In Vivo mRNA CAR T Cell Engineering via Targeted Ionizable Lipid Nanoparticles with Extrahepatic Tropism.

With six therapies approved by the Food and Drug Association, chimeric antigen receptor (CAR) T cells have reshaped cancer immunotherapy. However, these therapies rely on ex vivo viral transduction to induce permanent CAR expression in T cells, which contributes to high production costs and long-term side effects. Thus, this work aims to develop an in vivo CAR T cell engineering platform to streamline production while using mRNA to induce transient, tunable CAR expression. Specifically, an ionizable lipid nanoparticle (LNP) is utilized as these platforms have demonstrated clinical success in nucleic acid delivery. Though LNPs often accumulate in the liver, the LNP platform used here achieves extrahepatic transfection with enhanced delivery to the spleen, and it is further modified via antibody conjugation (Ab-LNPs) to target pan-T cell markers. The in vivo evaluation of these Ab-LNPs confirms that targeting is necessary for potent T cell transfection. When using these Ab-LNPs for the delivery of CAR mRNA, antibody and dose-dependent CAR expression and cytokine release are observed along with B cell depletion of up to 90%. In all, this work conjugates antibodies to LNPs with extrahepatic tropism, evaluates pan-T cell markers, and develops Ab-LNPs capable of generating functional CAR T cells in vivo.

In situ PEGylation of CAR T cells alleviates cytokine release syndrome and neurotoxicity.

Chimeric antigen receptor T (CAR T) cell immunotherapy is successful at treating many cancers. However, it often induces life-threatening cytokine release syndrome (CRS) and neurotoxicity. Here, we show that in situ conjugation of polyethylene glycol (PEG) to the surface of CAR T cells ('PEGylation') creates a polymeric spacer that blocks cell-to-cell interactions between CAR T cells, tumour cells and monocytes. Such blockage hinders intensive tumour lysing and monocyte activation by CAR T cells and, consequently, decreases the secretion of toxic cytokines and alleviates CRS-related symptoms. Over time, the slow expansion of CAR T cells decreases PEG surface density and restores CAR T cell-tumour-cell interactions to induce potent tumour killing. This occurs before the restoration of CAR T cell-monocyte interactions, opening a therapeutic window for tumour killing by CAR T cells before monocyte overactivation. Lethal neurotoxicity is also lower when compared with treatment with the therapeutic antibody tocilizumab, demonstrating that in situ PEGylation of CAR T cells provides a materials-based strategy for safer cellular immunotherapy.

mRNA Lipid Nanoparticles for Ex Vivo Engineering of Immunosuppressive T Cells for Autoimmunity Therapies.

Cell-based therapies for autoimmune diseases have gained significant traction, with several approaches centered around the regulatory T (Treg) cell─a well-known immunosuppressive cell characterized by its expression of the transcription factor Foxp3. Unfortunately, due to low numbers of Treg cells available in circulation, harvesting and culturing Treg cells remains a challenge. It has been reported that engineering Foxp3 expression in CD4+ T cells can result in a Treg-like phenotype; however, current methods result in the inefficient engineering of these cells. Here, we develop an ionizable lipid nanoparticle (LNP) platform to effectively deliver Foxp3 mRNA to CD4+ T cells. We successfully engineer CD4+ T cells into Foxp3-T (FP3T) cells that transiently exhibit an immunosuppressive phenotype and functionally suppress the proliferation of effector T cells. These results demonstrate the promise of an LNP platform for engineering immunosuppressive T cells with potential applications in autoimmunity therapies.

Ionizable Lipid Nanoparticles for In Vivo mRNA Delivery to the Placenta during Pregnancy.

Ionizable lipid nanoparticles (LNPs) are the most clinically advanced nonviral platform for mRNA delivery. While they have been explored for applications including vaccines and gene editing, LNPs have not been investigated for placental insufficiency during pregnancy. Placental insufficiency is caused by inadequate blood flow in the placenta, which results in increased maternal blood pressure and restricted fetal growth. Therefore, improving vasodilation in the placenta can benefit both maternal and fetal health. Here, we engineered ionizable LNPs for mRNA delivery to the placenta with applications in mediating placental vasodilation. We designed a library of ionizable lipids to formulate LNPs for mRNA delivery to placental cells and identified a lead LNP that enables in vivo mRNA delivery to trophoblasts, endothelial cells, and immune cells in the placenta. Delivery of this top LNP formulation encapsulated with VEGF-A mRNA engendered placental vasodilation, demonstrating the potential of mRNA LNPs for protein replacement therapy during pregnancy to treat placental disorders.

