Quarterly Report for Quarter Ending September 30, 2024 (Form 10-Q)

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1. Nature of the Business and Basis of Presentation

Fulcrum Therapeutics, Inc. (the "Company" or "Fulcrum") was incorporated in Delaware on August 18, 2015. The Company is focused on developing small molecules to improve the lives of patients with genetically-defined rare diseases in areas of high unmet medical need.

The Company is subject to a number of risks similar to other companies in the biotechnology industry, including, but not limited to, risks of failure of preclinical studies and clinical trials, dependence on key personnel, protection of proprietary technology, reliance on third party organizations, risks of obtaining regulatory approval for any product candidate that it may develop, development by competitors of technological innovations, compliance with government regulations, and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing, and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel 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.

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America ("GAAP"). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification ("ASC") and Accounting Standards Updates ("ASU") of the Financial Accounting Standards Board ("FASB").

The accompanying consolidated financial statements and footnotes to the financial statements have been prepared on the same basis as the most recently audited annual consolidated financial statements and, in the opinion of management, reflect all normal recurring adjustments necessary for the fair presentation of the Company's financial position as of September 30, 2024 and the results of its operations and its cash flows for the three and nine months ended September 30, 2024 and 2023. The results for the three and nine months ended September 30, 2024 are not necessarily indicative of results to be expected for the year ending December 31, 2024, any other interim periods, or any future year or period. These consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements and the notes thereto for the year ended December 31, 2023 included in the Company's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on February 27, 2024 (the "Annual Report on Form 10-K").

Sales of Common Stock

In January 2023, the Company completed a public offering of its common stock and issued and sold 9,615,384shares of common stock at a public offering price of $13.00per share, resulting in net proceeds of $117.3million after deducting underwriting discounts and commissions and offering expenses.

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Liquidity

The Company has incurred recurring losses and negative cash flows from operations since inception and has primarily funded its operations with proceeds from the sale of shares of its capital stock and from upfront payments received from collaboration and license agreements. As of September 30, 2024, the Company had an accumulated deficit of $502.8million. The Company expects its operating losses and negative operating cash flows to continue into the foreseeable future as it continues to expand its research and development efforts. The Company expects to finance its future cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements.

The Company expects that its cash, cash equivalents, and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the date of issuance of these financial statements. However, the Company has based this estimate on assumptions that may prove to be wrong, and its operating plan may change as a result of many factors currently unknown to it. As a result, the Company could deplete its capital resources sooner than it currently expects. If the Company is unable to raise additional funds through equity or debt financings when needed, it may be required to delay, limit, reduce or terminate development or future commercialization efforts or grant rights to develop and market product candidates that it would otherwise prefer to develop and market itself.

2. Summary of Significant Accounting Policies

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3. Fair Value Measurements

There were notransfers between fair value levels during the three and nine months ended September 30, 2024.

4. Cash Equivalents and Marketable Securities

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There were nosales of marketable securities during the three and nine months ended September 30, 2024. As of September 30, 2024, the Company held 6debt securities that were in an unrealized loss position for less than 12 months with an aggregate fair value of $8.1million. As of September 30, 2024, the Company held 4debt securities that were in an unrealized loss position for greater than 12 months with an aggregate fair value of $14.1million. As of September 30, 2024, the aggregate fair value of marketable securities with a remaining contractual maturity of greater than one year was $10.9million.

The Company has the intent and ability to hold its debt securities until recovery. As a result, the Company did notrecord any charges for credit-related impairments for its marketable securities for the three and nine months ended September 30, 2024.

5. Property and Equipment, Net

Depreciation expense for the three months ended September 30, 2024 and 2023was $0.4million and $0.5million, respectively. Depreciation expense for the nine months ended September 30, 2024 and 2023was $1.2million and $1.7million, respectively.

6. Additional Balance Sheet Detail

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Accrued expenses and other current liabilities consisted of the following (in thousands):

7. Preferred Stock

As of September 30, 2024 and December 31, 2023, 5,000,000shares of undesignated preferred stock were authorized. Noshares of preferred stock were issued or outstanding as of September 30, 2024 and December 31, 2023.

Nodividends have been declared since inception.

