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At least 19 recordsLinked to original sources

Therapeutic in vivo delivery of gene editing agents.

In vivo gene editing therapies offer the potential to treat the root causes of many genetic diseases. Realizing the promise of therapeutic in vivo gene editing requires the ability to safely and efficiently deliver gene editing agents to relevant organs and tissues in vivo. Here, we review current delivery technologies that have been used to enable therapeutic in vivo gene editing, including viral vectors, lipid nanoparticles, and virus-like particles. Since no single delivery modality is likely to be appropriate for every possible application, we compare the benefits and drawbacks of each method and highlight opportunities for future improvements.

CRISPR-Cas Systems

Correction of pathogenic mitochondrial DNA in patient-derived disease models using mitochondrial base editors.

Mutations in the mitochondrial genome can cause maternally inherited diseases, cancer, and aging-related conditions. Recent technological progress now enables the creation and correction of mutations in the mitochondrial genome, but it remains relatively unknown how patients with primary mitochondrial disease can benefit from this technology. Here, we demonstrate the potential of the double-stranded DNA deaminase toxin A-derived cytosine base editor (DdCBE) to develop disease models and therapeutic strategies for mitochondrial disease in primary human cells. Introduction of the m.15150G > A mutation in liver organoids resulted in organoid lines with varying degrees of heteroplasmy and correspondingly reduced ATP production, providing a unique model to study functional consequences of different levels of heteroplasmy of this mutation. Correction of the m.4291T > C mutation in patient-derived fibroblasts restored mitochondrial membrane potential. DdCBE generated sustainable edits with high specificity and product purity. To prepare for clinical application, we found that mRNA-mediated mitochondrial base editing resulted in increased efficiency and cellular viability compared to DNA-mediated editing. Moreover, we showed efficient delivery of the mRNA mitochondrial base editors using lipid nanoparticles, which is currently the most advanced non-viral in vivo delivery system for gene products. Our study thus demonstrates the potential of mitochondrial base editing to not only generate unique in vitro models to study these diseases, but also to functionally correct mitochondrial mutations in patient-derived cells for future therapeutic purposes.

Humans

Extracellular vesicles-mediated delivery of SpCas9 RNPs for therapeutic gene editing in Spinocerebellar Ataxia Type 3.

Spinocerebellar Ataxia Type 3 (SCA3) is a neurodegenerative dominantly-inherited disorder caused by an overexpansion of a CAG tract within the ATXN3 gene, conferring toxic properties to the ataxin-3 protein. Genome editing with CRISPR-Cas9 enzymes is a promising strategy to inactivate mutant ATXN3 alleles, however, in vivo delivery remains challenging. Extracellular vesicles (EVs) are promising delivery vehicles for Cas9 and single guide RNA (sgRNA) ribonucleoproteins that minimize genomic exposure to highly active endonucleases. In this study, we designed SpCas9 with a palmitoylation motif that enables SpCas9 and sgRNA enrichment into EVs. Introduction of a photocleavable linker - PhoCl - allowed the photo-inducible release of SpCas9 from the palmitoylation motif in EVs, increasing target engagement to ATXN3 in vitro. EVs loaded with SpCas9 ribonucleoproteins resulted in ATXN3 knockout in SCA3 patient-derived iPSCs and two SCA3 animal models. These findings highlight an innovative route for transient delivery of gene editing tools. This approach provides a promising therapeutic platform for the treatment of genetic diseases, including SCA3.

Humans

Targeting of the oncogenic fusion EWSR1-FLI1 in Ewing sarcoma by CRISPR/dCas9 silencers.