Orthogonal Design of Experiments for Engineering of Lipid Nanoparticles for mRNA Delivery to the Placenta.

During healthy pregnancy, the placenta develops to allow for exchange of nutrients and oxygen between the mother and the fetus. However, placental dysregulation can lead to several pregnancy disorders, such as preeclampsia and fetal growth restriction. Recently, lipid nanoparticle (LNP)-mediated delivery of messenger RNA (mRNA) has been explored as a promising approach to treat these disorders. Here, iterative libraries of LNPs with varied excipient molar ratios are screened in vitro for enhanced mRNA delivery to placental cells with minimal cytotoxicity when compared to an LNP formulation with a standard excipient molar ratio. LNP C5, the top formulation identified by these screens, demonstrates a fourfold increase in mRNA delivery in vitro compared to the standard formulation. Intravenous administration of LNP C5 to pregnant mice achieves improved in vivo placental mRNA delivery compared to the standard formulation and mediates mRNA delivery to placental trophoblasts, endothelial cells, and immune cells. These results identify LNP C5 as a promising optimized LNP formulation for placental mRNA delivery and further validates the design of experiments strategy for LNP excipient optimization to enhance mRNA delivery to cell types and organs of interest.

Orthogonal Design of Experiments for Optimization of Lipid Nanoparticles for mRNA Engineering of CAR T Cells.

Viral engineered chimeric antigen receptor (CAR) T cell therapies are potent, targeted cancer immunotherapies, but their permanent CAR expression can lead to severe adverse effects. Nonviral messenger RNA (mRNA) CAR T cells are being explored to overcome these drawbacks, but electroporation, the most common T cell transfection method, is limited by cytotoxicity. As a potentially safer nonviral delivery strategy, here, sequential libraries of ionizable lipid nanoparticle (LNP) formulations with varied excipient compositions were screened in comparison to a standard formulation for improved mRNA delivery to T cells with low cytotoxicity, revealing B10 as the top formulation with a 3-fold increase in mRNA delivery. When compared to electroporation in primary human T cells, B10 LNPs induced comparable CAR expression with reduced cytotoxicity while demonstrating potent cancer cell killing. These results demonstrate the impact of excipient optimization on LNP performance and support B10 LNPs as a potent mRNA delivery platform for T cell engineering.

One-Component Multifunctional Sequence-Defined Ionizable Amphiphilic Janus Dendrimer Delivery Systems for mRNA.

Efficient viral or nonviral delivery of nucleic acids is the key step of genetic nanomedicine. Both viral and synthetic vectors have been successfully employed for genetic delivery with recent examples being DNA, adenoviral, and mRNA-based Covid-19 vaccines. Viral vectors can be target specific and very efficient but can also mediate severe immune response, cell toxicity, and mutations. Four-component lipid nanoparticles (LNPs) containing ionizable lipids, phospholipids, cholesterol for mechanical properties, and PEG-conjugated lipid for stability represent the current leading nonviral vectors for mRNA. However, the segregation of the neutral ionizable lipid as droplets in the core of the LNP, the "PEG dilemma", and the stability at only very low temperatures limit their efficiency. Here, we report the development of a one-component multifunctional ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA that exhibits high activity at a low concentration of ionizable amines organized in a sequence-defined arrangement. Six libraries containing 54 sequence-defined IAJDs were synthesized by an accelerated modular-orthogonal methodology and coassembled with mRNA into dendrimersome nanoparticles (DNPs) by a simple injection method rather than by the complex microfluidic technology often used for LNPs. Forty four (81%) showed activity in vitro and 31 (57%) in vivo. Some, exhibiting organ specificity, are stable at 5 °C and demonstrated higher transfection efficiency than positive control experiments in vitro and in vivo. Aside from practical applications, this proof of concept will help elucidate the mechanisms of packaging and release of mRNA from DNPs as a function of ionizable amine concentration, their sequence, and constitutional isomerism of IAJDs.

Ionizable Lipid Nanoparticle-Mediated mRNA Delivery for Human CAR T Cell Engineering.

