Current progress and limitations of AAV mediated delivery of protein therapeutic genes and the importance of developing quantitative pharmacokinetic/pharmacodynamic (PK/PD) models

Clinical Pharmacology Perspective on Development of Adeno-Associated Virus Vector-Based Retina Gene Therapy

Adeno-associated virus (AAV) vector-based gene therapy is an innovative modality being increasingly investigated to treat diseases by modifying or replacing defective genes or expressing therapeutic entities. With its unique anatomic and physiological characteristics, the eye constitutes a very attractive target for gene therapy. Specifically, the ocular space is easily accessible and is generally considered "immune-privileged" with a low risk of systemic side effects following local drug administration. As retina cells have limited cellular turnover, a one-time gene delivery has the potential to provide long-term transgene expression. Despite the initial success with voretigene neparvovec (Luxturna), the first approved retina gene therapy, there are still challenges to be overcome for successful clinical development of these products and scientific questions to be answered. The current review paper aims to integrate published experience learned thus far for AAV-based retina gene therapy related to preclinical to clinical translation; first-in-human dose selection; relevant bioanalytical assays and strategies; clinical development considerations including trial design, biodistribution and vector shedding, immunogenicity, transgene expression, and pediatric populations; opportunities for model-informed drug development; and regulatory perspectives. The information presented herein is intended to serve as a guide to inform the clinical development strategy for retina gene therapy with a focus on clinical pharmacology.

Short cell-penetration peptide conjugated bioreducible polymer enhances gene editing of CRISPR system

CRISPR-based gene therapy offers precise targeting and specific editing of disease-related gene sequences, potentially yielding long-lasting treatment effects. However, efficient delivery remains a significant challenge for its widespread application. In this study, we design a novel short peptide-conjugated bioreducible polymer named TSPscp as a safe and effective delivery vector for the CRISPR system. Our results show that TSPscp markedly boosts transcriptional activation and genome editing activities of multiple CRISPR systems as confirmed by decomposition-seq and Deep-seq, which is resulted from its capability in facilitating delivery of plasmid DNA by promoting cellular uptake and lysosomal escape. Additionally, TSPscp further enhances genome editing of CRISPR by delivery of minicircle DNA, a condensed form of regular plasmid DNA. More importantly, TSPscp significantly improves delivery and genome editing of CRISPR system in vivo. In summary, our study highlights TSPscp as a promising delivery tool for CRISPR applications in vivo.

Engineered nanoparticles promote cardiac tropism of AAV vectors

Cardiac muscle targeting is a notoriously difficult task. Although various nanoparticle (NP) and adeno-associated viral (AAV) strategies with heart tissue tropism have been developed, their performance remains suboptimal. Significant off-target accumulation of i.v.-delivered pharmacotherapies has thwarted development of disease-modifying cardiac treatments, such as gene transfer and gene editing, that may address both rare and highly prevalent cardiomyopathies and their complications. Here, we present an intriguing discovery: cargo-less, safe poly (lactic-co-glycolic acid) particles that drastically improve heart delivery of AAVs and NPs. Our lead formulation is referred to as ePL (enhancer polymer). We show that ePL increases selectivity of AAVs and virus-like NPs (VLNPs) to the heart and de-targets them from the liver. Serotypes known to have high (AAVrh.74) and low (AAV1) heart tissue tropisms were tested with and without ePL. We demonstrate up to an order of magnitude increase in heart-to-liver accumulation ratios in ePL-injected mice. We also show that ePL exhibits AAV/NP-independent mechanisms of action, increasing glucose uptake in the heart, increasing cardiac protein glycosylation, reducing AAV neutralizing antibodies, and delaying blood clearance of AAV/NPs. Current approaches utilizing AAVs or NPs are fraught with challenges related to the low transduction of cardiomyocytes and life-threatening immune responses; our study introduces an exciting possibility to direct these modalities to the heart at reduced i.v. doses and, thus, has an unprecedented impact on drug delivery and gene therapy. Based on our current data, the ePL system is potentially compatible with any therapeutic modality, opening a possibility of cardiac targeting with numerous pharmacological approaches.

Investigation of Antibody Pharmacokinetics in the Brain Following Intra-CNS Administration and Development of PBPK Model to Characterize the Data

Despite the promising potential of direct central nervous system (CNS) antibody administration to enhance brain exposure, there remains a significant gap in understanding the disposition of antibodies following different intra-CNS injection routes. To bridge this knowledge gap, this study quantitatively investigated the brain pharmacokinetics (PK) of antibodies following intra-CNS administration. The microdialysis samples from the striatum (ST), cerebrospinal fluid (CSF) samples through cisterna magna (CM) puncture, plasma, and brain homogenate samples were collected to characterize the pharmacokinetics (PK) profiles of a non-targeting antibody, trastuzumab, following intracerebroventricular (ICV), intracisternal (ICM), and intrastriatal (IST) administration. For a comprehensive analysis, these intra-CNS injection datasets were juxtaposed against our previously acquired intravenous (IV) injection data obtained under analogous experimental conditions. Our findings highlighted that direct CSF injections, either through ICV or ICM, resulted in ~ 5-6-fold higher interstitial fluid (ISF) drug exposure than IV administration. Additionally, the low bioavailability observed following IST administration indicates the existence of a local degradation process for antibody elimination in the brain ISF along with the ISF bulk flow. The study further refined a physiologically based pharmacokinetic (PBPK) model based on new observations by adding the perivascular compartments, oscillated CSF flow, and the nonspecific uptake and degradation of antibodies by brain parenchymal cells. The updated model can well characterize the antibody PK following systemic and intra-CNS administration. Thus, our research offers quantitative insight into antibody brain disposition pathways and paves the way for determining optimal dosing and administration strategies for antibodies targeting CNS disorders.

