Dyne Therapeutics, Inc. (DYN)

Overview

We are a clinical-stage neuromuscular disease company focused on discovering and advancing innovative life-transforming therapeutics for people living with genetically driven neuromuscular diseases. Leveraging the modularity of our FORCE platform, we are developing targeted therapeutics that are designed to overcome limitations in delivery to muscle tissue and the central nervous system, or CNS. Our proprietary FORCE platform therapeutics consist of a payload that we rationally design to target the genetic basis of the disease we are seeking to treat, a linker and an antigen-binding fragment, or Fab, that we attach to the payload using the linker. With our FORCE platform, we have the flexibility to deploy different classes of payloads (such as oligonucleotides and enzymes) with specific mechanisms of action that modify target functions. We leverage this modularity to focus on neuromuscular diseases with high unmet need, with etiologic targets and with clear translational potential from preclinical disease models to well-defined clinical development and regulatory pathways.

Using our FORCE platform, we are assembling a broad portfolio of product candidates, including product candidates being developed for myotonic dystrophy type 1, or DM1, Duchenne muscular dystrophy, or DMD, facioscapulohumeral dystrophy, or FSHD, and Pompe disease. In addition, we plan to expand our portfolio through development efforts focused on rare skeletal muscle diseases, as well as cardiac and metabolic muscle diseases, including some with larger patient populations, and diseases involving the CNS. We have identified product candidates for each of our DM1, DMD, FSHD and Pompe programs that are in varying stages of preclinical and clinical development.

Our product candidate DYNE-101 is being evaluated in ACHIEVE, an ongoing Phase 1/2 global clinical trial in patients with DM1. ACHIEVE, which is designed to be a registrational trial, consists of a 24-week multiple ascending dose, or MAD, randomized, placebo-controlled period, a 24-week open-label extension, or OLE, a 96-week long-term extension, and a registrational expansion cohort. In January 2025, we announced the completion of the MAD portion of the trial and our plans to initiate a registrational expansion cohort to support submission for Accelerated Approval in the U.S. We plan to complete enrollment of the registrational expansion cohort in mid-2025 with data from this cohort in the first half of 2026 and potential submission for U.S. Accelerated Approval in the first half of 2026.

Our product candidate DYNE-251 is being evaluated in DELIVER, an ongoing Phase 1/2 global clinical trial in patients with DMD who have mutations amenable to exon 51 skipping. DELIVER, which is designed to be a registrational trial, consists of a 24-week MAD, randomized, placebo-controlled period, a 24-week OLE, a 192-week long-term extension, and a registrational expansion cohort. In September 2024, we announced the completion of the MAD portion of the trial, and in November 2024 we announced the initiation of the registrational expansion cohort to support submission for Accelerated Approval in the U.S. We plan to complete enrollment of the registrational expansion cohort in the first quarter of 2025 with data from this cohort in late 2025 and potential submission for U.S. Accelerated Approval in early 2026.

We were incorporated and commenced operations in 2017. Since our incorporation, we have devoted substantially all of our financial resources and efforts to organizing and staffing our company, business planning, raising capital, conducting research and development activities and filing and prosecuting

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patent applications. We do not have any products for sale and have not generated any revenue from product sales or otherwise. To date, we have principally raised capital through sales of equity securities.

Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more product candidates. For the years ended December 31, 2024, 2023 and 2022, we reported net losses of $317.4 million, $235.9 million and $168.1 million, respectively. As of December 31, 2024, we had an accumulated deficit of $949.9 million.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We expect that our expenses and capital expenditure requirements will increase substantially in connection with our ongoing activities, particularly if and as we:

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advance our product candidates for DM1, DMD, FSHD and Pompe and conduct research programs in additional indications;

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expand the capabilities of our proprietary FORCE platform;

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seek marketing approvals for any product candidates that successfully complete clinical trials;

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obtain, expand, maintain, defend and enforce our intellectual property portfolio;

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hire additional clinical, regulatory and scientific personnel;

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establish manufacturing sources for any product candidate we may develop, including the Fab antibody, linkers and therapeutic payload that will comprise the product candidate, and secure supply chain capacity to provide sufficient quantities for preclinical and clinical development and commercial supply;

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ultimately establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval; and

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add operational, legal, compliance, financial and management information systems and personnel to support our research, product development and future commercialization efforts, as well as to support our operations as a public company.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for any product candidates we may develop. If we obtain regulatory approval for or otherwise commercialize any product candidates we may develop, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more product candidates we may develop.

Because of the numerous risks and uncertainties associated with product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to raise capital, maintain our research and development efforts, expand our business or continue our operations at planned levels, and as a result we may be forced to substantially reduce or terminate our operations.

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We believe that our existing cash, cash equivalents and marketable securities, including the net proceeds from sales of common stock under our at-the-market offering program during the first quarter of 2025, will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2026. We have based our estimates as to how long we expect we will be able to fund our operations on assumptions that may prove to be wrong. We could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing, which may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See “—Liquidity and capital resources” below.

Components of our results of operations

Revenue

We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products for at least a couple of years, if at all. If our development efforts are successful and we commercialize products, or if we enter into collaboration or license agreements with third parties, we may generate revenue in the future from product sales, as well as upfront, milestone and royalty payments from such collaboration or license agreements, or a combination thereof.

Research and development expenses

Research and development expenses consist primarily of costs incurred for our research activities and development of our product candidates. These expenses include:

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development and operation of our proprietary FORCE platform;

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employee-related expenses, including salaries, related benefits and stock-based compensation expense, for employees engaged in research and development functions;

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expenses incurred in connection with our research programs and development of our product candidates, including those incurred under agreements with third parties, such as consultants and contract research organizations, or CROs, to conduct preclinical studies and clinical trials;

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the cost of laboratory supplies and acquiring, developing and manufacturing materials for use in our research, preclinical studies and clinical trials, including those incurred under agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs;

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facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance of facilities and insurance; and

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costs related to compliance with regulatory requirements.

We expense research and development costs as incurred. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Our direct external research and development expenses consist of costs that include fees, reimbursed materials and other costs paid to consultants, contractors, CMOs and CROs in connection with our development, manufacturing and clinical activities. We have not allocated our direct external research and development costs to specific programs or product candidates that are not in clinical development.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. Accordingly, we expect that our research and development expenses will increase substantially as we advance DYNE-101 and DYNE-251 through clinical trials, in connection with our preclinical and clinical development activities of DYNE-302, our FSHD product candidate, and DYNE-401, our Pompe disease product candidate, and if and as we advance any other product candidates through preclinical studies and clinical trials. At this time, we cannot accurately estimate or know the nature, timing

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and costs of the efforts that will be necessary to complete the preclinical and clinical development of any product candidates we may develop. The successful development of any product candidate is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following:

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the timing and progress of preclinical and clinical development activities;

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the number and scope of programs we decide to pursue and their regulatory paths to market;

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the need to raise funding to complete preclinical and clinical development of any product candidates we may develop;

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our ability to establish new licensing or collaboration arrangements and the progress of the development efforts of third parties with whom we may enter into such arrangements;

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our ability to maintain our current research and development programs and to establish new programs;

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the successful initiation, enrollment and completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority;

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the receipt and related terms of regulatory approvals from applicable regulatory authorities for any product candidates we may develop;

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the availability of specialty raw materials for use in production of any product candidate we may develop;

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establishing agreements with third-party manufacturers for supply of product candidate components for our clinical trials;

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our ability to obtain and maintain patents, trade secret protection and regulatory exclusivity, both in the United States and internationally;

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our ability to protect our other rights in our intellectual property portfolio;

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commercializing product candidates, if and when approved, whether alone or in collaboration with others; and

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obtaining and maintaining third-party insurance coverage and adequate reimbursement for any approved products.

A change in the outcome of any of these variables with respect to the development of any product candidate we may develop could significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any product candidate we may develop.

General and administrative expenses

General and administrative expenses consist primarily of employee-related expenses, including salaries, related benefits and stock-based compensation for employees in executive, finance, corporate and business development and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax and administrative consulting services; insurance costs; administrative travel expenses; and facility-related expenses, which include allocated expenses for rent, depreciation and maintenance of facilities and other operating costs.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our growth strategy. In addition, if we obtain regulatory approval for a product candidate and do not enter into a third-party commercialization collaboration, we expect to incur significant expenses related to building a sales and marketing team to support product sales, marketing and distribution activities.

Interest income

Interest income consists of interest earned on our cash, cash equivalents and marketable securities.

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Other income (expense), net

Other income (expense), net consists of realized gains and losses on sales of marketable securities and foreign currency gains and losses.

Income taxes

Since our inception, we have not recorded any U.S. federal or state income tax benefits for the net losses we have incurred in any year or for our earned research and development tax credits, due to our uncertainty of realizing a benefit from those items. As of December 31, 2024, we had federal and state net operating loss carryforwards of $315.7 million and $332.2 million, respectively. The federal net operating loss carryforwards are indefinite lived and the state net operating loss carryforwards begin to expire in 2038. As of December 31, 2024, we also had federal and state research and development tax credit carryforwards of $31.2 million and $4.7 million which begin to expire in 2039 and 2033, respectively.

Results of operations

Comparison of the years ended December 31, 2024 and 2023

The following table summarizes our results of operations for the years ended December 31, 2024 and 2023:

Research and development expenses

The following table summarizes our research and development expenses for the years ended December 31, 2024 and 2023:

Expenses related to DYNE-101 increased in the year ended December 31, 2024 compared to the year ended December 31, 2023. This was attributable to higher manufacturing activity in 2024 to produce a

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sufficient clinical supply of drug product for the ongoing ACHIEVE trial and an increase in clinical trial activity for the ACHIEVE trial. Expenses related to DYNE-251 increased in the year ended December 31, 2024 compared to the year ended December 31, 2023. This was attributable to higher manufacturing activity in 2024 to produce a sufficient clinical supply of drug product for the ongoing DELIVER trial and an increase in clinical trial activity for the DELIVER trial.

The increase in platform and external research and development expenses in the year ended December 31, 2024 was primarily due to increased external research activity associated with our preclinical programs and product candidates. The increase in personnel-related expenses was primarily due to increased headcount in our research and development function. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel.

General and administrative expenses

The following table summarizes our general and administrative expenses for the years ended December 31, 2024 and 2023:

The increase in personnel-related expenses in the year ended December 31, 2024 compared to the year ended December 31, 2023 was due to increased headcount in our general and administrative function. The increase in stock-based compensation expense in the year ended December 31, 2024 was primarily the result of acceleration of vesting terms and modification of previously granted awards in connection with entering into separation and consulting agreements with our former chief executive officer, former chief business officer and former chief operating officer. Professional and consulting fees increased in the year ended December 31, 2024 due to the higher consulting costs to support the growth of the organization in 2024. Facility-related and other expenses decreased primarily due to decreased general business expenses, including the cost of corporate insurance policies.

