Avidity says partial hold on lead muscle wasting disorder asset has been 'eased' but not lifted

The FDA has “eased” but not lifted a partial clinical hold on Avidity Biosciences' lead program for an inherited muscle wasting disorder seven months after it was placed, a spokesperson confirmed to Fierce Biotech. 

The company is now able to double the number of participants with myotonic dystrophy type 1 (DM1) in a phase 2 open-label extension study called Marina who received the 4 mg/kg dose of treatment, according to a Wednesday press release. The FDA is also allowing recruitment to continue for the 2 mg/kg dose. But a spokesperson clarified that the partial hold has yet to fully be lifted. 

The partial hold was placed on the phase 1/2, double-blind, randomized study in September 2022 after a serious adverse event was reported in one patient treated with AOC 1001. That has not deterred Avidity from reading out the placebo-controlled study. The company reported in April that there were “directional improvements in multiple functional assessments.” It’s unclear whether the treatment posted a statistically significant difference in function compared to patients given the placebo. 

The therapy fuses a short interfering RNA with a monoclonal antibody to target the transferrin receptor 1 to treat patients with DM1. Like others in the dystrophy family, DM1 is an inherited disorder that leads to progressive muscle weakness and difficulty relaxing muscles. 

Avidity is maintaining earlier guidance that a first glimpse of the open-label data should be ready before the end of the year. That data will be used to finalize the pivotal dose and phase 3 study design for adult patients with DM1. Thirty-six out of 38 patients enrolled in the phase 1/2 trial moved on to the open-label extension. 

The company has plenty of cash to advance the Marina program and additional clinical programs, with $586.3 million in cash on hand as of the end of March, enough to last into the middle of 2025. Avidity’s treatment for Duchenne muscular dystrophy with exon 44 skipping—AOC 1044—should have data from a healthy volunteer study in the second half of the year. And an interim readout of AOC 1020 for patients with facioscapulohumeral muscular dystrophy, is slated for the first half of 2024. 

Editor's note: This story was updated to include a response from an Avidity spokesperson.