Structural basis for nuclear import of bat adeno-associated virus capsid protein

Adeno-associated viruses (AAV) are one of the world's most promising gene therapy vectors and as a result, are one of the most intensively studied viral vectors. Despite a wealth of research into these vectors, the precise characterisation of AAVs to translocate into the host cell nucleus remains unclear. Recently we identified the nuclear localization signals of an AAV porcine strain and determined its mechanism of binding to host importin proteins. To expand our understanding of diverse AAV import mechanisms we sought to determine the mechanism in which the Cap protein from a bat-infecting AAV can interact with transport receptor importins for translocation into the nucleus. Using a high-resolution crystal structure and quantitative assays, we were able to not only determine the exact region and residues of the N-terminal domain of the Cap protein which constitute the functional NLS for binding with the importin alpha two protein, but also reveal the differences in binding affinity across the importin-alpha isoforms. Collectively our results allow for a detailed molecular view of the way AAV Cap proteins interact with host proteins for localization into the cell nucleus.

Optimization strategies and advances in the research and development of AAV-based gene therapy to deliver large transgenes

Adeno-associated virus (AAV)-based therapies are recognized as one of the most potent next-generation treatments for inherited and genetic diseases. However, several biological and technological aspects of AAV vectors remain a critical issue for their widespread clinical application. Among them, the limited capacity of the AAV genome significantly hinders the development of AAV-based gene therapy. In this context, genetically modified transgenes compatible with AAV are opening up new opportunities for unlimited gene therapies for many genetic disorders. Recent advances in de novo protein design and remodelling are paving the way for new, more efficient and targeted gene therapeutics. Using computational and genetic tools, AAV expression cassette and transgenic DNA can be split, miniaturized, shuffled or created from scratch to mediate efficient gene transfer into targeted cells. In this review, we highlight recent advances in AAV-based gene therapy with a focus on its use in translational research. We summarize recent research and development in gene therapy, with an emphasis on large transgenes (>4.8 kb) and optimizing strategies applied by biomedical companies in the research pipeline. We critically discuss the prospects for AAV-based treatment and some emerging challenges. We anticipate that the continued development of novel computational tools will lead to rapid advances in basic gene therapy research and translational studies.

Cervical Cancer Therapeutics: An In-depth Significance of Herbal and Chemical Approaches of Nanoparticles

Cervical cancer emerges as a prominent health issue, demanding attention on a global level for women's well-being, which frequently calls for more specialized and efficient treatment alternatives. Traditional therapies may have limited tumour targeting and adverse side effects. Recent breakthroughs have induced a transformative shift in the strategies employed against cervical cancer. biocompatible herbal nanoparticles and metallic particles made of gold, silver, and iron have become promising friends in the effort to fight against this serious disease and understand the possibility of these nanoparticles for targeted medication administration. this review article delves into the latest advancements in cervical cancer research. The safety and fabrication of these nanomaterials and their remarkable efficacy against cervical tumour spots are addressed. This review study, in short, provides an extensive introduction to the fascinating field of metallic and herbal nanoparticles in cervical cancer treatment. The information that has been examined points to a bright future in which women with cervical cancer may experience fewer side effects, more effective therapy, and an improved quality of life. This review holds promise and has the potential to fundamentally reshape the future of cervical cancer treatment by addressing urgent issues and unmet needs in the field.

Whole-Body Disposition and Physiologically Based Pharmacokinetic Modeling of Adeno-Associated Viruses and the Transgene Product

To facilitate model-informed drug development (MIDD) of adeno-associated virus (AAV) therapy, here we have developed a physiologically based pharmacokinetic (PBPK) model for AAVs following preclinical investigation in mice. After 2E11 Vg/mouse dose of AAV8 and AAV9 encoding a monoclonal antibody (mAb) gene, whole-body disposition of both the vector and the transgene mAb was evaluated over 3 weeks. At steady-state, the following tissue-to-blood (T/B) concentration ratios were found for AAV8/9: ∼50 for liver; ∼10 for heart and muscle; ∼2 for brain, lung, kidney, adipose, and spleen; ≤1 for bone, skin, and pancreas. T/B values for mAb were compared with the antibody biodistribution coefficients, and five different clusters of organs were identified based on their transgene expression profile. All the biodistribution data were used to develop a novel AAV PBPK model that incorporates: (i) whole-body distribution of the vector; (ii) binding, internalization, and intracellular processing of the vector; (iii) transgene expression and secretion; and (iv) whole-body disposition of the secreted transgene product. The model was able to capture systemic and tissue PK of the vector and the transgene-produced mAb reasonably well. Pathway analysis of the PBPK model suggested that liver, muscle, and heart are the main contributors for the secreted transgene mAb. Unprecedented PK data and the novel PBPK model developed here provide the foundation for quantitative systems pharmacology (QSP) investigations of AAV-mediated gene therapies. The PBPK model can also serve as a quantitative tool for preclinical study design and preclinical-to-clinical translation of AAV-based gene therapies.

