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Lipid nanoparticles for delivering mRNA therapeutics hold immense promise for the treatment of a wide range of lung-associated diseases. However, the lack of effective methodologies capable of identifying the pulmonary delivery profile of chemically distinct lipid libraries poses a significant obstacle to the advancement of mRNA therapeutics. Here we report the implementation of a barcoded high-throughput screening system as a means to identify the lung-targeting efficacy of cationic, degradable lipid-like materials. We combinatorially synthesize 180 cationic, degradable lipids which are initially screened in vitro. We then use barcoding technology to quantify how the selected 96 distinct lipid nanoparticles deliver DNA barcodes in vivo. The top-performing nanoparticle formulation delivering Cas9-based genetic editors exhibits therapeutic potential for antiangiogenic cancer therapy within a lung tumor model in female mice. These data demonstrate that employing high-throughput barcoding technology as a screening tool for identifying nanoparticles with lung tropism holds potential for the development of next-generation extrahepatic delivery platforms. Identifying pulmonary delivery of lipid libraries poses an obstacle for mRNA drugs. Here, the authors use a barcoded screening system to identify lung-targeting of cationic, degradable lipid-like materials for mRNA delivery and gene editing in female preclinical models.

Lipid nanoparticles (LNPs) have emerged as a viable, clinically-validated platform for the delivery of mRNA therapeutics. LNPs have been utilized as mRNA delivery systems for applications including vaccines, gene therapy, and cancer immunotherapy. However, LNPs, which are typically composed of ionizable lipids, cholesterol, helper lipids, and lipid-anchored polyethylene glycol, often traffic to the liver which limits the therapeutic potential of the platform. Several approaches have been proposed to resolve this tropism such as post-synthesis surface modification or the addition of synthetic cationic lipids. Here, we present a strategy for achieving extrahepatic delivery of mRNA involving the incorporation of bile acids, a naturally-occurring class of cholesterol analogs, during LNP synthesis. We synthesized a series of bile acid-containing C14-4 LNPs by replacing cholesterol with bile acids (cholic acid, chenodeoxycholic acid, deoxycholic acid, or lithocholic acid) at various ratios. Bile acid-containing LNPs (BA-LNPs) were able to reduce delivery to liver cells and improve delivery in a variety of other cell types, including T cells, B cells, and epithelial cells. Our subsequent screening of selected LNP candidates injected intraperitoneally or intravenously identified a highly spleen tropic BA-LNP: CA-100, a four-component LNP containing cholic acid and no cholesterol. These screens also identified BA-LNP candidates demonstrating promise for other mRNA therapeutic applications such as for gastrointestinal or immune cell delivery. We further found that the substitution of cholic acid for cholesterol in an LNP formulation utilizing a different ionizable lipid, C12-200, also shifted mRNA delivery from the liver to the spleen, suggesting that this cholic acid replacement strategy may be generalizable. These results demonstrate the potential of a four-component BA-LNP formulation, CA-100, for extrahepatic mRNA delivery that could potentially be utilized for a range of therapeutic and vaccine applications.

Peptides and biologics provide unique opportunities to modulate intracellular targets not druggable by conventional small molecules. Most peptides and biologics are fused with cationic uptake moieties or formulated into nanoparticles to facilitate delivery, but these systems typically lack potency due to low uptake and/or entrapment and degradation in endolysosomal compartments. Because most delivery reagents comprise cationic lipids or polymers, there is a lack of reagents specifically optimized to deliver cationic cargo. Herein, we demonstrate the utility of the cytocompatible polymer poly(propylacrylic acid) (PPAA) to potentiate intracellular delivery of cationic biomacromolecules and nano-formulations. This approach demonstrates superior efficacy over all marketed peptide delivery reagents and enhances delivery of nucleic acids and gene editing ribonucleoproteins (RNPs) formulated with both commercially-available and our own custom-synthesized cationic polymer delivery reagents. These results demonstrate the broad potential of PPAA to serve as a platform reagent for the intracellular delivery of cationic cargo. Most reagents designed to deliver cargo into cells are cationic and so cannot deliver cationic cargo. Here the authors show that pretreating cells with the anionic polymer poly(propylacrylic acid) facilitates the uptake and endosomal escape of a wide variety of cationic cargo in numerous cell types.

