DYN US Equity☆

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and related notes appearing at the end of this Annual Report on Form 10-K. Some of the information contained in this discussion and analysis or set forth elsewhere in this Annual Report on Form 10-K, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the “Risk Factors” section of this Annual Report on Form 10-K, our actual results could differ materially from the results described in, or implied by, the forward-looking statements contained in the following discussion and analysis.

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:

Year Ended December 31,

Operating expenses:

Other income (expense):

Other income (expense), net (1,416 ) (54 ) (1,362 )

Research and development expenses

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

Year Ended December 31,

Direct research and development expenses by product candidate:

Unallocated research and development expenses:

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:

Year Ended December 31,

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:

Year Ended December 31,

Net cash used in operating activities $ (188,158 ) $ (153,645 )

Net cash provided by (used in) investing activities 83,311 87,202

Net cash provided by financing activities 54,322 37,390

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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Item 7A. Quantitative and Qualitative Disclosures About Market Risk.

We are a smaller reporting company as defined by Rule 12b‐2 of the Exchange Act and are not required to provide the information required under this item.

Item 8. Financial Statements and Supplementary Data.

The financial statements required to be filed pursuant to this Item 8 are appended to this Annual Report on Form 10-K. An index of those financial statements is found in Item 15 of Part IV of this Annual Report on Form 10-K.

Item 9. Changes in and Disagreements With Accountants on Accounting and Financial Disclosure.

None.

Item 9A. Controls and Procedures.

Evaluation of Disclosure Controls and Procedures

Our management, under the supervision and with the participation of our Chief Executive Officer and Senior Vice President, Head of Finance and Administration (our principal executive officer and principal financial officer, respectively), evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2023. The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act means controls and other procedures of an issuer that are designed to ensure that information required to be disclosed by an issuer in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the SEC’s rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by an issuer in the reports that it files or submits under the Exchange Act is accumulated and communicated to the issuer’s management, including its principal executive and principal financial officers, or persons performing similar functions, as appropriate to allow timely decisions regarding required disclosure.

Management recognizes that any disclosure controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures. Based on the evaluation of our disclosure controls and procedures as of December 31, 2023, our Chief Executive Officer and Senior Vice President, Head of Finance and Administration concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.

Management’s Annual Report on Internal Control Over Financial Reporting and Attestation Report of Registered Public Accounting Firm

Our management is responsible for establishing and maintaining adequate internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act). Our internal control over financial reporting is a process designed under the supervision of our principal executive and principal financial officer to provide reasonable assurance regarding the reliability of our financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. Management assessed our internal control over financial reporting as of December 31, 2023. Management based its assessment on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on that evaluation, our management concluded that our internal control over financial reporting was effective as of December 31, 2023.

This Annual Report does not include an attestation report of our independent registered public accounting firm due to an exemption established by the JOBS Act for “emerging growth companies”.

Changes in Internal Control over Financial Reporting

129

There were no changes in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d‐15(f) under the Exchange Act) that occurred during the three months ended December 31, 2023 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Item 9B. Other Information.

Director and Officer Trading Arrangements

A portion of the compensation of our directors and officers (as defined in Rule 16a-1(f) under the Securities Exchange Act of 1934, as amended, or the Exchange Act, is in the form of equity awards and, from time to time, directors and officers engage in open-market transactions with respect to the securities acquired pursuant to such equity awards or other securities of ours, including to satisfy tax withholding obligations when equity awards vest or are exercised, and for diversification or other personal reasons.

Transactions in our securities by directors and officers are required to be made in accordance with our insider trading policy, which requires that the transactions be in accordance with applicable U.S. federal securities laws that prohibit trading while in possession of material nonpublic information. Rule 10b5-1 under the Exchange Act provides an affirmative defense that enables directors and officers to prearrange transactions in our securities in a manner that avoids concerns about initiating transactions while in possession of material nonpublic information.