8. Common Stock

As of September 30, 2024 and December 31, 2023, 200,000,000shares of common stock, $0.001par value per share, were authorized.

Each share of common stock entitles the holder to onevote on all matters submitted to a vote of the Company's stockholders. Common stockholders are not entitled to receive dividends, unless declared by the Company's board of directors, subject to the preferential dividend rights of any preferred stock then outstanding. Nodividends have been declared or paid by the Company since its inception.

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The Company assessed the pre-funded warrants for appropriate classification as either equity or liability pursuant to the Company's accounting policy described in Note 2, "Summary of Significant Accounting Policies." The Company determined the pre-funded warrants are freestanding instruments that do not meet the definition of a liability pursuant to ASC 480 and do not meet the definition of a derivative pursuant to ASC 815. The pre-funded warrants are indexed to the Company's common stock and meet all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the pre-funded warrants are classified as equity and are accounted for as a component of additional paid-in capital at the time of issuance. The Company also determined that the pre-funded warrants should be included in the determination of basic and diluted earnings per share.

9. Stock-based Compensation Expense

2016 Stock Incentive Plan

In July 2016, the Company adopted the 2016 Stock Incentive Plan (the "2016 Plan"), which provided for the grant of restricted stock awards, restricted stock units, incentive stock options, non-statutory stock options, and other stock-based awards to the Company's eligible employees, officers, directors, consultants, and advisors. As of the effective date of the 2019 Stock Incentive Plan (the "2019 Plan"), and as of September 30, 2024, noshares remained available for future issuance under the 2016 Plan. Any options or other awards outstanding under the 2016 Plan remain outstanding and effective.

2019 Stock Incentive Plan

On July 2, 2019, the Company's stockholders approved the 2019 Plan, which became effective on July 17, 2019. The 2019 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to the Company's officers, employees, directors, consultants and advisors. The number of shares initially reserved for issuance under the 2019 Plan was 2,017,142shares, plus the shares of common stock remaining available for issuance under the 2016 Plan as of July 17, 2019. The number of shares reserved was annually increased on January 1, 2020 and will be increased each January 1 thereafter through January 1, 2029 by the least of (i) 2,000,000shares, (ii) 4% of the number of shares of the Company's common stock outstanding on the first day of each such year or (iii) an amount determined by the Company's board of directors. On January 1, 2024, the number of shares reserved for issuance under the 2019 Plan was increased by 2,000,000shares. As of September 30, 2024, there were 4,351,368shares available for future issuance under the 2019 Plan.

The shares of common stock underlying any awards that expire, terminate, or are otherwise surrendered, cancelled, forfeited or repurchased by the Company under the 2016 Plan or the 2019 Plan will be added back to the shares of common stock available for issuance under the 2019 Plan. As of July 17, 2019, no further awards will be made under the 2016 Plan.

2022 Inducement Stock Incentive Plan

In February 2022, the Company's board of directors adopted the 2022 Inducement Stock Incentive Plan (the "Inducement Plan"), pursuant to which the Company may grant, subject to the terms of the Inducement Plan and Nasdaq rules, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, and other stock-based awards. The Company initially reserved a total of 1,750,000shares of common stock for the issuance of awards under the Inducement Plan. The number of shares reserved and available for issuance under the Inducement Plan can be increased at any time with the approval of the Company's board of directors. The Inducement Plan permits the board of directors, a delegated committee of the board of directors, or a delegated officer of the Company to grant the stock-based awards available under the Inducement Plan to attract key employees for the growth of the Company. Effective March 8, 2023, the Company's board of directors amended the Inducement Plan to increase the number of shares reserved for issuance by 2,000,000shares. Effective May 18, 2023, the Company's board of directors amended the Inducement Plan to increase the number of shares reserved for issuance by 1,400,000shares. Effective June 17, 2024, the Company's board of directors amended the Inducement Plan to increase the number of shares reserved for issuance by 1,000,000shares. As of September 30, 2024, there were 1,348,270shares available for future issuance under the Inducement Plan.

