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AVIDITY BIOSCIENCES Exhibit 99.1 Avidity Biosciences Reports First Quarter 2021 Financial Results and Recent Highlights LA JOLLA , Calif . , May 12 , 2021 / PRNewswire / -- Avidity Biosciences , Inc. ( Nasdaq : RNA ) , a biopharmaceutical company pioneering a new class of oligonucleotide - based therapies called Antibody Oligonucleotide Conjugates ( AOCS ™ ) , today reported financial results for the first quarter ended March 31 , 2021 and highlighted recent corporate progress . " AOC 1001 , the first program from our AOC platform , is advancing toward the clinic and is on track to begin a Phase 1/2 study in adults with DM1 in the second half of this year . Our skeletal muscle pipeline is also progressing as planned while we continue to expand our discovery efforts to other indications , " said Sarah Boyce , president and chief executive officer . “ We are proud to be at the forefront of RNA innovation by delivering on the promise of our AOC platform and pipeline . " Mike MacLean , chief financial officer , added , " We are off to a great start this year with a strong financial position of over $ 300 million at the end of the first quarter . This allows us to progress AOC 1001 while continuing to invest in our other pipeline programs and our AOC platform , which we believe is a sustainable engine with the potential to have a broad impact across both rare and other serious diseases . " AOC Platform and Pipeline Highlights • Advanced Lead Program , AOC 1001 for DM1 , and Broad Pipeline for Untreated Rare Muscle Diseases . In April 2021 , Avidity presented preclinical data for AOC 1001 for myotonic dystrophy type 1 ( DM1 ) in an oral presentation as part of the Emerging Science Session at the American Academy of Neurology ( AAN ) 2021 Virtual Annual Meeting . Avidity scientists have demonstrated activity and potency of siRNAs against the dystrophy protein kinase ( DMPK ) gene in muscle cells derived from patients with DM1 . These data demonstrated activity in the nucleus and cytoplasm . The presentation also showed that single doses of AOC 1001 produced 75 % reductions in DMPK mRNA expression in preclinical studies that were maintained for months post - dosing . Following regulatory clearance , Avidity remains on track with plans to begin a Phase 1/2 clinical study of AOC 1001 in adults with DM1 in the second half of 2021 . Avidity also advanced additional programs in its muscle franchise including a program for facioscapulohumeral muscular dystrophy ( FSHD ) and three programs for Duchenne muscular dystrophy ( DMD ) . The AOC FSHD program and the lead AOC DMD program targeting Exon 44 are the most advanced . Avidity remains on track with plans to commence clinical trials for both programs in 2022 , following additional preparatory preclinical studies and regulatory clearance .