Spinal muscular atrophy (SMA), the leading genetic cause of infant mortality, is characterized by the deterioration of alpha motor neurons in the brainstem and spinal cord. Currently, there is no cure for SMA, which calls for an urgent need to explore affordable and effective therapies and to maximize patients’ independence and quality of life. Adeno-associated virus (AAV) vector, one of the most promising and well-investigated vehicles for delivering transgenes, is a compelling candidate for gene therapy. Some of the hallmarks of AAVs are their nonpathogenicity, inability to incur an immune response, potential to achieve robust transgene expression, and varied tropism for several tissues of the body. Recently, these features were harnessed in a clinical trial conducted by AveXis in SMA patients, where AAV9 was employed as a vehicle for one-time administration of the SMN gene, the causative gene in SMA. The trial demonstrated remarkable improvements in motor milestones and rates of survival in the patients. This review focuses on the advent of SMA gene therapy and summarizes different preclinical studies that were conducted leading up to the AAV9–SMA trial in SMA patients.
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Prior TW. Spinal muscular atrophy: a time for screening. Curr Opin Pediatr. 2010;22:696–702.
Cherry JJ, Kobayashi DT, Lynes MM, Naryshkin NN, Tiziano FD, Zaworski PG, et al. Assays for the identification and prioritization of drug candidates for spinal muscular atrophy. Assay Drug Dev Technol. 2014;12:315–41.
Farrar MA, Vucic S, Lin CS-Y, Park SB, Johnston HM, du Sart D, et al. Dysfunction of axonal membrane conductances in adolescents and young adults with spinal muscular atrophy. Brain 2011;134:3185–97.
Finkel RS, McDermott MP, Kaufmann P, Darras BT, Chung WK, Sproule DM, et al. Observational study of spinal muscular atrophy type I and implications for clinical trials. Neurology 2014;83:810–7.
Sugarman EA, Nagan N, Zhu H, Akmaev VR, Zhou Z, Rohlfs EM, et al. Pan-ethnic carrier screening and prenatal diagnosis for spinal muscular atrophy: clinical laboratory analysis of >72,400 specimens. Eur J Hum Genet. 2012;20:27–32.
Prior TW, Nagan N, Sugarman EA, Batish SD, Braastad C. Technical standards and guidelines for spinal muscular atrophy testing. Genet Med. 2011;13:686–94.
Lefebvre S, Bürglen L, Reboullet S, Clermont O, Burlet P, Viollet L, et al. Identification and characterization of a spinal muscular atrophy-determining gene. Cell 1995;80:155–65.
Kolb SJ, Kissel JT. Spinal muscular atrophy. Neurol Clin. 2015;33:831–46.
Rochette CF, Gilbert N, Simard LR. SMN gene duplication and the emergence of the SMN2 gene occurred in distinct hominids: SMN2 is unique to Homo sapiens. Hum Genet. 2001;108:255–66.
Monani UR, De Vivo DC. Neurodegeneration in spinal muscular atrophy: from disease phenotype and animal models to therapeutic strategies and beyond. Future Neurol. 2014;9:49–65.
Burghes AHM, Beattie CE. Spinal muscular atrophy: why do low levels of survival motor neuron protein make motor neurons sick? Nat Rev Neurosci. 2009;10:597–609.
Garcera A, Bahi N, Periyakaruppiah A, Arumugam S, Soler RM. Survival motor neuron protein reduction deregulates autophagy in spinal cord motoneurons in vitro. Cell Death Dis. 2013;4:e686.
Stabley DL, Harris AW, Holbrook J, Chubbs NJ, Lozo KW, Crawford TO, et al. SMN1 and SMN2 copy numbers in cell lines derived from patients with spinal muscular atrophy as measured by array digital PCR. Mol Genet Genomic Med. 2015;3:248–57.
Coovert DD, Le TT, McAndrew PE, Strasswimmer J, Crawford TO, Mendell JR, et al. The survival motor neuron protein in spinal muscular atrophy. Hum Mol Genet. 1997;6:1205–14.
Lefebvre S, Burlet P, Liu Q, Bertrandy S, Clermont O, Munnich A, et al. Correlation between severity and SMN protein level in spinal muscular atrophy. Nat Genet. 1997;16:265–9.
Liu Q, Dreyfuss G. A novel nuclear structure containing the survival of motor neurons protein. EMBO J. 1996;15:3555–65.
Faravelli I, Nizzardo M, Comi GP, Corti S. Spinal muscular atrophy—recent therapeutic advances for an old challenge. Nat Rev Neurol. 2015;11:351–9.