Pharmacokinetics of AAV9 Mediated Trastuzumab Expression in Rat Brain Following Systemic and Local Administration

INTRODUCTION

Recombinant adeno-associated viruses(rAAVs) are an attractive tool to ensure long-term expression monoclonal antibody(mAb) in the central nervous system(CNS). It is still unclear whether systemic injection or local CNS administration of AAV9 is more beneficial for the exposure of the expressed mAb in the brain. Hence, we compared the biodistribution and transgene expression following AAV9-Trastuzumab administration through different routes.

METHODS AND RESULT

In-house generated AAV9-Trastuzumab vectors were administered at 5E+11 Vgs/rat through intravenous(IV), intracerebroventricular(ICV), intra-cisterna magna(ICM) and intrastriatal(IST) routes. Vector and trastuzumab blood/plasma concentrations were assessed at different time points up to the terminal time point of 21 days. Different brain regions in addition to the spinal cord, cerebrospinal fluid(CSF) and interstitial fluid(ISF), were also analyzed at the terminal time point. Our results show that vector biodistribution and Trastuzumab expression in the brain could the ranked as follows: IST>ICM>ICV>IV. Rapid clearance of vector was observed after administration via the ICM and ICV routes. The ICV route produced similar expression levels across different brain regions, while the ICM route had better expression in the hindbrain and spinal cord region. The IST route had higher expression in the forebrain region compared to the hindbrain region. A sharp decline in trastuzumab plasma concentration was observed across all routes of administration due to anti-trastuzumab antibody response.

CONCLUSION

In this study we have characterized vector biodistribution and transgene mAb expression after AAV9 vector administration through different routes in rats. IST and ICM represent the best administration routes to deliver antibody genes to the brain.

Production of therapeutic levels of human FIX-R338L by engineered B cells using GMP-compatible medium

B cells can differentiate into plasmablast and plasma cells, capable of producing antibodies for decades. Gene editing using zinc-finger nucleases (ZFN) enables the engineering of B cells capable of secreting sustained and high levels of therapeutic proteins. In this study, we established an advanced in vitro good manufacturing practice-compatible culturing system characterized by robust and consistent expansion rate, high viability, and efficient B cell differentiation. Using this process, an optimized B cell editing protocol was developed by combining ZFN/adeno-associated virus 6 technology to achieve site-specific insertion of the human factor IX R338L Padua into the silent TRAC locus. In vitro analysis revealed high levels of secreted human immunoglobulins and human factor IX-Padua. Following intravenous infusion in a mouse model, human plasma cells were detected in spleen and bone marrow, indicating successful and potentially long-term engraftment in vivo. Moreover, high levels of human immunoglobin and therapeutic levels of human factor IX-Padua were detected in mouse plasma, correlating with 15% of normal human factor IX activity. These data suggest that the proposed process promotes the production of functional and differentiated engineered B cells. In conclusion, this study represents an important step toward the development of a manufacturing platform for potential B cell-derived therapeutic products.

Extracellular matrix turnover in salivary gland disorders and regenerative therapies: Obstacles and opportunities

Salivary gland (SG) extracellular matrix (ECM) has a major influence on tissue development, homeostasis, and tissue regeneration after injury. During aging, disease, and physical insult, normal remodeling of the SG microenvironment (i.e. ECM) becomes dysregulated, leading to alterations in matrix composition which disrupt tissue architecture/structure, alter cell activity, and negatively impact gland function. Matrix metalloproteinases (MMPs) are a large and diverse family of metalloendopeptidases which play a major role in matrix degradation and are intimately involved in regulating development and cell function; dysregulation of these enzymes leads to the production of a fibrotic matrix. In the SG this altered fibrotic ECM (or cell microenvironment) negatively impacts normal cell function and the effectiveness of gene and stem cell therapies which serve as a foundation for many SG regenerative therapies. For this reason, prospective regenerative strategies should prioritize the maintenance and/or restoration of a healthy SG ECM. Mesenchymal stem cells (MSCs) have great potential for mitigating damage to the SG microenvironment by ameliorating inflammation, reducing fibrosis, and repairing the damaged milieu of extracellular regulatory cues, including the matrix. This review addresses our current understanding of the impact of aging and disease on the SG microenvironment and suggests critical deficiencies and opportunities in ECM-targeted therapeutic interventions.

Prospective approaches to gene therapy computational modeling - spotlight on viral gene therapy

Clinical studies have found there still exists a lack of gene therapy dose-toxicity and dose-efficacy data that causes gene therapy dose selection to remain elusive. Model informed drug development (MIDD) has become a standard tool implemented throughout the discovery, development, and approval of pharmaceutical therapies, and has the potential to inform dose-toxicity and dose-efficacy relationships to support gene therapy dose selection. Despite this potential, MIDD approaches for gene therapy remain immature and require standardization to be useful for gene therapy clinical programs. With the goal to advance MIDD approaches for gene therapy, in this review we first provide an overview of gene therapy types and how they differ from a bioanalytical, formulation, route of administration, and regulatory standpoint. With this biological and regulatory background, we propose how MIDD can be advanced for AAV-based gene therapies by utilizing physiological based pharmacokinetic modeling and quantitative systems pharmacology to holistically inform AAV and target protein dynamics following dosing. We discuss how this proposed model, allowing for in-depth exploration of AAV pharmacology, could be the key the field needs to treat these unmet disease populations.

