Avidity Biosciences Reports Second Quarter 2020 Financial Results and Recent Highlights Successful completion of $300 million initial public offering; cash and cash equivalents of over $350 million as of

Avidity Biosciences Reports Second Quarter 2020 Financial Results and Recent Highlights

Successful completion of $300 million initial public offering; cash and cash equivalents of over

$350 million as of June 30, 2020

Strengthened leadership team with additions of Michael MacLean as Chief Financial Officer and

Jae Kim, M.D., as Chief Medical Officer

SAN DIEGO, Aug. 10, 2020 /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 quarter and six months ended June 30, 2020 and highlighted

recent corporate progress.

The second quarter of 2020 was transformational for Avidity. With the substantial funds raised through our successful

IPO and key additions to our leadership team and board, we are well-positioned to advance a meaningful pipeline of novel AOC therapeutics, said Sarah Boyce, President and CEO of Avidity. We are focused on the execution of our research

and development plans that include selection of clinical candidates directed towards diseases with significant unmet medical needs, with the goal to initiate three

first-in-human studies by 2022.

Second Quarter 2020 and Recent

Corporate Highlights

About Avidity Biosciences

Avidity Biosciences, Inc. is pioneering a new class of oligonucleotide-based therapies called AOCs designed to overcome the current limitations of

oligonucleotide therapies in order to treat a wide range of serious diseases. Avidity utilizes its proprietary AOC platform to design, engineer and develop therapeutics that combine the tissue selectivity of monoclonal antibodies and the precision

of oligonucleotide therapies in order to access previously undruggable tissue and cell types and more effectively target underlying genetic drivers of diseases. Avidity s lead product candidate, AOC 1001, is designed to treat myotonic dystrophy

type 1, and its four other muscle programs are focused on the treatment of muscle atrophy, Duchenne muscular dystrophy, facioscapulohumeral muscular dystrophy and Pompe disease. In addition to its muscle franchise, Avidity has research efforts

focused on immune and other cell types.

Forward-Looking Statements

Avidity cautions readers that statements contained in this press release regarding matters that are not historical facts are forward-looking statements. These

statements are based on our current beliefs and expectations. Such forward-looking statements include, but are not limited to, statements regarding: the potential to develop a meaningful pipeline of novel AOC therapeutics; the selection of clinical

candidates; the initiation of first-in-human studies; the anticipated timing of filing an IND for the treatment of DM1; and the broad potential of AOCs to treat serious

diseases. The inclusion of forward-looking statements should not be regarded as a representation by Avidity that any of our plans will be achieved. Actual results may differ from those set forth in this press release due to the risks and

uncertainties inherent in our business, including, without limitation: we are early in our development efforts and all of our development programs are in the preclinical or discovery stage; our approach to the discovery and development of product

candidates based on our AOC platform is unproven, and we do not know whether we will be able to develop any products of commercial value; potential delays in the commencement, enrollment and completion of clinical trials; disruption to our

operations from the COVID-19 pandemic; the success of our preclinical studies and clinical trials for our product candidates; the results of preclinical studies and early clinical trials are not necessarily

predictive of future results; our dependence on third parties in connection with preclinical testing and product manufacturing; unexpected adverse side effects or inadequate efficacy of our product candidates that may limit their development,

regulatory approval and/or commercialization, or may result in recalls or product liability claims; regulatory developments in the United States and foreign countries, including acceptance of INDs and similar foreign regulatory filings and our

proposed design of future clinical trials; risks related to integration of new management personnel; and other risks described in our prior press releases and in our filings with the Securities and Exchange Commission (SEC). Avidity cautions readers

not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and we undertake no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All

forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

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Avidity Biosciences, Inc.

Selected Condensed Financial Information

(In thousands, except per share data)