AAV9- microdystrophin (Solid Biosciences- SGT-001 ) For Duchenne Muscular Dystrophy Treatment: Update on Clinical Studies

 AAV9- microdystrophin (Solid Biosciences- SGT-001 )

Clinical Stage and Regulatory Timeline

SGT-001 is an investigational gene transfer therapy intended to deliver its micro-dystrophin-encoding gene to muscle tissue for the targeted production of the micro-dystrophin protein.(AAV9.CK.micro-dystrophin). Solid Biosciences is conducting phase 1/2 clinical study (IGNITE) to determine safety of SG-001 dose at 2e14 vg/kg dose.

Viral Vector and Gene Construct

AAV9.CK.micro-dystrophin gene construct consists of muscle specific CK promoter and drives the expression of the minidystrophin gene in the muscle tissue. AAV9 have shown to have high tropism for skeletal and cardiac muscle. 

Clinical Phase

Solid Biosciences is currently conducting a Phase 2 (NCT03368742) nonrandomized clinical study to evaluate safety of the exogenous gene transfer in DMD subjects. The immunofluorescence staining of the muscle biospy showed the successful transfer and expression of microdystrophin in first three patients. The study was on clinical hold from July 2020 to October 2020 as a result of serious adverse event. 

Clinical Trial hold and Resolution:

FDA enforced the clinical hold of IGNITE Study from July 2020 to October 2020 as a result of serious adverse event (SAE).

Resolution: 

Improvement of manufacturing process to lower the empty viral capsid allowing target dosing (2e13 vg/kg) to be achieved with fewer viral particles. This reduction in the total amount of virus delivered to each patient is intended to support safe dosing of SGT-001 for the duration of the IGNITE DMD trial. 

IGNITE DMD clinical protocol to include the prophylactic use of both anti-complement inhibitor eculizumab and C1 esterase inhibitor, and increasing the prednisone dose in the first month post dosing.

Number of Participants in Phase 3 Study- 16

Outcome Measures

Primary Outcome Measures

• Change from baseline in microdystrophin protein in muscle biopsies (active treatment group)
• Incidence of adverse events
• Incidence of clinical laboratory abnormalities

 Key Results from Phase 1/2

A single dose of up to 2e14 vg/kg AAV9.CK.microdystrophin was infused through a peripheral limb vein. 

Efficacy 

In the high does treatment cohort (n=3, 2e14vg/kg) showed increase in distribution of Dystrophin in muscle biopsy were observed by immunofluorescence staining. 

SGT-001 administration results in dose-dependent, muscle wide microdystrophin expression in muscle biopsies collected 90 days post-SGT-001 administration. SGT-001-driven microdystrophin expression resulted in stabilization of dystrophin associated proteins. SGT-001-driven microdystrophin expression resulted in restored enzymatically active neuronal nitric oxide synthase (nNOS) at the sarcolemma.

Durability:

Not available yet

Safety:

Serious Adverse Events:

Serious Adverse Event (SAE) is likely to occur in some subjects dosed with SGT-001. The event was characterized by a decrease in platelet count followed by a reduction in red blood cell count, transient renal impairment, and evidence of complement activation. 

No signs of bleeding or clotting abnormalities 

No laboratory evidence of liver dysfunction. 

The patient received standard medical care, a modified steroid regimen and a limited course of eculizumab for the observed complement activation. 

The SAE has been fully resolved. 

Immunogenicity

Antibody Response: Not Reported

T cell Response (ELISpot): Not Reported

Reference

Solid Biosciences Press Release

Clinicaltrail.gov