Short-term treatment of golden retriever muscular dystrophy (GRMD) dogs with rAAVrh74.MHCK7.GALGT2 induces muscle glycosylation and utrophin expression but has no significant effect on muscle strength

Abstract

We have examined the effects of intravenous (IV) delivery of rAAVrh74.MHCK7.GALGT2 in the golden retriever muscular dystrophy (GRMD) model of Duchenne Muscular Dystrophy (DMD). After baseline testing, GRMD dogs were treated at 3 months of age and reassessed at 6 months. This 3–6 month age range is a period of rapid disease progression, thus offering a relatively short window to establish treatment efficacy. Measures analyzed included muscle AAV transduction, GALGT2 transgene expression, GALGT2-induced glycosylation, muscle pathology, and muscle function. A total of five dogs were treated, 4 at 2x1014vg/kg and one at 6x1014vgkg. The 2x1014vg/kg dose led to transduction of regions of the heart with 1–3 vector genomes (vg) per nucleus, while most skeletal muscles were transduced with 0.25–0.5vg/nucleus. GALGT2-induced glycosylation paralleled levels of myofiber vg transduction, with about 90% of cardiomyocytes having increased glycosylation versus 20–35% of all myofibers across the skeletal muscles tested. Conclusions from phenotypic testing were limited by the small number of dogs. Treated dogs had less pronounced fibrosis and overall lesion severity when compared to control groups, but surprisingly no significant changes in limb muscle function measures. GALGT2-treated skeletal muscle and heart had elevated levels of utrophin protein expression and GALGT2-induced expression of glycosylated α dystroglycan, providing further evidence of a treatment effect. Serum chemistry, hematology, and cardiac function measures were largely unchanged by treatment. Cumulatively, these data show that short-term intravenous treatment of GRMD dogs with rAAVrh74.MHCK7.GALGT2 at high doses can induce muscle glycosylation and utrophin expression and may be safe over a short 3-month interval, but that such treatments had only modest effects on muscle pathology and did not significantly improve muscle strength.

Precision medicine using whole genome sequencing identifies a novel dystrophin (DMD) variant for X‐linked muscular dystrophy in a cat

“…Recently, delandistrogene moxeparvovec, which is an adeno‐associated virus (AAV) vector‐based gene therapy designed to deliver a gene encoding a micro‐dystrophin protein, has been approved in the United States for the treatment of ambulatory DMD pediatric patients and a defined variant in DMD . 54 The ongoing preclinical trials in canine models are supporting the treatment developments and options 55 , 56 , 57 and substantial advances have been made in a variety of treatments. 58 , 59 , 60 , 61 , 62 , 63 , 64 Defining the feline DMD variants supports the use of cats as a biomedical model in preclinical trials, like that of canine models.…”

Pre Clinical Assessment of AAVrh74.MCK.GNE Viral Vector Therapeutic Potential: Robust Activity Despite Lack of Consistent Animal Model for GNE Myopathy

“…Here we expanded this approach to deliver the same GNE cDNA driven by a striated muscle specific promoter -the MCK promoter-that was packaged into the capsid of the AAVrh.74 serotype. This serotype transduces muscle very efficiently when delivered via the vascular system (IV injection) and has been used in various preclinical studies [25][26][27][28][29][30] and even clinical trials in patients with DMD [31] and with limb-girdle muscular dystrophy types2E/R4, 2D/R3, and 2B/R2 (NCT02376816, NCT03769116, NCT03652259, NCT01976091, NCT02710500). This serotype has also the advantage to have a relatively low prevalence in the general population, thus allowing its potential delivery to more patients [32].…”

The Sda Carbohydrate Antigen and Its Biosynthetic Enzyme B4GALNT2 in Health and Disease.

“…The mechanisms underlying this phenomenon are very complex and only partially elucidated [74][75][76]. B4galnt2 gene delivery through a viral vector in a dog model of DMD has revealed to be safe and able to induce B4galnt2 expression, although with little or no improvement of the pathology [77]. The administration of the viral vector in two DMD-affected boys resulted in functional improvements only in the younger patient treated with a higher dose of B4GALNT2 vector [78].…”