Avidity Biosciences’ antibody oligonucleotide conjugate has shown signs of efficacy in an early-stage test in patients with a rare muscle-wasting disease.
Just last month, Leerink analysts were cautious about the path forward for the treatment, dubbed del-brax, noting there are “gaps in knowledge” for facioscapulohumeral muscular dystrophy (FSHD). But with the preliminary data, Avidity is now expediting plans for registrational development.
Early data shows del-brax achieved more than 50% mean reductions in DUX4-regulated gene expression in the muscles of 12 FSHD patients. Signs of functional improvement were also observed, including improved strength in the upper and lower limb muscles, although the study is not statistically powered to assess functional benefit, according to Avidity.
Avidity’s share price $RNA jumped by as much as 26% to $36 at market open Wednesday.
The placebo-controlled Phase 1/2 FORTITUDE trial tested two doses of del-brax. The condition is caused by an abnormal expression of the DUX4 gene and leads to lifelong loss of muscle function, pain and significant disability.
According to Avidity, del-brax addresses the root cause of the disease by reducing the expression of DUX4 mRNA and DUX4 protein in muscles. Ahead of Wednesday’s data release, the Leerink analysts said there are still questions on whether DUX4-regulated gene expression can be reliably measured in clinical studies.
Del-brax, which was previously known as AOC 1020, had favorable safety results in preliminary data with no serious side effects or treatment discontinuations, Avidity said. It will present the Phase 1/2 results in detail at the annual FSHD Society International Research Congress meeting this week in Denver, CO.
“With the unprecedented del-brax data from the FORTITUDE trial, we are now focused on accelerating our registrational plans as we understand the urgency to develop a treatment for people living with FSHD who have no treatment options,” said CEO Sarah Boyce. In particular, the biotech plans to expedite the initiation of registrational cohorts in the Phase 1/2 trial.
Del-brax was designed using Avidity’s antibody oligonucleotide conjugate platform. The approach combines “the specificity of monoclonal antibodies with the precision of oligonucleotide therapies” to hit targets traditionally deemed “unreachable.”
Editor’s Note: This article was updated to include information about Avidity’s share price.