Interest income

Interest income for the years ended December 31, 2024 and 2023 was $26.9 million and $7.6 million, respectively, due to interest earned on invested cash balances. The increase in interest income was due to an increased cash, cash equivalents and marketable securities balance due to the public sales of our common stock in the first and second quarters of 2024 on which we are earning interest.

Other expense, net

Other expense for the year ended December 31, 2024 was $0.5 million primarily due to foreign currency gains and losses. Other expense for the year ended December 31, 2023 was $1.4 million primarily due to foreign currency gains and losses.

Comparison of the years ended December 31, 2023 and 2022

Discussion and analysis of the results of operations for the year ended December 31, 2023 as compared to the results of operations for the year ended December 31, 2022 is included under the heading “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form 10-K for the year ended December 31, 2023 as filed with the SEC on March 5, 2024.

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Liquidity and capital resources

Sources of liquidity

Since our inception, we have incurred significant operating losses. We expect to incur significant expenses and operating losses for the foreseeable future as we support our continued research activities and development of our product candidates and platform. We have not yet commercialized any product candidates, and we do not expect to generate revenue from sales of any product candidates for at least a couple of years, if at all. To date, we have funded our operations primarily with proceeds from sales of equity securities. As of December 31, 2024, we had cash, cash equivalents and marketable securities of $642.3 million.

In November 2021, we filed a universal shelf registration statement on Form S-3, or the 2021 Shelf Registration Statement, to register for sale from time to time up to $400.0 million of common stock, preferred stock, debt securities, warrants and/or units in one or more offerings. Further, in November 2021, we entered into an Open Market Sale AgreementSM, or the Sales Agreement, with Jefferies LLC, or Jefferies, and included in the 2021 Shelf Registration Statement a prospectus relating to the Sales Agreement, pursuant to which, from time to time, we may offer and sell shares of our common stock having an aggregate offering price of up to $150.0 million, which we refer to as our at-the-market offering program. Sales of common stock under the Sales Agreement through Jefferies may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended or Securities Act. On January 4, 2024, we notified Jefferies that we were suspending and terminating the prospectus filed under our 2021 Shelf Registration Statement relating to the Sales Agreement for our at-the-market offering program.

On March 5, 2024, we filed a universal shelf registration statement on Form S-3, or the 2024 Shelf Registration Statement, and included a prospectus relating to the Sales Agreement. Under the 2024 Shelf Registration Statement, we may offer and sell debt securities, common stock, preferred stock, units and/or warrants from time to time at an indeterminate aggregate offering price in one or more offerings. In November 2024, we filed a prospectus supplement relating to the Sales Agreement, pursuant to which, in accordance with the Sales Agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $300.0 million in our at-the-market offering program.

During the year ended December 31, 2024, we issued and sold an aggregate of 3,800,465 shares of common stock pursuant to the Sales Agreement for aggregate net proceeds of $97.9 million, after deducting commissions and offering expenses payable by us. We sold such shares at a weighted average price of $26.86 per share.

In January 2024, we completed a follow-on public offering, which we refer to as the January 2024 offering, pursuant to which we issued and sold 19,722,500 shares of common stock. We received net proceeds of $323.9 million, after deducting underwriting discounts and commissions and offering expenses payable by us.

In May 2024, we completed a follow-on public offering, which we refer to as the May 2024 offering, pursuant to which we issued and sold 12,075,000 shares of common stock. We received net proceeds of $351.3 million, after deducting underwriting discounts and commissions and offering expenses payable by us.

In the first quarter of 2025, we issued and sold 10,660,159 shares of common stock through our at-the-market offering program pursuant to the Sales Agreement. We received net proceeds of $140.6 million, after deducting commissions and offering expenses payable by us.

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Cash flows

The following table summarizes our sources and uses of cash for each of the periods presented:

Operating activities

During the year ended December 31, 2024, operating activities used $292.4 million of cash, due to our net loss of $317.4 million and changes in our operating assets and liabilities of $19.5 million, partially offset by non-cash charges of $44.5 million. Net cash used in changes in our operating assets and liabilities primarily consisted of a $9.0 million decrease in accounts payable and other liabilities and a $10.5 million increase in prepaid expenses and other current assets. During the year ended December 31, 2023, operating activities used $188.2 million of cash, due to our net loss of $235.9 million partially offset by changes in our operating assets and liabilities of $26.3 million and non-cash charges of $21.4 million. Net cash used by changes in our operating assets and liabilities primarily consisted of a $23.0 million increase in accounts payable and other liabilities and a $3.3 million decrease in prepaid expenses and other current assets. Changes in our operating assets and liabilities during these periods were generally due to the growth of our business, increased clinical trial activity, increased manufacturing activities, advancement of our product candidates, the timing of vendor invoices and payments and annual bonus payments.

Investing activities

During the year ended December 31, 2024, net cash used in investing activities was $204.1 million due to purchases of marketable securities of $317.4 million and purchases of property and equipment of $2.4 million, partially offset by maturities of marketable securities of $105.2 million and sales of marketable securities of $10.6 million. During the year ended December 31, 2023, net cash provided by investing activities was $83.3 million due to maturities of marketable securities of $126.5 million and sales of marketable securities of $1.8 million, partially offset by purchases of marketable securities of $44.3 million and purchases of property and equipment of $0.7 million.

Financing activities

During the year ended December 31, 2024, net cash provided by financing activities was $809.9 million, consisting of $675.2 million in aggregate net proceeds from sales of common stock in our January 2024 and May 2024 offerings, $97.9 million in aggregate net proceeds from sales under our at-the-market offering program and $36.8 million in proceeds received from stock option exercises.

During the year ended December 31, 2023, net cash provided by financing activities was $54.3 million, consisting of $52.4 million in aggregate net proceeds from sales of common stock under our at-the-market offering program and $1.9 million in proceeds received from stock option exercises.

A discussion of changes in our financial condition for the year ended December 31, 2023 as compared to the year ended December 31, 2022 is included under the heading “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form 10-K for the year ended December 31, 2023 as filed with the SEC on March 5, 2024.

Funding requirements

We expect our expenses to increase in connection with our ongoing activities, particularly as we advance the clinical development of DYNE-101 and DYNE-251, the development of our FSHD and Pompe

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programs and additional research programs. The timing and amount of our operating expenditures will depend largely on:

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the identification of additional product candidates;

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the scope, progress, costs and results of preclinical and clinical development of any product candidates we may develop;

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the costs, timing and outcome of regulatory review of any product candidates we may develop;

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our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial;

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changes in laws or regulations applicable to any product candidates we may develop, including but not limited to clinical trial requirements for approvals;

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the cost and timing of obtaining materials to produce adequate product supply for any preclinical or clinical development of any product candidate we may develop;

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the costs and timing of future commercialization activities, including product manufacturing, marketing, sales and distribution, for any product candidate we may develop for which we obtain marketing approval;

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the legal costs involved in prosecuting patent applications and enforcing patent claims and other intellectual property claims;

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additions or departures of key scientific or management personnel;

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our ability to establish and maintain collaborations on favorable terms, if at all, as well as the costs and timing of any collaboration, license or other arrangement, including the terms and timing of any milestone payments thereunder; and

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the costs of operating as a public company.

We believe that our existing cash, cash equivalents and marketable securities, including the net proceeds from sales of common stock under our at-the-market offering program during the first quarter of 2025, will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2026. We have based this estimate on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities could include liquidation or other preferences that adversely affect the rights of holders of our common stock. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to take specified actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements other arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more of our product candidates we may develop. See Item 1A. “Risk factors” in this Annual Report on Form 10-K for additional risks associated with our substantial capital requirements.

Contractual and other obligations

We enter into contracts in the normal course of business with CROs, CMOs and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by us upon written

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notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of our service providers, up to the date of cancellation and in the case of certain arrangements with CROs and CMOs may include non-cancelable fees.

We have also entered into a license agreement with the University of Mons under which we are obligated to make specified milestone and royalty payments. The payment obligations under this agreement are contingent upon future events, such as our achievement of specified development, regulatory and commercial milestones, or generating product sales. We are unable to estimate the timing or likelihood of achieving these milestones or generating future product sales. For additional information about our license agreement with the University of Mons and amounts that could become payable in the future under that agreement, see Item 1. “Business—Intellectual Property—License Agreement with the University of Mons” in this Annual Report.

On December 4, 2020, we entered into a lease agreement for office and laboratory space, which was amended in January 2021, March 2021, and June 2021. The lease has a term of 8.5 years that commenced when we gained access to the office and laboratory space in September 2021. Our obligation for the payment of the base rent began in April 2022 and is $0.4 million per month, increasing to $0.5 million per month during the term of the lease. We have two options to extend the term of the lease, each for a period of an additional five years.

On January 15, 2025, we entered into a master manufacturing services agreement with a CMO which secures capacity at the CMO’s manufacturing facilities for certain of our product candidates and components thereof. The agreement obligates us to compensate the CMO at least $60 million for producing certain of our product candidates and components thereof through 2026. In specified termination circumstances, the agreement requires us to pay the CMO for services completed, the cost of the CMO’s raw materials that cannot be repurposed and specified cancellation fees. This agreement formalizes and supersedes a letter agreement that we entered into with the CMO on July 18, 2024.

Critical accounting estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

We define our critical accounting policies as those accounting principles generally accepted in the United States of America that require us to make subjective estimates and judgments about matters that are uncertain and are likely to have a material impact on our financial condition and results of operations as well as the specific manner in which we apply those principles. Management has determined that our most critical accounting policies are those relating to accrued research and development expenses and stock-based compensation. As we advance our product candidates into and through clinical development, we expect research and development expenses and, in particular, our accounting for accrued research and development expenses to be an increasingly important critical accounting policy. We believe the following accounting estimates used in the preparation of our consolidated financial statements have the most significant level of estimation uncertainty and have and are reasonably likely to have a material impact on our financial condition and results of operations. For a more detailed description of our significant accounting policies, refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements.

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Accrued research and development expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves reviewing open contracts and purchase orders, communicating with our service providers and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of these estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include fees paid to:

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CROs in connection with the ACHIEVE and DELIVER clinical trials;

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CROs and investigative sites in connection with research activities;

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CMOs in connection with the production of research materials; and

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vendors in connection with preclinical development activities.

We measure the expense recognized based on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple CMOs and CROs that supply, conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the achievement of specified milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred.