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Stock Options

Stock options granted by the Company typically vest over a four-yearperiod and have a ten yearcontractual term. Shares issued upon the exercise of stock options are issued from the Company's pool of authorized but unissued common stock. In addition to stock options granted under the 2019 Plan and 2016 Plan, the Company has granted stock options as material inducements to employment in accordance with Nasdaq Listing Rule 5635(c)(4), which were granted outside of the 2019 Plan and 2016 Plan. The following table summarizes the Company's stock option activity during the nine months ended September 30, 2024:

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company's common stock as of the balance sheet date for those options that had exercise prices lower than the fair value of the Company's common stock.

The weighted average grant date fair value of stock options granted in the three and nine months ended September 30, 2024was $7.17per share and $6.44per share, respectively. The weighted average grant date fair value of stock options granted in the three and nine months ended September 30, 2023was $3.26per share and $4.67per share, respectively. The total intrinsic value of stock options exercised during the three and nine months ended September 30, 2024was $0.6million and $1.4million, respectively. The total intrinsic value of stock options exercised during the three and nine months ended September 30, 2023was zeroand $0.2million, respectively.

Restricted Stock Units

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Stock-based Compensation Expense

As of September 30, 2024, the Company had an aggregate of $29.6million of unrecognized stock-based compensation expense, which is expected to be recognized over a weighted average period of 2.64 years.

2019 Employee Stock Purchase Plan

On July 2, 2019, the Company's stockholders approved the 2019 Employee Stock Purchase Plan (the "ESPP"), which became effective on July 17, 2019. A total of 252,142shares of common stock were initially reserved for issuance under the ESPP. In addition, the number of shares of common stock reserved under the ESPP was increased on January 1, 2020, and will be increased annually on each January 1 thereafter through January 1, 2029, by the least of (i) 428,571shares of common stock, (ii) 1% of the number of shares of the Company's common stock outstanding on the first day of each such year or (iii) an amount determined by the Company's board of directors. On January 1, 2024, the number of shares reserved for issuance under the 2019 ESPP was increased by 428,571shares. As of September 30, 2024, there were 1,701,485shares available for future issuance under the ESPP.

10. License and Collaboration Agreements

Sanofi Agreement

In May 2024, the Company entered into a collaboration and license agreement (the "Sanofi Agreement") with Genzyme Corporation ("Sanofi") pursuant to which the Company granted Sanofi an exclusive license under certain intellectual property rights to commercialize losmapimod, an oral small molecule for the treatment of facioscapulohumeral muscular dystrophy ("FSHD"), outside of the United States.

Pursuant to a mutually agreed global development plan, the Company agreed to continue to conduct the ongoing Phase 3 clinical trial for losmapimod for the treatment of FSHD and the Company and Sanofi equally share global development costs. In addition to activities conducted under a mutually agreed global development plan, Sanofi also has the right to conduct certain development activities that are solely intended to support obtaining or maintaining regulatory approval outside of the United States. The Company has the sole right to manufacture for its activities under the global development plan and for commercialization in the United States and, subject to the terms of a supply agreement, the Company will supply Sanofi's clinical and commercial supply requirements of losmapimod until Sanofi elects to take over such manufacturing responsibilities.

Per the terms of the Sanofi Agreement, Sanofi made an upfront license payment of $80.0million to the Company during the second quarter of 2024. The Company is also eligible to receive up to an additional $975.0million in specified regulatory and sales-based milestones, and Sanofi will pay the Company tiered royalties ranging from low-teens to mid-twenties percent of Sanofi's and any of its affiliates' and sublicensees' annual net sales of losmapimod outside the United States. The royalties are payable on a product-by-product basis during a specified royalty term, and may be reduced in specified circumstances.

During the term of the Sanofi Agreement, the Company may not research, develop, manufacture, commercialize, use, or otherwise exploit any compound or product that binds or otherwise modulates p38a/b MAPK anywhere in the world, other than losmapimod in the United States.

The Sanofi Agreement continues on a country-by-country and product-by-product basis until the last to expire royalty term for a product in a country, at which time the Sanofi Agreement expires with respect to such product in such country. Either party has the right to terminate the Sanofi Agreement if the other party has materially breached its obligations under the Sanofi Agreement and such breach has not been cured within the applicable cure period. Sanofi also has the right to terminate the Sanofi Agreement for convenience in its entirety or on a product-by-product or region-by-region (or country-by-country with respect to certain major

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markets) basis. The Company also has the right to terminate the Sanofi Agreement if Sanofi terminates all bona fide material development and commercialization activities for a specified period and such cessation is not the result of certain agreed upon reasons.

