Forward Looking Statements We caution the reader that this presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements other than statements of historical facts conta

Virtual Investor & Analyst Event

Series - Volume 1 Engineering AOC's Exhibit 99.1

Forward Looking Statements We caution

the reader that this presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements other than statements of historical facts contained in this presentation, including statements regarding our

future results of operations and financial position, business strategy, the anticipated timing, costs, design and conduct of our ongoing and planned preclinical studies and planned clinical trials, research and development plans, timing and

likelihood of success, prospective products, product approvals, plans and objectives of management for future operations, and future results of anticipated product development efforts, are forward-looking statements. In some cases, the reader can

identify forward-looking statements by terms such as "may," "will," "should," "expect," "plan," "anticipate," "could," "intend," "target,"

"project," "contemplates," "believes," "estimates," "predicts," "potential" or "continue" or the negative of these terms or other similar expressions. 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 presentation 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; 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; potential delays in the commencement, enrollment and completion of clinical trials; our dependence on third parties in connection with preclinical testing and product manufacturing;

disruption to our operations from the COVID-19 pandemic; 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; our ability to obtain and maintain

intellectual property protection for our product candidates and proprietary technologies; we may use our capital resources sooner than we expect; and other risks described in our filings with the SEC, including under the heading "Risk

Factors" in our Form 10K for the year ending on December 31, 2020, filed with the SEC on March 15, 2021, and any subsequent filings with the SEC. The reader is cautioned not to place undue reliance on these forward-looking statements, which

speak only as of the date hereof, and except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances

or otherwise. 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. This presentation also contains

estimates and other statistical data made by independent parties and by us relating to market size and growth and other data about our industry. This data involves a number of assumptions and limitations, and the reader is cautioned not to give

undue weight to such estimates. In addition, projections, assumptions, and estimates of our future performance and the future performance of the markets in which we operate are necessarily subject to a high degree of uncertainty and risk. These and

other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

Our Vision To profoundly improve

people's lives by revolutionizing the delivery of RNA therapeutics Luke Living with DM1

Delivering on Our Vision Progressing

robust pipeline in muscle Entering the clinic with AOC 1001 in 2H 2021 Planning clinical initiations for both AOC 1044 in DMD and our AOC FSHD program in 2022 Leveraging expertise in clinical and commercial execution Assembling an experienced team

in rare & RNA therapies Building an integrated and diverse company in service of our patients DISRUPTIVE & BROAD PLATFORM ADVANCING & EXPANDING PIPELINE AGILE & DIVERSE COMPANY Delivering a New Class of RNA Therapies Demonstrating

preclinical proof of concept in multiple tissues Broadening to other tissues & cell types through partnerships & internal discovery

PROGRAM / INDICATION TARGET DISCOVERY /

LEAD OPTIMIZATION IND ENABLING CLINICAL MUSCLE DISORDERS AOC 1001: Myotonic Dystrophy Type 1 (DM1) DMPK AOC FSHD: Facioscapulohumeral Muscular Dystrophy (FSHD) DUX4 AOC 1044: Duchenne Muscular Dystrophy (DMD) Exon 44 Dystrophin Next AOC DMD Programs

Exon 51 Dystrophin Exon 45 Dystrophin AOC Muscle Atrophy: Muscle Atrophy* MuRF1 AOC Pompe Disease: Pompe Disease GYS1 Advancing our Muscle Disease Franchise of AOCs * Opportunity for a rare disease indication Planned Phase 1/2 Trial in H2 2021

Clinical trial initiations planned for 2022 Clinical trial initiations planned for 2022

Goals for the Day Provide a deep dive

into the years of engineering supporting our AOCTM platform Demonstrate how we are delivering on the power of the platform through our pipeline Offer a broader perspective on the history and future of RNA therapeutics Take your questions mAb

What's New: Deep Dive on the AOC

Platform: Demonstrating data-driven choices in engineering each component of our AOCs Showing the previously unseen data used to choose a mAb AOC 1001 safety profile supports entry into the clinic: Sharing additional Non-GLP data Presenting outcomes

and data from our GLP Tox Studies Pipeline Progress: Announcing AOC 1044 - our lead DMD program targeting Exon 44 - entering IND enabling studies Remaining on track for both AOC 1044 and our AOC FSHD program to enter clinical studies in

2022 Delivering on Progress Highlights from Today

Agenda Welcome & Introduction

Engineering the Future of RNA Therapeutics Translating RNA Research Into Medicines Q&A Session Closing Remarks Sarah Boyce, President & CEO Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO (Moderator) Steven F. Dowdy, Ph.D., UCSD Phillip D.