Stock-based compensation

We measure stock-based awards granted to employees and directors based on fair value on the date of the grant using the Black-Scholes option-pricing model for options, and we measure awards of restricted stock units based on the closing price of our common stock on the date of grant. Compensation expense for these awards is recognized over the requisite service period, which is generally the vesting period of the respective award. We use the straight-line method to record the expense of awards with service-based vesting conditions. We use the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing when achievement of the performance condition becomes probable. During 2024, all of our outstanding awards only include time-based vesting conditions.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our stock options, the risk-free interest rate for a period that approximates the expected term of our stock options and our expected dividend yield.

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Prior to our IPO, there was no public market for our common stock, and consequently, the estimated fair value of our common stock was determined by our board of directors as of the date of each option grant, with input from management, considering third-party valuations of our common stock as well as our board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent third-party valuation through the date of the grant. Since our IPO, we have determined the fair market value of our common stock using the closing price of our common stock as reported on the Nasdaq Global Select Market.

Recently issued accounting pronouncements

Refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements for a discussion of significant accounting policies. There are no recently issued accounting pronouncements that have not yet been adopted that are expected to have a material impact on the Company’s financial statements.

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Overview

We are a clinical-stage muscle disease company focused on advancing innovative life-transforming therapeutics for people living with genetically driven diseases. We are utilizing our proprietary FORCE platform to overcome the current limitations of muscle tissue delivery and advance modern oligonucleotide therapeutics for muscle diseases. Our proprietary FORCE platform therapeutics consist of an oligonucleotide payload that we rationally design to target the genetic basis of the disease we are seeking to treat, a clinically validated linker and an antigen-binding fragment, or Fab, that we attach to the payload using the linker. With our FORCE platform, we have the flexibility to deploy different types of oligonucleotide payloads with specific mechanisms of action that modify target functions. We leverage this modularity to focus on muscle diseases with high unmet need, with etiologic targets and with clear translational potential from preclinical disease models to well-defined clinical development and regulatory pathways.

Using our FORCE platform, we are assembling a broad portfolio of muscle disease therapeutics, including our programs in myotonic dystrophy type 1, or DM1, Duchenne muscular dystrophy, or DMD, and facioscapulohumeral dystrophy, or FSHD. In addition, we plan to expand our portfolio through development efforts focused on rare skeletal muscle diseases, as well as cardiac and metabolic muscle diseases and diseases involving the central nervous system, or CNS, including some with larger patient populations. We have identified product candidates for each of our DM1, DMD and FSHD programs that are in varying stages of preclinical and clinical development.

Our product candidate DYNE-101 is being evaluated in ACHIEVE, an ongoing Phase 1/2 global clinical trial in patients with DM1. ACHIEVE, which is designed to be a registrational trial, consists of a 24-week multiple ascending dose, or MAD, randomized, placebo-controlled period, a 24-week open-label extension, or OLE, and a 96-week long-term extension.

Our product candidate DYNE-251 is being evaluated in DELIVER, an ongoing Phase 1/2 global clinical trial in patients with DMD who have mutations amenable to exon 51 skipping. DELIVER, which is designed to be a registrational trial, consists of a 24-week MAD, randomized, placebo-controlled period, a 24-week OLE and a 96-week long-term extension.

In January 2024, we announced positive initial clinical data from the ACHIEVE trial and the DELIVER trial which we believe validates the promise of the FORCE platform. For more information on the clinical data, see Item 1. “Business” in this Annual Report on Form 10-K.

We were incorporated and commenced operations in 2017. Since our incorporation, we have devoted substantially all of our financial resources and efforts to organizing and staffing our company, business planning, raising capital, conducting research and development activities and filing and prosecuting patent applications. We do not have any products for sale and have not generated any revenue from product sales or otherwise. To date, we have principally raised capital through sales of equity securities.

Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more product candidates. For the years ended December 31,

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2023 and 2022, we reported net losses of $235.9 million and $168.1 million, respectively. As of December 31, 2023, we had an accumulated deficit of $632.5 million.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We expect that our expenses and capital expenditure requirements will increase substantially in connection with our ongoing activities, particularly if and as we:

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advance our product candidates for DM1, DMD and FSHD and conduct research programs in additional indications;

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expand the capabilities of our proprietary FORCE platform;

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seek marketing approvals for any product candidates that successfully complete clinical trials;

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obtain, expand, maintain, defend and enforce our intellectual property portfolio;

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hire additional clinical, regulatory and scientific personnel;

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establish manufacturing sources for any product candidate we may develop, including the Fab antibody, Val-cit linker and therapeutic payload that will comprise the product candidate, and secure supply chain capacity to provide sufficient quantities for preclinical and clinical development and commercial supply;

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ultimately establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval; and

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add operational, legal, compliance, financial and management information systems and personnel to support our research, product development and future commercialization efforts, as well as to support our operations as a public company.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for any product candidates we may develop. If we obtain regulatory approval for or otherwise commercialize any product candidates we may develop, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more product candidates we may develop.

Because of the numerous risks and uncertainties associated with product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to raise capital, maintain our research and development efforts, expand our business or continue our operations at planned levels, and as a result we may be forced to substantially reduce or terminate our operations.

We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements through 2025. We have based our estimates as to how long we expect we will be able to fund our operations on assumptions that may prove to be wrong. We could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing, which may not be available to us on acceptable terms, or at all.

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Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See “—Liquidity and capital resources” below.

Components of our results of operations

Revenue

We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products in the near future, if at all. If our development efforts are successful and we commercialize products, or if we enter into collaboration or license agreements with third parties, we may generate revenue in the future from product sales, as well as upfront, milestone and royalty payments from such collaboration or license agreements, or a combination thereof.

Research and development expenses

Research and development expenses consist primarily of costs incurred for our research activities and development of our product candidates. These expenses include:

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development and operation of our proprietary FORCE platform;

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employee-related expenses, including salaries, related benefits and stock-based compensation expense, for employees engaged in research and development functions;

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expenses incurred in connection with our research programs and development of our product candidates, including those incurred under agreements with third parties, such as consultants and contract research organizations, or CROs to conduct preclinical studies and clinical trials;

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the cost of laboratory supplies and acquiring, developing and manufacturing materials for use in our research, preclinical studies and clinical trials, including those incurred under agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs;

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facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance of facilities and insurance; and

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costs related to compliance with regulatory requirements.

We expense research and development costs as incurred. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Our direct external research and development expenses consist of costs that include fees, reimbursed materials and other costs paid to consultants, contractors, CMOs and CROs in connection with our development, manufacturing and clinical activities. We have not allocated our direct external research and development costs to specific programs or product candidates that are not in clinical development.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. Accordingly, we expect that our research and development expenses will increase substantially as we advance DYNE-101 and DYNE-251 through clinical trials and in connection with our preclinical and clinical development activities if and as we advance any other product candidates through preclinical studies and clinical trials. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any product candidates we may develop. The successful development of any product candidate is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following:

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the timing and progress of preclinical and clinical development activities;

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the number and scope of programs we decide to pursue and their regulatory paths to market;

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the need to raise funding to complete preclinical and clinical development of any product candidates we may develop;

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our ability to establish new licensing or collaboration arrangements and the progress of the development efforts of third parties with whom we may enter into such arrangements;

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our ability to maintain our current research and development programs and to establish new programs;

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the successful initiation, enrollment and completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority;

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the receipt and related terms of regulatory approvals from applicable regulatory authorities for any product candidates we may develop;

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the availability of specialty raw materials for use in production of any product candidate we may develop;

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establishing agreements with third-party manufacturers for supply of product candidate components for our clinical trials;

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our ability to obtain and maintain patents, trade secret protection and regulatory exclusivity, both in the United States and internationally;

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our ability to protect our other rights in our intellectual property portfolio;

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commercializing product candidates, if and when approved, whether alone or in collaboration with others; and

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obtaining and maintaining third-party insurance coverage and adequate reimbursement for any approved products.

A change in the outcome of any of these variables with respect to the development of any product candidate we may develop could significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any product candidate we may develop.

General and administrative expenses

General and administrative expenses consist primarily of employee-related expenses, including salaries, related benefits and stock-based compensation for employees in executive, finance, corporate and business development and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax and administrative consulting services; insurance costs; administrative travel expenses; and facility-related expenses, which include allocated expenses for rent, depreciation and maintenance of facilities and other operating costs.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our growth strategy. In addition, if we obtain regulatory approval for a product candidate and do not enter into a third-party commercialization collaboration, we expect to incur significant expenses related to building a sales and marketing team to support product sales, marketing and distribution activities.

Interest income

Interest income consists of interest earned on our cash, cash equivalents and marketable securities.

Other income (expense), net

Other income (expense), net consists of realized gains and losses on sales of marketable securities and foreign currency gains and losses.

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Income taxes

Since our inception, we have not recorded any U.S. federal or state income tax benefits for the net losses we have incurred in any year or for our earned research and development tax credits, due to our uncertainty of realizing a benefit from those items. As of December 31, 2023, we had federal and state net operating loss carryforwards of $273.5 million and $279.5 million, respectively. The federal net operating loss carryforwards are indefinite lived and the state net operating loss carryforwards begin to expire in 2038. As of December 31, 2023, we also had federal and state research and development tax credit carryforwards of $17.1 million and $2.9 million which begin to expire in 2039 and 2033, respectively.

Results of operations

Comparison of the years ended December 31, 2023 and 2022

The following table summarizes our results of operations for the years ended December 31, 2023 and 2022:

Research and development expenses

The following table summarizes our research and development expenses for the years ended December 31, 2023 and 2022:

Expenses related to DYNE-101 increased in the year ended December 31, 2023 compared to the year ended December 31, 2022. This was attributable to higher manufacturing activity in 2023 to produce a sufficient clinical supply of drug product for the ongoing ACHIEVE trial and an increase in clinical trial activity for the ACHIEVE trial. Expenses related to DYNE-251 increased in the year ended December 31, 2023 compared to the year ended December 31, 2022. This was attributable to higher manufacturing activity in 2023 to produce a sufficient clinical supply of drug product for the ongoing DELIVER trial and an increase in clinical trial activity for the DELIVER trial.

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The increase in platform and external research and development expenses in the year ended December 31, 2023 was primarily due to increased external research activity associated with our preclinical programs. The increase in personnel-related expenses was primarily due to increased headcount in our research and development function. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel.

General and administrative expenses

The following table summarizes our general and administrative expenses for the years ended December 31, 2023 and 2022:

The increase in personnel-related expenses and stock-based compensation expense in the year ended December 31, 2023 compared to the year ended December 31, 2022 was due to increased headcount in our general and administrative function. Professional and consulting fees increased in the year ended December 31, 2023 due to the higher consulting costs to support the growth of the organization in 2023. Facility-related and other expenses decreased primarily due to decreased general business expenses, including the cost of corporate insurance policies.