Chimeric antigen receptor (CAR) T cell therapy relies on the ex vivo manipulation of patient T cells to create potent, cancer-targeting therapies, shown to be capable of inducing remission in patients with acute lymphoblastic leukemia and large B cell lymphoma. However, current CAR T cell engineering methods use viral delivery vectors, which induce permanent CAR expression and could lead to severe adverse effects. Messenger RNA (mRNA) has been explored as a promising strategy for inducing transient CAR expression in T cells to mitigate the adverse effects associated with viral vectors, but it most commonly requires electroporation for T cell mRNA delivery, which can be cytotoxic. Here, ionizable lipid nanoparticles (LNPs) were designed for ex vivo mRNA delivery to human T cells. A library of 24 ionizable lipids was synthesized, formulated into LNPs, and screened for luciferase mRNA delivery to Jurkat cells, revealing seven formulations capable of enhanced mRNA delivery over lipofectamine. The top-performing LNP formulation, C14-4, was selected for CAR mRNA delivery to primary human T cells. This platform induced CAR expression at levels equivalent to electroporation, with substantially reduced cytotoxicity. CAR T cells engineered via C14-4 LNP treatment were then compared to electroporated CAR T cells in a coculture assay with Nalm-6 acute lymphoblastic leukemia cells, and both CAR T cell engineering methods elicited potent cancer-killing activity. These results demonstrate the ability of LNPs to deliver mRNA to primary human T cells to induce functional protein expression, and indicate the potential of LNPs to enhance mRNA-based CAR T cell engineering methods.

Evaluating the Mechanisms of Light-Triggered siRNA Release from Nanoshells for Temporal Control Over Gene Regulation.

The ability to regulate intracellular gene expression with exogenous nucleic acids such as small interfering RNAs (siRNAs) has substantial potential to improve the study and treatment of disease. However, most transfection agents and nanoparticle-based carriers that are used for the intracellular delivery of nucleic acids cannot distinguish between diseased and healthy cells, which may cause them to yield unintended widespread gene regulation. An ideal delivery system would only silence targeted proteins in diseased tissue in response to an external stimulus. To enable spatiotemporal control over gene silencing, researchers have begun to develop nucleic acid-nanoparticle conjugates that keep their nucleic acid cargo inactive until it is released from the nanoparticle on-demand by externally applied near-infrared laser light. This strategy can overcome several limitations of other nucleic acid delivery systems, but the mechanisms by which these platforms operate remain ill understood. Here, we perform a detailed investigation of the mechanisms by which silica core/gold shell nanoshells (NSs) release conjugated siRNA upon excitation with either pulsed or continuous wave (CW) near-infrared (NIR) light, with the goal of providing insight into how these nanoconjugates can enable on-demand gene regulation. We demonstrate that siRNA release from NSs upon pulsed laser irradiation is a temperature-independent process that is substantially more efficient than siRNA release triggered by CW irradiation. Contrary to literature, which suggests that only pulsed irradiation releases siRNA duplexes, we found that both modes of irradiation release a mixture of siRNA duplexes and single-stranded oligonucleotides, but that pulsed irradiation results in a higher percentage of released duplexes. To demonstrate that the siRNA released from NSs upon pulsed irradiation remains functional, we evaluated the use of NSs coated with green fluorescent protein (GFP)-targeted siRNA (siGFP-NS) for on-demand knockdown of GFP in cells. We found that GFP-expressing cells treated with siGFP-NS and irradiated with a pulsed laser experienced a 33% decrease in GFP expression compared to cells treated with no laser. Further, we observed that light-triggered gene silencing mediated by siGFP-NS is more potent than using commercial transfection agents to deliver siRNA into cells. This work provides unprecedented insight into the mechanisms by which plasmonic NSs release siRNA upon light irradiation and demonstrates the importance of thoroughly characterizing photoresponsive nanosystems for applications in triggered gene regulation.

Emerging strategies for nanomedicine in autoimmunity.