The following table describes, for the fourth quarter of 2023, each trading arrangement for the sale or purchase of our securities adopted or terminated by our directors and officers that is either (1) a contract, instruction or written plan intended to satisfy the affirmative defense conditions of Rule 10b5-1(c), which we refer to as a “Rule 10b5-1 trading arrangement” or (2) a “non-Rule 10b5-1 trading arrangement” (as defined in Item 408(c) of Regulation S-K):

______________

(1)

This trading plan had a scheduled expiration date of March 31, 2025. The number of shares of the Company's common stock to be sold under the plan was up to 223,065 shares.

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspection

Not applicable.

130

PART III

Item 10. Directors, Executive Officers and Corporate Governance.

Except to the extent provided below, the information required by this Item 10 will be included in our definitive proxy statement to be filed with the SEC with respect to our 2024 Annual Meeting of Stockholders which we intend to file not later than 120 days after the end of our fiscal year ended December 31, 2023 and is incorporated herein by reference.

We have adopted a written code of business conduct and ethics that applies to our directors, officers, employees and designated agents, including our principal executive officer, principal financial officer, principal accounting officer, or persons performing similar functions. A current copy of the code is posted on the investor relations section of our website, which is located at http://www.dyne-tx.com. If we make any substantive amendments to, or grant any waivers from, the code of business conduct and ethics for any officer or director, we will disclose the nature of such amendment or waiver on our website.

Item 11. Executive Compensation.

The information required by this Item 11 will be included in our definitive proxy statement to be filed with the SEC with respect to our 2024 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

The information required by this Item 12 will be included in our definitive proxy statement to be filed with the SEC with respect to our 2024 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 13. Certain Relationships and Related Transactions, and Director Independence.

The information required by this Item 13 will be included in our definitive proxy statement to be filed with the SEC with respect to our 2024 Annual Meeting of Stockholders and is incorporated herein by reference.

Item 14. Principal Accounting Fees and Services.

The information required by this Item 14 will be included in our definitive proxy statement to be filed with the SEC with respect to our 2024 Annual Meeting of Stockholders and is incorporated herein by reference.

131

PART IV

Item 15. Exhibits and Financial Statement Schedules.

(1) Consolidated Financial Statements

The following documents are included on pages F-1 through F-20 attached hereto and are filed as part of this Annual Report on Form 10-K.

Report of Independent Registered Public Accounting Firm F-2

Consolidated Balance Sheets F-3

Consolidated Statements of Operations and Comprehensive Loss F-4

Consolidated Statements of Cash Flows F-6

Notes to Consolidated Financial Statements F-7

(2) Financial Statement Schedules

All financial statement schedules have been omitted because they are either not required or not applicable or the information is included in the consolidated financial statements or the notes thereto.

(3) Exhibits

The following is a list of exhibits filed as part of this Annual Report on Form 10-K.

ExhibitNumber Description

132

133

21.1* Subsidiaries of the Registrant

97* Dodd-Frank Compensation Recovery Policy

101.INS XBRL Instance Document

101.SCH Inline XBRL Taxonomy Extension Schema With Embedded Linkbase Documents

* Filed herewith.

† Portions of this exhibit have been omitted pursuant to Item 601(b)(10)(iv) of Regulation S-K.

# Management contract or compensatory plan or arrangement filed in response to Item 15(a)(3) of the Instructions to the Annual Report on Form 10-K.

Item 16. Form 10-K Summary

None.

134

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this Report to be signed on its behalf by the undersigned, thereunto duly authorized.

DYNE THERAPEUTICS, INC.

Date: March 5, 2024 By: /s/ Joshua Brumm

Joshua Brumm

President and Chief Executive Officer

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, this Report has been signed below by the following persons on behalf of the Registrant in the capacities and on the dates indicated.

Name Title Date

Joshua Brumm

Richard Scalzo

/s/ Jason Rhodes Director and Chairman of the Board March 5, 2024

Jason Rhodes

/s/ Ed Hurwitz Director March 5, 2024

Ed Hurwitz

/s/ Carlo Incerti, M.D. Director March 5, 2024

Carlo Incerti, M.D.