PK/PD and Bioanalytical Considerations of AAV-Based Gene Therapies: an IQ Consortium Industry Position Paper

Interest and efforts to use recombinant adeno-associated viruses (AAV) as gene therapy delivery tools to treat disease have grown exponentially. However, gaps in understanding of the pharmacokinetics/pharmacodynamics (PK/PD) and disposition of this modality exist. This position paper comes from the Novel Modalities Working Group (WG), part of the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ). The pan-industry WG effort focuses on the nonclinical PK and clinical pharmacology aspects of AAV gene therapy and related bioanalytical considerations.Traditional PK concepts are generally not applicable to AAV-based therapies due to the inherent complexity of a transgene-carrying viral vector, and the multiple steps and analytes involved in cell transduction and transgene-derived protein expression. Therefore, we explain PK concepts of biodistribution of AAV-based therapies and place key terminologies related to drug exposure and PD in the proper context. Factors affecting biodistribution are presented in detail, and guidelines are provided to design nonclinical studies to enable a stage-gated progression to Phase 1 testing. The nonclinical and clinical utility of transgene DNA, mRNA, and protein analytes are discussed with bioanalytical strategies to measure these analytes. The pros and cons of qPCR vs. ddPCR technologies for DNA/RNA measurement and qualitative vs. quantitative methods for transgene-derived protein are also presented. Last, best practices and recommendations for use of clinical and nonclinical data to project human dose and response are discussed. Together, the manuscript provides a holistic framework to discuss evolving concepts of PK/PD modeling, bioanalytical technologies, and clinical dose selection in gene therapy.

Mechanism-based pharmacokinetic and pharmacodynamic modeling for bispecific antibodies: challenges and opportunities

INTRODUCTION

Unlike conventional antibodies, bispecific antibodies (bsAbs) are engineered antibody- or antibody fragment-based molecules that can simultaneously recognize two different epitopes or antigens. Over the past decade, there has been an explosion of bsAbs being developed across therapeutic areas. Development of bsAbs presents unique challenges and mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) modeling has served as a powerful tool to optimize their development and realize their clinical utility.

AREAS COVERED

In this review, the guiding principles and case examples of how fit-for-purpose, mechanism-based PK/PD models have been applied to answer questions commonly encountered in bsAb development are presented. Such models characterize the key pharmacological elements of bsAbs, and they can be utilized for model-informed drug development. We also include the discussion of challenges, knowledge gaps and future direction for such models.

EXPERT OPINION

Mechanistic PK/PD modeling is a powerful tool to support the development of bsAbs. These models can be extrapolated to predict treatment outcomes based on mechanisms of action (MoA) and clinical observations to form positive learn-and-confirm cycles during drug development, due to their abilities to differentiate system- and drug-specific parameters. Meanwhile, the models should keep being adapted according to novel drug design and MoA, providing continuous opportunities for model-informed drug development.

Deferoxamine has the Potential to Improve the COVID-19-Related Inflammatory Response in Diabetic Patients

The clinical state of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been considered a pandemic disease (COVID-19) that is rapidly spreading worldwide. Despite all global efforts, the only treatment for COVID-19 is supportive care and there has been no efficient treatment to fight this plague. It is confirmed that patients with chronic diseases such as cardiovascular disorder and diabetes; are more vulnerable to COVID-19. In the severe type of COVID-19, laboratory findings showed a remarkably enhanced C-reactive protein, IL-6 serum, Iron, and ferritin, which suggest an inflammatory response. Inflammation results in iron homeostasis imbalance and causes iron overload, exacerbating the SARSCOV2 infection. More importantly, recent studies have established that SARS-CoV-2 needs iron for viral replication and also activation. As a result, managing iron overload in diabetic patients with COVID-19 could be an early therapeutic approach to limit the lethal inflammatory response of COVID-19. In this review, Deferoxamine (DFO) has been proposed as an effective iron chelator agent.

Graphical Abstract

Autologous mesenchymal stem cells offer a new paradigm for salivary gland regeneration

Salivary gland (SG) dysfunction, due to radiotherapy, disease, or aging, is a clinical manifestation that has the potential to cause severe oral and/or systemic diseases and compromise quality of life. Currently, the standard-of-care for this condition remains palliative. A variety of approaches have been employed to restore saliva production, but they have largely failed due to damage to both secretory cells and the extracellular matrix (niche). Transplantation of allogeneic cells from healthy donors has been suggested as a potential solution, but no definitive population of SG stem cells, capable of regenerating the gland, has been identified. Alternatively, mesenchymal stem cells (MSCs) are abundant, well characterized, and during SG development/homeostasis engage in signaling crosstalk with the SG epithelium. Further, the trans-differentiation potential of these cells and their ability to regenerate SG tissues have been demonstrated. However, recent findings suggest that the "immuno-privileged" status of allogeneic adult MSCs may not reflect their status post-transplantation. In contrast, autologous MSCs can be recovered from healthy tissues and do not present a challenge to the recipient's immune system. With recent advances in our ability to expand MSCs in vitro on tissue-specific matrices, autologous MSCs may offer a new therapeutic paradigm for restoration of SG function.