Autoimmune disorders have risen to be among the most prevalent chronic diseases across the globe, affecting approximately 5-7% of the population. As autoimmune diseases steadily rise in prevalence, so do the number of potential therapeutic strategies to combat them. In recent years, fundamental research investigating autoimmune pathologies has led to the emergence of several cellular targets that provide new therapeutic opportunities. However, key challenges persist in terms of accessing and specifically combating the dysregulated, self-reactive cells while avoiding systemic immune suppression and other off-target effects. Fortunately, the continued advancement of nanomedicines may provide strategies to address these challenges and bring innovative autoimmunity therapies to the clinic. Through precise engineering and rational design, nanomedicines can possess a variety of physicochemical properties, surface modifications, and cargoes, allowing for specific targeting of therapeutics to pathological cell and organ types. These advances in nanomedicine have been demonstrated in cancer therapies and have the broad potential to advance applications in autoimmunity therapies as well. In this review, we focus on leveraging the power of nanomedicine for prevalent autoimmune disorders throughout the body. We expand on three key areas for the development of autoimmunity therapies - avoiding systemic immunosuppression, balancing interactions with the immune system, and elevating current platforms for delivering complex cargoes - and emphasize how nanomedicine-based strategies can overcome these barriers and enable the development of next-generation, clinically relevant autoimmunity therapies.

Small-molecule-mediated control of the anti-tumour activity and off-tumour toxicity of a supramolecular bispecific T cell engager.

The broader clinical use of bispecific T cell engagers for inducing anti-tumour toxicity is hindered by their on-target off-tumour toxicity and the associated neurotoxicity and cytokine-release syndrome. Here we show that the off-tumour toxicity of a supramolecular bispecific T cell engager binding to the T cell co-receptor CD3 and to the human epidermal growth factor receptor 2 on breast tumour cells can be halted by disengaging the T cells from the tumour cells via the infusion of the small-molecule drug amantadine, which disassembles the supramolecular aggregate. In mice bearing human epidermal growth factor receptor 2-expressing tumours and with a human immune system, high intravenous doses of such a 'switchable T cell nanoengager' elicited strong tumour-specific adaptive immune responses that prevented tumour relapse, while the infusion of amantadine restricted off-tumour toxicity, cytokine-release syndrome and neurotoxicity. Supramolecular chemistry may be further leveraged to control the anti-tumour activity and off-tumour toxicity of bispecific antibodies.

Ionizable lipid nanoparticles for RAS protease delivery to inhibit cancer cell proliferation.

Mutations in RAS, a family of proteins found in all human cells, drive a third of cancers, including many pancreatic, colorectal, and lung cancers. However, there is a lack of clinical therapies that can effectively prevent RAS from causing tumor growth. Recently, a protease was engineered that specifically degrades active RAS, offering a promising new tool for treating these cancers. However, like many other intracellularly acting protein-based therapies, this protease requires a delivery vector to reach its site of action within the cell. In this study, we explored the incorporation of cationic lipids into ionizable lipid nanoparticles (LNPs) to develop a RAS protease delivery platform capable of inhibiting cancer cell proliferation in vitro and in vivo. A library of 13 LNPs encapsulating RAS protease was designed, and each formulation was evaluated for in vitro delivery efficiency and toxicity. A subset of four top-performing LNP formulations was identified and further evaluated for their impact on cancer cell proliferation in human colorectal cancer cells with mutated KRAS in vitro and in vivo, as well as their in vivo biodistribution and toxicity. In vivo, both the concentration of cationic lipid and type of cargo influenced LNP and cargo distribution. All lead candidate LNPs showed RAS protease functionality in vitro, and the top-performing formulation achieved effective intracellular RAS protease delivery in vivo, decreasing cancer cell proliferation in an in vivo xenograft model and significantly reducing tumor growth and size. Overall, this work demonstrates the use of LNPs as an effective delivery platform for RAS proteases, which could potentially be utilized for cancer therapies.

High-Throughput In Vivo Screening Identifies Differential Influences on mRNA Lipid Nanoparticle Immune Cell Delivery by Administration Route.