Battle DJ, Kasim M, Yong J, Lotti F, Lau C-K, Mouaikel J, et al. The SMN complex: an assembly machine for RNPs. Cold Spring Harb Symp Quant Biol. 2006;71:313–20.
Chari A, Golas MM, Klingenhäger M, Neuenkirchen N, Sander B, Englbrecht C, et al. An assembly chaperone collaborates with the SMN complex to generate spliceosomal SnRNPs. Cell 2008;135:497–509.
Pellizzoni L. Chaperoning ribonucleoprotein biogenesis in health and disease. EMBO Rep. 2007;8:340–5.
Boulisfane N, Choleza M, Rage F, Neel H, Soret J, Bordonné R. Impaired minor tri-snRNP assembly generates differential splicing defects of U12-type introns in lymphoblasts derived from a type I SMA patient. Hum Mol Genet. 2011;20:641–8.
Gabanella F, Butchbach MER, Saieva L, Carissimi C, Burghes AHM, Pellizzoni L. Ribonucleoprotein assembly defects correlate with spinal muscular atrophy severity and preferentially affect a subset of spliceosomal snRNPs. PLoS ONE. 2007;2:e921.
Li DK, Tisdale S, Lotti F, Pellizzoni L. SMN control of RNP assembly: from post-transcriptional gene regulation to motor neuron disease. Semin Cell Dev Biol. 2014;32:22–9.
Zhang Z, Lotti F, Dittmar K, Younis I, Wan L, Kasim M, et al. SMN deficiency causes tissue-specific perturbations in the repertoire of snRNAs and widespread defects in splicing. Cell 2008;133:585–600.
Boyer JG, Murray LM, Scott K, De Repentigny Y, Renaud J-M, Kothary R. Early onset muscle weakness and disruption of muscle proteins in mouse models of spinal muscular atrophy. Skelet Muscle. 2013;3:24.
Fayzullina S, Martin LJ. Skeletal muscle DNA damage precedes spinal motor neuron DNA damage in a mouse model of spinal muscular atrophy (SMA). PLoS ONE. 2014;9:e93329.
Goulet BB, Kothary R, Parks RJ. At the “junction” of spinal muscular atrophy pathogenesis: the role of neuromuscular junction dysfunction in SMA disease progression. Curr Mol Med. 2013;13:1160–74.
Kariya S, Obis T, Garone C, Akay T, Sera F, Iwata S, et al. Requirement of enhanced survival motoneuron protein imposed during neuromuscular junction maturation. J Clin Investig. 2014;124:785–800.
Martinez TL, Kong L, Wang X, Osborne MA, Crowder ME, Van Meerbeke JP, et al. Survival motor neuron protein in motor neurons determines synaptic integrity in spinal muscular atrophy. J Neurosci. 2012;32:8703–15.
McWhorter ML, Monani UR, Burghes AHM, Beattie CE. Knockdown of the survival motor neuron (Smn) protein in zebrafish causes defects in motor axon outgrowth and pathfinding. J Cell Biol. 2003;162:919–31.
Akten B, Kye MJ, Hao LT, Wertz MH, Singh S, Nie D, et al. Interaction of survival of motor neuron (SMN) and HuD proteins with mRNA cpg15 rescues motor neuron axonal deficits. Proc Natl Acad Sci USA. 2011;108:10337–42.
Hao LT, Duy PQ, An M, Talbot J, Iyer CC, Wolman M, et al. HuD and the survival motor neuron protein interact in motoneurons and are essential for motoneuron development, function and mRNA regulation. J Neurosci. 2017;37:1528–17.
Mulcahy PJ, Iremonger K, Karyka E, Herranz-Martín S, Shum K-T, Tam JKV, et al. Gene therapy: a promising approach to treating spinal muscular atrophy. Hum Gene Ther. 2014;25:575–86.
Zanetta C, Nizzardo M, Simone C, Monguzzi E, Bresolin N, Comi GP, et al. Molecular therapeutic strategies for spinal muscular atrophies: current and future clinical trials. Clin Ther. 2014;36:128–40.
DeVos SL, Miller TM. Antisense oligonucleotides: treating neurodegeneration at the level of RNA. Neurotherapeutics 2013;10:486–97.
Groen EJN, Talbot K, Gillingwater TH. Advances in therapy for spinal muscular atrophy: promises and challenges. Nat Rev Neurol. 2018;14:214–24.
Hua Y, Sahashi K, Hung G, Rigo F, Passini MA, Bennett CF, et al. Antisense correction of SMN2 splicing in the CNS rescues necrosis in a type III SMA mouse model. Genes Dev. 2010;24:1634–44.