/s/ Dirk Kersten Director March 5, 2024

Dirk Kersten

/s/ David Lubner Director March 5, 2024

David Lubner

/s/ Catherine Stehman-Breen, M.D. Director March 5, 2024

Catherine Stehman-Breen, M.D.

135

Index to Consolidated Financial Statements

Report of Independent Registered Public Accounting Firm (PCAOB ID No. 34) F-2

Consolidated Balance Sheets F-3

Consolidated Statements of Operations and Comprehensive Loss F-4

Consolidated Statements of Stockholders’ Equity F-5

Consolidated Statements of Cash Flows F-6

Notes to Consolidated Financial Statements F-7

Report of Independent Registered Public Accounting Firm

To the stockholders and board of directors of Dyne Therapeutics, Inc.

Opinion on the financial statements

We have audited the accompanying consolidated balance sheets of Dyne Therapeutics, Inc. and subsidiary (the “Company”) as of December 31, 2023 and 2022, and the related consolidated statements of operations and comprehensive loss, stockholders’ equity, and cash flows for the years then ended and the related notes to the financial statements (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the years then ended, in conformity with accounting principles generally accepted in the United States of America.

Basis for opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulation of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

/s/ Deloitte & Touche LLP

Boston, Massachusetts

March 5, 2024

We have served as the Company’s auditor since 2020.

F-2

Dyne Therapeutics, Inc.

Consolidated Balance Sheets

December 31,

(in thousands, except share and per share data) 2023 2022

Assets

Current assets:

Prepaid expenses and other current assets 6,275 9,582

Liabilities and Stockholders’ Equity

Current liabilities:

Accrued expenses and other current liabilities 23,439 18,219

Lease liabilities, net of current portion 22,695 25,873

Commitments and contingencies (Note 10)

Stockholders’ equity

Accumulated other comprehensive loss — (571 )

Total liabilities and stockholders’ equity $ 165,082 $ 306,325

The accompanying notes are an integral part of these financial statements.

F-3

Dyne Therapeutics, Inc.

Consolidated Statements of Operations and Comprehensive Loss

Year Ended December 31,

(in thousands, except share and per share data) 2023 2022

Operating expenses:

Other (expense) income:

Other income (expense), net (1,416 ) (54 )

Total other (expense) income, net 6,225 2,863

Net loss per share, basic and diluted $ (3.95 ) $ (3.23 )

Comprehensive loss:

Other comprehensive loss:

Unrealized gains (losses) on marketable securities, net 571 (302 )

The accompanying notes are an integral part of these financial statements.

F-4

Dyne Therapeutics, Inc.

Consolidated Statements of Stockholders’ Equity

(in thousands, except share data) Shares Amount

Vesting of restricted shares 38,141 — — — — —

Vesting of restricted stock units 289,626 — — — — —

Unrealized losses on marketable securities — — — (302 ) — (302 )

Vesting of restricted stock units 490,269 — — — — —

Unrealized gains on marketable securities — — — 571 — 571

The accompanying notes are an integral part of these financial statements.

F-5

Dyne Therapeutics, Inc.

Consolidated Statements of Cash Flows

Year Ended December 31,

Cash flows from operating activities:

Adjustments to reconcile net loss to net cash used in operating activities:

Depreciation and amortization expense 1,673 1,683

Loss on sale of marketable securities 23 34

Loss on disposal of property and equipment 118 —

Changes in operating assets and liabilities:

Prepaid expenses and other current assets 3,337 (4,144 )

Accounts payable and other liabilities 22,970 (1,235 )

Cash flows from investing activities:

Purchases of property and equipment (729 ) (3,067 )

Sales of marketable securities 1,829 3,154

Net cash provided by investing activities 83,311 87,202

Cash flows from financing activities:

Proceeds from exercise of stock options 1,953 529

Net cash provided by financing activities 54,322 37,390

Net decrease in cash, cash equivalents and restricted cash (50,525 ) (29,053 )

Cash, cash equivalents and restricted cash, beginning of year 174,466 203,519

Cash, cash equivalents and restricted cash, end of year $ 123,941 $ 174,466

Supplemental disclosures of cash flow information:

Purchase of property and equipment in accounts payable $ 12 $ 85

The accompanying notes are an integral part of these financial statements.