Pre-eclampsia is a placental disorder that affects 3–5% of all pregnancies and is a leading cause of maternal and fetal morbidity worldwide 1 , 2 . With no drug available to slow disease progression, engineering ionizable lipid nanoparticles (LNPs) for extrahepatic messenger RNA (mRNA) delivery to the placenta is an attractive therapeutic option for pre-eclampsia. Here we use high-throughput screening to evaluate a library of 98 LNP formulations in vivo and identify a placenta-tropic LNP (LNP 55) that mediates more than 100-fold greater mRNA delivery to the placenta in pregnant mice than a formulation based on the Food and Drug Administration-approved Onpattro LNP (DLin-MC3-DMA) 3 . We propose an endogenous targeting mechanism based on β 2 -glycoprotein I adsorption that enables LNP delivery to the placenta. In both inflammation- and hypoxia-induced models of pre-eclampsia, a single administration of LNP 55 encapsulating vascular endothelial growth factor (VEGF) mRNA resolves maternal hypertension until the end of gestation. In addition, with our VEGF mRNA LNP 55 therapeutic, we demonstrate improvements in fetal health and partially restore placental vasculature, the local and systemic immune landscape and serum levels of soluble Fms-like tyrosine kinase-1, a clinical biomarker of pre-eclampsia 1 . Together, these results demonstrate the potential of this mRNA LNP platform for treating placental disorders such as pre-eclampsia. A platform for mRNA lipid nanoparticle delivery to the placenta to treat pre-eclampsia is shown to improve fetal and maternal health in mice and has potential clinical applications in obstetric disorders and women’s health.

Solid tumors remain difficult to treat via conventional and novel therapeutic strategies. Immunotherapies such as chimeric antigen receptor T (CAR‐T) cell therapy have been remarkably effective in treating hematological cancers, but their efficacy is limited in solid tumors. Recently, CAR macrophages (CAR‐Ms) have emerged as a promising solid tumor immunotherapy, primarily for their intrinsic tumor infiltration and effector functions. However, CAR‐Ms are engineered using viral transduction, which is associated with aberrant immunogenicity and toxicity. To overcome these challenges, we developed a bioinspired oxidized lipid nanoparticle (LNP) platform for mRNA‐based engineering of human CAR‐Ms. A library of 24 ionizable lipids was synthesized, formulated into LNPs, and screened for delivery to human macrophages. The top LNP was subsequently optimized using an orthogonal design of experiments and the physicochemical properties, such as size and mRNA encapsulation, were tuned via optimization of microfluidic mixing parameters, yielding an LNP formulation that significantly outperformed a gold standard C12‐200 LNP. Utilizing small molecule and antibody inhibitors, we demonstrate that uptake of optimized LNPs into macrophages is driven by apolipoprotein E independent macropinocytosis, which is further supported by potent extrahepatic spleen tropism upon intravenous administration to mice. Lastly, we demonstrate the translatability of this LNP platform and utilize it to engineer functional primary human HER2‐CAR‐Ms ex vivo with potent antigen‐specific tumor cell killing, validated in an ex vivo co‐culture with ovarian cancer cells. This bioinspired oxidized LNP platform demonstrates potential for engineering a range of human CAR‐M immunotherapies to treat various types of solid tumors.

Chimeric antigen receptor (CAR) monocyte and CAR macrophage therapy have recently emerged as promising new therapies for solid tumor immunotherapies. These therapies utilize viruses to engineer permanent CAR expression in patient-derived macrophages and monocytes that enables these immune cells to recognize and kill cancer cells in an antigen specific manner and simultaneously stimulate a broader anti-tumor immune response. However, virally engineered CARs targeted towards solid tumor antigens have a well-documented clinical history of inducing severe on-target-off-tumor toxicity. Further, due to their immunogenicity, viruses can be challenging to administer directly in vivo to engineer immune cells within the patient themselves. These engineering challenges pose significant barriers both to the successful clinical translation of these exciting therapies and their widespread adoption. Therefore, alternative approaches are needed to engineer these cells for safer tumor-targeted CAR therapies, and to enable their use as “off-the-shelf-therapies” with facile clinical access. In Chapter 2 of this work, we formulated a library of novel ionizable lipids into mRNA lipid nanoparticles (mRNA-LNPs), assess their mRNA delivery to human macrophages and identify a lead candidate LNP whose composition and physicochemical characteristics are optimized using statistical methods and microfluidics. We use the optimized macrophage LNPs to engineer functional patient-derived primary human CAR macrophages in an ex vivo tumor killing assay. In Chapter 3, we synthesized a second-generation structurally analogous ionizable lipid library complimentary to the bioactive lipids identified in Aim 1. We used these libraries to directly study the effect of electronegative spacing groups within the ionizable lipid on LNP physiochemical characteristics, in vitro and ex vivo mRNA delivery to immune cells, and in vivo biodistribution to immune cells. We demonstrate that an LNP with tropism to monocytes can be used to successfully engineer functional CD19-CAR monocytes directly in vivo. Lastly, in Chapter 4 of this work, we combined LNPs and monoclonal antibodies (mAb) to build hierarchical biomaterials with intrinsic immunostimulatory properties. We applied microfluidic droplet emulsions to precisely synthesize mAb-crosslinked LNPs that are capable of agonizing surface receptors of tumor-resident immune cells and can be applied as a novel intratumoral immunotherapy. Taken together, this work highlights materials and approaches that can be applied for robust immune cell engineering with applications to solid tumor immunotherapy and beyond.