Interest income

Interest income for the years ended December 31, 2023 and 2022 was $7.6 million and $2.9 million, respectively, due to interest earned on invested cash balances. The increase in interest income was due to an overall increase in interest rates, partially offset by the impact of having a lower cash, cash equivalents and marketable securities balance on which we are earning interest.

Other (expense) income, net

Other expense for the year ended December 31, 2023 was $1.4 million due to foreign currency gains and losses. Other expense for the year ended December 31, 2022 was $0.1 million due to realized losses on the sale of marketable securities and foreign currency gains and losses.

Liquidity and capital resources

Sources of liquidity

Since our inception, we have incurred significant operating losses. We expect to incur significant expenses and operating losses for the foreseeable future as we support our continued research activities and development of our product candidates and platform. We have not yet commercialized any product candidates, and we do not expect to generate revenue from sales of any product candidates for several years, if at all. To date, we have funded our operations primarily with proceeds from sales of equity securities. As of December 31, 2023 we had cash, cash equivalents and marketable securities of $123.1 million.

In November 2021, we filed a universal shelf registration statement on Form S-3 to register for sale from time to time up to $400.0 million of common stock, preferred stock, debt securities, warrants and/or units in one or more offerings. Further, in November 2021, we entered into an Open Market Sale AgreementSM, or the Sales Agreement, with Jefferies LLC, or Jefferies, pursuant to which, from time to time, we may offer and sell shares of our common stock having an aggregate offering price of up to $150.0 million, which we refer to as our at-the-market offering program. Sales of common stock through Jefferies may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the

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Securities Act of 1933, as amended or Securities Act. During the year ended December 31, 2023, we issued and sold an aggregate of 4,509,063 shares of common stock pursuant to the Sales Agreement for aggregate net proceeds of $52.4 million, after deducting fees. We sold such shares at a weighted average price of $12.01 per share.

On January 11, 2024, we completed a follow-on public offering, which we refer to as the January 2024 offering, pursuant to which we issued and sold 19,722,500 shares of our common stock. We received net proceeds of $323.9 million, after deducting underwriting discounts and commissions and offering expenses payable by us.

Cash flows

The following table summarizes our sources and uses of cash for each of the periods presented:

Operating activities

During the year ended December 31, 2023, operating activities used $188.2 million of cash, due to our net loss of $235.9 million, partially offset by changes in our operating assets and liabilities of $26.3 million and non-cash charges of $21.4 million. Net cash provided by changes in our operating assets and liabilities primarily consisted of a $23.0 million increase in accounts payable and other liabilities and a $3.3 million decrease in prepaid expenses and other current assets. During the year ended December 31, 2022, operating activities used $153.6 million of cash, due to our net loss of $168.1 million and changes in our operating assets and liabilities of $5.4 million, partially offset by non-cash charges of $19.8 million. Net cash used by changes in our operating assets and liabilities primarily consisted of a $1.2 million decrease in accounts payable and other liabilities and a $4.1 million increase in prepaid expenses and other current assets. Changes in our operating assets and liabilities during these periods were generally due to the growth of our business, increased clinical trial activity, increased manufacturing activities, advancement of our product candidates, the timing of vendor invoices and payments and annual bonus payments.

Investing activities

During the year ended December 31, 2023, net cash provided by investing activities was $83.3 million due to maturities of marketable securities of $126.5 million and sales of marketable securities of $1.8 million, partially offset by purchases of marketable securities of $44.3 million and purchases of property and equipment of $0.7 million. During the year ended December 31, 2022, net cash provided by investing activities was $87.2 million due to maturities of marketable securities of $208.3 million and sales of marketable securities of $3.2 million, partially offset by purchases of marketable securities of $121.2 million and purchases of property and equipment of $3.1 million.

Financing activities

During the year ended December 31, 2023, net cash provided by financing activities was $54.3 million, consisting of $52.4 million in aggregate net proceeds from sales under our at-the-market offering program in 2023 and $1.9 million in proceeds received from stock option exercises.

During the year ended December 31, 2022, net cash provided by financing activities was $37.4 million, consisting of $36.9 million in aggregate net proceeds from sales under our at-the-market offering program in 2022 and $0.5 million in proceeds received from stock option exercises.

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Funding requirements

We expect our expenses to increase in connection with our ongoing activities, particularly as we advance the clinical development of DYNE-101 and DYNE-251, the development of our FSHD program and additional research programs. The timing and amount of our operating expenditures will depend largely on:

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the identification of additional research programs and product candidates;

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the scope, progress, costs and results of preclinical and clinical development of any product candidates we may develop;

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the costs, timing and outcome of regulatory review of any product candidates we may develop;

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our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial;

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changes in laws or regulations applicable to any product candidates we may develop, including but not limited to clinical trial requirements for approvals;

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the cost and timing of obtaining materials to produce adequate product supply for any preclinical or clinical development of any product candidate we may develop;

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the costs and timing of future commercialization activities, including product manufacturing, marketing, sales and distribution, for any product candidate we may develop for which we obtain marketing approval;

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the legal costs involved in prosecuting patent applications and enforcing patent claims and other intellectual property claims;

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additions or departures of key scientific or management personnel;

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our ability to establish and maintain collaborations on favorable terms, if at all, as well as the costs and timing of any collaboration, license or other arrangement, including the terms and timing of any milestone payments thereunder; and

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the costs of operating as a public company.

We believe that our existing cash, cash equivalents and marketable securities, including the net proceeds from the January 2024 offering, will enable us to fund our operating expenses and capital expenditure requirements through 2025. We have based this estimate on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities could include liquidation or other preferences that adversely affect the rights of holders of our common stock. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to take specified actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements other arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more of our product candidates we may develop. See Item 1A. “Risk factors” in this Annual Report on Form 10-K for additional risks associated with our substantial capital requirements.

Contractual and other obligations

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We enter into contracts in the normal course of business with CROs, CMOs and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by us upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of our service providers, up to the date of cancellation and in the case of certain arrangements with CROs and CMOs may include non-cancelable fees.

We have also entered into a license agreement with the University of Mons under which we are obligated to make specified milestone and royalty payments. The payment obligations under this agreement are contingent upon future events, such as our achievement of specified development, regulatory and commercial milestones, or generating product sales. We are unable to estimate the timing or likelihood of achieving these milestones or generating future product sales. For additional information about our license agreement with the University of Mons and amounts that could become payable in the future under that agreement, see Item 1. “Business—Intellectual Property—License Agreement with the University of Mons” in this Annual Report.

On December 4, 2020, we entered into a lease agreement for office and laboratory space, which was amended in January 2021, March 2021, and June 2021. The lease has a term of 8.5 years that commenced when we gained access to the office and laboratory space in September 2021. Our obligation for the payment of the base rent began in April 2022 and is $0.4 million per month, increasing to $0.5 million per month during the term of the lease. We have two options to extend the term of the lease, each for a period of an additional five years.

Critical accounting estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

We define our critical accounting policies as those accounting principles generally accepted in the United States of America that require us to make subjective estimates and judgments about matters that are uncertain and are likely to have a material impact on our financial condition and results of operations as well as the specific manner in which we apply those principles. Management has determined that our most critical accounting policies are those relating to accrued research and development expenses and stock-based compensation. As we advance our product candidates into and through clinical development, we expect research and development expenses and, in particular, our accounting for accrued research and development expenses to be an increasingly important critical accounting policy. We believe the following accounting estimates used in the preparation of our consolidated financial statements have the most significant level of estimation uncertainty and have and are reasonably likely to have a material impact on our financial condition and results of operations. For a more detailed description of our significant accounting policies, refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements.

Accrued research and development expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves reviewing open contracts and purchase orders, communicating with our service providers and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined

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schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of these estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include fees paid to:

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CROs in connection with the ACHIEVE and DELIVER clinical trials;

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CROs and investigative sites in connection with research activities;

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CMOs in connection with the production of research materials; and

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vendors in connection with preclinical development activities.

We measure the expense recognized based on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple CMOs and CROs that supply, conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the achievement of specified milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred.

Stock-based compensation

We measure stock-based awards granted to employees and directors based on fair value on the date of the grant using the Black-Scholes option-pricing model for options, and we measure awards of restricted stock units based on the closing price of our common stock on the date of grant. Compensation expense for these awards is recognized over the requisite service period, which is generally the vesting period of the respective award. We use the straight-line method to record the expense of awards with service-based vesting conditions. We use the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing when achievement of the performance condition becomes probable. During 2023, all of our outstanding awards only include time-based vesting conditions.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our stock options, the risk-free interest rate for a period that approximates the expected term of our stock options and our expected dividend yield.

Prior to our IPO, there was no public market for our common stock, and consequently, the estimated fair value of our common stock was determined by our board of directors as of the date of each option grant, with input from management, considering third-party valuations of our common stock as well as our board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent third-party valuation through the date of the grant. Since our IPO, we have determined the fair market value of our common stock using the closing price of our common stock as reported on the Nasdaq Global Select Market.

Recently issued accounting pronouncements

Refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements for a discussion of significant accounting policies. There are no recently

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issued accounting pronouncements that have not yet been adopted that are expected to have a material impact on the Company’s financial statements.

Emerging growth company and smaller reporting company status

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. We may take advantage of these exemptions until we are no longer an “emerging growth company.” Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. We have elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, our financial statements may not be comparable to companies that comply with public company effective dates. We may take advantage of these exemptions until December 31, 2025 or until such earlier time that we are no longer an “emerging growth company.”

We are also a “smaller reporting company” as defined in Rule 12b-2 under the Exchange Act. We may continue to be a smaller reporting company if either (i) the market value of our shares held by non-affiliates is less than $250 million as of the last business day of our most recently completed second fiscal quarter or (ii) our annual revenue is less than $100 million during the most recently completed fiscal year and the market value of our shares held by non-affiliates is less than $700 million as of the last business day of our most recently completed second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies.

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Overview

We are a clinical-stage muscle disease company dedicated to advancing innovative life-transforming therapeutics for people living with genetically driven diseases. We are utilizing our proprietary FORCE platform to overcome the current limitations of muscle tissue delivery and advance modern oligonucleotide therapeutics for muscle diseases. Our proprietary FORCE platform therapeutics consist of an oligonucleotide payload that we rationally design to target the genetic basis of the disease we are seeking to treat, a clinically validated linker and an antigen-binding fragment, or Fab, that we attach to the payload using the linker. With our FORCE platform, we have the flexibility to deploy different types of oligonucleotide payloads with specific mechanisms of action that modify target functions. We leverage this modularity to focus on muscle diseases with high unmet need, with etiologic targets and with clear translational potential from preclinical disease models to well-defined clinical development and regulatory pathways.

