1
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Glenn JD, Negash H, Henry W, Qian R, Liu Y, Danos O, Bruder JT, Karumuthil-Melethil S. The presence of CpGs in AAV gene therapy vectors induces a plasmacytoid dendritic cell-like population very early after administration. Cell Immunol 2024; 399-400:104823. [PMID: 38520831 DOI: 10.1016/j.cellimm.2024.104823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 03/01/2024] [Accepted: 03/18/2024] [Indexed: 03/25/2024]
Abstract
AAV-mediated gene transfer is a promising platform still plagued by potential host-derived, antagonistic immune responses to therapeutic components. CpG-mediated TLR9 stimulation activates innate immune cells and leads to cognate T cell activation and suppression of transgene expression. Here, we demonstrate that CpG depletion increased expression of an antibody transgene product by 2-3-fold as early as 24 h post-vector administration in mice. No significant differences were noted in anti-transgene product/ anti-AAV capsid antibody production or cytotoxic gene induction. Instead, CpG depletion significantly reduced the presence of a pDC-like myeloid cell population, which was able to directly bind the antibody transgene product via Fc-FcγR interactions. Thus, we extend the mechanisms of TLR9-mediated antagonism of transgene expression in AAV gene therapy to include the actions of a previously unreported pDC-like cell population.
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Affiliation(s)
- Justin D Glenn
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA.
| | - Henos Negash
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
| | - William Henry
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
| | - Randolph Qian
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
| | - Ye Liu
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
| | - Olivier Danos
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
| | - Joseph T Bruder
- REGENXBIO Inc., 9804 Medical Center Drive, Rockville, MD 20850, USA
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2
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Wang JH, Gessler DJ, Zhan W, Gallagher TL, Gao G. Adeno-associated virus as a delivery vector for gene therapy of human diseases. Signal Transduct Target Ther 2024; 9:78. [PMID: 38565561 PMCID: PMC10987683 DOI: 10.1038/s41392-024-01780-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 02/08/2024] [Accepted: 02/19/2024] [Indexed: 04/04/2024] Open
Abstract
Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.
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Affiliation(s)
- Jiang-Hui Wang
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, 3002, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, East Melbourne, VIC, 3002, Australia
| | - Dominic J Gessler
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Neurological Surgery, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Neurosurgery, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Wei Zhan
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Thomas L Gallagher
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA
| | - Guangping Gao
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA.
- Department of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA.
- Li Weibo Institute for Rare Diseases Research, University of Massachusetts Chan Medical School, Worcester, MA, 01605, USA.
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3
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Wang H, Zhang C, Dong Z, Zhu X, Zheng X, Liu Z, Zhou J, Yu S, Wu X, Dong X. Using an In Vivo Mouse Model to Determine the Exclusion Criteria of Preexisting Anti-AAV9 Neutralizing Antibody Titer of Pompe Disease Patients in Clinical Trials. Viruses 2024; 16:400. [PMID: 38543765 PMCID: PMC10976115 DOI: 10.3390/v16030400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 02/24/2024] [Accepted: 03/01/2024] [Indexed: 05/23/2024] Open
Abstract
The efficacy of adeno-associated virus (AAV)-based gene therapy is dependent on effective viral transduction, which might be inhibited by preexisting immunity to AAV acquired from infection or maternal delivery. Anti-AAV neutralizing Abs (NAbs) titer is usually measured by in vitro assay and used for patient enroll; however, this assay could not evaluate NAbs' impacts on AAV pharmacology and potential harm in vivo. Here, we infused a mouse anti-AAV9 monoclonal antibody into Balb/C mice 2 h before receiving 1.2 × 1014 or 3 × 1013 vg/kg of rAAV9-coGAA by tail vein, a drug for our ongoing clinical trials for Pompe disease. The pharmacokinetics, pharmacodynamics, and cellular responses combined with in vitro NAb assay validated the different impacts of preexisting NAbs at different levels in vivo. Sustained GAA expression in the heart, liver, diaphragm, and quadriceps were observed. The presence of high-level NAb, a titer about 1:1000, accelerated vector clearance in blood and completely blocked transduction. The AAV-specific T cell responses tended to increase when the titer of NAb exceeded 1:200. A low-level NAbs, near 1:100, had no effect on transduction in the heart and liver as well as cellular responses, but decreased transduction in muscles slightly. Therefore, we propose to preclude patients with NAb titers > 1:100 from rAAV9-coGAA clinical trials.