F-6

Dyne Therapeutics, Inc.

Notes to Consolidated Financial Statements

1. Nature of Business and Basis of Presentation

Dyne Therapeutics, Inc. (the “Company”) is a clinical-stage muscle disease company focused on advancing innovative life-transforming therapeutics for people living with genetically driven diseases. The Company was incorporated in Delaware on December 1, 2017 and has a principal place of business in Waltham, Massachusetts.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for its product candidates, fluctuations in operating results, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes and the ability to secure additional capital to fund operations. Product candidates and programs currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization of a product. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The accompanying consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Since inception, the Company has funded its operations with proceeds from the sales of equity securities. The Company expects to continue to generate operating losses for the foreseeable future. In January 2024, the Company received net proceeds of $323.9 million in a public offering of the Company's common stock (see Note 11). The Company expects that its cash, cash equivalents, marketable securities and the proceeds from the January 2024 offering will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance of these consolidated financial statements.

To continue its development efforts, the Company will need to obtain substantial additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and/or licensing arrangements in order to fund its research and development and ongoing operating expenses. The Company may not be able to obtain financing on acceptable terms, when needed or at all, and the Company may not be able to enter into collaborations, strategic alliances or licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Any collaborations, strategic alliances or licensing arrangements may require the Company to relinquish rights to certain of its technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to the Company. If the Company is unable to obtain funding, the Company could be forced to delay, limit, reduce or eliminate some or all of its research and development programs, pipeline expansion or future commercialization efforts or grant rights to develop and market product candidates, which could adversely affect its business prospects. Although management will continue to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations when needed or at all.

2. Summary of Significant Accounting Policies

The accompanying consolidated financial statements reflect the operations of the Company and the Company’s wholly-owned subsidiary, Dyne Therapeutics Securities Corporation. Intercompany balances and transactions have been eliminated in consolidation. The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles (“GAAP”) in the United States of America. Any reference in these notes to applicable guidance is meant to refer to the

F-7

authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual of research and development expenses and stock-based compensation expense. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results may differ from those estimates or assumptions.

Concentrations of credit risk and of significant suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company believes the depository institutions in which the cash and cash equivalents are held are of high-credit quality. The Company maintains its cash equivalents in money market funds that invest in U.S. treasury securities and highly liquid investments maturing within 90 days from the date of purchase. The Company’s marketable securities as of December 31, 2023 consisted of commercial paper, certificates of deposit, corporate debt securities and U.S. treasury securities. The Company has adopted an investment policy that limits the amounts the Company may invest in the securities of any single issuer with the exclusion of the U.S. government. The Company has not experienced any credit losses.

The Company is dependent on a small number of third-party suppliers for its drug substance and drug product. In particular, the Company relies, and expects to continue to rely, on third-party suppliers for certain materials and components required for the development of its programs and future production of any product candidates it may develop for its programs. These programs could be adversely affected by a significant interruption in the supply process.

Marketable securities

The Company’s marketable securities consist of commercial paper, certificates of deposit, U.S. treasury notes and corporate debt securities and are classified as available-for-sale which are reported at fair value. Unrealized losses on available-for-sale debt securities are reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses are based on the specific identification method and are included as a component of other income (expense), net in the consolidated statements of operations and comprehensive loss.

The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the statement of operations and comprehensive loss. No such adjustments were necessary during the periods presented.

