FDA grants breakthrough therapy designation to myotonic dystrophy type 1 drug

The FDA has granted breakthrough therapy designation to a proprietary oligonucleotide conjugate for the treatment of myotonic dystrophy type 1, according to the manufacturer.

“The FDA breakthrough therapy designation is a significant milestone for the community as it highlights the potential of del-desiran to be an effective treatment and the urgency needed to bring this treatment to patients who have no treatment options,” Steve Hughes, MD, chief medical officer at Avidity Biosciences, told Healio in an email. “We are focused on initiating our global phase 3 HARBOR study to rapidly advance del-desiran for people living with [myotonic dystrophy type 1].”

AOC 1001 (delpacibart etedesiran) was developed to address the root cause of myotonic dystrophy type 1 (DM1) by reducing levels of a disease-related mRNA called DMPK, according to a press release from Avidity Biosciences. The investigative therapeutic consists of a proprietary monoclonal antibody that binds to the transferrin receptor 1 along with a siRNA which specifically targets DMPK.

AOC 1001 is currently being investigated in the open-label extension portion of the phase 2 MARINA study, featuring 37 individuals out of the original 38 who completed the parent 6-month MARINA trial, in which AOC 1001 was administered intravenously at quarterly intervals over 24 months.

In the OLE, all those in the parent study initially given 2 mg/kg continued on the same dose, eventually escalating to 4 mg/kg, while those initially given 4 mg/kg remained on that dose.

In addition to breakthrough therapy designation, AOC 1001 had previously been granted orphan drug and fast track designations by the FDA, as well as orphan designation by the European Medicines Agency.

In the release, Avidity said it would initiate the phase 3 HARBOR study of AOC 1001 during the second quarter of 2024. The primary endpoint is expected to be video hand opening time, with key secondary endpoints including muscle strength as measured by hand grip strength and quantitative muscle testing total score, alongside activities of daily living as measured by the myotonic dystrophy type 1 activity and participation scale.