Solid tumors remain difficult to treat via conventional and novel therapeutic strategies. Immunotherapies such as chimeric antigen receptor T (CAR-T) cell therapy have been remarkably effective in treating hematological cancers, but their efficacy is limited in solid tumors. Recently, CAR macrophages (CAR-Ms) have emerged as a promising solid tumor immunotherapy, primarily for their intrinsic tumor infiltration and effector functions. However, CAR-Ms are engineered using viral transduction, which is associated with aberrant immunogenicity and toxicity. To overcome these challenges, we developed a bioinspired oxidized lipid nanoparticle (LNP) platform for mRNA-based engineering of human CAR-Ms. A library of 24 ionizable lipids was synthesized, formulated into LNPs, and screened for delivery to human macrophages. The composition of the top LNP was subsequently optimized using an orthogonal design of experiments (DoE) and physicochemical properties, such as size and mRNA encapsulation, were tuned via optimization of microfluidic mixing parameters, yielding a particle that significantly outperformed a gold standard C12-200 LNP. Utilizing small molecule and antibody inhibitors, we demonstrate that uptake of optimized LNPs into macrophages is driven by apolipoprotein E (ApoE) independent macropinocytosis, which is further supported by potent extrahepatic spleen tropism upon intravenous administration to mice. Lastly, we demonstrate the translatability of this LNP platform and utilize it to engineer functional primary human HER2-CAR-Ms ex vivo with potent antigen-specific tumor killing, validated in an ex vivo co-culture with ovarian cancer cells. This bioinspired oxidized LNP platform can potentially be utilized to engineer a range of human CAR-M immunotherapies to treat various types of solid tumors.

Selective drug delivery to injured regions of the brain is an elusive, but biomedically important, goal. It is tempting to co-opt migrating white blood cells (WBC) to carry drugs to the injured brain, using natural WBC tropism. Current approaches to load cargoes to WBC have limited utility, particularly in acute conditions, due to the need for time consuming ex vivo manipulation and loading of cells. Physiological, in vivo loading of WBC may be advantageous in this scenario. Here we devised such a strategy, capitalizing on the unique features of the direct blood exchange between brain and lungs. Mediators emanating from the injured brain directly travel to the pulmonary vasculature via venous flow. In response to these mediators, WBCs, transiently residing in the pulmonary microvascular lumen, disembark and flow with arterial blood to the brain microvasculature, where they adhere and transmigrate to the brain parenchyma via the local chemoattractant gradient. We posited that direct in vivo targeting of cargoes to the pulmonary WBC pool may provide drug transfer to brain via this natural mechanism. To test this, we intravenously injected agents targeted to intercellular adhesion molecule 1 (ICAM) in mice with acute brain inflammation caused by direct injection of tumor necrosis factor alpha (TNF-α). We found that: A) At 2 hours, >20% of ICAM/NP accumulated in lungs, predominantly in WBCs; B) At 6 and 22 hours, ICAM/NP pulmonary uptake markedly decreased; C) In contrast, ICAM/NP uptake in brain increased ~5-fold in this time interval, concomitantly with migration of WBCs to the brain. Cranial window fluorescent microscopy confirmed WBC transport of ICAM/NP to the brain in TNF-α-challenged mice beyond the BBB. Importantly, demonstrating the pharmacologic relevance of this strategy, dexamethasone-loaded ICAM/liposomes abrogated brain edema in this model. In sum, coopting the natural homing of WBC from the lungs via ICAM-targeting to injured brain is an attractive strategy for precise interventions for treatment of acute brain injuries. Competing Interest Statement The authors have declared no competing interest.