Leases

Under ASC 842, at the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances presented in the arrangement, including whether the Company controls the use of identified assets. The Company classifies leases with

F-8

a term greater than one year as either operating or finance leases at the lease commencement date and records a right-of-use assets and current and non-current lease liabilities, as applicable on the balance sheet. The Company has elected not to recognize on the balance sheet leases with terms of one year or less, but payments are recognized as expense on a straight-line basis over the lease term. If a lease includes options to extend the lease term, the Company does not assume the option will be exercised in its initial lease term assessment unless there is reasonable certainty that the Company will renew based on an assessment of economic factors present as of the lease commencement date. The Company monitors its plans to renew its material lease each reporting period.

Lease liabilities and the corresponding right-of-use assets are recorded based on the present value of lease payments over the remaining lease term. The present value of future lease payments are discounted using the interest rate implicit in lease contracts if that rate is readily determinable; otherwise the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis over a similar term, the amount of the lease payments in a similar economic environment. After lease commencement and the establishment of a right-to-use asset and operating lease liability, lease expense is recorded on a straight-line basis over the lease term.

The Company enters into contracts that contain both lease and non-lease components. Non-lease components include costs that do not provide a right-to-use a leased asset but instead provide a service, such as maintenance costs. The Company has elected to account for the lease and non-lease components together as a single component for all classes of underlying assets. Variable costs associated with the lease, such as maintenance and utilities, are not included in the measurement of right-to-use assets and lease liabilities but rather are expensed when the events determining the amount of variable consideration to be paid have occurred.

Property and equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset class.

Costs for capital assets not yet placed into service are capitalized as construction-in-process and depreciated once placed into service. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance which do not improve or extend the life of the respective assets are charged to expense as incurred.

Impairment of long-lived assets

Long-lived assets consist of property and equipment. The Company evaluates the recoverability of its long-lived assets when circumstances indicate that an event of impairment may have occurred. The Company recognizes an impairment loss only if the carrying amount of a long-lived asset is not recoverable based on its undiscounted future cash flows. Impairment is measured based on the difference between the carrying value of the related assets and the fair value of such assets. The Company has not recorded any impairment charges in the periods presented in these financial statements.

Segment information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer (“CEO”). The CEO views the Company’s operations and manages the business as one operating segment.

F-9

Research and development costs

Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, laboratory supplies, depreciation and amortization, manufacturing expenses and external costs of vendors engaged to conduct clinical and preclinical development activities as well as the cost of licensing technology.

Upfront payments and milestone payments made for the licensing of technology are expensed as research and development expenses in the period in which they are incurred. Advance payments 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 consumed or the services are performed.

Research and manufacturing contract costs and accruals

The Company has entered into various research and development and manufacturing contracts. These agreements are generally cancelable, and related payments are recorded as the corresponding expenses are incurred. The Company records accruals for estimated ongoing costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the research studies and manufacturing activities, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Income taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Fair value measurements

Certain assets and liabilities are carried at fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most

F-10

advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

Level 1—Unadjusted quoted prices in active markets that are accessible to the reporting entity at the measurement date for identical assets and liabilities.

•

Level 2—Inputs other than quoted prices in active markets for identical assets and liabilities that are observable either directly or indirectly for substantially the full term of the asset or liability. Level 2 inputs include the following:

•

quoted prices for similar assets and liabilities in active markets;

•

quoted prices for identical or similar assets or liabilities in markets that are not active;

•

observable inputs other than quoted prices that are used in the valuation of the asset or liabilities (e.g., interest rate and yield curve quotes at commonly quoted intervals); and

•

inputs that are derived principally from or corroborated by observable market data by correlation or other means.

•

Level 3—Unobservable inputs for the assets or liability (i.e., supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

Net loss per share

Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. Diluted net loss is computed by adjusting net loss to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents.

