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 3 Delivering on AOCs: FSHD 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 many 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 submissions 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 10-K 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 Phase 1/2 MARINATM trial of AOC 1001 ongoing Anticipated clinical trial initiations for both AOC 1044 for DMD and AOC 1020 for FSHD by the end of 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 Committed to delivering a

new class of RNA therapies Dosed first person with an AOC - a first for the platform Broadening to other tissues & cell types through partnerships & internal discovery

PROGRAM / INDICATION TARGET

DISCOVERY / LEAD OPTIMIZATION IND ENABLING PHASE 1/2 MUSCLE DISORDERS AOC 1001: Myotonic Dystrophy Type 1 (DM1) DMPK AOC 1020: 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

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

Goals for the Day Demonstrate how our

AOC platform expertise is leveraged across the pipeline Review the preclinical package supporting AOC 1020 Offer a broader perspective on the current treatment landscape for FSHD Answer your questions mAb OLIGO

What's New: AOC 1001 Phase 1/2

MARINA trial ongoing: First participants dosed; marked the first time a person was dosed with an AOC Anticipate preliminary assessment of the MARINA trial in Q4 of 2022 Pipeline Progress Announcing AOC 1020 - our candidate for FSHD entering

IND enabling studies Anticipate clinical trial initiations by the end of 2022 for both AOC 1020 and AOC 1044, our lead DMD program targeting Exon 44 Delivering on Progress Highlights from Today

Agenda Sarah Boyce, President & CEO

Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO Jeffrey M. Statland, M.D., Professor of Neurology University of Kansas Medical Center Sarah Boyce, President and CEO Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO Jeffrey

M. Statland, M.D., Professor of Neurology Mike MacLean, CFO (Moderator) Sarah Boyce, President & CEO Welcome & Introduction Building on our AOC Expertise Facioscapulohumeral Muscular Dystrophy (FSHD) Program FSHD: Disease

Overview and Endpoints Q&A Session Closing Remarks

Building on our AOC Expertise Art

Levin, Ph.D., Chief Scientific Officer

FSHD AOC 1020 Monoclonal antibody

linked to an siRNA to DUX4 mAb siRNA

AOC COMPONENTS DATA-DRIVEN COMPONENT

CHARACTERISTICS OUR ENGINEERING IMPACT Monoclonal antibody Approved mAbs offer: Well-established safety profiles High specificity and affinity Long half-lives Designed through engineering to be effector function null Epitope selection designed for

optimal activity Linker Known linker Applicable to multiple oligo modalities Enhanced for durability Engineered sites of conjugation Optimized ratio of oligonucleotides to antibodies siRNA Approved siRNA drugs have shown: Attractive safety profiles

- 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 siRNA selected to

maximize reduction of target mRNA in vitro and in vivo We Follow the Data for Each Component to Engineer the Optimal AOCs for our Programs

Durable ~75% Reduction of DMPK mRNA

Observed in Monkey Skeletal Muscles After a Single Dose of 2mg/kg of siDMPK.19

The AOC 1001 siRNA Reduced DMPK mRNA

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

AOC 1001 Reduced Muscle DMPK mRNA in

Concentration Responsive Manner in Non-human Primates Necropsy was at 7 weeks, following 3 doses at 0, 3, and 6 weeks NHP Study 6 Gastrocnemius biopsies collected 21 or 28 days after single doses ranging from 0.6 to 15 mg/kg siRNA EC50 <0.1 nM

Day 21 or 28 Post Dosing

Engineering AOCs: Following the Data

to Deliver RNA AOCs are designed to deliver RNA therapeutics with specificity, potency and precision AOCs are the result of years of in-house engineering AOCs are designed to exploit the well characterized safety and efficacy profiles of approved

mAb and siRNA drugs Potential for consistent delivery to muscle Focused today on rare disease with potential for much broader application mAb OLIGO

Agenda Sarah Boyce, President &

CEO Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO Jeffrey M. Statland, M.D., Professor of Neurology University of Kansas Medical Center Sarah Boyce, President and CEO Art Levin, Ph.D., CSO Mike Flanagan, Ph.D., CTO Jeffrey

M. Statland, M.D., Professor of Neurology Mike MacLean, CFO (Moderator) Sarah Boyce, President & CEO Welcome & Introduction Building on our AOC Expertise Facioscapulohumeral Muscular Dystrophy (FSHD) Program FSHD: Disease

Overview and Endpoints Q&A Session Closing Remarks

Facioscapulohumeral Muscular

Dystrophy (FSHD) Program W. Michael Flanagan, Ph.D., Chief Technical Officer

Amy, Living with FSHD "Living

with FSHD feels like an imprisonment in your own body."