Various AAV Serotypes and Their Applications in Gene Therapy: An Overview

Despite scientific discoveries in the field of gene and cell therapy, some diseases still have no effective treatment. Advances in genetic engineering methods have enabled the development of effective gene therapy methods for various diseases based on adeno-associated viruses (AAVs). Today, many AAV-based gene therapy medications are being investigated in preclinical and clinical trials, and new ones are appearing on the market. In this article, we present a review of AAV discovery, properties, different serotypes, and tropism, and a following detailed explanation of their uses in gene therapy for disease of different organs and systems.

Nanoparticle biodistribution coefficients: A quantitative approach for understanding the tissue distribution of nanoparticles

The objective of this manuscript is to provide quantitative insights into the tissue distribution of nanoparticles. Published pharmacokinetics of nanoparticles in plasma, tumor and 13 different tissues of mice were collected from literature. A total of 2018 datasets were analyzed and biodistribution of graphene oxide, lipid, polymeric, silica, iron oxide and gold nanoparticles in different tissues was quantitatively characterized using Nanoparticle Biodistribution Coefficients (NBC). It was observed that typically after intravenous administration most of the nanoparticles are accumulated in the liver (NBC = 17.56 %ID/g) and spleen (NBC = 12.1 %ID/g), while other tissues received less than 5 %ID/g. NBC values for kidney, lungs, heart, bones, brain, stomach, intestine, pancreas, skin, muscle and tumor were found to be 3.1 %ID/g, 2.8 %ID/g, 1.8 %ID/g, 0.9 %ID/g, 0.3 %ID/g, 1.2 %ID/g, 1.8 %ID/g, 1.2 %ID/g, 1.0 %ID/g, 0.6 %ID/g and 3.4 %ID/g, respectively. Significant variability in nanoparticle distribution was observed in certain organs such as liver, spleen and lungs. A large fraction of this variability could be explained by accounting for the differences in nanoparticle physicochemical properties such as size and material. A critical overview of published nanoparticle physiologically-based pharmacokinetic (PBPK) models is provided, and limitations in our current knowledge about in vitro and in vivo pharmacokinetics of nanoparticles that restrict the development of robust PBPK models is also discussed. It is hypothesized that robust quantitative assessment of whole-body pharmacokinetics of nanoparticles and development of mathematical models that can predict their disposition can improve the probability of successful clinical translation of these modalities.

Assessment of AAV9 distribution and transduction in rats after administration through Intrastriatal, Intracisterna magna and Lumbar Intrathecal routes

Challenges in obtaining efficient transduction of brain and spinal cord following systemic AAV delivery have led to alternative administration routes being used in clinical trials that directly infuse the virus into the CNS. However, data comparing different direct AAV injections into the brain remain limited making it difficult to choose optimal routes. Here we tested both AAV9-egfp and AAV9-fLuc delivery via intrastriatal (IST), intracisterna magna (ICM) and lumbar intrathecal (LIT) routes in adult rats and assessed vector distribution and transduction in brain, spinal cord and peripheral tissues. We find that IST infusion leads to robust transgene expression in the striatum, thalamus and cortex with lower peripheral tissue transduction and anti-AAV9 capsid titers compared to ICM or LIT. ICM delivery provided strong GFP and luciferase expression across more brain regions than the other routes and similar expression in the spinal cord to LIT injections, which itself largely failed to transduce the rat brain. Our data highlight the strengths and weaknesses of each direct CNS delivery route which will help with future clinical targeting.

Structural Characterization of Porcine Adeno-Associated Virus Capsid Protein with Nuclear Trafficking Protein Importin Alpha Reveals a Bipartite Nuclear Localization Signal

Adeno-associated viruses (AAV) are important vectors for gene therapy, and accordingly, many aspects of their cell transduction pathway have been well characterized. However, the specific mechanisms that AAV virions use to enter the host nucleus remain largely unresolved. We therefore aimed to reveal the interactions between the AAV Cap protein and the nuclear transport protein importin alpha (IMPα) at an atomic resolution. Herein we expanded upon our earlier research into the Cap nuclear localization signal (NLS) of a porcine AAV isolate, by examining the influence of upstream basic regions (BRs) towards IMPα binding. Using a high-resolution crystal structure, we identified that the IMPα binding determinants of the porcine AAV Cap comprise a bipartite NLS with an N-terminal BR binding at the minor site of IMPα, and the previously identified NLS motif binding at the major site. Quantitative assays showed a vast difference in binding affinity between the previously determined monopartite NLS, and bipartite NLS described in this study. Our results provide a detailed molecular view of the interaction between AAV capsids and the nuclear import receptor, and support the findings that AAV capsids enter the nucleus by binding the nuclear import adapter IMPα using the classical nuclear localization pathway.

Prospects for gene replacement therapies in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating and incurable neurodegenerative disease characterized by the progressive loss of upper and lower motor neurons. ALS causes death, usually within 2-5 years of diagnosis. Riluzole, the only drug currently approved in Europe for the treatment of this condition, offers only a modest benefit, increasing survival by 3 months on average. Recent advances in our understanding of causative or disease-modifying genetic variants and in the development of genetic therapy strategies present exciting new therapeutic opportunities for ALS. In addition, the approval of adeno-associated virus-mediated delivery of functional copies of the SMN1 gene to treat spinal muscular atrophy represents an important therapeutic milestone and demonstrates the potential of gene replacement therapies for motor neuron disorders. In this Review, we describe the current landscape of genetic therapies in ALS, highlighting achievements and critical challenges. In particular, we discuss opportunities for gene replacement therapy in subgroups of people with ALS, and we describe loss-of-function mutations that are known to contribute to the pathophysiology of ALS and could represent novel targets for gene replacement therapies.