The Company determined that the Sanofi Agreement contained three material promises: (i) the license granted to Sanofi to develop and commercialize losmapimod outside of the United States (the "losmapimod license"); (ii) the parties' joint global development activities for losmapimod; and (iii) the Sanofi territory-specific manufacturing activities for losmapimod, subject to the terms of a supply agreement. The Company considered the guidance in ASC 606 to determine which, if any, of the components of the losmapimod agreement are performance obligations with a customer and concluded that the losmapimod license and the Sanofi territory-specific manufacturing activities are within the scope of ASC 606 because Sanofi is the Company's customer in those transactions.

The Company evaluated the losmapimod license under ASC 606 and concluded that the losmapimod license is a functional intellectual property license and is a distinct performance obligation. The Company determined that Sanofi benefited from the losmapimod license at the time of grant, and therefore the related performance obligation is satisfied at a point in time.

The Company evaluated the Sanofi territory-specific manufacturing activities under ASC 606 and identified one material promise associated with manufacturing activities related to development and commercial supply of losmapimod. Given that Sanofi is not obligated to purchase any minimum amount or quantities of the development and commercial supply from the Company, the Company concluded that, for the purpose of ASC 606, the provision of manufacturing activities related to development and commercial supply of losmapimod in the Sanofi territory was an option but not a performance obligation of the Company at the inception of the Sanofi agreement and will be accounted for if and when exercised. The Company also concluded that there is no separate material right in connection with the development and commercial supply of losmapimod, as the expected pricing was not issued at a significant and incremental discount. Therefore, the manufacturing activities were excluded as a performance obligation at the outset of the arrangement. Additionally, the Company is entitled to sales milestones and royalties from Sanofi upon future sales of losmapimod in the Sanofi territory, and revenue will be recognized when the related sales occur. Costs that are incurred associated with the Sanofi territory-specific manufacturing activities are reimbursable from Sanofi and will be recognized as revenue.

For the purposes of ASC 606, the transaction price of the Sanofi Agreement as of the outset of the arrangement consists of the upfront cash payment of $80.0 million, which was allocated to the performance obligation related to the losmapimod license. The other potential milestone payments that the Company is eligible to receive under the Sanofi agreement have been excluded from the transaction price, as all the remaining milestone amounts were fully constrained based on the probability of achievement. The Company will re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and if necessary, the Company will adjust its estimate of the transaction price, and any addition to the transaction price would be recognized as revenue when it becomes probable that inclusion would not lead to a significant revenue reversal. During the nine months ended September 30, 2024, the Company recognized $80.0million of revenue associated with the upfront license payment.

For the parties' participation in global development for losmapimod, the Company concluded that those activities and cost-sharing payments related to such activities are within the scope of ASC 808, as both parties are active participants in the development activities and are exposed to significant risks and rewards of those activities under the Sanofi agreement. The Company assessed its relationship with Sanofi, the economics and nature of the global development activities, and the contractual terms of the Sanofi Agreement and concluded that, in accordance with its policy, payments to or reimbursements from Sanofi related to the global development activities will be accounted for as an increase to or reduction of research and development expenses. During the three and nine months ended September 30, 2024, the Company recorded a reduction in research and development expenses in connection with global development activities for losmapimod of $3.7million and $6.0million, respectively.

GSK Agreement

In February 2019, the Company entered into the right of reference and license agreement, as amended (the "GSK Agreement"), with subsidiaries of GlaxoSmithKline plc (collectively referred to as "GSK"), pursuant to which the Company has been granted an exclusive worldwide license to develop and commercialize losmapimod. Under the GSK Agreement, the Company also acquired reference rights to relevant regulatory and manufacturing documents and GSK's existing supply of losmapimod drug substance and product. The Company also has the right to sublicense its rights under the license agreement, subject to certain conditions. The Company is obligated to use commercially reasonable efforts to develop and commercialize losmapimod at its sole cost. The Company is also responsible for costs related to the filing and maintenance of the licensed patent rights.