The following potentially dilutive common stock equivalents, presented based on amounts outstanding at each period end, were excluded from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:

Year Ended December 31,

Stock-based compensation

The Company accounts for stock option awards at fair value and measures fair value using the Black-Scholes option-pricing model as of the grant date. For restricted stock unit awards, the fair value is based on the closing price of the Company's common stock on the date of grant. Stock-based compensation costs are recognized as expense over the requisite service period, which is generally the vesting period, on a straight-line basis for all time-vested awards. For awards with performance based vesting conditions, the timing of expense recognition is based upon management’s estimation of the probability of the performance condition being achieved. Upon determination of the performance condition being deemed probable of achievement, expense is recognized over the remaining service period for performance-based awards. Forfeitures are recognized as they occur for all awards.

F-11

Comprehensive loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive loss was unrealized gains (losses) on marketable securities.

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for the Company in the consolidated financial statements for the year ending December 31, 2024, and interim periods beginning after January 1, 2025. The adoption of this standard only impacts disclosures and is not expected to have a material impact on the Company’s consolidated financial statements.

3. Cash, Cash Equivalents and Restricted Cash

Cash includes cash in readily available checking accounts and cash equivalents include money market funds that invest in U.S. treasury securities and all highly liquid investments maturing within 90 days from the date of purchase.

Amounts included in restricted cash represent amounts pledged as collateral for letters of credit required for security deposits on the Company’s leased facilities.

Cash, cash equivalents and restricted cash consisted of the following:

December 31, December 31,

4. Fair Value Measurements

The following tables set forth marketable securities for the periods presented:

(in thousands) Amortized Cost Unrealized Gains Unrealized Losses Total

Corporate debt securities 1,474 — — 1,474

(in thousands) Amortized Cost Unrealized Gains Unrealized Losses Total

The scheduled maturity for the Company's marketable securities at December 31, 2023 was less than one year.

F-12

The following tables set forth by level, within the fair value hierarchy (see Note 2), the assets carried at fair value on a recurring basis for the periods presented:

Fair Value Measurements as of December 31, 2023

(in thousands) Level 1 Level 2 Level 3 Total

Assets:

Cash equivalents

Marketable securities

Corporate debt securities — 1,474 — 1,474

Fair Value Measurements as of December 31, 2022

(in thousands) Level 1 Level 2 Level 3 Total

Assets:

Cash equivalents

Money market funds $ 9,381 $ — $ — $ 9,381

Corporate debt securities — 3,852 — 3,852

U.S. treasury notes 811 — — 811

Marketable securities

The fair value of U.S. government treasury notes and commercial paper were determined by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. Certificates of deposit and corporate debt securities were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy.

There were no transfers between Level 1, Level 2, or Level 3 during the periods presented.

Financial instruments not recorded at fair value

The carrying values of cash, cash equivalents, accounts payable and accrued expenses that are reported on the balance sheets approximate their fair value due to the short-term nature of these assets and liabilities.

5. Property and Equipment

Property and equipment consisted of the following:

December 31,

Office and computer equipment 2,091 1,898

Construction in process 431 906

Less accumulated depreciation and amortization (5,288 ) (3,629 )

Property and equipment—net $ 4,780 $ 5,945

Depreciation expense totaled $1.7 million and $1.7 million for the years ended December 31, 2023 and 2022, respectively.

F-13

6. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:

December 31,

Facility costs — 1

7. Stockholders' Equity

Common Stock

In November 2021, the Company entered into an Open Market Sale Agreement (the "Sales Agreement") with Jefferies LLC ("Jefferies") as the Company's sales agent, pursuant to which, from time to time, the Company may offer and sell shares of our common stock having an aggregate offering price of up to $150.0 million in an "at-the-market" offering. During the fiscal year ended December 31, 2023, the Company 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. The Company sold such shares at a weighted average price of $12.01 per share.