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Affiliation(s)
- Hanqing Wang
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Cengceng Zhang
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Zheyue Dong
- Beijing FivePlus Gene Technology Co., Ltd., Beijing 102629, China;
| | - Xueyang Zhu
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Xuchu Zheng
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Ziyang Liu
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Jianfang Zhou
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Shuangqing Yu
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Xiaobing Wu
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
| | - Xiaoyan Dong
- Genecradle Therapeutics Inc., Beijing 100176, China; (H.W.); (C.Z.); (X.Z.); (X.Z.); (Z.L.); (J.Z.); (X.D.)
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4
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Dhungel BP, Winburn I, Pereira CDF, Huang K, Chhabra A, Rasko JEJ. Understanding AAV vector immunogenicity: from particle to patient. Theranostics 2024; 14:1260-1288. [PMID: 38323309 PMCID: PMC10845199 DOI: 10.7150/thno.89380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 12/04/2023] [Indexed: 02/08/2024] Open
Abstract
Gene therapy holds promise for patients with inherited monogenic disorders, cancer, and rare genetic diseases. Naturally occurring adeno-associated virus (AAV) offers a well-suited vehicle for clinical gene transfer due to its lack of significant clinical pathogenicity and amenability to be engineered to deliver therapeutic transgenes in a variety of cell types for long-term sustained expression. AAV has been bioengineered to produce recombinant AAV (rAAV) vectors for many gene therapies that are approved or in late-stage development. However, ongoing challenges hamper wider use of rAAV vector-mediated therapies. These include immunity against rAAV vectors, limited transgene packaging capacity, sub-optimal tissue transduction, potential risks of insertional mutagenesis and vector shedding. This review focuses on aspects of immunity against rAAV, mediated by anti-AAV neutralizing antibodies (NAbs) arising after natural exposure to AAVs or after rAAV vector administration. We provide an in-depth analysis of factors determining AAV seroprevalence and examine clinical approaches to managing anti-AAV NAbs pre- and post-vector administration. Methodologies used to quantify anti-AAV NAb levels and strategies to overcome pre-existing AAV immunity are also discussed. The broad adoption of rAAV vector-mediated gene therapies will require wider clinical appreciation of their current limitations and further research to mitigate their impact.
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Affiliation(s)
- Bijay P. Dhungel
- Gene and Stem Cell Therapy Program Centenary Institute, The University of Sydney, NSW, Australia
- Faculty of Medicine and Health, The University of Sydney, NSW, Australia
| | | | | | | | | | - John E. J. Rasko
- Gene and Stem Cell Therapy Program Centenary Institute, The University of Sydney, NSW, Australia
- Faculty of Medicine and Health, The University of Sydney, NSW, Australia
- Cell and Molecular Therapies, Royal Prince Alfred Hospital, Sydney, NSW, Australia
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5
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Wei C, Li D, Zhang M, Zhao Y, Liu Y, Fan Y, Wang L, Liu J, Chang X, Jiang Y, Xiong H. Prevalence of Adeno-Associated Virus-9-Neutralizing Antibody in Chinese Patients with Duchenne Muscular Dystrophy. Hum Gene Ther 2024; 35:26-35. [PMID: 38084965 DOI: 10.1089/hum.2023.117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023] Open
Abstract
The delivery of a mini-dystrophin gene to skeletal muscles using recombinant adeno-associated virus serotype (AAV) holds great potential as a gene therapy for Duchenne muscular dystrophy (DMD). However, the presence of anti-AAV-neutralizing antibodies (NAbs) may impede the effectiveness of gene transduction. This study aimed to evaluate the prevalence of anti-AAV9 NAbs in Chinese patients with DMD, and to characterize the target population for an AAV gene therapy. A total of one hundred male patients with DMD were included in this study, and demographic and clinical data were collected. A blood specimen was obtained from each participant for the purpose of evaluating the existence of anti-AAV9 NAbs through a cell-based functional assay conducted at a central laboratory. A NAb titer exceeding 1:4 was considered positive. The positivity rates of anti-AAV9 NAb were compared among different subgroups. The median age of this DMD cohort was 8 years old, ranging from 3 to 15 years of age. Forty-two percent of patients tested positive for anti-AAV9 NAb. Notably, all samples from patients under 4 years of age tested negative, and the positivity rates of anti-AAV9 NAb differed significantly across the three age subgroups (<4 years old, ≥4 years old and <12 years old, and ≥12 years old, χ2 = 7.221, p = 0.023). Further investigation into the living environment revealed a higher positivity rate of anti-AAV9 NAb in rural patients compared with urban patients (χ2 = 3.923, p = 0.048). Moreover, the prevalence in patients from different cities/provinces varied greatly (χ2 = 16.550, p = 0.003). There was no statistically significant difference in the positivity rate of NAb among subgroups of patients with different motor functions (ambulatory or nonambulatory) and different treatment strategies (taking or not taking glucocorticoid). In Chinese DMD patients, the prevalence of anti-AAV9 NAb was found to reach 42%. Moreover, the antibody-positive rate in children <4 years of age was low and revealed notable regional discrepancies.