Passini MA, Bu J, Richards AM, Kinnecom C, Sardi SP, Stanek LM, et al. Antisense oligonucleotides delivered to the mouse CNS ameliorate symptoms of severe spinal muscular atrophy. Sci Transl Med. 2011;3:72ra18.
Williams JH, Schray RC, Patterson CA, Ayitey SO, Tallent MK, Lutz GJ. Oligonucleotide-mediated survival of motor neuron protein expression in CNS improves phenotype in a mouse model of spinal muscular atrophy. J Neurosci. 2009;29:7633–8.
Hamilton G, Gillingwater TH. Spinal muscular atrophy: going beyond the motor neuron. Trends Mol Med. 2013;19:40–50.
Shababi M, Lorson CL, Rudnik-Schöneborn SS. Spinal muscular atrophy: a motor neuron disorder or a multi-organ disease? J Anat. 2014;224:15–28.
Chiriboga CA, Swoboda KJ, Darras BT, Iannaccone ST, Montes J, De Vivo DC, et al. Results from a phase 1 study of nusinersen (ISIS-SMNRx) in children with spinal muscular atrophy. Neurology 2016;86:890–7.
Stein CA, Castanotto D. FDA-approved oligonucleotide therapies in 2017. Mol Ther. 2017;25:1069–75.
Singh NN, Howell MD, Androphy EJ, Singh RN. How the discovery of ISS-N1 led to the first medical therapy for spinal muscular atrophy. Gene Ther. 2017;24:520–6.
Bevan AK, Hutchinson KR, Foust KD, Braun L, McGovern VL, Schmelzer L, et al. Early heart failure in the SMNΔ7 model of spinal muscular atrophy and correction by postnatal scAAV9-SMN delivery. Hum Mol Genet. 2010;19:3895–905.
Wijngaarde CA, Blank AC, Stam M, Wadman RI, van den Berg LH, van der Pol WL. Cardiac pathology in spinal muscular atrophy: a systematic review. Orphanet J Rare Dis. 2017;12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5387385/.
Azzouz M, Le T, Ralph GS, Walmsley L, Monani UR, Lee DCP, et al. Lentivector-mediated SMN replacement in a mouse model of spinal muscular atrophy. J Clin Investig. 2004;114:1726–31.
Sinn PL, Sauter SL Jr, PBM. Gene therapy progress and prospects: development of improved lentiviral and retroviral vectors—design, biosafety, and production. Gene Ther. 2005;12:1089–98.
Hacein-Bey-Abina S, Von Kalle C, Schmidt M, McCormack MP, Wulffraat N, Leboulch P, et al. LMO2-associated clonal T cell proliferation in two patients after gene therapy for SCID-X1. Science 2003;302:415–9.
Hacein-Bey-Abina S, von Kalle C, Schmidt M, Le Deist F, Wulffraat N, McIntyre E, et al. A serious adverse event after successful gene therapy for X-linked severe combined immunodeficiency. 2009. https://www.nejm.org/doi/10.1056/NEJM200301163480314?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dwww.ncbi.nlm.nih.gov.
Gruber K. Europe gives gene therapy the green light. Lancet 2012;380:e10.
Daya S, Berns KI. Gene therapy using adeno-associated virus vectors. Clin Microbiol Rev. 2008;21:583–93.
Colella P, Ronzitti G, Mingozzi F. Emerging issues in AAV-mediated in vivo gene therapy. Mol Ther Methods Clin Dev. 2017;8:87–104.
Cao L, During M, Xiao W. Replication competent helper functions for recombinant AAV vector generation. Gene Ther. 2002;9:1199–206.
Drouin LM, Agbandje-McKenna M. Adeno-associated virus structural biology as a tool in vector development. Future Virol. 2013;8:1183–99.
Zhang H-G, Wang YM, Xie JF, Liang X, Hsu H-C, Zhang X, et al. Recombinant adenovirus expressing adeno-associated virus cap and rep proteins supports production of high-titer recombinant adeno-associated virus. Gene Ther. 2001;8:704–12.
Kantor B, Bailey RM, Wimberly K, Kalburgi SN, Gray SJ. Methods for gene transfer to the central nervous system. Adv Genet. 2014;87:125–97.
Ferrari FK, Samulski T, Shenk T, Samulski RJ. Second-strand synthesis is a rate-limiting step for efficient transduction by recombinant adeno-associated virus vectors. J Virol. 1996;70:3227–34.
