Gene Delivery for Limb-Girdle Muscular Dystrophy Type 2D by Isolated Limb Infusion

Abstract

In a previous limb-girdle muscular dystrophy type 2D (LGMD2D) clinical trial, robust alpha-sarcoglycan gene expression was confirmed following intramuscular gene (SGCA) transfer. This paved the way for first-in-human isolated limb infusion (ILI) gene transfer trial to the lower limbs. Delivery of scAAVrh74 .tMCK.hSGCA via an intravascular route through the femoral artery predicted improved ambulation. This method was initially chosen to avoid safety concerns required for large systemic vascular delivery viral loads. ILI methods were adopted from the extensive chemotherapy experience for treatment of malignancies confined to the extremities. Six LGMD2D subjects were enrolled in a dose-ascending openlabel clinical trial. Safety of the procedure was initially assessed in the single limb of a non-ambulant affected adult at a dose of 1 • 10 12 vg/kg. Subsequently, ambulatory children (aged 8-13 years) were enrolled and dosed bilaterally with either 1 • 10 12 vg/kg/limb or 3 • 10 12 vg/kg/limb. The six-minute walk test (6MWT) served as the primary clinical outcome; secondary outcomes included muscle strength (maximum voluntary isometric force testing) and SGCA expression at 6 months. All ambulatory participants except one had pre-and post-treatment muscle biopsies. All four subjects biopsied had confirmed SGCA gene delivery by immunofluorescence, Western blot analysis (14-25% of normal), and vector genome copies (5.4 • 10 3 -7.7 • 10 4 vg/lg). Muscle strength in the knee extensors (assessed by force generation in kilograms) showed improvement in two subjects that correlated with an increase in fiber diameter post gene delivery. Six-minute walk times decreased or remained the same. Vascular delivery of AAVrh74.tMCK.hSGCA was effective at producing SGCA protein at low doses that correlated with vector copies and local functional improvement restricted to targeted muscles. Future trials will focus on systemic administration to enable targeting of proximal muscles to maximize clinical benefit.

Molecular diagnosis of muscular diseases in outpatient clinics

“…Indeed, several studies are in clinical trials and have shown the potential of this method. [41][42][43][44][45][46] This shows the importance of having a diagnosis for these patients.…”

Clinical development on the frontier: gene therapy for duchenne muscular dystrophy

“…Because AAV vectors integrate into chromosome only at a very low rate, the potential for oncogenesis is minimized. Furthermore, the safety profile and tolerability of this AAVrh74 vector have also been shown in human studies [80]. The safety profile of AAVrh74 will continue to be evaluated across multiple gene transfer clinical development programs using this vector, including programs targeting various LGMD subtypes [80,81].…”

The ties that bind: functional clusters in limb-girdle muscular dystrophy

“…Though none has been approved by the FDA to date, it is becoming increasingly likely that such approvals will occur in the near future. Single gene replacement strategies have been investigated in animal models for some time, primarily using adeno-associated virus (AAV) vectors that contain DNA sequences for individual LGMD genes, such as CAPN3 [84,85], DYSF [86][87][88][89], FKRP [90][91][92][93], SGCA [94][95][96][97][98][99][100], SGCB [95,101,102], and SGCD [103][104][105], and SGCG [106,107]. Such efforts have accelerated and moved into human clinical trials for genes such as SGCG [108], inspired in part by an FDA-approved gene therapy for spinal muscular atrophy [109] and ongoing human studies of microdystrophin gene therapy for DMD [110].…”