Under the GSK Agreement, the Company issued 12,500,000shares of Series B Preferred Stock to GSK (all of which converted to common stock in connection with the Company's 2019 initial public offering). In addition, the Company may owe GSK up to $37.5million in certain specified clinical and regulatory milestones, including a $5.0million milestone that was achieved during 2022 and a $2.5million milestone that was achieved 2019, and up to $60.0million in certain specified sales milestones. The Company agreed to

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pay tiered royalties on annual net sales of losmapimod that range from mid single-digit percentages to a low double-digit, but less than teens, percentage. The royalties are payable on a product-by-product and country-by-country basis, and may be reduced in specified circumstances.

The GSK Agreement may be terminated by either party for a material breach by the other, subject to notice and cure provisions. Unless earlier terminated, the GSK Agreement will continue in effect until the expiration of the Company's royalty obligations, which expire on a country-by-country basis on the later of (i) ten years after the first commercial sale in the country or (ii) approval of a generic version of losmapimod by the applicable regulatory agency.

The Company recognizes clinical and regulatory milestone payments when the underlying contingency is resolved and the consideration is paid or becomes payable. The milestone payments are capitalized or expensed depending on the nature of the associated asset as of the date of recognition.

MyoKardia Agreement

On July 20, 2020, the Company entered into the MyoKardia Collaboration Agreement, as amended, pursuant to which the Company granted to MyoKardia an exclusive worldwide license under certain intellectual property rights to research, develop, make, have made, use, have used, sell, have sold, offer for sale, have offered for sale, import, have imported, export, have exported, distribute, have distributed, market, have marketed, promote, have promoted, or otherwise exploit products directed against certain biological targets identified by the Company that are capable of modulating up to a certain number of genes of interest with relevance to certain genetically defined cardiomyopathies.

Pursuant to a mutually agreed research plan, the Company will perform assay screening and related research activities to identify and validate up to a specified number of potential cardiomyopathy gene targets ("Identified Targets") for further research, development, manufacture and commercialization by MyoKardia. The Company and MyoKardia will work together to determine how best to advance at each stage of the research activities under the research plan and to identify which of the Identified Targets, if any, meet the criteria set forth in the research plan (the "Cardiomyopathy Target Candidates"). Upon completion of the research plan, the parties will work together to prepare a final data package and MyoKardia may designate certain Cardiomyopathy Target Candidates for MyoKardia's further exploitation under the MyoKardia Collaboration Agreement (the "Cardiomyopathy Targets"). If MyoKardia does not designate any Cardiomyopathy Targets during the designated period, then the MyoKardia Collaboration Agreement will automatically terminate. If MyoKardia designates one or more Cardiomyopathy Targets, then MyoKardia will be obligated to use commercially reasonable efforts to seek regulatory approval for and to commercialize one product directed against an Identified Target in certain specified countries.

During the period in which the Company is performing the research activities pursuant to the research plan (the "Research Term") and for a specified period beyond the Research Term if MyoKardia designates a Cardiomyopathy Target, the Company may only use the data generated from such research activities for MyoKardia in accordance with the MyoKardia Collaboration Agreement. During the Research Term and for a specified period thereafter, the Company may not research, develop, manufacture, commercialize, use, or otherwise exploit any compound or product (a) that is a Compound or Product under the MyoKardia Collaboration Agreement that is directed against the Cardiomyopathy Target Candidates for the treatment, prophylaxis, or diagnosis of any indication or (b) for the treatment of any genetically defined cardiomyopathies shown to be related to certain specified genes of interest that are modulated by the Cardiomyopathy Targets.

