ligand-receptor interaction. Fingolimod is an FDA-approved small-molecule drug that, upon in vivo phosphorylation, binds to the sphingosine-1-phosphate receptor 1 (S1P1), which is highly expressed on lymphocytes. Compared to its non-fingolimod-conjugated analogue, the fingolimod-conjugated CART achieved superior transfection of activated human and murine T and B lymphocytes in vitro. The higher transfection of the fingolimod-conjugated CARTs was lost when cells were exposed to a free fingolimod before transfection. In vivo, the fingolimod-conjugated CART showed increased mRNA delivery to marginal zone B cells and NK cells in the spleen, relative to CARTs lacking fingolimod. Moreover, fingolimod-CART-mediated mRNA delivery induces peripheral blood T-cell depletion similar to free fingolimod. Thus, we show that functionalization of CARTs with a pharmacologically validated small molecule can increase transfection of a cellular population of interest while conferring some of the targeting properties of the conjugated small molecule to the CARTs.

An mRNA SARS-CoV-2 Vaccine Employing Charge-Altering Releasable Transporters with a TLR-9 Agonist Induces Neutralizing Antibodies and T Cell Memory

The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with lipid nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called charge-altering releasable transporters (CARTs). Using these inherently nonimmunogenic vehicles, we can tailor the vaccine immunogenicity by inclusion of coformulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of receptor binding domain (RBD)-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long-lasting RBD-specific T_H1 T cell responses including CD4⁺ and CD8⁺ T cell memory.

An mRNA SARS-CoV-2 vaccine employing Charge-Altering Releasable Transporters with a TLR-9 agonist induces neutralizing antibodies and T cell memory

The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with Lipid Nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called Charge-Altering Releasable Transporters (CARTs). Using these inherently nonimmunogenic vehicles we can tailor the vaccine immunogenicity by inclusion of co-formulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of RBD-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long lasting RBD-specific T _H 1 T cell responses including CD4 ⁺ and CD8 ⁺ T cell memory.

Synthesis and mechanistic investigations of pH-responsive cationic poly(aminoester)s

The synthesis and degradation mechanisms of a class of pH-sensitive, rapidly degrading cationic poly(α-aminoester)s are described. These reactive, cationic polymers are stable at low pH in water, but undergo a fast and selective degradation at higher pH to liberate neutral diketopiperazines. Related materials incorporating oligo(α-amino ester)s have been shown to be effective gene delivery agents, as the charge-altering degradative behavior facilitates the delivery and release of mRNA and other nucleic acids in vitro and in vivo. Herein, we report detailed studies of the structural and environmental factors that lead to these rapid and selective degradation processes in aqueous buffers. At neutral pH, poly(α-aminoester)s derived from N-hydroxyethylglycine degrade selectively by a mechanism involving sequential 1,5- and 1,6-O→N acyl shifts to generate bis(N-hydroxyethyl) diketopiperazine. A family of structurally related cationic poly(aminoester)s was generated to study the structural influences on the degradation mechanism, product distribution, and pH dependence of the rate of degradation. The kinetics and mechanism of the pH-induced degradations were investigated by 1H NMR, model reactions, and kinetic simulations. These results indicate that polyesters bearing α-ammonium groups and appropriately positioned N-hydroxyethyl substituents are readily cleaved (by intramolecular attack) or hydrolyzed, representing dynamic "dual function" materials that are initially polycationic and transform with changing environment to neutral products.

Reversible RNA acylation for control of CRISPR-Cas9 gene editing

We report the development of post-transcriptional chemical methods that enable control over CRISPR–Cas9 gene editing activity both in in vitro assays and in living cells. We show that an azide-substituted acyl imidazole reagent (NAI-N₃) efficiently acylates CRISPR single guide RNAs (sgRNAs) in 20 minutes in buffer. Poly-acylated (“cloaked”) sgRNA was completely inactive in DNA cleavage with Cas9 in vitro, and activity was quantitatively restored after phosphine treatment. Delivery of cloaked sgRNA and Cas9 mRNA into HeLa cells was enabled by the use of charge-altering releasable transporters (CARTs), which outperformed commercial transfection reagents in transfecting sgRNA co-complexed with Cas9 encoding functional mRNA. Genomic DNA cleavage in the cells by CRISPR–Cas9 was efficiently restored after treatment with phosphine to remove the blocking acyl groups. Our results highlight the utility of reversible RNA acylation as a novel method for temporal control of genome-editing function.

We report the development of post-transcriptional chemical methods that enable control over CRISPR–Cas9 gene editing activity both in in vitro assays and in living cells.