Formulation and Evaluation of Polymer-Based Nanoparticles for Intravitreal Gene-Delivery Applications

The advent of the first-ever retinal gene therapy product, involving subretinal administration of a virus-based gene delivery platform, has garnered hope that this state-of-the-art therapeutic modality may benefit a broad spectrum of patients with diverse retinal disorders. On the other hand, clinical studies have revealed limitations of the applied delivery strategy that may restrict its universal use. To this end, intravitreal administration of synthetic gene-delivery platforms, such as polymer-based nanoparticles (PNPs), has emerged as an attractive alternative to the current mainstay. To achieve success, however, it is imperative that synthetic platforms overcome key biological barriers in human eyes encountered following intravitreal administration, including the vitreous gel and inner limiting membrane (ILM). Here, we introduce a series of experiments, from the fabrication of PNPs to a comprehensive evaluation in relevant experimental models, to determine whether PNPs overcome these barriers and efficiently deliver therapeutic gene payloads to retinal cells. We conclude the article by discussing a few important considerations for successful implementation of the strategy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Preparation and characterization of PNPs Basic Protocol 2: Evaluation of in vitro transfection efficacy Basic Protocol 3: Evaluation of PNP diffusion in vitreous gel Basic Protocol 4: Ex vivo assessment of PNP penetration within vitreoretinal explant culture Basic Protocol 5: Assessment of in vivo transgene expression mediated by intravitreally administered PNPs.

Identification of a novel fusion Iduronidase with improved activity in the cardiovascular system

Background

Lysosomal diseases are a group of over 70 rare genetic conditions in which a protein deficiency (most often an enzyme deficiency) leads to multi-system disease. Current therapies for lysosomal diseases are limited in their ability to treat certain tissues that are major contributors to morbidity and mortality, such as the central nervous system (CNS) and cardiac valves. For this study, the lysosomal disease mucopolysaccharidosis type I (MPS I) was selected as the disease model. In MPS I, mutations in the IDUA gene cause a deficiency of the α-L-iduronidase (IDUA) enzyme activity, leading to disease pathology in tissues throughout the body, including the CNS and cardiac valves. Current therapies have been unable to prevent neurodevelopmental deficits and cardiac valvular disease in patients with MPS I. This study aimed to evaluate the delivery of IDUA enzyme, via a novel gene therapy construct, to target tissues.

Methods

MPS I mice were hydrodynamically injected through the tail vein with plasmids containing either a codon-optimized cDNA encoding the wild-type IDUA protein or one of four modified IDUAs under the control of the liver-specific human α1-antitrypsin (hAAT) promoter. Two modified IDUAs contained a ligand for the CB1 receptor, which is a highly expressed receptor in the CNS. Iduronidase activity levels were measured in the tissues and plasma using an enzyme activity assay.

Results

The modified IDUAs did not appear to have improved activity levels in the brain compared with the unmodified IDUA. However, one modified IDUA exhibited higher activity levels than the unmodified IDUA in the heart (p = 0.0211). This modified iduronidase (LT-IDUA) contained a sequence for a six amino acid peptide termed LT. LT-IDUA was further characterized using a noncompartmental pharmacokinetic approach that directly analyzed enzyme activity levels after gene delivery. LT-IDUA had a 2-fold higher area under the curve (AUC) than the unmodified IDUA (p = 0.0034) when AUC was estimated using enzyme activity levels in the plasma.

Conclusion

The addition of a six amino acid peptide improved iduronidase's activity levels in the heart and plasma. The short length of this LT peptide facilitates its use as fusion enzymes encoded as gene therapy or administered as enzyme replacement therapy. More broadly, the LT peptide may aid in developing therapies for numerous lysosomal diseases.

Regulatory Consideration for the Nonclinical Safety Assessment of Gene Therapies

The nonclinical safety assessments for gene therapies are evolving, leveraging over 20 years of experimental and clinical experience. Despite the growing experience with these therapeutics, there are no approved harmonized global regulatory documents for developing gene therapies with only the ICH (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use) S12 guidance on nonclinical biodistribution currently under discussion. Several health authorities have issued guidance over the last 15 years on the nonclinical safety aspects for gene therapy products, but many of the recommendations are limited to high-level concepts on nonclinical safety aspects or altogether silent on key topics. Historically, this approach was appropriately vague given our relatively small dataset of nonclinical experience, where a comprehensive and detailed regulatory guidance approach was unlikely to be appropriate to address all scenarios. However, harmonization of key considerations and assumptions can provide a consistent basis for developing the appropriate nonclinical safety development plans for individual programs, reducing uncertainty across regulatory regions and unnecessary animal use. Several key areas of nonclinical safety testing are nearing maturation for a harmonized approach, including species selection, certain aspects of study design, study duration, and unintended genomic integration risks. Furthermore, several emerging topics are unaddressed in current regulatory guidance for gene therapy products, which will become key areas of differentiation for the next generation of therapeutics. These topics include redosing, juvenile/pediatric safety, and reproductive/developmental safety testing, where relevant experience from other modalities can be applied. The rationale and potential study design considerations for these topics will be proposed, acknowledging that certain aspects of gene therapy development are not considered appropriate for harmonization. This article provides an overview of the current nonclinical safety regulatory landscape, summarizes typical nonclinical safety study designs, highlights areas of uncertainty, and discusses emerging topics that warrant consideration. Specific recommendations and perspectives are provided to inform future regulatory discussions and harmonization efforts.