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Affiliation(s)
- Cuijie Wei
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Dongliang Li
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Meng Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Yanping Zhao
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Yidan Liu
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Yanbin Fan
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Lu Wang
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Jieyu Liu
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Xingzhi Chang
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Yuwu Jiang
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
| | - Hui Xiong
- Department of Pediatrics, Peking University First Hospital, Beijing, P.R. China
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6
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Jacobs R, Dogbey MD, Mnyandu N, Neves K, Barth S, Arbuthnot P, Maepa MB. AAV Immunotoxicity: Implications in Anti-HBV Gene Therapy. Microorganisms 2023; 11:2985. [PMID: 38138129 PMCID: PMC10745739 DOI: 10.3390/microorganisms11122985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 11/30/2023] [Accepted: 12/11/2023] [Indexed: 12/24/2023] Open
Abstract
Hepatitis B virus (HBV) has afflicted humankind for decades and there is still no treatment that can clear the infection. The development of recombinant adeno-associated virus (rAAV)-based gene therapy for HBV infection has become important in recent years and research has made exciting leaps. Initial studies, mainly using mouse models, showed that rAAVs are non-toxic and induce minimal immune responses. However, several later studies demonstrated rAAV toxicity, which is inextricably associated with immunogenicity. This is a major setback for the progression of rAAV-based therapies toward clinical application. Research aimed at understanding the mechanisms behind rAAV immunity and toxicity has contributed significantly to the inception of approaches to overcoming these challenges. The target tissue, the features of the vector, and the vector dose are some of the determinants of AAV toxicity, with the latter being associated with the most severe adverse events. This review discusses our current understanding of rAAV immunogenicity, toxicity, and approaches to overcoming these hurdles. How this information and current knowledge about HBV biology and immunity can be harnessed in the efforts to design safe and effective anti-HBV rAAVs is discussed.
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Affiliation(s)
- Ridhwaanah Jacobs
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Infectious Diseases and Oncology Research Institute (IDORI), Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
| | - Makafui Dennis Dogbey
- Medical Biotechnology and Immunotherapy Research Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa; (M.D.D.)
| | - Njabulo Mnyandu
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Infectious Diseases and Oncology Research Institute (IDORI), Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
| | - Keila Neves
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Infectious Diseases and Oncology Research Institute (IDORI), Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
| | - Stefan Barth
- Medical Biotechnology and Immunotherapy Research Unit, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa; (M.D.D.)
- South African Research Chair in Cancer Biotechnology, Department of Integrative Biomedical Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town 7700, South Africa
| | - Patrick Arbuthnot
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Infectious Diseases and Oncology Research Institute (IDORI), Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
| | - Mohube Betty Maepa
- Wits/SAMRC Antiviral Gene Therapy Research Unit, Infectious Diseases and Oncology Research Institute (IDORI), Faculty of Health Sciences, University of the Witwatersrand, Parktown 2193, South Africa
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7
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Notarte KI, Catahay JA, Macasaet R, Liu J, Velasco JV, Peligro PJ, Vallo J, Goldrich N, Lahoti L, Zhou J, Henry BM. Infusion reactions to adeno-associated virus (AAV)-based gene therapy: Mechanisms, diagnostics, treatment and review of the literature. J Med Virol 2023; 95:e29305. [PMID: 38116715 DOI: 10.1002/jmv.29305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 11/03/2023] [Accepted: 11/14/2023] [Indexed: 12/21/2023]
Abstract
The use of adeno-associated virus (AAV) vectors in gene therapy has demonstrated great potential in treating genetic disorders. However, infusion-associated reactions (IARs) pose a significant challenge to the safety and efficacy of AAV-based gene therapy. This review provides a comprehensive summary of the current understanding of IARs to AAV therapy, including their underlying mechanisms, clinical presentation, and treatment options. Toll-like receptor activation and subsequent production of pro-inflammatory cytokines are associated with IARs, stimulating neutralizing antibodies (Nabs) and T-cell responses that interfere with gene therapy. Risk factors for IARs include high titers of pre-existing Nabs, previous exposure to AAV, and specific comorbidities. Clinical presentation ranges from mild flu-like symptoms to severe anaphylaxis and can occur during or after AAV administration. There are no established guidelines for pre- and postadministration tests for AAV therapies, and routine laboratory requests are not standardized. Treatment options include corticosteroids, plasmapheresis, and supportive medications such as antihistamines and acetaminophen, but there is no consensus on the route of administration, dosage, and duration. This review highlights the inadequacy of current treatment regimens for IARs and the need for further research to improve the safety and efficacy of AAV-based gene therapy.