Zamore, Ph.D., UMASS Art Levin, Ph.D., CSO Management and Drs. Dowdy and Zamore Sarah Boyce, President & CEO

Avidity Management Team Participants

Art Levin, Ph.D. Chief Scientific Officer Art Levin is an expert in the RNA therapeutics field who led teams responsible for the development of many oligonucleotides. He serves as the Chief Scientific Officer at Avidity Biosciences. Previously, he

held the position of Executive Vice President of Research and Development at miRagen Therapeutics. Prior to that, he held senior drug development roles at Ionis Pharmaceuticals and Santaris Pharma. He is on the scientific advisory boards of multiple

institutions. Dr. Levin received a doctorate in toxicology from the University of Rochester, and a bachelor's degree in biology from Muhlenberg College. Mike Flanagan, Ph.D. Chief Technical Officer (Panel Moderator) Mike Flanagan has extensive

experience developing multiple therapeutic modalities, including RNA therapeutics, antibody drug conjugates, and bispecific antibodies. Prior to joining Avidity, Dr. Flanagan was at Genentech, Inc., where he advanced programs through late-stage

research to end of Phase 2 development. Prior to Genentech, he was at Sunesis Pharmaceuticals, Inc., Gilead Sciences, Inc., and Merck & Co., Inc. Dr. Flanagan received a B.S. in Genetics from the UC at Davis, a Ph.D. in Biological Sciences from

the UC at Irvine and was an American Cancer Society postdoctoral fellow at the Howard Hughes Medical Institute, Stanford University.

Agenda Welcome & Introduction

Engineering the Future of RNA Therapeutics Translating RNA Research Into Medicines Q&A Session Closing Remarks Sarah Boyce, President & CEO Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO (Moderator) Steven F. Dowdy, Ph.D., UCSD Phillip D.

Zamore, Ph.D., UMASS Art Levin, Ph.D., CSO Management and Drs. Dowdy and Zamore Sarah Boyce, President & CEO

Engineering the Future of RNA

Therapeutics Art Levin, Ph.D., CSO

PIPELINE Established delivery

mechanism and built a pipeline of AOCs AVIDITY FOUNDING Founded to solve delivery challenge of oligonucleotides We Followed the Data to AOCs TRANSFERRIN Solidified as first transporter ANTIBODY-OLIGO CONJUGATES Demonstrated more efficient, targeted

delivery Antibody-targeted Nanoparticles Ruled out due to high complexity with less efficient delivery AND BEYOND Expanded into more cell and tissue types

Engineering AOCs: Following the Data

AOCs: Engineering the delivery of RNA therapies AOC 1001: First clinical proof-of-concept program beginning in 2H 2021 Delivering Next: AOCs in rare muscle diseases and beyond mAb OLIGO

AOCs - A Powerful New Class of Drugs

We employ mAbs to cell surface receptors for targeted delivery of oligonucleotides to a range of cell types and tissues Our AOCs combine the proven and safe technologies of monoclonal antibodies and oligonucleotides Specificity of targeting with

mAbs Potency & precision of oligonucleotides Targets tissues with potent and durable agents We optimized each of component of AOCs and engineered the molecules to maximize activity, durability, and safety Utilizing decades of proven science to

deliver the power of oligonucleotides

Following the Data: Choosing a mAb

to Expand Delivery Beyond the Liver mAbs Offer Safe and Effective Targeting to Many Cells and Tissues Plasma PK in a Non-Human Primate To deliver oligonucleotide therapeutics, we followed the data to select the delivery moiety Experiments showed

that mAbs are superior Monoclonal antibodies (mAbs) are a proven technology that have been in use for 30 years Chronic therapies with well-established safety profile High specificity and affinity Long half-life We optimized our mAbs through

engineering to ensure: Specific epitope binding to not compete with transferrin Antibody is effector function null Placement of the oligo itself on the antibody Fab siRNA (6mg/kg) mAb siRNA (6mg/kg)

Following the data: Engineering the

Linker Our Linkers are Optimized for Stability and Durability In addition to engineering our linker, we optimize several other key aspects including: sites of conjugation the ratio of oligonucleotides to antibodies AOCs with Different Linkers at 0.5

Following the data: Choosing the

Oligonucleotide siRNA was a deliberate choice based on safety, potency and efficacy Selected siRNAs for activity and specificity and engineered them to withstand lysosomal enzymes siRNAs are well characterized Attractive safety profile with no

known thrombocytopenia, liver or renal toxicity Potency in the nanomolar or picomolar range Sustained activity in both the cytoplasm and the nucleus Readily reproducible with many experienced manufacturers Leveraging this approach across the

pipeline in different tissue and cell types Target mRNA Expression in Gastrocnemius* Modification 1 Modification 2 Modification 3 *Target is myostatin, or MSTN in mouse