On January 4, 2024, the Company notified Jefferies that it was suspending and terminating the prospectus related to the Sales Agreement for the Company's "at-the-market" offering. As of December 31, 2023, the Company had issued and sold an aggregate of 7,934,148 shares of its Common Stock under its “at-the-market” offering program with Jefferies for aggregate net sale proceeds of $89.2 million, after deducting sales commissions and offering expenses.

2020 Stock Incentive Plan

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Stock Incentive Plan (the "2020 Plan"), which became effective on September 16, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to employees, directors, consultants and advisors of the Company. The 2020 Plan is administered by the Company’s board of directors or by a committee appointed by the board of directors. Upon the effectiveness of the 2020 Plan, the Company ceased granting awards under the 2018 Stock Incentive Plan. The number of shares initially reserved for issuance under the 2020 Plan was 4,884,233. The number of shares of common stock reserved for issuance under the 2020 Plan may automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lower of (1) 5% of the shares of common stock outstanding on such date and (2) an amount determined by the Company’s board of directors. On January 1, 2024, 3,073,437 shares were added to the shares reserved for issuance under the 2020 Plan in the fourth of these annual increases.

As of December 31, 2023, 2,272,111 shares remained available for future issuance under the 2020 Plan.

2020 Employee Stock Purchase Plan

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective September 16, 2020. The 2020 ESPP is administered by the Company’s board of directors or by a committee appointed by the board of directors. The 2020 ESPP initially provides participating employees with the opportunity to

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purchase up to an aggregate of 488,414 shares of common stock. The number of shares of common stock reserved for issuance under the 2020 ESPP may automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lowest of (1) 1,953,656 shares of common stock, (2) 1% of the shares of common stock outstanding on such date, and (3) an amount determined by the board of directors. As of December 31, 2023, no offering periods have commenced under the 2020 ESPP and 488,414 shares remained available for issuance.

Stock option valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The fair value is determined based upon the quoted price of the Company’s common stock. The Company lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The assumptions that the Company used to determine the grant-date fair value of options granted were as follows:

Year Ended December 31,

Expected volatility 66% 68%

Expected term (in years) 6 6

Expected dividend yield — —

Stock option activity

A summary of the Company's stock option activity and related information for the year ended December 31, 2023 is as follows:

The intrinsic value of options exercised for the years ended December 31, 2023 and 2022 totaled $8.1 million and $3.2 million, respectively. The weighted-average grant date fair value of the options granted during the years ended December 31, 2023 and 2022 was $7.28 per share and $6.24 per share, respectively. As of December 31, 2023 there was $28.3 million of unrecognized compensation expense, which the Company expects to recognize over a weighted-average period of 2.4 years.

Restricted stock units

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A restricted stock unit (“RSU”) represents the right to receive one share of common stock upon vesting of the RSU. The Company grants RSUs with service conditions that vest in four equal annual installments provided that the employee remains employed with the Company, RSUs with service conditions that vest in sixteen equal quarterly installments provided that the employee remains employed with the Company and RSUs with performance-based vesting conditions. As of December 31, 2023, there are no RSUs with performance-based vesting conditions outstanding. The fair value of each RSU is based on the closing price of the Company’s common stock on the date of grant. A summary of the Company’s RSU activity and related information for the year ended December 31, 2023 is as follows:

Number of Shares Underlying RSUs Weighted AverageGrant Date Fair Value

The weighted average grant date fair value of RSUs granted during the year ended December 31, 2022 was $10.41. As of December 31, 2023, there was $36.2 million of unrecognized compensation costs ​​​​​​​related to unvested RSUs, which are expected to be recognized over a weighted-average period of 3.4 years.