Application of physiologically-based pharmacokinetic models for therapeutic proteins and other novel modalities

The past two decades have seen diversification of drug development pipelines and approvals from traditional small molecule therapies to alternative modalities including monoclonal antibodies, engineered proteins, antibody drug conjugates (ADCs), oligonucleotides and gene therapies. At the same time, physiologically-based pharmacokinetic (PBPK) models for small molecules have seen increased industry and regulatory acceptance.This review focusses on the current status of the application of PBPK models to these newer modalities and give a perspective on the successes, challenges and future directions of this field.There is greatest experience in the development of PBPK models for therapeutic proteins, and PBPK models for ADCs benefit from prior experience for both therapeutic proteins and small molecules. For other modalities, the application of PBPK models is in its infancy.Challenges are discussed and a common theme is lack of availability of physiological and experimental data to characterise systems and drug parameters to enable a priori prediction of pharmacokinetics. Furthermore, sufficient clinical data are required to build confidence in developed models.The PBPK modelling approach provides a quantitative framework for integrating knowledge and data from multiple sources and can be built on as more data becomes available.

Biocompatible Iron Oxide Nanoparticles for Targeted Cancer Gene Therapy: A Review

In recent years, gene therapy has made remarkable achievements in tumor treatment. In a successfully cancer gene therapy, a smart gene delivery system is necessary for both protecting the therapeutic genes in circulation and enabling high gene expression in tumor sites. Magnetic iron oxide nanoparticles (IONPs) have demonstrated their bright promise for highly efficient gene delivery target to tumor tissues, partly due to their good biocompatibility, magnetic responsiveness, and extensive functional surface modification. In this review, the latest progress in targeting cancer gene therapy is introduced, and the unique properties of IONPs contributing to the efficient delivery of therapeutic genes are summarized with detailed examples. Furthermore, the diagnosis potentials and synergistic tumor treatment capacity of IONPs are highlighted. In addition, aiming at potential risks during the gene delivery process, several strategies to improve the efficiency or reduce the potential risks of using IONPs for cancer gene therapy are introduced and addressed. The strategies and applications summarized in this review provide a general understanding for the potential applications of IONPs in cancer gene therapy.

CPEB3 suppresses gastric cancer progression by inhibiting ADAR1-mediated RNA editing via localizing ADAR1 mRNA to P bodies

Deciphering the crosstalk between RNA-binding proteins and corresponding RNAs will provide a better understanding of gastric cancer (GC) progression. The comprehensive bioinformatics study identified cytoplasmic polyadenylation element-binding protein 3 (CPEB3) might play a vital role in GC progression. Then we found CPEB3 was downregulated in GC and correlated with prognosis. In addition, CPEB3 suppressed GC cell proliferation, invasion and migration in vitro, as well as tumor growth and metastasis in vivo. Mechanistic study demonstrated CPEB3 interacted with 3'-UTR of ADAR1 mRNA through binding to CPEC nucleotide element, and then inhibited its translation by localizing it to processing bodies (P bodies), eventually leading to the suppression of ADAR1-mediated RNA editing. Microscale thermophoresis assay further revealed that the direct interaction between CPEB3 and GW182, the P-body's major component, was through the 440-698AA region of CPEB3 binding to the 403-860AA region of GW182. Finally, AAV9-CPEB3 was developed and administrated in mouse models to assess its potential value in gene therapy. We found AAV9-CPEB3 inhibited GC growth and metastasis. Besides, AAV9-CPEB3 induced hydropic degeneration in mouse liver, but did not cause kidney damage. These findings concluded that CPEB3 suppresses GC progression by inhibiting ADAR1-mediated RNA editing via localizing ADAR1 mRNA to P bodies.

Pharmacokinetic analysis identifies a factor VIII immunogenicity threshold after AAV gene therapy in hemophilia A mice

Advances in the development of novel treatment options for hemophilia A are prevalent. However, the anti-factor VIII (FVIII) neutralizing antibody (inhibitor) response to existing FVIII products remains a major treatment challenge. Although some novel products are designed to function in the presence of inhibitors, they do not specific address the immunogenicity risk or mechanistic causes of inhibitor development, which remain unclear. Furthermore, most preclinical studies supporting clinical gene therapy programs have reported immunogenicity signals in animal models, especially at higher vector doses and sometimes using multiple vector designs. In these settings, immunogenicity risk factor determination, comparative immunogenicity of competing vector designs, and the potential for obtaining meaningful prognostic data remain relatively unexplored. Additionally, there remains the opportunity to investigate clinical gene therapy as an alternative to standard immune tolerance induction therapy. The current study was designed to address these issues through longitudinal dose-response evaluation of 4 adeno-associated viral (AAV) vector candidates encoding 2 different FVIII transgenes in a murine model of hemophilia A. Plasma FVIII activity and anti-FVIII antibody data were used to generate a pharmacokinetic model that (1) identifies initial AAV-FVIII product expression kinetics as the dominant risk factor for inhibitor development, (2) predicts a therapeutic window where immune tolerance is achieved, and (3) demonstrates evidence of gene therapy-based immune tolerance induction. Although there are known limitations to the predictive value of preclinical immunogenicity testing, these studies can uncover or support the development of design principles that can guide the development of safe and effective genetic medicines.