Immune modulation through the intracellular delivery of nucleoside-modified mRNA to immune cells is an attractive approach for in vivo immunoengineering, with applications in infectious disease, cancer immunotherapy, and beyond. Lipid nanoparticles (LNPs) have come to the fore as a promising nucleic acid delivery platform, but LNP design criteria remain poorly defined, making the rate-limiting step for LNP discovery the screening process. In this study, we employed high-throughput in vivo LNP screening based on molecular barcoding to investigate the influence of LNP composition on immune tropism with applications in vaccines and systemic immunotherapies. Screening a large LNP library under both intramuscular (i.m.) and intravenous (i.v.) injection, we observed differential influences on LNP uptake by immune populations across the two administration routes, gleaning insight into LNP design criteria for in vivo immunoengineering. In validation studies, the lead LNP formulation for i.m. administration demonstrated substantial mRNA translation in the spleen and draining lymph nodes with a more favorable biodistribution profile than LNPs formulated with the clinical standard ionizable lipid DLin-MC3-DMA (MC3). The lead LNP formulations for i.v. administration displayed potent immune transfection in the spleen and peripheral blood, with one lead LNP demonstrating substantial transfection of splenic dendritic cells and another inducing substantial transfection of circulating monocytes. Altogether, the immunotropic LNPs identified by high-throughput in vivo screening demonstrated significant promise for both locally- and systemically-delivered mRNA and confirmed the value of the LNP design criteria gleaned from our screening process, which could potentially inform future endeavors in mRNA vaccine and immunotherapy applications.

Bile acid-containing lipid nanoparticles enhance extrahepatic mRNA delivery.

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. Methods: 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. Results: Bile acid-containing LNPs (BA-LNPs) were able to reduce delivery to liver cells in vitro and improve delivery in a variety of other cell types, including T cells, B cells, and epithelial cells. Our subsequent in vivo 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. Conclusion: 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.

Antigen Presenting Cell Mimetic Lipid Nanoparticles for Rapid mRNA CAR T Cell Cancer Immunotherapy.

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable clinical success in the treatment of hematological malignancies. However, producing these bespoke cancer-killing cells is a complicated ex vivo process involving leukapheresis, artificial T cell activation, and CAR construct introduction. The activation step requires the engagement of CD3/TCR and CD28 and is vital for T cell transfection and differentiation. Though antigen-presenting cells (APCs) facilitate activation in vivo, ex vivo activation relies on antibodies against CD3 and CD28 conjugated to magnetic beads. While effective, this artificial activation adds to the complexity of CAR T cell production as the beads must be removed prior to clinical implementation. To overcome this challenge, this work develops activating lipid nanoparticles (aLNPs) that mimic APCs to combine the activation of magnetic beads and the transfection capabilities of LNPs. It is shown that aLNPs enable one-step activation and transfection of primary human T cells with the resulting mRNA CAR T cells reducing tumor burden in a murine xenograft model, validating aLNPs as a promising platform for the rapid production of mRNA CAR T cells.

Testing the In Vitro and In Vivo Efficiency of mRNA-Lipid Nanoparticles Formulated by Microfluidic Mixing.

Lipid nanoparticles (LNPs) have attracted widespread attention recently with the successful development of the COVID-19 mRNA vaccines by Moderna and Pfizer/BioNTech. These vaccines have demonstrated the efficacy of mRNA-LNP therapeutics and opened the door for future clinical applications. In mRNA-LNP systems, the LNPs serve as delivery platforms that protect the mRNA cargo from degradation by nucleases and mediate their intracellular delivery. The LNPs are typically composed of four components: an ionizable lipid, a phospholipid, cholesterol, and a lipid-anchored polyethylene glycol (PEG) conjugate (lipid-PEG). Here, LNPs encapsulating mRNA encoding firefly luciferase are formulated by microfluidic mixing of the organic phase containing LNP lipid components and the aqueous phase containing mRNA. These mRNA-LNPs are then tested in vitro to evaluate their transfection efficiency in HepG2 cells using a bioluminescent plate-based assay. Additionally, mRNA-LNPs are evaluated in vivo in C57BL/6 mice following an intravenous injection via the lateral tail vein. Whole-body bioluminescence imaging is performed by using an in vivo imaging system. Representative results are shown for the mRNA-LNP characteristics, their transfection efficiency in HepG2 cells, and the total luminescent flux in C57BL/6 mice.

Ligand-tethered lipid nanoparticles for targeted RNA delivery to treat liver fibrosis.

