Avidity Biosciences, Inc. presented new data regarding its clinical study of AOC 1001 for adults with myotonic dystrophy type 1 (DM1) at the 28th Annual Congress of the World Muscle Society ("WMS"). New data presented at WMS demonstrate improvement in additional functional measures augmenting previously reported positive data which showed improvements in myotonia, muscle strength and mobility. These new data include: Multiple additional measures of strength: Hand grip.

Manual Muscle Testing (MMT) composite score. Both upper and lower Quantitative Muscle Testing total score composites. DM1-Activ, a patient reported outcome (PRO) that measures activities of daily living (e.g., taking a shower, visiting family or friends, and walking up stairs).

New data presented at WMS also addressed favorable long-term safety and tolerability of AOC 1001 from the MARINA-OLE? study, with over 200 infusions totaling 46.2 patient-years of exposure. The most common adverse events (AEs) in the MARINA-OLE study were procedural pain (22%), pain in extremity (such as arm, leg or foot pain/soreness) (16%) and headache (16%).

There was one resolved AE of mild increase in liver enzymes. There have been no reported AEs of anemia in the MARINA-OLE study. In the Phase 1/2 MARINA ® clinical program, anemia has been asymptomatic except for one participant who did not require treatment.

There have been no discontinuations in the MARINA-OLE study. The Company has completed the dose-escalation of 12 participants from 2 mg/kg to 4 mg/kg of AOC 1001 in the MARINA-OLE study, as permitted by the U.S. Food and Drug Administration ("FDA") in connection with the FDA's easing of the partial clinical hold on AOC 1001 in May 2023. Data from this dose escalation showed no neurological events and no MRI changes following dosing.

The Company continues to work with the FDA regarding a resolution to the partial clinical hold. The Company remains on track to share a first look at efficacy data of AOC 1001 from the MARINA-OLE study during the first half of 2024.