Avidity Biosciences, Inc. announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to AOC 1020 for the treatment of facioscapulohumeral muscular dystrophy (FSHD). FSHD is a serious, rare, hereditary muscle-weakening condition marked by life-long, progressive loss of muscle function that causes significant pain, fatigue, and disability. AOC 1020 is being studied in the Phase 1/2 FORTITUDE(TM) clinical trial in adults with FSHD and is the company's second muscle-targeting small interfering RNA (siRNA) AOC in clinical development. Avidity plans to share data from a preliminary assessment of AOC 1020 in approximately half of study participants from the FORTITUDE trial in the first half of 2024. Fast Track designation enables more frequent interactions with the FDA to expedite the development and review process for drugs intended to treat serious or life-threatening conditions and that demonstrate the potential to address unmet medical needs. Currently, there are no FDA-approved treatments for people living with FSHD. Avidity's proprietary AOCs are designed to combine the specificity of monoclonal antibodies (mAbs) with the precision of oligonucleotide therapies to target the root cause of diseases previously untreatable with RNA therapeutics. AOC 1020 consists of a proprietary mAb that binds to the transferrin receptor 1 (TfR1) conjugated with a siRNA targeting double homeobox 4 (DUX4) mRNA. The abnormal expression of DUX4 protein leads to changes in gene expression in muscle cells that are associated with the life-long, progressive loss of muscle function in patients with FSHD. Avidity has three distinct rare disease programs in the clinic. In addition to AOC 1020, the company is also evaluating AOC 1001 in the Phase 1/2 MARINA(TM) and MARINA open-label extension (MARINA-OLE(TM)) clinical trials for the treatment of myotonic dystrophy type 1 (DM1) and AOC 1044 in the Phase 1/2 EXPLORE44(TM) trial for the treatment of Duchenne muscular dystrophy (DMD) mutations amenable to exon 44 skipping (DMD44). The FORTITUDE(TM) Phase 1/2 Trial of AOC 1020 in Adults with FSHD The FORTITUDE(TM) trial is a randomized, placebo-controlled, double-blind, Phase 1/2 clinical trial designed to evaluate AOC 1020 in approximately 70 adult participants with FSHD. FORTITUDE will evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of AOC 1020 administered intravenously, with the primary objective being the
safety and tolerability of AOC 1020 in FSHD patients. Activity of AOC 1020 will be assessed using key biomarkers, including magnetic resonance imaging (MRI) measures of muscle volume and composition. Though the Phase 1/2 trial is not statistically powered to assess functional benefit, it will explore the clinical activity of AOC 1020 including measures of mobility and muscle strength as well as patient reported outcomes and quality of life measures. Participants will have the option to enroll in an open-label extension study at the end of the treatment period in the FORTITUDE study.