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Affiliation(s)
- Kin Israel Notarte
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jesus Alfonso Catahay
- Department of Medicine, Saint Peter's University Hospital, New Brunswick, New Jersey, USA
| | - Raymart Macasaet
- Department of Medicine, Monmouth Medical Center, Long Branch, New Jersey, USA
| | - Jin Liu
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | | | - Jolaine Vallo
- Faculty of Medicine and Surgery, University of Santo Tomas, Manila, Philippines
| | | | - Lokesh Lahoti
- Department of Medicine, Saint Peter's University Hospital, New Brunswick, New Jersey, USA
| | - Jiayan Zhou
- Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
| | - Brandon Michael Henry
- Clinical Laboratory, Division of Nephrology and Hypertension, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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8
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Gardin A, Ronzitti G. Current limitations of gene therapy for rare pediatric diseases: Lessons learned from clinical experience with AAV vectors. Arch Pediatr 2023; 30:8S46-8S52. [PMID: 38043983 DOI: 10.1016/s0929-693x(23)00227-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Gene therapy using adeno-associated viral (AAV) vectors is a promising therapeutic strategy for multiple inherited diseases. Following intravenous injection, AAV vectors carrying a copy of the missing gene or the genome-editing machinery reach their target cells and deliver the genetic material. Several clinical trials are currently ongoing and significant success has already been achieved with at least six AAV gene therapy products with market approval in Europe and the United States. Nonetheless, clinical trials and preclinical studies have uncovered several limitations of AAV gene transfer, which need to be addressed in order to improve the safety and enable the treatment of the largest patient population. Limitations include the occurrence of immune-mediated toxicities, the potential loss of correction in the long run, and the development of neutralizing antibodies against AAV vectors preventing re-administration. In this review, we summarize these limitations and discuss the potential technological developments to overcome them. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.
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Affiliation(s)
- Antoine Gardin
- Genethon, 91000 Evry, France; Université Paris-Saclay, Univ Evry, Inserm, Genethon, Integrare research unit UMR_S951, 91000 Evry, France; Hépatologie et Transplantation Hépatique Pédiatriques, Centre de référence de l'atrésie des voies biliaires et des cholestases génétiques, FSMR FILFOIE, Health Care Provider of the European Reference Network on Rare Liver Disorders (ERN RARE LIVER), Hôpital Bicêtre, AP-HP, Université Paris-Saclay, Le Kremlin-Bicêtre, France
| | - Giuseppe Ronzitti
- Genethon, 91000 Evry, France; Université Paris-Saclay, Univ Evry, Inserm, Genethon, Integrare research unit UMR_S951, 91000 Evry, France.
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9
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Kohn DB, Chen YY, Spencer MJ. Successes and challenges in clinical gene therapy. Gene Ther 2023; 30:738-746. [PMID: 37935854 PMCID: PMC10678346 DOI: 10.1038/s41434-023-00390-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 01/20/2023] [Accepted: 02/07/2023] [Indexed: 11/09/2023]
Abstract
Despite the ups and downs in the field over three decades, the science of gene therapy has continued to advance and provide enduring treatments for increasing number of diseases. There are active clinical trials approaching a variety of inherited and acquired disorders of different organ systems. Approaches include ex vivo modification of hematologic stem cells (HSC), T lymphocytes and other immune cells, as well as in vivo delivery of genes or gene editing reagents to the relevant target cells by either local or systemic administration. In this article, we highlight success and ongoing challenges in three areas of high activity in gene therapy: inherited blood cell diseases by targeting hematopoietic stem cells, malignant disorders using immune effector cells genetically modified with chimeric antigen receptors, and ophthalmologic, neurologic, and coagulation disorders using in vivo administration of adeno-associated virus (AAV) vectors. In recent years, there have been true cures for many of these diseases, with sustained clinical benefit that exceed those from other medical approaches. Each of these treatments faces ongoing challenges, namely their high one-time costs and the complexity of manufacturing the therapeutic agents, which are biological viruses and cell products, at pharmacologic standards of quality and consistency. New models of reimbursement are needed to make these innovative treatments widely available to patients in need.