Using our FORCE platform, we are assembling a broad portfolio of muscle disease therapeutics, including our programs in myotonic dystrophy type 1, or DM1, Duchenne muscular dystrophy, or DMD, and facioscapulohumeral dystrophy, or FSHD. In addition, we plan to expand our portfolio through development efforts focused on rare skeletal muscle diseases, as well as cardiac and metabolic muscle diseases, including some with larger patient populations. We have identified product candidates for each of our DM1, DMD and FSHD programs that are in varying stages of preclinical and clinical development.

For our product candidate DYNE-101, in September 2022 we began enrollment in ACHIEVE, an ongoing Phase 1/2 global clinical trial in adult patients with DM1. ACHIEVE, which is designed to be a registrational trial, consists of a 24-week multiple ascending dose, or MAD, randomized, placebo-controlled period, a 24-week open-label extension and a 96-week long-term extension. We anticipate reporting initial data on safety, tolerability and splicing from the MAD portion of the trial in the second half of 2023.

For our product candidate DYNE-251, in August 2022 we began enrollment in DELIVER, an ongoing Phase 1/2 global clinical trial in males with DMD who have mutations amenable to exon 51 skipping therapy. DELIVER, which is designed to be a registrational trial, consists of a 24-week MAD randomized, placebo-controlled period, a 24-week open-label extension and a 96-week long-term extension. We anticipate reporting initial data on safety, tolerability and dystrophin from the MAD portion of the trial in the second half of 2023.

In September 2022, we announced that we are prioritizing our focus and resources on our clinical programs, DYNE-101 for DM1 and DYNE-251 for DMD. As a result, we announced the deferral of the Investigational New Drug, or IND, application submission for our product candidate DYNE-301 for FSHD that we had originally targeted for the second half of 2022. We plan to provide an update on the FSHD program by the end of 2023.

We were incorporated and commenced operations in 2017. Since our incorporation, we have devoted substantially all of our financial resources and efforts to organizing and staffing our company, business planning, raising capital, conducting research and development activities and filing and prosecuting patent applications. We do not have any products for sale and have not generated any revenue from product sales or otherwise. To date, we have principally raised capital through sales of equity securities.

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On September 21, 2020, we completed our initial public offering, or IPO, pursuant to which we issued and sold 14,089,314 shares of our common stock, including 1,837,736 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares. We received net proceeds of $246.4 million, after deducting underwriting discounts and commissions and offering expenses payable by us. On January 25, 2021, we completed a follow-on public offering pursuant to which we issued and sold 6,000,000 shares of our common stock. We received net proceeds of $157.2 million, after deducting underwriting discounts and commissions and offering expenses payable by us. As of December 31, 2022, we have received net proceeds of $36.9 million, after deducting fees, from sales of an aggregate of 3,425,085 shares of our common stock under our at-the-market offering program.

Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more product candidates. For the years ended December 31, 2021 and 2022, we reported net losses of $149.3 million and $168.1 million, respectively. As of December 31, 2022, we had an accumulated deficit of $396.6 million.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We expect that our expenses and capital expenditure requirements will increase substantially in connection with our ongoing activities, particularly if and as we:

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advance our product candidates for DM1, DMD and FSHD and conduct research programs in additional indications;

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expand the capabilities of our proprietary FORCE platform;

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seek marketing approvals for any product candidates that successfully complete clinical trials;

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obtain, expand, maintain, defend and enforce our intellectual property portfolio;

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hire additional clinical, regulatory and scientific personnel;

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establish manufacturing sources for any product candidate we may develop, including the Fab antibody, Val-cit linker and therapeutic payload that will comprise the product candidate, and secure supply chain capacity to provide sufficient quantities for preclinical and clinical development and commercial supply;

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ultimately establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval; and

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add operational, legal, compliance, financial and management information systems and personnel to support our research, product development and future commercialization efforts, as well as to support our operations as a public company.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for any product candidates we may develop. If we obtain regulatory approval for or otherwise commercialize any product candidates we may develop, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more product candidates we may develop.

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Because of the numerous risks and uncertainties associated with product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to raise capital, maintain our research and development efforts, expand our business or continue our operations at planned levels, and as a result we may be forced to substantially reduce or terminate our operations.

We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements through 2024. We have based our estimates as to how long we expect we will be able to fund our operations on assumptions that may prove to be wrong. We could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing, which may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See “—Liquidity and capital resources” below.

Components of our results of operations

Revenue

We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products in the near future, if at all. If our development efforts are successful and we commercialize products, or if we enter into collaboration or license agreements with third parties, we may generate revenue in the future from product sales, as well as upfront, milestone and royalty payments from such collaboration or license agreements, or a combination thereof.

Research and development expenses

Research and development expenses consist primarily of costs incurred for our research activities and development of our programs. These expenses include:

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development and operation of our proprietary FORCE platform;

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employee-related expenses, including salaries, related benefits and stock-based compensation expense, for employees engaged in research and development functions;

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expenses incurred in connection with our research programs and development of our product candidates, including those incurred under agreements with third parties, such as consultants and contract research organizations, or CROs to conduct preclinical studies and clinical trials;

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the cost of laboratory supplies and acquiring, developing and manufacturing materials for use in our research, preclinical studies and clinical trials, including those incurred under agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs;

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facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance of facilities and insurance; and

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costs related to compliance with regulatory requirements.

We expense research and development costs as incurred. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Our direct external research and development expenses consist of costs that include fees, reimbursed materials and other costs paid to consultants, contractors, CMOs and CROs in connection with our development, manufacturing and clinical activities. We have not allocated our direct external research and development costs to specific programs or product candidates that are not in clinical development.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of

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later-stage clinical trials. Accordingly, we expect that our research and development expenses will increase substantially as we advance DYNE-101 and DYNE-251 through clinical trials and in connection with our preclinical and clinical development activities if and as we advance any other product candidates through preclinical studies and clinical trials. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any product candidates we may develop. The successful development of any product candidate is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following:

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the timing and progress of preclinical and clinical development activities;

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the number and scope of programs we decide to pursue and their regulatory paths to market;

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the need to raise funding to complete preclinical and clinical development of any product candidates we may develop;

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our ability to establish new licensing or collaboration arrangements and the progress of the development efforts of third parties with whom we may enter into such arrangements;

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our ability to maintain our current research and development programs and to establish new programs;

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the successful initiation, enrollment and completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority;

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the receipt and related terms of regulatory approvals from applicable regulatory authorities for any product candidates we may develop;

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the availability of specialty raw materials for use in production of any product candidate we may develop;

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establishing agreements with third-party manufacturers for supply of product candidate components for our clinical trials;

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our ability to obtain and maintain patents, trade secret protection and regulatory exclusivity, both in the United States and internationally;

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our ability to protect our other rights in our intellectual property portfolio;

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commercializing product candidates, if and when approved, whether alone or in collaboration with others; and

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obtaining and maintaining third-party insurance coverage and adequate reimbursement for any approved products.

A change in the outcome of any of these variables with respect to the development of any product candidate we may develop could significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any product candidate we may develop.

General and administrative expenses

General and administrative expenses consist primarily of employee-related expenses, including salaries, related benefits and stock-based compensation for employees in executive, finance, corporate and business development and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax and administrative consulting services; insurance costs; administrative travel expenses; and facility-related expenses, which include allocated expenses for rent, depreciation and maintenance of facilities and other operating costs.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our growth strategy. In addition, if we obtain regulatory approval for a product candidate and do not enter into a third-party commercialization collaboration, we expect to incur

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significant expenses related to building a sales and marketing team to support product sales, marketing and distribution activities.

Interest income

Interest income consists of interest earned on our cash, cash equivalents and marketable securities.

Other income (expense), net

Other income (expense), net consists of realized gains and losses on sales of marketable securities and foreign currency gains and losses.

Income taxes

Since our inception, we have not recorded any U.S. federal or state income tax benefits for the net losses we have incurred in any year or for our earned research and development tax credits, due to our uncertainty of realizing a benefit from those items. As of December 31, 2022, we had federal and state net operating loss carryforwards of $221.1 million and $221.9 million, respectively. The federal net operating loss carryforwards are indefinite lived and the state net operating loss carryforwards begin to expire in 2038. As of December 31, 2022, we also had federal and state research and development tax credit carryforwards of $9.9 million and $1.6 million which begin to expire in 2039 and 2033, respectively.

Results of operations

Comparison of the years ended December 31, 2022 and 2021

The following table summarizes our results of operations for the years ended December 31, 2022 and 2021:

Research and development expenses

The following table summarizes our research and development expenses for the years ended December 31, 2022 and 2021:

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The increase in expenses related to DYNE-101 was primarily due to increased clinical trial activity associated with the preparation and conduct of the ACHIEVE trial, which we initiated in the third quarter of 2022, and higher variable manufacturing costs in 2022 to produce a sufficient clinical supply of drug product for the ACHIEVE trial. The decrease in expenses related to DYNE-251 was primarily due to the timing of variable manufacturing costs incurred in 2021, including the purchase of raw materials to produce a sufficient clinical supply of drug product for the DELIVER trial, which we initiated in the third quarter of 2022, partially offset by increased clinical trial activity associated with the preparation and conduct of the DELIVER trial.

The decrease in platform and external research and development expenses was primarily due to the prioritization of our focus and resources on our clinical programs, which resulted in lower platform related costs associated with less preclinical and research activity. The increase in personnel-related expenses was primarily due to increased headcount in our research and development function. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel, their research efforts and increased rent expense related to our facility lease that commenced in September 2021.

General and administrative expenses

The following table summarizes our general and administrative expenses for the years ended December 31, 2022 and 2021:

The increase in personnel-related costs was primarily the result of an increase in headcount in our general and administrative function. The decrease in stock-based compensation expense was primarily due to the timing of recognizing stock-based compensation expense for awards with performance-based vesting conditions in 2021. Professional and consulting fees decreased primarily due to an increase in headcount in our general and administrative function, which allowed us to reduce our utilization of external professionals and consultants. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of general and administrative personnel and increased rent expense related to our new facility lease that commenced in September 2021.

Interest income

Interest income for the years ended December 31, 2022 and 2021 was $2.9 million and $0.7 million, respectively, due to interest earned on invested cash balances. The increase in interest income was due to an overall increase in interest rates, partially offset by the impact of having a lower cash, cash equivalents and marketable securities balance on which we are earning interest.

Other (expense) income, net

Other expense for the year ended December 31, 2022 was $0.1 million due to realized losses on the sale of marketable securities and foreign currency gains and losses. Other expense for the year ended December 31, 2021 was less than $0.1 million due to realized losses on the sale of marketable securities.