Delivering on AOCs: FSHD AOCs:

Direct targeting of DUX4, the underlying cause of FSHD AOC 1020: Designed to be a potent DUX4 inhibitor moving into IND-enabling studies mAb OLIGO

0 APPROVED THERAPIES FSHD is Often

Diagnosed in Young Adults with Few Treatment Options There are no approved therapeutics for Facioscapulohumeral Muscular Dystrophy AFFECTS ~16,000 - 38,000 PEOPLE IN THE US One of the most common forms of muscular dystrophy Autosomal dominant

disease caused by abnormal expression of double homeobox 4 (DUX4) Characterized by progressive, asymmetric skeletal muscle loss with onset often in teenage and adult years About 20% of patients will end up using a wheelchair

FSHD is Caused by Aberrant

Expression of DUX4 DUX4 activates genes that are toxic to muscle cells MECHANISM OF DISEASE THERAPEUTIC APPROACH Apoptotic, immune signaling, altered myogenesis inhibited X X Genetic Signature Shutdown by AOC 1020 X X AOC 1020 DUX4 X Genetic

Signature Activated by DUX4 Apoptotic, immune signaling, altered myogenesis activated DUX4

Small Reductions in DUX4 Expression

may have Large Clinical Benefit Avidity's AOC Targets DUX4 mRNA and is Designed to Eliminate the Cause of FSHD THERAPEUTIC HYPOTHESIS Asymptomatic FSHD MODERATE DUX4 HIGH DUX4 LOW DUX4 Slow/stop disease progression Jones, T.I., et al.,

Facioscapulohumeral muscular dystrophy family studies of DUX4 expression: evidence for disease modifiers and a quantitative model of pathogenesis. Human Mol Genet 21:4419 (2012) Ricci,G., et al., Large genotype-phenotype study in carriers of D4Z4

borderline alleles provides guidance for facioscapulohumeral muscular dystrophy diagnosis. Scientific Reports 10:21648 (2020) Wong C.J. et al., Longitudinal measures of RNA expression and disease activity in FSHD muscle biopsies. Hum Mol Genet

Delivering on AOCs: FSHD AOCs:

Direct targeting of DUX4, the underlying cause of FSHD AOC 1020: Designed to be a potent DUX4 inhibitor moving into IND-enabling studies mAb OLIGO

Antibody directed to human

Transferrin receptor 1 Non-cleavable linker designed to facilitate siRNA delivery to muscle Stabilized siRNA targeting DUX4 mRNA AOC 1020: FSHD Development Candidate is Designed to be a Potent and Specific Inhibitor of DUX4 Expression AOC 1020 Meets

our Target Candidate Profile AOC 1020 COMPLETED Transferrin mAb Screen DUX4 siRNAs in FSHD donor cells using gene signature Target Candidate Profile met Off-target analysis by RNA seq Select potent siRNAs with minimal off-target profile Evaluate in

FSHD mouse model & GLP studies

AOC 1020 siRNA Showed Potent

Inhibition of DUX4-mediated Gene Signature in FSHD-patient Derived Myoblasts IC50 = 0.127 nM FSHD Donor MB05 DUX4 gene signature (% mock) THERAPEUTIC APPROACH Apoptotic, immune signaling, altered myogenesis inhibited X X Genetic Signature Shutdown

by AOC 1020 X X AOC 1020 DUX4 X

Antibody directed to human

Transferrin receptor 1 Non-cleavable linker designed to facilitate siRNA delivery to muscle Stabilized siRNA targeting DUX4 mRNA AOC 1020: FSHD Development Candidate is Designed to be a Potent and Specific Inhibitor of DUX4 Expression AOC 1020 Meets

our Target Candidate Profile AOC 1020 COMPLETED Transferrin mAb Screen DUX4 siRNAs in FSHD donor cells using gene signature Target Candidate Profile met Off-target analysis by RNA seq Select siRNAs with minimal off-target profile Evaluate in FSHD

mouse model & GLP studies

Transgenic DUX4 Mouse Model*

Recapitulates Key Features of FSHD in Humans FSHD-like Mouse Model FSHD Aberrant DUX4 Muscle expression Muscle weakness Moderate DUX4 expression Disease Progression Fast Slow DUX4 Gene signature (apoptosis, immune signaling,

aberrant myogenesis) *ACTA1-MCM x FLexDUX4 mice express human DUX4 exclusively in skeletal muscle Jones et al. Transgenic mice expressing tunable levels of Dux4 develop characteristic facioscapulohumeral muscular dystrophy like pathophysiology

ranging in severity. Skeletal Muscle 10:8 (2020)

AOC 1020 siRNA Showed Potent

Inhibition of DUX4 Gene Signature in Transgenic Mouse Model Dose-dependent inhibition of DUX4-driven genes in skeletal muscles Next Steps: Functional studies are currently underway to support Phase 1 dose selection Gastrocnemius Gastrocnemius DUX4

gene signature (% mock) Gene expression (% PBS)

AOC 1020 Nonclinical Activities