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Affiliation(s)
- Donald B Kohn
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
- Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
- The Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA.
| | - Yvonne Y Chen
- Department of Microbiology, Immunology & Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Chemical and Biomolecular Engineering, Henry Samueli School of Engineering, University of California, Los Angeles, Los Angeles, CA, USA
- Parker Institute for Cancer Immunotherapy Center at UCLA, University of California, Los Angeles, Los Angeles, CA, USA
| | - Melissa J Spencer
- The Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
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10
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Butala-Flores E, Nguyen T, Selvan N, Armstrong L, Miller M, Kamen L, Lester T, Wernyj R, Khanna R, McNally J, Hays A. Validation of Anti-Adeno Associated Virus Serotype rh10 (AAVrh.10) Total and Neutralizing Antibody Immunogenicity Assays. Pharm Res 2023; 40:2383-2397. [PMID: 37880551 PMCID: PMC10661749 DOI: 10.1007/s11095-023-03625-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 10/12/2023] [Indexed: 10/27/2023]
Abstract
Immunogenicity assessment of Adeno-Associated Virus (AAV) vectors is a critical part of gene therapy drug development. Whether the assays are used for inclusion/exclusion criteria or to monitor the safety and efficacy of the gene therapy, they are critical bioanalytical assessments. While total anti-AAV assays are perceived as easier to develop and implement than neutralizing anti-AAV assays, the gene therapy field is still nascent, and it is not yet clear which of the assays should be implemented at what stage of drug development. Recently AAVrh.10 has gained interest for use in gene therapies targeting cardiac, neurological, and other diseases due to its enhanced transduction efficiency. There is limited information on anti-AAVrh.10 antibodies and their clinical impact; thus, the information presented herein documents the validation of both a total antibody assay (TAb) and a neutralizing antibody (NAb) assay for anti-AAVrh.10 antibodies. In this manuscript, the validation was performed in accordance with the 2019 FDA immunogenicity guidance with additional evaluations to comply with CLIA where applicable. The AAVrh.10 TAb and NAb assays were compared in terms of sensitivity, drug tolerance, and precision, along with a concordance analysis using the same individual serum samples. This comparison gave insight into the utility of each format as a screening assay for inclusion into clinical studies.
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11
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Emami MR, Espinoza A, Young CS, Ma F, Farahat PK, Felgner PL, Chamberlain JS, Xu X, Pyle AD, Pellegrini M, Villalta SA, Spencer MJ. Innate and adaptive AAV-mediated immune responses in a mouse model of Duchenne muscular dystrophy. Mol Ther Methods Clin Dev 2023; 30:90-102. [PMID: 37746243 PMCID: PMC10512012 DOI: 10.1016/j.omtm.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 06/08/2023] [Indexed: 09/26/2023]
Abstract
High systemic doses of adeno-associated viruses (AAVs) have been associated with immune-related serious adverse events (SAEs). Although AAV was well tolerated in preclinical models, SAEs were observed in clinical trials, indicating the need for improved preclinical models to understand AAV-induced immune responses. Here, we show that mice dual-dosed with AAV9 at 4-week intervals better recapitulate aspects of human immunity to AAV. In the model, anti-AAV9 immunoglobulin G (IgGs) increased in a linear fashion between the first and second AAV administrations. Complement activation was only observed in the presence of high levels of both AAV and anti-AAV IgG. Myeloid-derived pro-inflammatory cytokines were significantly induced in the same pattern as complement activation, suggesting that myeloid cell activation to AAV may rely on the presence of both AAV and anti-AAV IgG complexes. Single-cell RNA sequencing of peripheral blood mononuclear cells confirmed that activated monocytes were a primary source of pro-inflammatory cytokines and chemokines, which were significantly increased after a second AAV9 exposure. The same activated monocyte clusters expressed both Fcγ and complement receptors, suggesting that anti-AAV-mediated activation of myeloid cells through Fcγ receptors and/or complement receptors is one mechanism by which anti-AAV antigen complexes may prime antigen-presenting cells and amplify downstream immunity.
