Widespread and sustained target engagement in Huntington's disease minipigs upon intrastriatal microRNA-based gene therapy.

Huntingtin (HTT)-lowering therapies hold promise to slow down neurodegeneration in Huntington's disease (HD). Here, we assessed the translatability and long-term durability of recombinant adeno-associated viral vector serotype 5 expressing a microRNA targeting human (rAAV5-miHTT) administered by magnetic resonance imaging-guided convention-enhanced delivery in transgenic HD minipigs. rAAV5-miHTT (1.

Intrastriatal Administration of AAV5-miHTT in Non-Human Primates and Rats Is Well Tolerated and Results in miHTT Transgene Expression in Key Areas of Huntington Disease Pathology.

Huntington disease (HD) is a fatal, neurodegenerative genetic disorder with aggregation of mutant Huntingtin protein (mutHTT) in the brain as a key pathological mechanism. There are currently no disease modifying therapies for HD; however, -lowering therapies hold promise. Recombinant adeno-associated virus serotype 5 expressing a microRNA that targets mRNA (AAV5-miHTT) is in development for the treatment of HD with promising results in rodent and minipig HD models.

Enhanced Factor IX Activity following Administration of AAV5-R338L "Padua" Factor IX versus AAV5 WT Human Factor IX in NHPs.

Gene therapy for severe hemophilia B is advancing and offers sustained disease amelioration with a single treatment. We have reported the efficacy and safety of AMT-060, an investigational gene therapy comprising an adeno-associated virus serotype 5 capsid encapsidating the codon-optimized wild-type human factor IX (WT h) gene with a liver-specific promoter, in patients with severe hemophilia B. Treatment with 2 × 10 gc/kg AMT-060 showed sustained and durable FIX activity of 3%-13% and a substantial reduction in spontaneous bleeds without T cell-mediated hepatoxicity.

Immunoadsorption enables successful rAAV5-mediated repeated hepatic gene delivery in nonhuman primates.

Adeno-associated virus (AAV)-based liver gene therapy has been shown to be clinically successful. However, the presence of circulating neutralizing antibodies (NABs) against AAV vector capsids remains a major challenge as it may prevent successful transduction of the target cells. Therefore, there is a need to develop strategies that would enable AAV-mediated gene delivery to patients with preexisting anti-AAV NABs.

Therapeutic hFIX Activity Achieved after Single AAV5-hFIX Treatment in Hemophilia B Patients and NHPs with Pre-existing Anti-AAV5 NABs.

Currently, individuals with pre-existing neutralizing antibodies (NABs) against adeno-associated virus (AAV) above titer of 5 are excluded from systemic AAV-based clinical trials. In this study we explored the impact of pre-existing anti-AAV5 NABs on the efficacy of AAV5-based gene therapy. AMT-060 (AAV5-human FIX) was evaluated in 10 adults with hemophilia B who tested negative for pre-existing anti-AAV5 NABs using a GFP-based assay.

In-Depth Characterization of a Mifepristone-Regulated Expression System for AAV5-Mediated Gene Therapy in the Liver.

Gene therapy is being developed for the treatment of inherited diseases, whereby a therapeutic gene is continuously expressed in patients after delivery via viral vectors such as adeno-associated virus (AAV). Depending on the transgene, there could be a limited therapeutic window, and regulating timing and levels of transgene expression is advantageous. To control transgene transcription, the regulatory system GeneSwitch (GS) was evaluated in detail both and .

AAV5-miHTT Gene Therapy Demonstrates Sustained Huntingtin Lowering and Functional Improvement in Huntington Disease Mouse Models.

Huntington disease (HD) is a fatal neurodegenerative disorder caused by an autosomal dominant CAG repeat expansion in the () gene. The translated expanded polyglutamine repeat in the HTT protein is known to cause toxic gain of function. We showed previously that strong HTT lowering prevented neuronal dysfunction in HD rodents and minipigs after single intracranial injection of adeno-associated viral vector serotype 5 expressing a microRNA targeting human (AAV5-miHTT).

Targeting RNA-Mediated Toxicity in C9orf72 ALS and/or FTD by RNAi-Based Gene Therapy.

A hexanucleotide GGGGCC expansion in intron 1 of chromosome 9 open reading frame 72 (C9orf72) gene is the most frequent cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The corresponding repeat-containing sense and antisense transcripts cause a gain of toxicity through the accumulation of RNA foci in the nucleus and deposition of dipeptide-repeat (DPR) proteins in the cytoplasm of the affected cells. We have previously reported on the potential of engineered artificial anti-C9orf72-targeting miRNAs (miC) targeting C9orf72 to reduce the gain of toxicity caused by the repeat-containing transcripts.