Despite the revolutionary impact of genome engineering tools in medicine, the safe and effective intracellular delivery of CRISPR remains a major obstacle to clinical applications. Here, we utilize precision molecular targeting and delivery strategies based on CRISPR-nuclease-dead Cas9 (dCas9) systems adapted for epigenetic repression (dCas9-Krüppel-associated box [KRAB]) to silence oncogenic drivers with high selectivity. As proof of principle, we target the EWSR1-FLI1 translocation, which encodes a chimeric and hard-to-drug oncogenic transcription factor driving approximately 85% of the cases of Ewing sarcoma (EWS)-an aggressive childhood malignancy. We describe the development of a programmable, non-viral polymeric system for the delivery of dCas9-KRAB as ribonucleoprotein (RNP) payloads for EWSR1-FLI1 repression. We demonstrate highly efficient intracellular delivery of RNPs loaded in polyamide-amine (PAMAM) polymers functionalized by guanidino groups, resulting in robust silencing of EWSR1-FLI1 both in established cell line xenografts and in EWS-related patient-derived xenografts (PDXs) of EWS. We show that silencing of EWSR1-FLI1 is accompanied by potent anti-tumor effects. Collectively, we characterize an effective non-viral platform for in vivo delivery of dCas9-KRAB/RNPs, which could be adapted for the repression of any oncogene. We further outline dCas9/RNP formulations for future therapeutic applications to treat poor-prognosis cancers driven by hard-to-drug oncogenes.

CRISPR-dCas9

Bone-marrow-homing lipid nanoparticles for genome editing in diseased and malignant haematopoietic stem cells.

Therapeutic genome editing of haematopoietic stem cells (HSCs) would provide long-lasting treatments for multiple diseases. However, the in vivo delivery of genetic medicines to HSCs remains challenging, especially in diseased and malignant settings. Here we report on a series of bone-marrow-homing lipid nanoparticles that deliver mRNA to a broad group of at least 14 unique cell types in the bone marrow, including healthy and diseased HSCs, leukaemic stem cells, B cells, T cells, macrophages and leukaemia cells. CRISPR/Cas and base editing is achieved in a mouse model expressing human sickle cell disease phenotypes for potential foetal haemoglobin reactivation and conversion from sickle to non-sickle alleles. Bone-marrow-homing lipid nanoparticles were also able to achieve Cre-recombinase-mediated genetic deletion in bone-marrow-engrafted leukaemic stem cells and leukaemia cells. We show evidence that diverse cell types in the bone marrow niche can be edited using bone-marrow-homing lipid nanoparticles.

Animals

In Vivo Base Editing Partially Rescues Bone Dysplasia in a Mouse Model of Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a premature aging disorder affecting tissues of mesenchymal origin. Most patients harbor a c.1824C>T/p.G608= variant, commonly described as G608G, in exon 11 of LMNA that leads to aberrant splicing and production of the toxic progerin protein. In addition to cardiovascular, dermal, and adipose tissue deterioration, HGPS mouse models also develop progressive bone dysplasia that occurs in patients. Here we characterize the efficacy of in&#xa0;vivo mutation correction with an adenine base editor (ABE) to rescue structural and functional defects in HGPS transgenic murine bone tissue. Treatment of double-copy transgenic osteoblast cultures with a lentiviral-delivered CRISPR-Cas9 ABE achieved nearly 40% gene correction in&#xa0;vitro, resulting in significant reduction of progerin transcripts and protein, in the absence of selective agents. Furthermore, gene correction improved progeroid osteoblasts' capacity to deposit and mineralize extracellular matrix compared to untreated cultures. In&#xa0;vivo, a single intravenous dose of AAV9-delivered ABE corrected the mutation, achieving ~14%, ~22%, ~10% and <&#x2009;1% correction in bone by six months of age when administered at P3, P14, 1 and 4&#x2009;months of age, respectively. Partially rescued bone structural and physical parameters were observed in P14-treated mice with concomitant normalization of gene transcriptional programs and intracellular signaling pathways involved in bone remodeling. This work demonstrates in&#xa0;vivo delivery of a locus-specific DNA base editor to bone tissue, delineates the timing of treatment required for maximum efficacy, and suggests that this system might be tailored for application to other monogenic bone disorders.

Animals

In vitro and in vivo considerations of a novel matrix-controlled bovine progesterone-releasing intravaginal device.

