Systemic AAV Gene Therapy Close to Clinical Trials for Several Neuromuscular Diseases
Authors: Dominic J. Wells
Journal: Molecular Therapy (2017)

While there have been a number of gene therapy clinical trials using adeno-associated viral (AAV) vectors, the majority have been safety studies involving local intramuscular delivery. To date, only one trial has involved systemic delivery: AAV-SMN1Qiao C. Li J. Zheng H. Bogan J. Li J. Yuan Z. Zhang C. Bogan D. Kornegay J. Xiao X. Hydrodynamic limb vein injection of adeno-associated virus serotype 8 vector carrying canine myostatin propeptide gene into normal dogs enhances muscle growth.Hum. Gene Ther. 2009; 20: 1-10Crossref PubMed Scopus (74) Google Scholar for spinal muscular atrophy type 1 (Table 1). Likewise, many of the studies in large animals have focused on local or regional delivery (e.g., Qiao et al.1Qiao C. Li J. Zheng H. Bogan J. Li J. Yuan Z. Zhang C. Bogan D. Kornegay J. Xiao X. Hydrodynamic limb vein injection of adeno-associated virus serotype 8 vector carrying canine myostatin propeptide gene into normal dogs enhances muscle growth.Hum. Gene Ther. 2009; 20: 1-10Crossref PubMed Scopus (74) Google Scholar and Le Guiner et al.2Le Guiner C. Montus M. Servais L. Cherel Y. Francois V. Thibaud J.L. Wary C. Matot B. Larcher T. Guigand L. et al.Forelimb treatment in a large cohort of dystrophic dogs supports delivery of a recombinant AAV for exon skipping in Duchenne patients.Mol. Ther. 2014; 22: 1923-1935Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar) or have examined the effects of systemic delivery in young puppies (e.g., Yue et al.3Yue Y. Ghosh A. Long C. Bostick B. Smith B.F. Kornegay J.N. Duan D. A single intravenous injection of adeno-associated virus serotype-9 leads to whole body skeletal muscle transduction in dogs.Mol. Ther. 2008; 16: 1944-1952Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar). In this issue of Molecular Therapy, Mack and colleagues4Mack D.L. Poulard K. Goddard M.A. Latournerie V. Snyder J.M. Grange R.W. Elverman M.R. Denard J. Veron P. Buscara L. et al.Systemic AAV8-mediated gene therapy drives whole-body correction of myotubular myopathy in dogs.Mol Ther. 2017; 25 (this issue): 839-854Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar employed systemic intravenous delivery of an AAV serotype 8 (rAAV8) vector expressing the canine myotubularin (cMTM1) gene in the p.N155K canine model of X-linked myotubular myopathy (XLMTM). Skeletal muscle and cardiac expression was ensured by a muscle-specific desmin promoter. Importantly, they treated juvenile dogs with clinical signs of the disease and showed a clear dose-response to systemic treatment in terms of levels of expression of cMTM1 and the functional consequences of such expression. The effect of AAV-mediated gene therapy was to prolong life substantially with doses of 4 × 1014 vector genomes/kg (medium dose) or greater (high dose). Other outcome measures included global neurological function, spinal reflexes, forelimb extensor and flexor strength, hindlimb extensor and flexor strength, gait speed, stride length, peak inspiratory flow, and histopathology, all of which improved in the medium- and high-dose groups.Table 1A Summary of Human Clinical Trials of AAV-Based Gene Transfer in Neuromuscular DiseasesClinicaltrials.gov IdentifierTrialRouteAssociated PublicationsNCT00428935safety study of mini-dystrophin gene to treat Duchenne muscular dystrophyintramuscularMendell et al.11Mendell J.R. Campbell K. Rodino-Klapac L. Sahenk Z. Shilling C. Lewis S. Bowles D. Gray S. Li C. Galloway G. et al.Dystrophin immunity in Duchenne's muscular dystrophy.N. Engl. J. Med. 2010; 363: 1429-1437Crossref PubMed Scopus (453) Google ScholarNCT00494195gene transfer therapy for treating children and adults with limb girdle muscular dystrophy type 2D (LGMD2D)intramuscularMendell et al.12Mendell J.R. Rodino-Klapac L.R. Rosales X.Q. Coley B.D. Galloway G. Lewis S. Malik V. Shilling C. Byrne B.J. Conlon T. et al.Sustained alpha-sarcoglycan gene expression after gene transfer in limb-girdle muscular dystrophy, type 2D.Ann. Neurol. 