Lipid nanoparticle-mediated RNA delivery holds great potential to treat various liver diseases. However, targeted delivery of RNA therapeutics to activated liver-resident fibroblasts for liver fibrosis treatment remains challenging. Here, we develop a combinatorial library of anisamide ligand-tethered lipidoids (AA-lipidoids) using a one-pot, two-step modular synthetic method and adopt a two-round screening strategy to identify AA-lipidoids with both high potency and selectivity to deliver RNA payloads to activated fibroblasts. The lead AA-lipidoid AA-T3A-C12 mediates greater RNA delivery and transfection of activated fibroblasts than its analog without anisamide and the FDA-approved MC3 ionizable lipid. In a preclinical model of liver fibrosis, AA-T3A-C12 enables ~65% silencing of heat shock protein 47, a therapeutic target primarily expressed by activated fibroblasts, which is 2-fold more potent than MC3, leading to significantly reduced collagen deposition and liver fibrosis. These results demonstrate the potential of AA-lipidoids for targeted RNA delivery to activated fibroblasts. Furthermore, these synthetic methods and screening strategies open a new avenue to develop and discover potent lipidoids with targeting properties, which can potentially enable RNA delivery to a range of cell and tissue types that are challenging to access using traditional lipid nanoparticle formulations.

Lipid Nanoparticle Delivery of Small Proteins for Potent In Vivo RAS Inhibition.

Mutated RAS proteins are potent oncogenic drivers and have long been considered "undruggable". While RAS-targeting therapies have recently shown promise, there remains a clinical need for RAS inhibitors with more diverse targets. Small proteins represent a potential new therapeutic option, including K27, a designed ankyrin repeat protein (DARPin) engineered to inhibit RAS. However, K27 functions intracellularly and is incapable of entering the cytosol on its own, currently limiting its utility. To overcome this barrier, we have engineered a lipid nanoparticle (LNP) platform for potent delivery of functional K27-D30─a charge-modified version of the protein─intracellularly in vitro and in vivo. This system efficiently encapsulates charge-modified proteins, facilitates delivery in up to 90% of cells in vitro, and maintains potency after at least 45 days of storage. In vivo, these LNPs deliver K27-D30 to the cytosol of cancerous cells in the liver, inhibiting RAS-driven growth and ultimately reducing tumor load in an HTVI-induced mouse model of hepatocellular carcinoma. This work shows that K27 holds promise as a new cancer therapeutic when delivered using this LNP platform. Furthermore, this technology has the potential to broaden the use of LNPs to include new cargo types─beyond RNA─for diverse therapeutic applications.

Ionizable Lipid Nanoparticles with Integrated Immune Checkpoint Inhibition for mRNA CAR T Cell Engineering.

The programmed cell death protein 1 (PD-1) signaling pathway is a major source of dampened T cell activity in the tumor microenvironment. While clinical approaches to inhibiting the PD-1 pathway using antibody blockade have been broadly successful, these approaches lead to widespread PD-1 suppression, increasing the risk of autoimmune reactions. This study reports the development of an ionizable lipid nanoparticle (LNP) platform for simultaneous therapeutic gene expression and RNA interference (RNAi)-mediated transient gene knockdown in T cells. In developing this platform, interesting interactions are observed between the two RNA cargoes when co-encapsulated, leading to improved expression and knockdown characteristics compared to delivering either cargo alone. This messenger RNA (mRNA)/small interfering RNA (siRNA) co-delivery platform is adopted to deliver chimeric antigen receptor (CAR) mRNA and siRNA targeting PD-1 to primary human T cells ex vivo and strong CAR expression and PD-1 knockdown are observed without apparent changes to overall T cell activation state. This delivery platform shows great promise for transient immune gene modulation for a number of immunoengineering applications, including the development of improved cancer immunotherapies.

Ionizable Lipid Nanoparticles for Therapeutic Base Editing of Congenital Brain Disease.

Delivery of mRNA-based therapeutics to the perinatal brain holds great potential in treating congenital brain diseases. However, nonviral delivery platforms that facilitate nucleic acid delivery in this environment have yet to be rigorously studied. Here, we screen a diverse library of ionizable lipid nanoparticles (LNPs) via intracerebroventricular (ICV) injection in both fetal and neonatal mice and identify an LNP formulation with greater functional mRNA delivery in the perinatal brain than an FDA-approved industry standard LNP. Following in vitro optimization of the top-performing LNP (C3 LNP) for codelivery of an adenine base editing platform, we improve the biochemical phenotype of a lysosomal storage disease in the neonatal mouse brain, exhibit proof-of-principle mRNA brain transfection in vivo in a fetal nonhuman primate model, and demonstrate the translational potential of C3 LNPs ex vivo in human patient-derived brain tissues. These LNPs may provide a clinically translatable platform for in utero and postnatal mRNA therapies including gene editing in the brain.