The Company recorded stock-based compensation expense in the following expense categories of its statements of operations:

Year Ended December 31,

8. Income Taxes

There is no provision for income taxes because the Company has historically incurred net operating losses and maintains a full valuation allowance against its deferred tax assets.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:

Year Ended December 31,

Federal income tax expense at statutory rate 21 % 21 %

State taxes—net of federal benefit — 1

State tax law changes (10 ) —

Permanent differences and other (1 ) 4

Federal & state R&D credits 3 4

Increase in valuation allowance (13 ) (30 )

Effective income tax rate 0 % 0 %

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Significant components of the Company’s net deferred tax assets at December 31, 2023 and 2022 are as follows:

Year Ended December 31,

Deferred tax assets:

Total net deferred tax assets 6,011 8,802

Deferred tax liabilities:

Total deferred tax liability (6,011 ) (8,802 )

Total deferred tax assets (liabilities) $ — $ —

As of December 31, 2023, the Company 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, the Company also had federal and state research and development tax credit carryforwards $17.1 million and $2.9 million, respectively, which begin to expire in 2039 and 2033, respectively.

Utilization of the net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company completed a Section 382 study of transactions in its stock through January 25, 2021 and concluded that it had experienced ownership changes since inception that it believes under Section 382 and 383 of the Code will result in limitations on its ability to use certain pre-change NOLs and credits. In addition, the Company may experience subsequent ownership changes as a result of future equity offerings or other changes in the ownership of its stock, some of which are beyond the Company's control. As a result, the amount of the NOLs and tax credit carryforwards presented in these consolidated financial statements could be limited. Similar provisions of state tax law may also apply to limit the use of accumulated state tax attributes.

The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of net operating loss carryforwards and research and development tax credit carryforwards. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and concluded that it is more likely than not that the Company will not recognize the benefits of its federal and state deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 2023 and 2022. The increase in the valuation allowance for deferred tax assets during the years ended December 31, 2023 and 2022 related primarily to the increase in net operating loss carryforwards.

Changes in the valuation allowance were as follows:

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Year Ended December 31,

Valuation allowance at the beginning of year $ 113,622 $ 63,546

Decreases recorded as benefit to income tax provision — —

Increases recorded to income tax provision 32,153 50,076

The Company’s policy is to record estimated interest and penalties related to uncertain tax positions in income tax expense. The Company has no amounts recorded for any unrecognized tax positions, accrued interest or penalties as of December 31, 2023 and 2022.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by U.S. federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company’s tax returns are open under statute from 2020 to the present.

9. Leases

In December 2020, the Company entered into a lease agreement, (the “Lease”), pursuant to which the Company leases 68,187 square feet of office and laboratory space located in Waltham, Massachusetts (the “Premises”). The Lease has a term ofeight years and six months and the Company gained access to the Premises in September 2021. The Company has two options to extend the term of the Lease, each for a period of an additional five years; however, those renewals were not considered reasonably certain and were not included in the measurement of the right of use assets or lease obligation.

Summary of lease costs

The Company does not have any finance leases.

The components of lease cost were as follows:

Year Ended December 31,

Supplemental disclosure of cash flow information for the lease was as follows:

Year Ended December 31,

Operating cash payments for operating leases $ 4,632 $ 3,247

The Company was unable to determine the interest rate implicit in the lease and used the Company's IBR as determined from a market analysis of peer borrowings. The weighted-average remaining lease term and discount rate for the lease was as follows:

As of December 31,

Weighted-average remaining lease term - operating leases 6.25 years 7.25 years

Weighted-average discount rate - operating leases 5.80 % 5.80 %

Future minimum lease payments under the non-cancelable operating lease consisted of the following as of December 31, 2023:

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Year Ending December 31, (in thousands)

Total future minimum lease payments 32,770

Less: imputed interest (5,355 )

Present value of lease liabilities $ 27,415

Lease liability 4,720

Lease liability, net of current portion 22,695

Total lease liability $ 27,415

10. Commitments and Contingencies

Legal proceedings

The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to any such legal proceedings.

Other contractual obligations

The Company enters into contracts in the normal course of business with 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 the Company upon written notice. Payments due upon cancellation consist of payments for services provided or expenses incurred, including noncancelable obligations of the service providers, up to the date of cancellation and in the case of certain arrangements may include non-cancelable fees.

11. Subsequent Events

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

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