Following the Data: Utilizing

Multiple Non-Human Primate Studies to Inform our Clinical Studies Studies Key Hypothesis Tested NHP Study 1 & 2 Delivery moiety - Fab vs mAb NHP Study 3 Selection of lead mAb NHP Study 4 & 5 Selection of lead DMPK siRNA NHP Study 6

Non-GLP tox study of AOC 1001 at single and repeat doses, duration of action, intensive PK NHP GLP 1 GLP tox study of AOC 1001

AOC COMPONENTS DATA-DRIVEN COMPONENT

CHARACTERISTICS OUR ENGINEERING IMPACT Monoclonal antibody Well-established safety profile High specificity and affinity Long half-life Optimized through engineering to be effector function null Epitope selection for optimal activity Linker Known

linker Applicable to multiple oligo modalities Enhanced for safety and durability Engineered sites of conjugation Optimized ratio of oligonucleotides to antibodies siRNA Attractive safety profile - no known thrombocytopenia, liver or renal toxicity

Potency in the nanomolar range Sustained activity in the cytoplasm and nucleus Engineered to withstand lysosomal enzymes Selected and modified to diminish off-target effects Following the Data: Each Component was Engineered to Deliver the Optimal

Engineering AOCs: Following the Data

AOCs: Engineering the delivery of RNA therapies AOC 1001: First clinical proof-of-concept program beginning in 2H 2021 Next AOCs: Rare muscle diseases and beyond mAb OLIGO

DM1, Caused by a Toxic

Gain-of-Function mRNA, is Well Suited to an siRNA Approach (CUG) n DMPK DMPK mRNA DM1 Disease Manifestations Misprocessed RNAs Protein Errors CUG MBNL MBNL MBNL Mutant DMPK mRNA Toxic Gain-of-Function MECHANISM OF DISEASE: DM1 is Caused by a Toxic

Gain-of-Function of the Mutant DMPK mRNA Trinucleotide expansion in DMPK mRNA sequesters muscleblind-like (MBNL), an RNA splicing protein Depleted MBNL leads to RNA splicing errors in multiple muscle-related RNAs Therapeutic Approach: Reduce DMPK

mRNA to minimize RNA splicing errors, improve muscle function, and reverse the course of the disease

The AOC 1001 siRNA is Active in the

Nucleus and Cytoplasm DMPK expression % of mock treatment Cytoplasmic fraction Nuclear fraction Whole cell extract Control siDMPK.19 Nuclear and Cytoplasmic DMPK mRNA Levels in DM1 Patient-Derived Muscle Cells; Data: N=2 mean with range DM1 Patient

DMPK-Targeted siRNA Reduces Nuclear

Foci in DM1 Patient-Derived Muscle Cells Reduction of Nuclear Foci Containing Mutant DMPK mRNA DMPK RNA Foci MBNL1 DM1 Patient Cells

The AOC 1001 siRNA (siDMPK.19)

Produced a 56% Improvement in Splicing in DM1 Myotubes Treatment Signature (100 Splicing Events)

% DMPK mRNA Expression in Cynomolgus

Monkey Time (weeks) Quadriceps Gastrocnemius Durable ~75% Reduction of DMPK mRNA in Monkey Skeletal Muscles After a Single Dose of 2mg/kg of siDMPK.19

Robust and Durable Reductions of

DMPK Levels in Cardiac Muscle and Diaphragm After a Single Dose DMPK mRNA Expression in Cynomolgus Monkey (% PBS Control) siRNA Dose (mg/kg) Heart Diaphragm Weeks DMPK mRNA Expression in Cynomolgus Monkey (% PBS Control) Dose Response at Week 6 2

The AOC 1001 siRNA Reduces DMPK mRNA

in a Wide Range Skeletal Muscle at Nanomolar Concentrations DMPK Expression in Skeletal Muscle and GI After a Single i.v. Dose in Monkey

Plasma Profiles Demonstrate No

Neutralizing Antibodies to AOC 1001 in NHP Study 6 Study Termination 15 mg/kg 5 mg/kg 1.5 mg/kg Plasma half-life at 5 mg/kg ~ 24hrs No change in peak levels or slopes with repeated dosing, indicating an absence of neutralizing antibodies No

accumulation with repeated dosing (Q3W)

AOC 1001 Reduces Muscle DMPK mRNA in