Artificial MicroRNAs Targeting C9orf72 Can Reduce Accumulation of Intra-nuclear Transcripts in ALS and FTD Patients.

The most common pathogenic mutation in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is an intronic GGGGCC (GC) repeat in the chromosome 9 open reading frame 72 (C9orf72) gene. Cellular toxicity due to RNA foci and dipeptide repeat (DPR) proteins produced by the sense and antisense repeat-containing transcripts is thought to underlie the pathogenesis of both diseases. RNA sequencing (RNA-seq) data of C9orf72-ALS patients and controls were analyzed to better understand the sequence conservation of C9orf72 in patients.

Optimization of viral protein ratios for production of rAAV serotype 5 in the baculovirus system.

Recombinant adeno-associated virus (rAAV) has become the vector of choice for the development of novel human gene therapies. High-yield manufacturing of high-quality vectors can be achieved using the baculovirus expression vector system. However, efficient production of rAAV in this insect cell-based system requires a genetic redesign of the viral protein 1 (VP1) operon.

AAV5-miHTT Gene Therapy Demonstrates Broad Distribution and Strong Human Mutant Huntingtin Lowering in a Huntington's Disease Minipig Model.

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the huntingtin gene. Previously, we showed strong huntingtin reduction and prevention of neuronal dysfunction in HD rodents using an engineered microRNA targeting human huntingtin, delivered via adeno-associated virus (AAV) serotype 5 vector with a transgene encoding an engineered miRNA against HTT mRNA (AAV5-miHTT). One of the challenges of rodents as a model of neurodegenerative diseases is their relatively small brain, making successful translation to the HD patient difficult.

Successful Repeated Hepatic Gene Delivery in Mice and Non-human Primates Achieved by Sequential Administration of AAV5 and AAV1.

In the gene therapy field, re-administration of adeno-associated virus (AAV) is an important topic because a decrease in therapeutic protein expression might occur over time. However, an efficient re-administration with the same AAV serotype is impossible due to serotype-specific, anti-AAV neutralizing antibodies (NABs) that are produced after initial AAV treatment. To address this issue, we explored the feasibility of using chimeric AAV serotype 5 (AAV5) and AAV1 for repeated liver-targeted gene delivery.

Perspective on the Road toward Gene Therapy for Parkinson's Disease.

Many therapeutic strategies aimed at relieving symptoms of Parkinson's disease (PD) are currently used for treatment of this disease. With a hallmark of progressive degeneration of dopaminergic neurons, the absence of properly operational dopaminergic circuitry becomes a therapeutic target. Following diagnosis, dopamine replacement can be given in the form of L-DOPA (L-3,4-dihydroxyphenylalanine).

Phase I open label liver-directed gene therapy clinical trial for acute intermittent porphyria.

Background & Aims: Acute intermittent porphyria (AIP) results from porphobilinogen deaminase (PBGD) haploinsufficiency, which leads to hepatic over-production of the neurotoxic heme precursors porphobilinogen (PBG) and delta-aminolevulinic acid (ALA) and the occurrence of neurovisceral attacks. Severe AIP is a devastating disease that can only be corrected by liver transplantation. Gene therapy represents a promising curative option.

Pathogenic classification of LPL gene variants reported to be associated with LPL deficiency.

Background: Lipoprotein lipase (LPL) deficiency is a serious lipid disorder of severe hypertriglyceridemia (SHTG) with chylomicronemia. A large number of variants in the LPL gene have been reported but their influence on LPL activity and SHTG has not been completely analyzed. Gaining insight into the deleterious effect of the mutations is clinically essential.

Design, Characterization, and Lead Selection of Therapeutic miRNAs Targeting Huntingtin for Development of Gene Therapy for Huntington's Disease.

Huntington's disease (HD) is a neurodegenerative disorder caused by accumulation of CAG expansions in the huntingtin (HTT) gene. Hence, decreasing the expression of mutated HTT (mtHTT) is the most upstream approach for treatment of HD. We have developed HTT gene-silencing approaches based on expression cassette-optimized artificial miRNAs (miHTTs).

Recombinant AAV Integration Is Not Associated With Hepatic Genotoxicity in Nonhuman Primates and Patients.