Local Delivery of Ox40l, Cd80, and Cd86 mRNA Kindles Global Anticancer Immunity

Localized expression of effector molecules can initiate antitumor responses through engagement of specific receptors on target cells in the tumor microenvironment. These locally induced responses may also have a systemic effect, clearing additional tumors throughout the body. In this study, to evoke systemic antitumor responses, we utilized charge-altering releasable transporters (CART) for local intratumoral delivery of mRNA coding for costimulatory and immune-modulating factors. Intratumoral injection of the CART-mRNA complexes resulted in mRNA expression at the site of administration, transfecting a substantial proportion of tumor-infiltrating dendritic cells, macrophages, and T cells in addition to the tumor cells, resulting in a local antitumor effect. Using a two-tumor model, we further show that mRNA therapy locally administered to one tumor stimulated a systemic antitumor response, curing both tumors. The combination of Ox40l-, Cd80-, and Cd86-encoding mRNA resulted in the local upregulation of proinflammatory cytokines, robust local T-cell activation, and migration of immune cells to local draining lymph node or to an anatomically distant tumor. This approach delayed tumor growth, facilitated tumor regression, and cured tumors in both A20 and CT26 tumor models. These results highlight mRNA-CART therapy as a viable approach to induce systemic antitumor immunity from a single localized injection. SIGNIFICANCE: The mRNA-CART system is a highly effective delivery platform for delivering immunostimulatory genes into the tumor microenvironment for potential therapeutic development.

Organocatalytic ring-opening polymerization of morpholinones: new strategies to functionalized polyesters

The oxidative lactonization of N-substituted diethanolamines with the Pd catalyst [LPd(OAc)]2(2+)[OTf(-)]2 generates N-substituted morpholin-2-ones. The organocatalytic ring-opening polymerization of N-acyl morpholin-2-ones occurs readily to generate functionalized poly(aminoesters) with N-acylated amines in the polyester backbone. The thermodynamics of the ring-opening polymerization depends sensitively on the hybridization of the nitrogen of the heterocyclic lactone. N-Acyl morpholin-2-ones polymerize readily to generate polymorpholinones, but the N-aryl or N-alkyl substituted morpholin-2-ones do not polymerize. Experimental and theoretical studies reveal that the thermodynamics of ring opening correlates to the degree of pyramidalization of the endocyclic N-atom. Deprotection of the poly(N-Boc-morpholin-2-one) yields a water-soluble, cationic polymorpholinone.

Chemoselective Pd-catalyzed oxidation of polyols: synthetic scope and mechanistic studies

The regio- and chemoselective oxidation of unprotected vicinal polyols with [(neocuproine)Pd(OAc)]2(OTf)2 (1) (neocuproine = 2,9-dimethyl-1,10-phenanthroline) occurs readily under mild reaction conditions to generate α-hydroxy ketones. The oxidation of vicinal diols is both faster and more selective than the oxidation of primary and secondary alcohols; vicinal 1,2-diols are oxidized selectively to hydroxy ketones, whereas primary alcohols are oxidized in preference to secondary alcohols. Oxidative lactonization of 1,5-diols yields cyclic lactones. Catalyst loadings as low as 0.12 mol % in oxidation reactions on a 10 g scale can be used. The exquisite selectivity of this catalyst system is evident in the chemoselective and stereospecific oxidation of the polyol (S,S)-1,2,3,4-tetrahydroxybutane [(S,S)-threitol] to (S)-erythrulose. Mechanistic, kinetic, and theoretical studies revealed that the rate laws for the oxidation of primary and secondary alcohols differ from those of diols. Density functional theory calculations support the conclusion that β-hydride elimination to give hydroxy ketones is product-determining for the oxidation of vicinal diols, whereas for primary and secondary alcohols, pre-equilibria favoring primary alkoxides are product-determining. In situ desorption electrospray ionization mass spectrometry (DESI-MS) revealed several key intermediates in the proposed catalytic cycle.

A theoretical view of interstitial fluid pressure--volume measurements

A theoretical description of the mechanics of the interstitium is used to derive a relation for interstitial fluid pressure. The nature of this relation is examined and the dependence of fluid pressure on imbibed fluid, free fluid, and osmotic balances is defined. When the theory is applied to an idealized osmometer configuration, the predicted pressure-volume curve is analogous to the experimental observations of A. C. Guyton (1965, Circ. Res., 16, 452-460). Further, it is suggested that the similarity between the present theory and the experimental data of Guyton supports the hypothesis that a negative interstitial pressure and a dearth of free fluid is an expected and perhaps dominant state of normal tissue.

Analysis of transcapillary exchange and intraluminal transport in the microocclusion of single capillaries

A theoretical model, appropriate for data interpretation, is presented for the transcapillary fluid exchange and associated intraluminal hydrodynamic and solute transport occurring in the microocclusion of single capillaries. This analysis describes the spatial and temporal behavior of the intraluminal flow. A comparison of the theory with in vivo data suggests good qualitative agreement with that data and, further, the specification of filtration parameters in the model leads to good quantitative agreement regarding the displacement histories of erythrocytes. The model includes both natural and tagged colloidal osmotic influences and can, therefore, be used to represent experiments wherein the concentration of a dyed colloid is measured and related to fluid filtration. The relative merits of measuring colloidal concentration or erythrocyte displacement are discussed within the context of the model.