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Affiliation(s)
- Michael R. Emami
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Alejandro Espinoza
- Department of Human Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, USA
- Institute for Quantitative and Computational Biosciences – The Collaboratory, University of California, Los Angeles, Los Angeles, CA, USA
| | | | - Feiyang Ma
- Division of Rheumatology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Philip K. Farahat
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Philip L. Felgner
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - Jeffrey S. Chamberlain
- Department of Neurology, University of Washington School of Medicine, Seattle, WA, USA
- Senator Paul D. Wellstone Muscular Dystrophy Specialized Research Center, University of Washington School of Medicine, Seattle, WA, USA
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA, USA
- Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - Xiangmin Xu
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - April D. Pyle
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA, USA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA
| | - Matteo Pellegrini
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, USA
- Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA, USA
| | - S. Armando Villalta
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
- Institute of Immunology, University of California, Irvine, Irvine, CA, USA
- Department of Neurology, University of California, Irvine, Irvine, CA, USA
| | - Melissa J. Spencer
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA
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12
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Seker Yilmaz B, Gissen P. Genetic Therapy Approaches for Ornithine Transcarbamylase Deficiency. Biomedicines 2023; 11:2227. [PMID: 37626723 PMCID: PMC10452060 DOI: 10.3390/biomedicines11082227] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 08/06/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023] Open
Abstract
Ornithine transcarbamylase deficiency (OTCD) is the most common urea cycle disorder with high unmet needs, as current dietary and medical treatments may not be sufficient to prevent hyperammonemic episodes, which can cause death or neurological sequelae. To date, liver transplantation is the only curative choice but is not widely available due to donor shortage, the need for life-long immunosuppression and technical challenges. A field of research that has shown a great deal of promise recently is gene therapy, and OTCD has been an essential candidate for different gene therapy modalities, including AAV gene addition, mRNA therapy and genome editing. This review will first summarise the main steps towards clinical translation, highlighting the benefits and challenges of each gene therapy approach, then focus on current clinical trials and finally outline future directions for the development of gene therapy for OTCD.
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Affiliation(s)
- Berna Seker Yilmaz
- Genetics and Genomic Medicine Department, Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK;
| | - Paul Gissen
- Genetics and Genomic Medicine Department, Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, UK;
- National Institute of Health Research Great Ormond Street Biomedical Research Centre, London WC1N 1EH, UK
- Metabolic Medicine Department, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
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13
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Masri S, Carré L, Jaulin N, Vandamme C, Couzinié C, Guy-Duché A, Dupont JB, Pereira A, Charpentier E, David L, Gernoux G, Guilbaud M, Adjali O. Transcriptomic Analysis Reveals the Inability of Recombinant AAV8 to Activate Human Monocyte-Derived Dendritic Cells. Int J Mol Sci 2023; 24:10447. [PMID: 37445621 DOI: 10.3390/ijms241310447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/13/2023] [Accepted: 06/14/2023] [Indexed: 07/15/2023] Open
Abstract
Recombinant Adeno-Associated Virus (rAAV) is considered as one of the most successful and widely used viral vectors for in vivo gene therapy. However, host immune responses to the vector and/or the transgene product remain a major hurdle to successful AAV gene transfer. In contrast to antivector adaptive immunity, the initiation of the innate immunity towards rAAV is still poorly understood but is directly dependent on the interaction between the viral vector and innate immune cells. Here, we used a quantitative transcriptomic-based approach to determine the activation of inflammatory and anti-viral pathways after rAAV8-based infection of monocyte-derived dendritic cells (moDCs) obtained from 12 healthy human donors. We have shown that rAAV8 particles are efficiently internalized, but that this uptake does not induce any detectable transcriptomic change in moDCs in contrast to an adenoviral infection, which upregulates anti-viral pathways. These findings suggest an immunologically favorable profile for rAAV8 serotype with regard to in vitro activation of moDC model. Transcriptomic analysis of rAAV-infected innate immune cells is a powerful method to determine the ability of the viral vector to be seen by these sensor cells, which remains of great importance to better understand the immunogenicity of rAAV vectors and to design immune-stealth products.