Under the MyoKardia Collaboration Agreement, MyoKardia made a $10.0million upfront payment and a $2.5million payment as prepaid research funding to the Company in July 2020. MyoKardia agreed to reimburse the Company for the costs of the research activities not covered by the prepaid research funding, up to a maximum amount of total research funding (including the prepaid research funding). Upon the achievement of specified preclinical, development and sales milestones, the Company will be entitled to preclinical milestone payments, development milestone payments and sales milestone payments of up to $298.5million in the aggregate per target for certain Identified Targets, and of up to $150.0million in the aggregate per target for certain other Identified Targets. To date, the Company has achieved a $2.5million specified preclinical milestone. MyoKardia will also pay the Company tiered royalties ranging from a mid single-digit percentage to a low double-digit percentage based on MyoKardia's, and any of its affiliates' and sublicensees', annual worldwide net sales of products under the MyoKardia Collaboration Agreement directed against any Identified Target. The royalties are payable on a product-by-product basis during a specified royalty term, and may be reduced in specified circumstances.

The MyoKardia Collaboration Agreement continues on a country-by-country and product-by-product basis until the last to expire royalty term for a product, at which time the MyoKardia Collaboration Agreement expires with respect to such product in such country. Either party has the right to terminate the MyoKardia Collaboration Agreement if the other party has materially breached in the performance of its obligations under the MyoKardia Collaboration Agreement and such breach has not been cured within the

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applicable cure period. MyoKardia also has the right to terminate the MyoKardia Collaboration Agreement for convenience in its entirety or on a target-by-target, product-by-product or molecule-by-molecule basis.

In July 2024, the Company entered into an amendment to the MyoKardia Collaboration Agreement, pursuant to which the Company and MyoKardia agreed to extend the Research Term.

Accounting Analysis

Identification of the Contract

The Company assessed the MyoKardia Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606.

Identification of the Promises and Performance Obligations

The Company determined that the MyoKardia Collaboration Agreement contains the following promises: (i) an exclusive worldwide license under certain intellectual property rights, including rights to a specified number of potential cardiomyopathy gene targets identified by the Company for further research, development, manufacture and commercialization for the treatment, prophylaxis, or diagnosis of certain genetically defined cardiomyopathies that was conveyed at the inception of the arrangement (the "MyoKardia License"), (ii) research services to identify and validate potential biological targets (the "MyoKardia Research Services"), and (iii) participation in the joint steering committee (the "MyoKardia JSC").

The Company assessed the above promises and concluded that the MyoKardia License is not capable of being distinct from the MyoKardia Research Services given that the MyoKardia License has limited value without the performance of the MyoKardia Research Services and the MyoKardia Research Services can only be performed by the Company due to their specialized nature. Therefore, the Company has concluded that the MyoKardia License and the MyoKardia Research Services represent a single combined performance obligation.

The Company also assessed the participation on the MyoKardia JSC and concluded that the promise is quantitatively and qualitatively immaterial in the context of the MyoKardia Collaboration Agreement. Accordingly, the Company has disregarded its participation on the MyoKardia JSC as a performance obligation.

Determination of the Transaction Price

The Company received a non-refundable upfront payment of $10.0million, which the Company included in the transaction price. In December 2021, the Company achieved a $2.5million specified preclinical milestone associated with the MyoKardia Collaboration Agreement, which was previously constrained due to the significant uncertainty regarding whether such preclinical milestone would be achieved. The Company included this amount in the transaction price as of December 31, 2021. Based on the continued uncertainty associated with the achievement of any of the remaining preclinical and development milestone payments that the Company is eligible to receive, the Company has constrained the variable consideration associated with those milestone payments and excluded them from the transaction price. As part of its evaluation of constraining the preclinical and development milestones, the Company considered numerous factors, including the fact that the achievement of the preclinical and development milestones are contingent upon the results of the underlying preclinical and development activities and are thus outside of the control of the Company.

The Company also included in the transaction price the expected amount of costs to be reimbursed for the MyoKardia Research Services, which includes the $2.5million prepaid research funding payment that the Company received in the third quarter of 2020.

The Company reassesses the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjusts its estimate of the transaction price. There was no change in the amount of variable consideration constrained during the three and nine months ended September 30, 2024.

Any consideration related to sales milestone payments (including royalties) will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to MyoKardia and therefore are recognized at the later of when the related sales occur or the performance obligation is satisfied.

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Allocation of the Transaction Price to Performance Obligations

As noted above, the Company has identified a single performance obligation associated with the MyoKardia Collaboration Agreement. Therefore, the Company will allocate the entire amount of the transaction price to the identified single performance obligation.