McCarty DM. Self-complementary AAV vectors; advances and applications. Mol Ther. 2008;16:1648–56.
Duque S, Joussemet B, Riviere C, Marais T, Dubreil L, Douar A-M, et al. Intravenous administration of self-complementary AAV9 enables transgene delivery to adult motor neurons. Mol Ther. 2009;17:1187–96.
Foust KD, Nurre E, Montgomery CL, Hernandez A, Chan CM, Kaspar BK. Intravascular AAV9 preferentially targets neonatal-neurons and adult-astrocytes in CNS. Nat Biotechnol. 2009;27:59–65.
Foust KD, Wang X, McGovern VL, Braun L, Bevan AK, Haidet AM, et al. Rescue of the spinal muscular atrophy phenotype in a mouse model by early postnatal delivery of SMN. Nat Biotechnol. 2010;28:271–4.
Dominguez E, Marais T, Chatauret N, Benkhelifa-Ziyyat S, Duque S, Ravassard P, et al. Intravenous scAAV9 delivery of a codon-optimized SMN1 sequence rescues SMA mice. Hum Mol Genet. 2011;20:681–93.
Valori CF, Ning K, Wyles M, Mead RJ, Grierson AJ, Shaw PJ, et al. Systemic delivery of scAAV9 expressing SMN prolongs survival in a model of spinal muscular atrophy. Sci Transl Med. 2010;2:35ra42–35ra42.
Alrafiah A, Karyka E, Coldicott I, Iremonger K, Lewis KE, Ning K, et al. Plastin 3 promotes motor neuron axonal growth and extends survival in a mouse model of spinal muscular atrophy. Mol Ther Methods Clin Dev. 2018;9:81–9.
Kaifer KA, Villalón E, Osman EY, Glascock JJ, Arnold LL, Cornelison DDW, et al. Plastin-3 extends survival and reduces severity in mouse models of spinal muscular atrophy. JCI Insight. 2017;2. https://insight.jci.org/articles/view/89970.
Powis RA, Karyka E, Boyd P, Côme J, Jones RA, Zheng Y, et al. Systemic restoration of UBA1 ameliorates disease in spinal muscular atrophy. JCI Insight. 2016;1. https://insight.jci.org/articles/view/87908.
Little D, Valori CF, Mutsaers CA, Bennett EJ, Wyles M, Sharrack B, et al. PTEN depletion decreases disease severity and modestly prolongs survival in a mouse model of spinal muscular atrophy. Mol Ther. 2015;23:270–7.
Bevan AK, Duque S, Foust KD, Morales PR, Braun L, Schmelzer L, et al. Systemic gene delivery in large species for targeting spinal cord, brain, and peripheral tissues for pediatric disorders. Mol Ther. 2011;19:1971–80.
Dehay B, Dalkara D, Dovero S, Li Q, Bezard E. Systemic scAAV9 variant mediates brain transduction in newborn rhesus macaques. Sci Rep. 2012;2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3275921/.
Meyer K, Ferraiuolo L, Schmelzer L, Braun L, McGovern V, Likhite S, et al. Improving single injection CSF delivery of AAV9-mediated gene therapy for SMA: a dose–response study in mice and nonhuman primates. Mol Ther. 2015;23:477–87.
Mendell JR, Al-Zaidy S, Shell R, Arnold WD, Rodino-Klapac LR, Prior TW, et al. Single-dose gene-replacement therapy for spinal muscular atrophy. N Engl J Med. 2017;377:1713–22.
Possible $4M Price for AVXS-101, “Foundational” SMA gene therapy, could be cost-effective, Novartis says. https://smanewstoday.com/2018/11/09/possible-4m-price-for-avxs-101-foundational-sma-gene-therapy-could-be-cost-effective-novartis-says/.
Wu Z, Asokan A, Samulski RJ. Adeno-associated virus serotypes: vector toolkit for human gene therapy. Mol Ther. 2006;14:316–27.
Chira S, Jackson CS, Oprea I, Ozturk F, Pepper MS, Diaconu I, et al. Progresses towards safe and efficient gene therapy vectors. Oncotarget 2015;6:30675.
Finer M, Glorioso J. A brief account of viral vectors and their promise for gene therapy. Gene Ther. 2017;24:1–2.
This work was supported by the Blazer Foundation.
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Pattali, R., Mou, Y. & Li, XJ. AAV9 Vector: a Novel modality in gene therapy for spinal muscular atrophy. Gene Ther 26, 287–295 (2019). https://doi.org/10.1038/s41434-019-0085-4
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