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Affiliation(s)
- Samer Masri
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Laure Carré
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Nicolas Jaulin
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Céline Vandamme
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Célia Couzinié
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Aurélien Guy-Duché
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Jean-Baptiste Dupont
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Allwyn Pereira
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Eric Charpentier
- Nantes Université, CHU Nantes, CNRS, INSERM, SFR Santé, UMS 3556, UMS016, F-44000 Nantes, France
| | - Laurent David
- Nantes Université, CHU Nantes, INSERM, Center for Research in Transplantation and Translational Immunology, UMR 1064, ITUN, F-44000 Nantes, France
| | - Gwladys Gernoux
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Mickaël Guilbaud
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
| | - Oumeya Adjali
- Nantes Université, CHU Nantes, INSERM, TaRGeT-Translational Research in Gene Therapy, UMR 1089, F-44200 Nantes, France
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14
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Maguire CA. Accessorizing viral vectors with extracellular vesicles for enhanced performance. Mol Ther 2023; 31:1204-1206. [PMID: 37044086 PMCID: PMC10188910 DOI: 10.1016/j.ymthe.2023.03.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 03/29/2023] [Accepted: 03/29/2023] [Indexed: 04/14/2023] Open
Affiliation(s)
- Casey A Maguire
- Harvard Medical School, The Massachusetts General Hospital, Boston, MA, USA.
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15
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Arjomandnejad M, Dasgupta I, Flotte TR, Keeler AM. Immunogenicity of Recombinant Adeno-Associated Virus (AAV) Vectors for Gene Transfer. BioDrugs 2023; 37:311-329. [PMID: 36862289 PMCID: PMC9979149 DOI: 10.1007/s40259-023-00585-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2023] [Indexed: 03/03/2023]
Abstract
Recombinant adeno-associated viruses (AAVs) have emerged as promising gene delivery vehicles resulting in three US Food and Drug Administration (FDA) and one European Medicines Agency (EMA)-approved AAV-based gene therapies. Despite being a leading platform for therapeutic gene transfer in several clinical trials, host immune responses against the AAV vector and transgene have hampered their widespread application. Multiple factors, including vector design, dose, and route of administration, contribute to the overall immunogenicity of AAVs. The immune responses against the AAV capsid and transgene involve an initial innate sensing. The innate immune response subsequently triggers an adaptive immune response to elicit a robust and specific response against the AAV vector. AAV gene therapy clinical trials and preclinical studies provide important information about the immune-mediated toxicities associated with AAV, yet studies suggest preclinical models fail to precisely predict the outcome of gene delivery in humans. This review discusses the contribution of the innate and adaptive immune response against AAVs, highlighting the challenges and potential strategies to mitigate these responses, thereby enhancing the therapeutic potential of AAV gene therapy.
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Affiliation(s)
- Motahareh Arjomandnejad
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, 386 Plantation Street, Worcester, MA, 01605, USA
| | - Ishani Dasgupta
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, 386 Plantation Street, Worcester, MA, 01605, USA
| | - Terence R Flotte
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, 386 Plantation Street, Worcester, MA, 01605, USA
- Department of Pediatrics, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Allison M Keeler
- Horae Gene Therapy Center, University of Massachusetts Chan Medical School, 386 Plantation Street, Worcester, MA, 01605, USA.
- Department of Pediatrics, University of Massachusetts Chan Medical School, Worcester, MA, USA.
- NeuroNexus Institute, University of Massachusetts Chan Medical School, Worcester, MA, USA.
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16
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West C, Federspiel J, Rogers K, Khatri A, Rao-Dayton S, Fernandez Ocana M, Lim S, D'Antona AM, Casinghino S, Somanathan S. Complement activation by AAV-neutralizing antibody complexes. Hum Gene Ther 2023. [PMID: 37082966 DOI: 10.1089/hum.2023.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023] Open
Abstract
Treatment of monogenetic disorders using adeno-associated viral vectors (AAV) is an area of intense interest. AAV is a human pathogen and pre-existing capsid antibodies are prevalent in the population posing a challenge to safety and efficacy of AAV-mediated gene therapies. Here we investigated the risk of AAV-mediated complement activation when sera from a cohort of human donors was exposed to AAV9 capsid. Seropositive donor sera carrying neutralizing antibodies from a previous environmental exposure activated complement when admixed with AAV9 capsids and complement-activation was associated with donors who had higher levels of ant-AAV IgG1 antibodies. These findings were consistent with Mass spectrometry analysis that identified increased binding of immunoglobulins and complement factors when AAV9 capsids were admixed with seropositive sera. Finally, complement activation was abrogated after IgG-depletion using affinity columns or serum pre-treatment with an IgG degrading enzyme. Overall, these results demonstrate an important role of pre-existing neutralizing antibodies in activating complement; a risk that can be mitigated by employing adequate immunosuppression strategies when dosing seropositive patients with vector.