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Liquidity and capital resources

Sources of liquidity

Since our inception, we have incurred significant operating losses. We expect to incur significant expenses and operating losses for the foreseeable future as we support our continued research activities and development of our programs and platform. We have not yet commercialized any product candidates, and we do not expect to generate revenue from sales of any product candidates for several years, if at all. To date, we have funded our operations primarily with proceeds from sales of equity securities. As of December 31, 2022 we had cash, cash equivalents and marketable securities of $256.0 million.

In November 2021, we filed a universal shelf registration statement on Form S-3 to register for sale from time to time up to $400.0 million of common stock, preferred stock, debt securities, warrants and/or units in one or more offerings. Further, in November 2021, we entered into an Open Market Sale AgreementSM, or the Sales Agreement, with Jefferies LLC, or Jefferies, pursuant to which, from time to time, we may offer and sell shares of our common stock having an aggregate offering price of up to $150.0 million, which we refer to as our at-the-market offering program. Sales of common stock through Jefferies may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended. During the fiscal year ended December 31, 2022, we issued and sold an aggregate of 3,425,085 shares of common stock pursuant to the Sales Agreement for aggregate net proceeds of $36.9 million, after deducting fees.

Cash flows

The following table summarizes our sources and uses of cash for each of the periods presented:

Operating activities

During the year ended December 31, 2022, operating activities used $153.6 million of cash, due to our net loss of $168.1 million and changes in our operating assets and liabilities of $5.4 million, partially offset by non-cash charges of $19.8 million. Net cash used by changes in our operating assets and liabilities primarily consisted of a $1.2 million decrease in accounts payable and other liabilities and a $4.1 million increase in prepaid expenses and other current assets. During the year ended December 31, 2021, operating activities used $119.6 million of cash, due to our net loss of $149.3 million, partially offset by non-cash charges of $20.4 million and net cash provided by changes in our operating assets and liabilities of $9.3 million. Net cash provided by changes in our operating assets and liabilities primarily consisted of a $13.7 million increase in accounts payable and other liabilities, partially offset by a $2.9 million increase in prepayments made for lessor-owned lease assets, and a $1.5 million increase in prepaid expenses and other current assets. Changes in our operating assets and liabilities during these periods were generally due to growth in our business, increased manufacturing activities, the advancement of our research programs and product candidates, clinical trial activity and the timing of vendor invoices and payments.

Investing activities

During the year ended December 31, 2022, net cash provided by investing activities was $87.2 million due to maturities of marketable securities of $208.3 million and sales of marketable securities of $3.2 million, partially offset by purchases of marketable securities of $121.2 million and purchases of property and equipment of $3.1 million. During the year ended December 31, 2021, net cash used in investing activities was $137.9 million due to the purchases of marketable securities of $236.7 million and

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purchases of property and equipment of $3.6 million, partially offset by maturities of marketable securities of $98.0 million and sales of marketable securities of $4.4 million.

Financing activities

During the year ended December 31, 2022, net cash provided by financing activities was $37.4 million, consisting of $36.9 million in aggregate net proceeds from sales under our at-the-market offering program in 2022 and $0.5 million in proceeds received from stock option exercises.

During the year ended December 31, 2021, net cash provided by financing activities was $157.8 million, consisting of $157.2 million in aggregate net proceeds from our follow-on offering completed in January 2021 and $0.6 million in proceeds received from stock option exercises.

Funding requirements

We expect our expenses to increase in connection with our ongoing activities, particularly as we advance the clinical development of DYNE-101 and DYNE-251, the development of DYNE-301 and additional research programs. The timing and amount of our operating expenditures will depend largely on:

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the identification of additional research programs and product candidates;

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the scope, progress, costs and results of preclinical and clinical development of any product candidates we may develop;

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the costs, timing and outcome of regulatory review of any product candidates we may develop;

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our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial;

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changes in laws or regulations applicable to any product candidates we may develop, including but not limited to clinical trial requirements for approvals;

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the cost and timing of obtaining materials to produce adequate product supply for any preclinical or clinical development of any product candidate we may develop;

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the costs and timing of future commercialization activities, including product manufacturing, marketing, sales and distribution, for any product candidate we may develop for which we obtain marketing approval;

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the legal costs involved in prosecuting patent applications and enforcing patent claims and other intellectual property claims;

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additions or departures of key scientific or management personnel;

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our ability to establish and maintain collaborations on favorable terms, if at all, as well as the costs and timing of any collaboration, license or other arrangement, including the terms and timing of any milestone payments thereunder; and

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the costs of operating as a public company.

We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements through 2024. We expect that our liquidity will be sufficient to achieve proof-of-concept data readouts for DYNE-101 and DYNE-251. We have based these estimates on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities could include liquidation or other preferences that adversely affect the rights of holders of our common stock. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to take specified actions, such as incurring additional debt, making capital expenditures or declaring

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dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements other arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more of our product candidates we may develop. See Item 1A. “Risk factors” in this Annual Report on Form 10-K for additional risks associated with our substantial capital requirements.

Contractual and other obligations

We enter into contracts in the normal course of business with CROs, CMOs and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by us upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of our service providers, up to the date of cancellation and in the case of certain arrangements with CROs and CMOs may include non-cancelable fees.

We have also entered into a license agreement with the University of Mons under which we are obligated to make specified milestone and royalty payments. The payment obligations under this agreement are contingent upon future events, such as our achievement of specified development, regulatory and commercial milestones, or generating product sales. We are unable to estimate the timing or likelihood of achieving these milestones or generating future product sales. For additional information about our license agreement with the University of Mons and amounts that could become payable in the future under that agreement, see Item 1. “Business—Intellectual Property—License Agreement with the University of Mons” in this Annual Report.

On December 4, 2020, we entered into a lease agreement for office and laboratory space, which was amended in January 2021, March 2021, and June 2021. The lease has a term of 8.5 years that commenced when we gained access to the office and laboratory space in September 2021. Our obligation for the payment of the base rent began in April 2022 and is $0.4 million per month, increasing to $0.5 million per month during the term of the lease. We have two options to extend the term of the lease, each for a period of an additional five years.

Critical accounting estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

We define our critical accounting policies as those accounting principles generally accepted in the United States of America that require us to make subjective estimates and judgments about matters that are uncertain and are likely to have a material impact on our financial condition and results of operations as well as the specific manner in which we apply those principles. Management has determined that our most critical accounting policies are those relating to accrued research and development expenses and stock-based compensation. As we advance our product candidates into clinical development, we expect research and development expenses and, in particular, our accounting for accrued research and development expenses to be an increasingly important critical accounting policy. We believe the following accounting estimates used in the preparation of our consolidated financial statements have the most significant level of estimation uncertainty and have and are reasonably likely to have a material impact on

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our financial condition and results of operations. For a more detailed description of our significant accounting policies, refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements.

Accrued research and development expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves reviewing open contracts and purchase orders, communicating with our service providers and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of these estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include fees paid to:

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CROs in connection with the ACHIEVE and DELIVER clinical trials;

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CROs and investigative sites in connection with research activities;

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CMOs in connection with the production of research materials; and

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vendors in connection with preclinical development activities.

We measure the expense recognized based on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple CMOs and CROs that supply, conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the achievement of specified milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred.

Stock-based compensation

We measure stock-based awards granted to employees and directors based on fair value on the date of the grant using the Black-Scholes option-pricing model for options, and we measure awards of restricted stock units based on the closing price of our common stock on the date of grant. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the respective award. We use the straight-line method to record the expense of awards with service-based vesting conditions. We use the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing when achievement of the performance condition becomes probable. During 2022, all of our awards with performance conditions were fully vested and our outstanding awards only include time-based vesting conditions.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our stock options, the risk-free interest rate for a period that approximates the expected term of our stock options and our expected dividend yield.

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Prior to our IPO, there was no public market for our common stock, and consequently, the estimated fair value of our common stock was determined by our board of directors as of the date of each option grant, with input from management, considering third-party valuations of our common stock as well as our board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent third-party valuation through the date of the grant. Since our IPO, we have determined the fair market value of our common stock using the closing price of our common stock as reported on the Nasdaq Global Select Market.

Recently issued accounting pronouncements

Refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements for a discussion of recent accounting pronouncements that were adopted in 2021. There are no recently issued accounting pronouncements that have not yet been adopted that are expected to have a material impact on the Company’s financial statements.

Emerging growth company and smaller reporting company status

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. We may take advantage of these exemptions until we are no longer an “emerging growth company.” Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. We have elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, our financial statements may not be comparable to companies that comply with public company effective dates. We may take advantage of these exemptions until December 31, 2025 or until such earlier time that we are no longer an “emerging growth company.”

We are also a “smaller reporting company” as defined in Rule 12b-2 under the Exchange Act. We may continue to be a smaller reporting company if either (i) the market value of our shares held by non-affiliates is less than $250 million or (ii) our annual revenue is less than $100 million during the most recently completed fiscal year and the market value of our shares held by non-affiliates is less than $700 million as of the last business day of our most recently completed second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies.

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Overview

We are building a leading muscle disease company dedicated to advancing innovative life-transforming therapeutics for people living with genetically driven diseases. We are utilizing our proprietary FORCE platform to overcome the current limitations of muscle tissue delivery and advance modern oligonucleotide therapeutics for muscle diseases. Our proprietary FORCE platform therapeutics consist of an oligonucleotide payload that we rationally design to target the genetic basis of the disease we are seeking to treat, a clinically validated linker and an antigen-binding fragment, or Fab, that we attach to the payload using the linker. With our FORCE platform, we have the flexibility to deploy different types of oligonucleotide payloads with specific mechanisms of action that modify target functions. We leverage this modularity to focus on muscle diseases with high unmet need, with etiologic targets and with clear translational potential from preclinical disease models to well-defined clinical development and regulatory pathways.

Using our FORCE platform, we are assembling a broad portfolio of muscle disease therapeutics, including our lead programs in myotonic dystrophy type 1, or DM1, Duchenne muscular dystrophy, or DMD, and facioscapulohumeral dystrophy, or FSHD. In addition, we plan to expand our portfolio through development efforts focused on rare skeletal muscle diseases, as well as cardiac and metabolic muscle diseases, including some with larger patient populations. We have identified product candidates for each of our lead programs that are in varying stages of preclinical development.

We expect to submit regulatory filings in multiple countries for our DM1 product candidate, DYNE-101, in the second quarter of 2022 and, subject to clearance by regulatory authorities, we plan to begin dosing patients in a global multiple ascending dose, or MAD, clinical trial of DYNE-101 in mid-2022. The FDA has placed on clinical hold our investigational new drug, or IND, application to initiate a clinical trial of our product candidate DYNE-251 for patients with DMD amenable to skipping exon 51 and requested additional clinical and non-clinical information for DYNE-251. We expect to submit our response to the FDA in the second quarter of 2022 with data from existing and ongoing studies and, if satisfactory to the FDA, plan to begin dosing patients in a Phase 1/2 global MAD clinical trial of DYNE-251 in mid-2022. We also anticipate submitting an IND for our FSHD product candidate, DYNE-301, in the second half of 2022.