An in vitro system measuring progesterone release from silicone matrixes into serum is described. Drug release followed a matrix-controlled diffusion model in which the cumulative quantity released was linear with the square root of time. A bovine intravaginal device, consisting of a steel coil coated on both sides with a progesterone silicone matrix, was used as an in vivo drug delivery system. In vivo drug release also was matrix controlled, with rates comparable to those obtained in vitro. However, lag times of 1.7 and 4.2 days before reaching the steady-state rate were obtained for the outer and inner surfaces, respectively. The combination of effects resulted in a pseudo-zero-order drug-releasing device in which cumulative drug released was linear with time for at least 16 days.

Animals

Delivery of genome editors with engineered virus-like particles.

Genome editing technologies have revolutionized biomedical sciences and biotechnology. However, their delivery in vivo remains one of the major obstacles for clinical translation. Here, we introduce various emerging genome editing systems and review different delivery systems have been developed to realize the promise of in vivo gene editing therapies. In particular, we focus on virus-like particles (VLPs), an emerging delivery platform and provide in depth analysis on recent advancements to improve VLPs delivery potential and highlight opportunities for future improvements. To this end, we also provide detail workflows for engineered VLP (eVLP) selection, production, and purification, along with methods for characterization and validation.

Gene Editing

Adeno-associated Virus (AAV) Capsid Chimeras with Enhanced Infectivity Reveal a Core Element in the AAV Genome Critical for both Cell Transduction and Capsid Assembly.

Adeno-associated viruses (AAV) have attracted significant attention in the field of gene and cell therapy due to highly effective delivery of therapeutic genes into human cells. The ability to generate recombinant AAV vectors compromised of unique or substituted protein sequences has led to the development of capsid variants with improved therapeutic properties. Seeking novel AAV vectors capable of enhanced transduction for therapeutic applications, we have developed a series of unique capsid variants termed AAV X-Vivo (AAV-XV) derived from chimeras of AAV12 VP1/2 sequences and the VP3 sequence of AAV6. These AAV variants showed enhanced infection of human primary T cells, hematopoietic stem cells, and neuronal cell lines over wildtype parental viruses, and superiority over AAV6 for genomic integration of DNA sequences by AAV alone or in combination with CRISPR gene editing. AAV-XV variants demonstrate transduction efficiency equivalent to AAV6 at multiplicities of infection 2 logs lower, enabling T cell engineering at low AAV doses. The protein coding sequence of these novel AAV chimeras revealed disruptions within the assembly-activating protein (AAP) which likely accounted for observed lower virus yield. A series of genome alterations, reverting the AAP sequence back to wildtype AAV6, had a negative impact on the enhanced transduction seen with AAV-VX, indicating overlapping functions within this sequence for both viral assembly and effective T cell transduction. Our findings show these AAV-XV variants are highly efficient at cell transduction at low dose and demonstrates the importance of the AAP coding region in both viral particle assembly and cell infection.IMPORTANCE A major hurdle to the therapeutic potential of AAV in gene therapy lies in achieving clinically meaningful AAV doses, and secondarily, ability to manufacture commercially viable titers of AAV to support this. By virtue of neutralizing antibodies against AAV that impede patient repeat-dosing, the dose of AAV for in vivo gene delivery has been high, which has resulted in unfortunate recent safety concerns and deaths in patients given higher-dose AAV gene therapy. We have generated new AAV variants possessing unique combinations of capsid proteins for gene and cell therapy applications termed AAV-XV, which have high levels of cell transduction and gene delivery at lower MOI. Furthermore, we demonstrate a novel finding, and an important consideration for recombinant AAV design, that a region of the AAV genome encoding the capsid viral protein and AAP is critical for both virus yield and the enhancement of infection/transduction.

Journal Article

Rewriting the script: gene therapy and genome editing for von Willebrand Disease.