Recombinant adeno-associated viral vectors (rAAV) currently constitute a real therapeutic strategy for the sustained correction of diverse genetic conditions. Though a wealth of preclinical and clinical studies have been conducted with rAAV, the oncogenic potential of these vectors is still controversial, particularly when considering liver-directed gene therapy. Few preclinical studies and the recent discovery of incomplete wild-type AAV2 genomes integrated in human hepatocellular carcinoma biopsies have raised concerns on rAAV safety.

Long-term increased carnitine palmitoyltransferase 1A expression in ventromedial hypotalamus causes hyperphagia and alters the hypothalamic lipidomic profile.

Lipid metabolism in the ventromedial hypothalamus (VMH) has emerged as a crucial pathway in the regulation of feeding and energy homeostasis. Carnitine palmitoyltransferase (CPT) 1A is the rate-limiting enzyme in mitochondrial fatty acid β-oxidation and it has been proposed as a crucial mediator of fasting and ghrelin orexigenic signalling. However, the relationship between changes in CPT1A activity and the intracellular downstream effectors in the VMH that contribute to appetite modulation is not fully understood.

Immune Responses to AAV-Vectors, the Glybera Example from Bench to Bedside.

Alipogene tiparvovec (Glybera(®)) is an adeno-associated virus serotype 1 (AAV1)-based gene therapy that has been developed for the treatment of patients with lipoprotein lipase (LPL) deficiency. Alipogene tiparvovec contains the human LPL naturally occurring gene variant LPL(S447X) in a non-replicating viral vector based on AAV1. Such virus-derived vectors administered to humans elicit immune responses against the viral capsid protein and immune responses, especially cellular, mounted against the protein expressed from the administered gene have been linked to attenuated transgene expression and loss of efficacy.

Safety profile of recombinant adeno-associated viral vectors: focus on alipogene tiparvovec (Glybera®).

There has been great interest over the past two decades in developing gene therapies (GTs) to treat a variety of diseases; however, translating research findings into clinical treatments have proved to be a challenge. A major milestone in the development of GT has been achieved with the approval of alipogene tiparvovec (Glybera(®)) in Europe for the treatment of familial lipoprotein lipase deficiency. At this important stage with the evolution of GT into the clinic, this review will examine the safety aspects GT with adeno-associated virus (AAV) vectors.

Immune responses to intramuscular administration of alipogene tiparvovec (AAV1-LPL(S447X)) in a phase II clinical trial of lipoprotein lipase deficiency gene therapy.

Cellular immune responses to adeno-associated viral (AAV) vectors used for gene therapy have been linked to attenuated transgene expression and loss of efficacy. The impact of such cellular immune responses on the clinical efficacy of alipogene tiparvovec (Glybera; AAV1-LPL(S447X); uniQure), a gene therapy consisting of intramuscular administration of a recombinant AAV1 mediating muscle-directed expression of lipoprotein lipase (LPL), was investigated. Five subjects with LPL deficiency (LPLD) were administered intramuscularly with a dose of 1 × 10(12) gc/kg alipogene tiparvovec.

Safety and liver transduction efficacy of rAAV5-cohPBGD in nonhuman primates: a potential therapy for acute intermittent porphyria.

Acute intermittent porphyria (AIP) results from haplo-insufficient activity of porphobilinogen deaminase (PBGD) and is characterized clinically by life-threatening, acute neurovisceral attacks. To date, liver transplantation is the only curative option for AIP. The aim of the present preclinical nonhuman primate study was to determine the safety and transduction efficacy of an adeno-associated viral vector encoding PBGD (recombinant AAV serotype 5-codon-optimized human porphobilinogen deaminase, rAAV5-cohPBGD) administered intravenously as part of a safety program to start a clinical study in patients with AIP.

A largely random AAV integration profile after LPLD gene therapy.

The clinical application of adeno-associated virus vectors (AAVs) is limited because of concerns about AAV integration-mediated tumorigenicity. We performed integration-site analysis after AAV1-LPL(S447X) intramuscular injection in five lipoprotein lipase-deficient subjects, revealing random nuclear integration and hotspots in mitochondria. We conclude that AAV integration is potentially safe and that vector breakage and integration may occur from each position of the vector genome.

Mir-142-3p target sequences reduce transgene-directed immunogenicity following intramuscular adeno-associated virus 1 vector-mediated gene delivery.

Background: Muscle represents an important tissue target for adeno-associated virus (AAV) vector-mediated gene transfer in muscular, metabolic or blood-related genetic disorders. However, several studies have demonstrated the appearance of immune responses against the transgene product after intramuscular AAV vector delivery that resulted in a limited efficacy of the treatment. Use of microRNAs that are specifically expressed in antigen-presenting cells (APCs) is a promising approach for avoiding those immune responses.