We were incorporated and commenced operations in 2017. Since our incorporation, we have devoted substantially all of our financial resources and efforts to organizing and staffing our company, business planning, raising capital, conducting research activities and filing and prosecuting patent applications. We do not have any products for sale and have not generated any revenue from product sales or otherwise. To date, we have principally raised capital through sales of equity securities and borrowings under a loan and security agreement, or our loan agreement, with a commercial bank. On September 21, 2020, we completed our initial public offering, or IPO, pursuant to which we issued and sold 14,089,314 shares of our common stock, including 1,837,736 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares. We received net proceeds of $246.4 million, after deducting underwriting discounts and commissions and offering expenses payable by us. On January 25, 2021, we completed a follow-on public offering pursuant to which we issued and sold 6,000,000 shares of our common stock. We received net proceeds of $157.2 million, after deducting underwriting discounts and commissions and offering expenses payable by us.

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Since our inception, we have incurred significant operating losses. Our ability to generate any product revenue or product revenue sufficient to achieve profitability will depend on the successful development and eventual commercialization of one or more product candidates. For the years ended December 31, 2020 and 2021, we reported net losses of $59.4 million and $149.3 million, respectively. As of December 31, 2021, we had an accumulated deficit of $228.5 million.

We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We expect that our expenses and capital expenditure requirements will increase substantially in connection with our ongoing activities, particularly if and as we:

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continue our current lead programs in DM1, DMD and FSHD and conduct research programs in additional indications;

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advance our product candidates and any additional product candidates we identify through and into IND-enabling studies and clinical trials;

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expand the capabilities of our proprietary FORCE platform;

•
seek marketing approvals for any product candidates that successfully complete clinical trials;

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obtain, expand, maintain, defend and enforce our intellectual property portfolio;

•
hire additional clinical, regulatory and scientific personnel;

•
establish manufacturing sources for any product candidate we may develop, including the Fab antibody, Val-cit linker and therapeutic payload that will comprise the product candidate, and secure supply chain capacity to provide sufficient quantities for preclinical and clinical development and commercial supply;

•
ultimately establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval; and

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add operational, legal, compliance, financial and management information systems and personnel to support our research, product development and future commercialization efforts, as well as to support our operations as a public company.

We will not generate revenue from product sales unless and until we successfully complete clinical development and obtain regulatory approval for any product candidates we may develop. If we obtain regulatory approval for or otherwise commercialize any product candidates we may develop, we expect to incur significant expenses related to developing our commercialization capabilities to support product sales, marketing and distribution. Further, we expect to continue to incur additional costs associated with operating as a public company.

As a result, we will need substantial additional funding to support our continuing operations and pursue our growth strategy. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements or arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more product candidates we may develop.

Because of the numerous risks and uncertainties associated with product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to raise capital, maintain our research and development efforts, expand our business or continue our operations at planned levels, and as a result we may be forced to substantially reduce or terminate our operations.

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We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2024. We have based our estimates as to how long we expect we will be able to fund our operations on assumptions that may prove to be wrong. We could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing, which may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See “—Liquidity and capital resources” below.

Impact of COVID-19 on our business

The worldwide COVID-19 pandemic may affect our ability to initiate and complete preclinical studies, delay the initiation of our planned clinical trials, disrupt regulatory activities or have other adverse effects on our business, results of operations, financial condition and prospects. In addition, the pandemic has caused substantial disruption to supply chains and may adversely impact economies worldwide, both of which could adversely affect our business and operations.

To date, we have not experienced material business disruptions, including with our vendors, or impairments of any of our assets as a result of the pandemic. We continue to take actions as may be required or recommended by government authorities or as we determine are in the best interests of our employees and other business partners regarding workplace policies, practices and procedures. We are continuing to monitor the potential impact of the pandemic, but we cannot be certain what the overall impact will be on our business, financial condition, results of operations and prospects.

Components of our results of operations

Revenue

We have not generated any revenue since our inception and do not expect to generate any revenue from the sale of products in the near future, if at all. If our development efforts are successful and we commercialize products, or if we enter into collaboration or license agreements with third parties, we may generate revenue in the future from product sales, as well as upfront, milestone and royalty payments from such collaboration or license agreements, or a combination thereof.

Research and development expenses

Research and development expenses consist primarily of costs incurred for our research activities and development of our programs. These expenses include:

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development and operation of our proprietary FORCE platform;

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employee-related expenses, including salaries, related benefits and stock-based compensation expense, for employees engaged in research and development functions;

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expenses incurred in connection with our research programs and development of our product candidates, including under agreements with third parties, such as consultants and contract research organizations, or CROs;

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the cost of laboratory supplies and acquiring, developing and manufacturing materials for use in our research and preclinical studies, including under agreements with third parties, such as consultants and contract manufacturing organizations, or CMOs;

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facilities, depreciation and other expenses, which include direct or allocated expenses for rent and maintenance of facilities and insurance; and

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costs related to compliance with regulatory requirements.

We expense research and development costs as incurred. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

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Our direct external research and development expenses consist of costs that include fees, reimbursed materials and other costs paid to consultants, contractors, CMOs and CROs in connection with our development, manufacturing and clinical activities. We do not allocate our research and development costs to specific programs or product candidates because costs are deployed across multiple programs and product candidates as well as our platform and, as such, are not separately classified.

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages of clinical development, primarily due to the increased size and duration of later-stage clinical trials. Accordingly, we expect that our research and development expenses will increase substantially in connection with our preclinical and clinical development activities in the future as we advance our program candidates through IND-enabling studies and into clinical trials. At this time, we cannot accurately estimate or know the nature, timing and costs of the efforts that will be necessary to complete the preclinical and clinical development of any product candidates we may develop. The successful development of any product candidate is highly uncertain. This is due to the numerous risks and uncertainties associated with product development, including the following:

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the timing and progress of preclinical and clinical development activities;

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the number and scope of programs we decide to pursue and their regulatory paths to market;

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the need to raise funding to complete preclinical and clinical development of any product candidates we may develop;

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our ability to establish new licensing or collaboration arrangements and the progress of the development efforts of third parties with whom we may enter into such arrangements;

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our ability to maintain our current research and development programs and to establish new programs;

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the successful initiation, enrollment and completion of clinical trials with safety, tolerability and efficacy profiles that are satisfactory to the FDA or any comparable foreign regulatory authority;

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the receipt and related terms of regulatory approvals from applicable regulatory authorities for any product candidates we may develop;

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the availability of specialty raw materials for use in production of any product candidate we may develop;

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establishing agreements with third-party manufacturers for supply of product candidate components for our clinical trials;

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our ability to obtain and maintain patents, trade secret protection and regulatory exclusivity, both in the United States and internationally;

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our ability to protect our other rights in our intellectual property portfolio;

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commercializing product candidates, if and when approved, whether alone or in collaboration with others; and

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obtaining and maintaining third-party insurance coverage and adequate reimbursement for any approved products.

A change in the outcome of any of these variables with respect to the development of any product candidate we may develop could significantly change the costs and timing associated with the development of that product candidate. We may never succeed in obtaining regulatory approval for any product candidate we may develop.

General and administrative expenses

General and administrative expenses consist primarily of employee-related expenses, including salaries, related benefits and stock-based compensation, for employees in executive, finance, corporate and business development and administrative functions. General and administrative expenses also include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax and administrative consulting services; insurance costs; administrative travel expenses; and facility-related expenses, which include direct depreciation costs and allocated expenses for rent and maintenance of facilities and other operating costs.

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We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our growth strategy. We also anticipate that we will incur increased accounting, audit, legal, regulatory, compliance and director and officer insurance costs as well as investor and public relations expenses associated with our operations as a public company. In addition, if we obtain regulatory approval for a product candidate and do not enter into a third-party commercialization collaboration, we expect to incur significant expenses related to building a sales and marketing team to support product sales, marketing and distribution activities.

Interest income

Interest income consists of interest earned on our cash, cash equivalents and marketable securities.

Interest expense

Interest expense consisted of interest on borrowings under our loan agreement as well as amortization of debt discount and debt issuance costs. In October 2020, all outstanding borrowings under our loan agreement were repaid.

Change in success fee obligation

In February 2020, we entered into a loan agreement with Pacific Western Bank, or PWB, under which we borrowed an aggregate principal amount of $10.0 million in the form of a term loan. Our loan agreement required us to pay a success fee upon the occurrence of a specified liquidity event, as defined in the agreement, which included our initial public offering. In September 2020, following the completion of our initial public offering, we paid the success fee of $0.5 million, and in October 2020, we paid PWB $10.0 million as repayment of the outstanding principal and less than $0.1 million as accrued interest on the term loan. At inception of the loan agreement, this contingent obligation was considered immaterial. The fair value of the liability was remeasured at each reporting date, with changes in fair value recorded as a component of other income (expense) on the statement of operations.

Other income (expense), net

Other expense consists of realized losses on sales of marketable securities.

Income taxes

Since our inception, we have not recorded any U.S. federal or state income tax benefits for the net losses we have incurred in any year or for our earned research and development tax credits, due to our uncertainty of realizing a benefit from those items. As of December 31, 2021, we had federal and state net operating loss carryforwards of $188.7 million and $188.0 million, respectively. The federal net operating loss carryforwards are indefinite lived and the state net operating loss carryforwards begin to expire in 2038. As of December 31, 2021, we also had federal and state research and development tax credit carryforwards $3.6 million and $1.6 million which begin to expire in 2039 and 2033, respectively.

Results of operations

Comparison of the years ended December 31, 2021 and 2020

The following table summarizes our results of operations for the years ended December 31, 2021 and 2020:

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Research and development expenses

The following table summarizes our research and development expenses for the years ended December 31, 2021 and 2020:

The increase in personnel-related costs and stock-based compensation expense was primarily due to increased headcount in our research and development function. The increase in facility-related and other expenses was primarily due to the increased costs of supporting a larger number of research and development personnel, their research efforts and increased rent expense related to our new facility lease. The increase in external manufacturing and research costs and professional and consulting fees was primarily due to the development of our manufacturing process, increased research activity, and the advancement of our programs and product candidates, including conducting IND-enabling studies.

General and administrative expenses

The following table summarizes our general and administrative expenses for the years ended December 31, 2021 and 2020:

The increase in personnel-related costs and stock-based compensation expense was primarily the result of an increase in headcount in our general and administrative function. Professional and consulting fees increased primarily due to accounting, audit and legal services as well as costs associated with ongoing business activities and the costs of operating as a public company. The increase in facility-related and

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other expenses was primarily due to the increased costs of supporting a larger number of general and administrative personnel and increased rent expense related to our new facility lease.