In recent years gene therapy has emerged as a powerful technology for treatment of a large variety of inherited disorders. With the FDA approval of in vivo gene therapy of hemophilia A and B using AAV-mediated transgene delivery to hepatocytes, the path towards a new treatment era seemed paved. Also, CRISPR-Cas based approaches have reached the clinic, as in the ex vivo treatment of hematopoietic stem cells for sickle cell disease and thalassemia patients. The question arises whether these innovative strategies will also be suitable for patients with von Willebrand Disease (VWD). Whilst in and ex vivo delivery to endothelial cells (ECs) has been demonstrated, and CRISPR-Cas9 gene editing has been successful in ECs, there are currently no gene therapy options available for VWD. The wide variety of pathogenic VWF mutations makes development of broadly applicable, cost-effective gene therapies challenging. While delivery of von Willebrand factor (VWF) as a therapeutic transgene would be optimal, the size of VWF challenges efficient delivery. Therefore, treatment of VWD requires targeted, personalized gene therapy; for instance by using the newest CRISPR-Cas technologies which can be tailored to facilitate alteration and restoration of various pathogenic VWD variants. This review describes the inherited bleeding disorder VWD and potential gene therapy approaches for management of the disease. Thereby we are exploring different CRISPR-Cas technologies and recent developments in the field. Moreover, we will discuss the ongoing advances of in vivo delivery systems, all with the scope on ECs.

CRISPR-Cas, in vivo delivery

A survey of ex vivo/in vitro transduction efficiency of mammalian primary cells and cell lines with Nine natural adeno-associated virus (AAV1-9) and one engineered adeno-associated virus serotype.

BACKGROUND: The ability to deliver a gene of interest into a specific cell type is an essential aspect of biomedical research. Viruses can be a useful tool for this delivery, particularly in difficult to transfect cell types. Adeno-associated virus (AAV) is a useful gene transfer vector because of its ability to mediate efficient gene transduction in numerous dividing and quiescent cell types, without inducing any known pathogenicity. There are now a number of natural for that designed AAV serotypes that each has a differential ability to infect a variety of cell types. Although transduction studies have been completed, the bulk of the studies have been done in vivo, and there has never been a comprehensive study of transduction ex vivo/in vitro. METHODS: Each cell type was infected with each serotype at a multiplicity of infection of 100,000 viral genomes/cell and transduction was analyzed by flow cytometry + . RESULTS: We found that AAV1 and AAV6 have the greatest ability to transduce a wide range of cell types, however, for particular cell types, there are specific serotypes that provide optimal transduction. CONCLUSIONS: In this work, we describe the transduction efficiency of ten different AAV serotypes in thirty-four different mammalian cell lines and primary cell types. Although these results may not be universal due to numerous factors such as, culture conditions and/ or cell growth rates and cell heterogeneity, these results provide an important and unique resource for investigators who use AAV as an ex vivo gene delivery vector or who work with cells that are difficult to transfect.

Animals

AAV vectors: The Rubik's cube of human gene therapy.

Defective genes account for &#x223c;80% of the total of more than 7,000 diseases known to date. Gene therapy brings the promise of a one-time treatment option that will fix the errors in patient genetic coding. Recombinant viruses are highly efficient vehicles for in&#xa0;vivo gene delivery. Adeno-associated virus (AAV) vectors offer unique advantages, such as tissue tropism, specificity in transduction, eliciting of a relatively low immune responses, no incorporation into the host chromosome, and long-lasting delivered gene expression, making them the most popular viral gene delivery system in clinical trials, with three AAV-based gene therapy drugs already approved by the US Food and Drug Administration (FDA) or European Medicines Agency (EMA). Despite the success of AAV vectors, their usage in particular scenarios is still limited due to remaining challenges, such as poor transduction efficiency in certain tissues, low organ specificity, pre-existing humoral immunity to AAV capsids, and vector dose-dependent toxicity in patients. In the present review, we address the different approaches to improve AAV vectors for gene therapy with a focus on AAV capsid selection and engineering, strategies to overcome anti-AAV immune response, and vector genome design, ending with a glimpse at vector production methods and the current state of recombinant AAV (rAAV) at the clinical level.

United States

Residues on Adeno-associated Virus Capsid Lumen Dictate Interactions and Compatibility with the Assembly-Activating Protein.