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Affiliation(s)
- Cara West
- Pfizer Inc, 2253, Rare Diseases Research Unit, Cambridge, Massachusetts, United States;
| | - Joel Federspiel
- Pfizer Inc, 2253, Drug Safety Research and Development, Andover, Massachusetts, United States;
| | - Kara Rogers
- Pfizer Inc, 2253, Drug Safety Research & Development, Groton, Connecticut, United States;
| | - Arpana Khatri
- Pfizer Inc, 2253, Rare Disease Research Unit, Cambridge, Massachusetts, United States;
| | - Sheila Rao-Dayton
- Pfizer Inc, 2253, Biomedicine Design, Morrisville, North Carolina, United States;
| | - Mireia Fernandez Ocana
- Pfizer Inc, 2253, Drug Safety Research and Development, Andover, Massachusetts, United States;
| | - Sean Lim
- Pfizer Inc, 2253, Biomedicine design, Cambridge, Massachusetts, United States;
| | | | - Sandra Casinghino
- Pfizer Inc, 2253, Drug Safety Research & Development, Groton, Connecticut, United States;
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17
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Schulz M, Levy DI, Petropoulos CJ, Bashirians G, Winburn I, Mahn M, Somanathan S, Cheng SH, Byrne BJ. Binding and neutralizing anti-AAV antibodies: Detection and implications for rAAV-mediated gene therapy. Mol Ther 2023; 31:616-630. [PMID: 36635967 PMCID: PMC10014285 DOI: 10.1016/j.ymthe.2023.01.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 12/21/2022] [Accepted: 01/06/2023] [Indexed: 01/13/2023] Open
Abstract
Assessment of anti-adeno-associated virus (AAV) antibodies in patients prior to systemic gene therapy administration is an important consideration regarding efficacy and safety of the therapy. Approximately 30%-60% of individuals have pre-existing anti-AAV antibodies. Seroprevalence is impacted by multiple factors, including geography, age, capsid serotype, and assay type. Anti-AAV antibody assays typically measure (1) transduction inhibition by detecting the neutralizing capacity of antibodies and non-antibody neutralizing factors, or (2) total anti-capsid binding antibodies, regardless of neutralizing activity. Presently, there is a paucity of head-to-head data and standardized approaches associating assay results with clinical outcomes. In addition, establishing clinically relevant screening titer cutoffs is complex. Thus, meaningful comparisons across assays are nearly impossible. Although complex, establishing screening assays in routine clinical practice to identify patients with antibody levels that may impact favorable treatment outcomes is achievable for both transduction inhibition and total antibody assays. Formal regulatory approval of such assays as companion diagnostic tests will confirm their suitability for specific recombinant AAV gene therapies. This review covers current approaches to measure anti-AAV antibodies in patient plasma or serum, their potential impact on therapeutic safety and efficacy, and investigative strategies to mitigate the effects of pre-existing anti-AAV antibodies in patients.
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Affiliation(s)
- Martin Schulz
- Pfizer, 235 East 42nd Street, New York, NY 10017, USA
| | - Daniel I Levy
- Pfizer, 235 East 42nd Street, New York, NY 10017, USA
| | | | | | - Ian Winburn
- Pfizer, 235 East 42nd Street, New York, NY 10017, USA
| | - Matthias Mahn
- Pfizer, 235 East 42nd Street, New York, NY 10017, USA
| | | | - Seng H Cheng
- Pfizer, 235 East 42nd Street, New York, NY 10017, USA
| | - Barry J Byrne
- University of Florida, 1600 SW Archer Road, Gainesville, FL 32610, USA.
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18
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Abstract
Gene therapy is poised to revolutionize modern medicine, with seemingly unlimited potential for treating and curing genetic disorders. For otherwise incurable indications, including most inherited metabolic liver disorders, gene therapy provides a realistic therapeutic option. In this Review, we discuss gene supplementation and gene editing involving the use of recombinant adeno-associated virus (rAAV) vectors for the treatment of inherited liver diseases, including updates on several ongoing clinical trials that are producing promising results. Clinical testing has been essential in highlighting many key translational challenges associated with this transformative therapy. In particular, the interaction of a patient's immune system with the vector raises issues of safety and the duration of treatment efficacy. Furthermore, several serious adverse events after the administration of high doses of rAAVs suggest greater involvement of innate immune responses and pre-existing hepatic conditions than initially anticipated. Finally, permanent modification of the host genome associated with rAAV genome integration and gene editing raises concerns about the risk of oncogenicity that require careful evaluation. We summarize the main progress, challenges and pathways forward for gene therapy for liver diseases.
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