2010; 68: 629-638Crossref PubMed Scopus (183) Google ScholarNCT01344798clinical study of AAV1-gamma-sarcoglycan gene therapy for limb girdle muscular dystrophy type 2CintramuscularnoneNCT01519349follistatin gene transfer to patients with Becker muscular dystrophy and sporadic inclusion body myositisintramuscularMendell et al.13Mendell J.R. Sahenk Z. Malik V. Gomez A.M. Flanigan K.M. Lowes L.P. Alfano L.N. Berry K. Meadows E. Lewis S. et al.A phase 1/2a follistatin gene therapy trial for becker muscular dystrophy.Mol. Ther. 2015; 23: 192-201Abstract Full Text Full Text PDF PubMed Scopus (167) Google Scholar and Al-Zaidy14Al-Zaidy S.A. Sahenk Z. Rodino-Klapac L.R. Kaspar B. Mendell J.R. Follistatin gene therapy improves ambulation in becker muscular dystrophy.J Neuromuscul Dis. 2015; 2: 185-192Crossref PubMed Scopus (29) Google ScholarNCT02122952gene transfer clinical trial for spinal muscular atrophy type 1systemic (IV)ongoingNCT02354781clinical intramuscular gene transfer of rAAV1.CMV.huFollistatin344 trial to patients with Duchenne muscular dystrophyintramuscularongoing Open table in a new tab XLMTM is a consequence of mutations in the MTM1 gene and the associated deficiency of myotubularin, a 3-phosphoinositide phosphatase enzyme. Most XLMTM patients develop severe muscle weakness, leading to respiratory failure and death, typically before 2 years of age. The study by Mack and colleagues4Mack D.L. Poulard K. Goddard M.A. Latournerie V. Snyder J.M. Grange R.W. Elverman M.R. Denard J. Veron P. Buscara L. et al.Systemic AAV8-mediated gene therapy drives whole-body correction of myotubular myopathy in dogs.Mol Ther. 2017; 25 (this issue): 839-854Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar not only sets a potential dose for human clinical trials, but also carefully documents the differences in vector biodistribution and expression of myotubularin between different skeletal muscles in the canine model. Indeed, the muscle maps of these features are, in themselves, works of art. This study follows up on a regional delivery trial of the same vector in the same model.5Childers M.K. Joubert R. Poulard K. Moal C. Grange R.W. Doering J.A. Lawlor M.W. Rider B.E. Jamet T. Danièle N. et al.Gene therapy prolongs survival and restores function in murine and canine models of myotubular myopathy.Sci. Transl. Med. 2014; 6: 220ra10Crossref PubMed Scopus (116) Google Scholar The previous study had shown remarkable results from a regional infusion of AAV8-cMTM1, leading to a halt in the progression of the disease, dramatically improved muscle strength, and dramatically extended survival. That the regional infusion had a body-wide effect was a surprise, and the authors speculated that the widespread delivery might have been due to an inefficient tourniquet or the presence of substantial amounts of the AAV that could enter the circulation after release of the tourniquet. From this previous study, it appeared that relatively small levels of myotubularin expression are sufficient for the rescue of the pathological phenotype, and this was confirmed in the present study. Few studies are without flaws. Randomization led to a preponderance of females in the control group, while experimental groups were predominately male, and this may have affected the statistical analysis. However, as the authors note, the study was not sufficiently powered for robust statistical analysis, a common problem with breeding mutant dog colonies. Although the authors report no difference between affected homozygous females and hemizygous males, there are different hormonal profiles between the two sexes that might influence aspects of the manifestation of disease. Estrogen has been implicated in muscle membrane stability,6Dorchies O.M. Reutenauer-Patte J. Dahmane E. Ismail H.M. Petermann O. Patthey- Vuadens O. Comyn S.A. Gayi E. Piacenza T. Handa R.J. et al.The anticancer drug tamoxifen counteracts the pathology in a mouse model of duchenne muscular dystrophy.Am. J. Pathol. 