Modulation of myosin by cardiac myosin binding protein-C peptides improves cardiac contractility in ex-vivo experimental heart failure models

Cardiac myosin binding protein-C (cMyBP-C) is an important regulator of sarcomeric function. Reduced phosphorylation of cMyBP-C has been linked to compromised contractility in heart failure patients. Here, we used previously published cMyBP-C peptides 302A and 302S, surrogates of the regulatory phosphorylation site serine 302, as a tool to determine the effects of modulating the dephosphorylation state of cMyBP-C on cardiac contraction and relaxation in experimental heart failure (HF) models in vitro. Both peptides increased the contractility of papillary muscle fibers isolated from a mouse model expressing cMyBP-C phospho-ablation (cMyBP-CAAA) constitutively. Peptide 302A, in particular, could also improve the force redevelopment rate (ktr) in papillary muscle fibers from cMyBP-CAAA (nonphosphorylated alanines) mice. Consistent with the above findings, both peptides increased ATPase rates in myofibrils isolated from rats with myocardial infarction (MI), but not from sham rats. Furthermore, in the cMyBP-CAAA mouse model, both peptides improved ATPase hydrolysis rates. These changes were not observed in non-transgenic (NTG) mice or sham rats, indicating the specific effects of these peptides in regulating the dephosphorylation state of cMyBP-C under the pathological conditions of HF. Taken together, these studies demonstrate that modulation of cMyBP-C dephosphorylation state can be a therapeutic approach to improve myosin function, sarcomere contractility and relaxation after an adverse cardiac event. Therefore, targeting cMyBP-C could potentially improve overall cardiac performance as a complement to standard-care drugs in HF patients.

The Perspective of DMPK on Recombinant Adeno-Associated Virus-Based Gene Therapy: Past Learning, Current Support, and Future Contribution

Given the recent success of gene therapy modalities and the growing number of cell and gene-based therapies in clinical development across many different therapeutic areas, it is evident that this evolving field holds great promise for the unmet medical needs of patients. The recent approvals of Luxturna® and Zolgensma® prove that recombinant adeno-associated virus (rAAV)-based gene therapy is a transformative modality that enables curative treatment for genetic disorders. Over the last decade, Takeda has accumulated significant experience with rAAV-based gene therapies, especially in the early stage of development. In this review, based on the learnings from Takeda and publicly available information, we aim to provide a guiding perspective on Drug Metabolism and Pharmacokinetics (DMPK) substantial role in advancing therapeutic gene therapy modalities from nonclinical research to clinical development, in particular the characterization of gene therapy product biodistribution, elimination (shedding), immunogenicity assessment, multiple platform bioanalytical assays, and first-in-human (FIH) dose projection strategies.

Structural characterization of the porcine adeno-associated virus Po1 capsid protein binding to the nuclear trafficking protein importin alpha

Adeno-associated viruses (AAVs) are key vectors for gene therapy; thus, many aspects of their cell transduction pathway have been revealed in detail. However, the specific mechanisms AAV virions use to enter the host nucleus remain largely unresolved. We therefore aimed to reveal the structural interactions between the AAV capsid (Cap) protein and the nuclear transport protein importin alpha (IMPα). A putative nuclear localization sequence (NLS) in the virion protein 1 capsid protein of the porcine AAV Po1 was identified. This region was complexed with IMPα and a structure solved at 2.26 Å. This is the first time that an NLS of AAV Cap complexed with IMPα has been determined structurally. Our results support the findings that AAV capsids enter the nucleus through binding the nuclear import adapter IMPα.

Modeling Pharmacokinetics and Pharmacodynamics of Therapeutic Antibodies: Progress, Challenges, and Future Directions

With more than 90 approved drugs by 2020, therapeutic antibodies have played a central role in shifting the treatment landscape of many diseases, including autoimmune disorders and cancers. While showing many therapeutic advantages such as long half-life and highly selective actions, therapeutic antibodies still face many outstanding issues associated with their pharmacokinetics (PK) and pharmacodynamics (PD), including high variabilities, low tissue distributions, poorly-defined PK/PD characteristics for novel antibody formats, and high rates of treatment resistance. We have witnessed many successful cases applying PK/PD modeling to answer critical questions in therapeutic antibodies’ development and regulations. These models have yielded substantial insights into antibody PK/PD properties. This review summarized the progress, challenges, and future directions in modeling antibody PK/PD and highlighted the potential of applying mechanistic models addressing the development questions.

Clinical Design and Analysis Strategies for the Development of Gene Therapies: Considerations for Quantitative Drug Development in the Age of Genetic Medicine

Cell and gene therapies have shown enormous promise across a range of diseases in recent years. Numerous adoptive cell therapy modalities as well as systemic and direct-to-target tissue gene transfer administrations are currently in clinical development. The clinical trial design, development, reporting, and analysis of novel cell and gene therapies can differ significantly from established practices for small molecule drugs and biologics. Here, we discuss important quantitative considerations and key competencies for drug developers in preclinical requirements, trial design, and lifecycle planning for gene therapies. We argue that the unique development path of gene therapies requires practicing quantitative drug developers-statisticians, pharmacometricians, pharmacokineticists, epidemiologists, and medical and translational science leads-to exercise active collaboration and cross-functional learning across development stages.