The adeno-associated virus (AAV) serves as a broadly used vector system for in vivo gene delivery. The process of AAV capsid assembly remains poorly understood. The viral cofactor assembly-activating protein (AAP) is required for maximum AAV production and has multiple roles in capsid assembly, namely, trafficking of the structural proteins (VP) to the nuclear site of assembly, promoting the stability of VP against multiple degradation pathways, and facilitating stable interactions between VP monomers. The N-terminal 60 amino acids of AAP (AAPN) are essential for these functions. Presumably, AAP must physically interact with VP to execute its multiple functions, but the molecular nature of the AAP-VP interaction is not well understood. Here, we query how structurally related AAVs functionally engage AAP from AAV serotype 2 (AAP2) toward virion assembly. These studies led to the identification of key residues on the lumenal capsid surface that are important for AAP-VP and for VP-VP interactions. Replacing a cluster of glutamic acid residues with a glutamine-rich motif on the conserved VP beta-barrel structure of variants incompatible with AAP2 creates a gain-of-function mutant compatible with AAP2. Conversely, mutating positively charged residues within the hydrophobic region of AAP2 and conserved core domains within AAPN creates a gain-of-function AAP2 mutant that rescues assembly of the incompatible variant. Our results suggest a model for capsid assembly where surface charge/neutrality dictates an interaction between AAPN and the lumenal VP surface to nucleate capsid assembly.IMPORTANCE Efforts to engineer the AAV capsid to gain desirable properties for gene therapy (e.g., tropism, reduced immunogenicity, and higher potency) require that capsid modifications do not affect particle assembly. The relationship between VP and the cofactor that facilitates its assembly, AAP, is central to both assembly preservation and vector production. Understanding the requirements for this compatibility can inform manufacturing strategies to maximize production and reduce costs. Additionally, library-based approaches that simultaneously examine a large number of capsid variants would benefit from a universally functional AAP, which could hedge against overlooking variants with potentially valuable phenotypes that were lost during vector library production due to incompatibility with the cognate AAP. Studying interactions between the structural and nonstructural components of AAV enhances our fundamental knowledge of capsid assembly mechanisms and the protein-protein interactions required for productive assembly of the icosahedral capsid.

Amino Acid Sequence

Pharmacokinetics of drug permeation through human skin.

Based on sorption and permeation characteristics of scopolamine in human skin in vitro and drug elimination kinetics obtained from pharmacokinetic studies, a mathematical model was developed for estimating and optimizing the temporal pattern of scopolamine delivery from a transdermal therapeutic system through human skin in vivo. Experimentally measured scopolamine delivery in vivo conformed to this model.

Administration, Oral

Testing of hypoxic cell radiosensitizers in vivo.

Use has been made of the transplantable KHT sarcoma in C3H mice to test the in vivo effectiveness of some 2-, 4-, and 5-nitroimidazoles as hypoxic cell radiosensitizers. A comparison of the in vivo versus the in vitro sensitizing ability of misonidazole and metronidazole indicates some differences, probably due to drug delivery problems in vivo. The relative sensitizing abilities of eight 2-nitroimidazoles, two 4-nigroimidazoles and two 5-nitroimidazoles are compared on the basis of the amount of drug injected and the plasma levels obtained.

Animals

Glucose delivery: a modulator of glucose uptake in contracting skeletal muscle.

To evaluate glucose delivery and neuromuscular activity as modulators of glucose uptake in skeletal muscle, rat hindlimbs from pentobarbital-anesthetized rats were perfused in the presence of electrically stimulated muscular contractions. Glucose delivery was varied by altering non-cyclic perfusate flow. When flow was increased from 3 to 12 ml/min glucose disappearance increased from 1.1 +/- 0.2 to 4.0 +/- 0.2 mumol/min per 100 g rat (P less than 0.001). When glucose delivery was held constant, glucose disappearance was unaltered during muscular contractions. Insulin enhanced glucose disappearance, and its effect was unaltered during muscular contractions. Muscular contractions increased oxygen disappearance by two- to 3.5-fold and lactate appearance by 4.5- to fivefold (P less than 0.02). It was concluded that glucose delivery and insulin modulate glucose disappearance in isolated perfused rat hindlimbs. Electrical stimulation of muscle enhances lactate appearance and oxygen disappearance but does not alter glucose disappearance when flow is held constant. Because blood flow to muscle increases during exercise in vivo, increased glucose delivery may be a modulator of the augmented muscle glucose consumption observed under these conditions.

Animals