2013; 182: 485-504Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar and testosterone has a well-known influence on muscle fiber size.7Sinha-Hikim I. Artaza J. Woodhouse L. Gonzalez-Cadavid N. Singh A.B. Lee M.I. Storer T.W. Casaburi R. Shen R. Bhasin S. Testosterone-induced increase in muscle size in healthy young men is associated with muscle fiber hypertrophy.Am. J. Physiol. Endocrinol. Metab. 2002; 283: E154-E164Crossref PubMed Scopus (310) Google Scholar Such differences might translate into functional differences between the treated and control groups. Thus, the reader might wish to focus on the comparisons between the different treatment groups, which show a clear dose response for many of the outcome measures performed with the dogs. Dog models have proven invaluable in the development of gene therapies for haemophilia8Nichols T.C. Whitford M.H. Arruda V.R. Stedman H.H. Kay M.A. High K.A. Translational data from adeno-associated virus-mediated gene therapy of hemophilia B in dogs.Hum. Gene Ther. Clin. Dev. 2015; 26: 5-14Crossref PubMed Scopus (28) Google Scholar and are likely to prove so for XLMTM, Duchenne muscular dystrophy (DMD), and other neuromuscular disorders. Quite recently, body-wide, but patchy, expression of a highly engineered microdystrophin was demonstrated in a dog model of DMD treated with intravenous AAV as juveniles.9Yue Y. Pan X. Hakim C.H. Kodippili K. Zhang K. Shin J.H. Yang H.T. McDonald T. Duan D. Safe and bodywide muscle transduction in young adult Duchenne muscular dystrophy dogs with adeno-associated virus.Hum. Mol. Genet. 2015; 24: 5880-5890Crossref PubMed Scopus (85) Google Scholar Importantly, the DMD dog study also did not report any safety concerns. Of course, it is important to recognize where there are differences between animal models and the human condition. Although the dog model of XLMTM shows many features of the human condition, it develops respiratory problems in the later stages of the disease, whereas infants with XLMTM present with respiratory failure at birth. Consequently, the dramatic amelioration of the disease seen in the murine and canine models of XLMTM may not be precisely replicated by a similar improvement in man. The current study lays the foundation for a human clinical trial of systemic AAV-MTN in myotubular myopathy. In parallel, there are a number of groups that propose to undertake human clinical trials of systemic AAV microdystrophin delivery for the treatment of DMD, although none are registered to date on https://clinicaltrials.gov/. Enthusiasm for such trials follows the presentation at the October 2016 Annual Congress of the World Muscle Society given by Jerry Mendell for the results of the AAV-SMN1 treatment of spinal muscular atrophy (SMA) type 1.10AveXis. AveXis reports interim data from ongoing phase 1 clinical trial of AVXS-101 in spinal muscular atrophy type 1 as presented at the International Annual Congress of the World Muscle Society. http://investors.avexis.com/phoenix.zhtml?c=254285&p=irol-newsArticle&ID=2210279.Google Scholar The presentation reported a good safety profile and an improved clinical outcome, especially in those infants treated at the earliest ages. All of the above information points toward a likely rapid increase in the number of clinical trials using systemic delivery of AAV-mediated gene therapies, and the next few years could see a resurgence of interest and potentially promising results for gene therapy of neuromuscular disorders. Systemic AAV8-Mediated Gene Therapy Drives Whole-Body Correction of Myotubular Myopathy in DogsMack et al.Molecular TherapyFebruary 9, 2017In BriefMack and colleagues conducted a gene therapy dose-finding study in a dog model of X-linked myotubular myopathy (XLMTM), a severe monogenic muscle disease. A single systemic treatment prolonged lifespan and corrected skeletal musculature throughout the body in a dose-dependent manner. These data support development of gene therapy clinical trials for XLMTM. Full-Text PDF Open Archive