SGT-001 is an experimental gene therapy being developed by Solid Biosciences to treat Duchenne muscular dystrophy (DMD), a common type of muscular dystrophy characterized by progressive muscle weakness and wasting.
How SGT-001 works
Duchenne is caused by mutations in the DMD gene, which provides instructions for making the dystrophin protein. Dystrophin is a structural protein that cushions muscle cells, preventing wear and tear during movement. Without dystrophin, or with very low levels of this protein, muscle contractions cause small tears in muscle tissue that cannot be repaired properly, and the muscles weaken.
SGT-001 is a gene therapy that uses a virus, modified to be harmless, to deliver an engineered version of the dystrophin gene (called microdystrophin) to muscle cells, so that they make a shorter yet functional protein. It is expected to slow or reverse disease progression for all types of DMD-causing mutations.
SGT-001 in clinical trials
A Phase 1/2 clinical trial called IGNITE-DMD (NCT03368742) is assessing the safety, tolerability, and efficacy of SGT-001 in 16 children and adolescents (ages 4 to 17) with DMD, both those able and unable to walk. The therapy is given in one of two dose levels — a low dose of 5E13 vector genomes (vg/kg) and a high dose of 2E14 vg/kg.
In this ascending dose study, participants are randomly assigned to an active treatment or an untreated control group. Patients under active treatment receive a single intravenous (into the bloodstream) infusion of SGT-001 and will be followed for approximately five years. Control group patients who continue to meet treatment criteria will receive SGT-001 after one year of study participation. The trial’s primary outcome measure is changes in the levels of microdystrophin present in muscle biopsies following treatment.
A total of nine participants have been given SGT-001 to date. Preliminary study results show a durable production of microdystrophin in samples collected one to two years after treatment with 2E14 vg/kg of the therapy.
These findings support previously reported improvements in functional abilities and patient-reported outcomes. More recent results found that treatment with SGT-001 also improved lung function one year after a single therapy infusion.
IGNITE DMD was twice put on clinical hold by the U.S. Food and Drug Administration. After the first clinical hold in March 2018 (lifted nearly three months later) due to a serious reaction in the first treated patient, a second hold was announced in November 2019 when the sixth boy treated (at high dose) experienced similar serious side effects. The boy showed low platelet and red blood cell levels, kidney damage, and activation of the complement system — a set of more than 30 blood proteins that form part of the body’s natural immune defenses. All these complications were fully resolved.
This second hold was lifted in October 2020, after Solid provided updated safety and effectiveness data, made modifications to the trial’s protocol, and took steps that improved the therapy’s manufacturing process.
SGT-001 received rare pediatric disease and fast track designations in the U.S., as well as orphan drug status in both the U.S. and the European Union as a potential DMD treatment. Orphan drug status is given to therapies aiming to treat patients with rare medical conditions or diseases. In the U.S., these benefits include a seven-year period of marketing exclusivity upon approval, tax credits for costs associated with clinical trials, and exemptions from certain fees.
Last updated: Feb. 18, 2022, by Teresa Carvalho MS
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