Interest income

Interest income for the years ended December 31, 2021 and 2020 was $0.7 million and $0.1 million, respectively, due to interest earned on invested cash balances.

Interest expense

Interest expense for the year ended December 31, 2020 was $0.4 million due to interest incurred on outstanding borrowings under our loan agreement. We did not incur any interest expense in the year ended December 31, 2021.

Change in success fee obligation

The fair value of the success fee obligation included in our loan agreement increased during the year ended December 31, 2020 by $0.5 million. The obligation was settled in September 2020 and no longer requires recognition.

Other (expense) income, net

Other expense for the year ended December 31, 2021 was less than $0.1 million due to realized losses on the sale of marketable securities. We did not incur any realized losses in the year ended December 31, 2020.

Liquidity and capital resources

Sources of liquidity

Since our inception, we have incurred significant operating losses. We expect to incur significant expenses and operating losses for the foreseeable future as we support our continued research activities and development of our programs and platform. We have not yet commercialized any product candidates, and we do not expect to generate revenue from sales of any product candidates for several years, if at all. To date, we have funded our operations primarily with proceeds from sales of equity securities, borrowings under our loan agreement and, most recently, with proceeds from the sale of common stock in our IPO and the January 2021 offering. As of December 31, 2021 we had cash, cash equivalents and marketable securities of $376.6 million.

In November 2021, we filed a universal shelf registration on Form S-3 to register for sale from time to time up to $400.0 million of common stock, preferred stock, debt securities, warrants and/or units in one or more offerings. Further, in November 2021, we entered into an Open Market Sale AgreementSM with Jefferies LLC, or Jefferies, pursuant to which, from time to time, we may offer and sell shares of our common stock having an aggregate offering price of up to $150.0 million. Sales of common stock through Jefferies may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended. To date, we have not made any sales under our at-the-market offering program.

Cash flows

The following table summarizes our sources and uses of cash for each of the periods presented:

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Operating activities

During the year ended December 31, 2021, operating activities used $119.6 million of cash, due to our net loss of $149.3 million, partially offset by non-cash charges of $20.4 million and net cash provided by changes in our operating assets and liabilities of $9.3 million. Net cash provided by changes in our operating assets and liabilities primarily consisted of a $13.7 million increase in accounts payable and other liabilities, partially offset by a $2.9 million increase in prepayments made for lessor-owned lease assets, and a $1.5 million increase in prepaid expenses and other current assets. During the year ended December 31, 2020, operating activities used $46.5 million of cash, due to our net loss of $59.4 million, partially offset by non-cash charges of $7.8 million and net cash provided by changes in our operating assets and liabilities of $5.1 million. Net cash provided by changes in our operating assets and liabilities primarily consisted of a $8.6 million increase in accounts payable and other liabilities, partially offset by a $3.5 million increase in prepaid expenses and other current assets. Changes in our operating assets and liabilities during these periods were generally due to growth in our business, increased manufacturing activities, the advancement of our research programs and product candidates, including the initiation and advancement of IND-enabling studies and the timing of vendor invoices and payments.

Investing activities

During the year ended December 31, 2021, net cash used in investing activities was $137.9 million due to the purchases of marketable securities of $236.7 million and purchases of property and equipment of $3.6 million, partially offset by maturities of marketable securities of $98.0 million and sales of marketable securities of $4.4 million. During the year ended December 31, 2020, net cash used in investing activities was $45.7 million due primarily to the purchases of marketable securities of $44.5 million and purchases of property and equipment of $1.2 million.

Financing activities

During the year ended December 31, 2021, net cash provided by financing activities was $157.8 million, consisting of $157.2 million in aggregate net proceeds from our follow-on offering completed in January 2021 and $0.6 million in proceeds received from stock option exercises.

During the year ended December 31, 2020, net cash provided by financing activities was $380.7 million, consisting of $246.4 million in aggregate net proceeds from our IPO in September 2020, $134.8 million in net proceeds from issuance of Preferred Stock, and an offset of $0.5 million in the settlement of our success fee obligation.

Funding requirements

We expect our expenses to increase substantially in connection with our ongoing activities, particularly as we advance our research programs into preclinical and clinical development and incur additional costs associated with operating as a public company. The timing and amount of our operating expenditures will depend largely on:

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the identification of additional research programs and product candidates;

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the scope, progress, costs and results of preclinical and clinical development of any product candidates we may develop;

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the costs, timing and outcome of regulatory review of any product candidates we may develop;

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our decision to initiate a clinical trial, not to initiate a clinical trial or to terminate an existing clinical trial;

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changes in laws or regulations applicable to any product candidates we may develop, including but not limited to clinical trial requirements for approvals;

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the cost and timing of obtaining materials to produce adequate product supply for any preclinical or clinical development of any product candidate we may develop;

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the costs and timing of future commercialization activities, including product manufacturing, marketing, sales and distribution, for any product candidate we may develop for which we obtain marketing approval;

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the legal costs involved in prosecuting patent applications and enforcing patent claims and other intellectual property claims;

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additions or departures of key scientific or management personnel;

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our ability to establish and maintain collaborations on favorable terms, if at all, as well as the costs and timing of any collaboration, license or other arrangement, including the terms and timing of any milestone payments thereunder; and

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the costs of operating as a public company.

We believe that our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements into the second half of 2024. We expect that our liquidity will be sufficient to enable us to submit INDs in each of our DM1, DMD and FSHD programs and achieve proof-of-concept data readouts in multiple programs. We have based these estimates on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, and marketing, distribution or licensing arrangements with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders may be materially diluted, and the terms of such securities could include liquidation or other preferences that adversely affect the rights of holders of our common stock. Debt financing and preferred equity financing, if available, may involve agreements that include restrictive covenants that limit our ability to take specified actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. We may be unable to raise additional funds or enter into such other agreements or arrangements when needed, on favorable terms, or at all. If we fail to raise capital or enter into such agreements other arrangements as and when needed, we may have to significantly delay, reduce or eliminate the development or future commercialization of one or more of our product candidates we may develop. See Item 1A. “Risk factors” in this Annual Report on Form 10-K for additional risks associated with our substantial capital requirements.

Contractual and other obligations

We enter into contracts in the normal course of business with CROs, CMOs and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These contracts typically do not contain minimum purchase commitments and are generally cancelable by us upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of our service providers, up to the date of cancellation and in the case of certain arrangements with CROs and CMOs may include non-cancelable fees.

We have also entered into a license agreement with the University of Mons under which we are obligated to make specified milestone and royalty payments. The payment obligations under this agreement are contingent upon future events, such as our achievement of specified development, regulatory and commercial milestones, or generating product sales. We are unable to estimate the timing or likelihood of achieving these milestones or generating future product sales. For additional information about our license agreement with the University of Mons and amounts that could become payable in the future under that agreement, see Item 1. “Business—Intellectual Property—License Agreement with the University of Mons” in this Annual Report.

On December 4, 2020, we entered into a lease agreement for office and laboratory space, which was amended in January 2021, March 2021, and June 2021. The lease has a term of 8.5 years that commenced when we gained access to the office and laboratory space in September 2021. Our obligation for the payment of the base rent begins in April 2022 and will be $0.4 million per month,

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increasing up to $0.5 million per month during the term of the lease. We have two options to extend the term of the lease, each for a period of an additional five years.

Critical accounting policies and significant judgments and estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States. The preparation of our consolidated financial statements and related disclosures requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, costs and expenses, and the disclosure of contingent assets and liabilities in our financial statements. We base our estimates on historical experience, known trends and events and various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. We evaluate our estimates and assumptions on an ongoing basis. Our actual results may differ from these estimates under different assumptions or conditions.

We define our critical accounting policies as those accounting principles generally accepted in the United States of America that require us to make subjective estimates and judgments about matters that are uncertain and are likely to have a material impact on our financial condition and results of operations as well as the specific manner in which we apply those principles. Management has determined that our most critical accounting policies are those relating to accrued research and development expenses and stock-based compensation. As we advance our product candidates into clinical development, we expect research and development expenses and, in particular, our accounting for accrued research and development expenses to be an increasingly important critical accounting policy. There have been no significant changes in estimates for accrued research and development expenses and stock-based compensation for the year ended December 31, 2021.

Accrued research and development expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves reviewing open contracts and purchase orders, communicating with our service providers and applicable personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of actual costs. The majority of our service providers invoice us in arrears for services performed, on a pre-determined schedule or when contractual milestones are met; however, some require advance payments. We make estimates of our accrued expenses as of each balance sheet date in the financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of these estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses include fees paid to:

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vendors in connection with preclinical development activities;

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CROs and investigative sites in connection with research activities; and

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CMOs in connection with the production of research materials.

We measure the expense recognized based on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple CMOs and CROs that supply, conduct and manage preclinical and clinical studies on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the achievement of specified milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or the amount of prepaid expenses accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, there

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have been no material differences between our estimates of such expenses and the amounts actually incurred.

Stock-based compensation

We measure stock-based awards granted to employees and directors based on fair value on the date of the grant using the Black-Scholes option-pricing model for options. Compensation expense for those awards is recognized over the requisite service period, which is generally the vesting period of the respective award. We use the straight-line method to record the expense of awards with service-based vesting conditions. We use the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing when achievement of the performance condition becomes probable.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of our common stock and assumptions we make for the volatility of our common stock, the expected term of our stock options, the risk-free interest rate for a period that approximates the expected term of our stock options and our expected dividend yield.

Prior to our IPO, there was no public market for our common stock, and consequently, the estimated fair value of our common stock was determined by our board of directors as of the date of each option grant, with input from management, considering third-party valuations of our common stock as well as our board of directors’ assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent third-party valuation through the date of the grant. Since our IPO, we have determined the fair market value of our common stock using the closing price of our common stock as reported on the Nasdaq Global Select Market.

Recently issued accounting pronouncements

Refer to Note 2, “Summary of Significant Accounting Policies,” in the accompanying notes to the consolidated financial statements for a discussion of recent accounting pronouncements that were adopted in 2021.

Emerging growth company and smaller reporting company status

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. We may take advantage of these exemptions until we are no longer an “emerging growth company.” Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. We have elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, our financial statements may not be comparable to companies that comply with public company effective dates. We may take advantage of these exemptions until December 31, 2025 or until such earlier time that we are no longer an “emerging growth company.”

We are also a “smaller reporting company” as defined in Rule 12b-2 under the Exchange Act. We may continue to be a smaller reporting company if either (i) the market value of our shares held by non-affiliates is less than $250 million or (ii) our annual revenue is less than $100 million during the most recently completed fiscal year and the market value of our shares held by non-affiliates is less than $700 million as of the last business day of our most recently completed second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies.

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