Recognition of Revenue

The Company recognizes revenue related to the MyoKardia Collaboration Agreement over time as the MyoKardia Research Services are rendered. The Company has concluded that an input method is a representative depiction of the transfer of services under the MyoKardia Collaboration Agreement. The method of measuring progress towards the delivery of the services incorporates actual cumulative internal and external costs incurred relative to total internal and external costs expected to be incurred to satisfy the performance obligation. The period over which total costs are estimated reflects the Company's estimate of the period over which it will perform the MyoKardia Research Services. Changes in estimates of total internal and external costs expected to be incurred are recognized in the period of change as a cumulative catch-up adjustment. The Company satisfied its obligation to perform research services as of December 31, 2023.

During the three and nine months ended September 30, 2024, the Company recognized nocollaboration revenue associated with the MyoKardia Collaboration Agreement. During the three and nine months ended September 30, 2023, the Company recognized $0.8million and $1.9million, respectively, of collaboration revenue associated with the MyoKardia Collaboration Agreement, which includes $0.2million and $0.6million, respectively, of revenue recognized that was in deferred revenue as of December 31, 2022. As of September 30, 2024 and December 31, 2023, the Company recorded nodeferred revenue or accounts receivable associated with the MyoKardia Collaboration Agreement. As of September 30, 2024, the Company had received $7.7million of cost reimbursement payments under the MyoKardia Collaboration Agreement and $2.5million associated with the achievement of a preclinical milestone. As of December 31, 2023, the Company had received $7.2million of cost reimbursement payments under the MyoKardia Collaboration Agreementand $2.5million associated with the achievement of a preclinical milestone. As of September 30, 2024, the Company recorded nounbilled accounts receivable related to reimbursable research and development costs under the MyoKardia Collaboration Agreement for activities performed during the three months ended September 30, 2024. As of December 31, 2023, the Company recorded unbilled accounts receivable of $0.5million related to reimbursable research and development costs under the MyoKardia Collaboration Agreement for activities performed during the three months ended December 31, 2023.

CAMP4 Agreement

In July 2023, the Company entered into a license agreement (the "CAMP4 Agreement") with CAMP4 Therapeutics Corporation ("CAMP4") pursuant to which the Company received a worldwide exclusive license (including the right to sublicense) from CAMP4 to rights under its Diamond Blackfan Anemia ("DBA") program, which includes certain small molecule compounds, composition of matter and method of use patent rights, and know-how for the Company to research, develop, manufacture, use, commercialize or otherwise exploit therapeutic products in any indication, including the grant of a sublicense under certain intellectual property rights that CAMP4 has licensed under an agreement with Children's Medical Center Corporation ("CMCC").

The Company made an undisclosed upfront non-refundable, non-creditable payment to CAMP4. If the Company succeeds in developing and commercializing licensed products, CAMP4 will be eligible to receive (i) up to $35.0million in development and regulatory milestone payments, and (ii) up to $35.0million in sales milestone payments. CAMP4 is also eligible to receive royalties on worldwide net sales of licensed products ranging from mid-single digit to low-double digit, subject to potential reduction following loss of patent coverage, the launch of certain generic products or royalty stacking for licenses of third party intellectual property. The royalties will expire on a product-by-product and country-by-country basis upon the latest to occur of (i) the expiration of all valid patent claims covering the compounds in such country, (ii) the expiration of all regulatory exclusivities in such country, and (iii) 10 years following the first commercial sale in such country. The Company is responsible for the costs associated with the development and regulatory approvals of licensed products.

Unless earlier terminated in accordance with its terms, the license agreement continues on a country-by-country and licensed product-by-licensed product basis until the expiration of the royalty term in each country, at which time the license agreement expires with respect to such licensed product in such country and the Company will have a fully-paid up, royalty-free and perpetual license to the licensed patent rights and know-how with respect to such licensed product in such country. CAMP4 has the right to terminate the license agreement in the event of the Company's non-payment (subject to cure periods and tolling for bona fide disputes). CAMP4 may also terminate the license agreement if the Company challenges certain patents sublicensed to the Company by CAMP4. Either party may terminate the license agreement in its entirety for the other party's material breach if such other party fails to cure the

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breach. Either party may also terminate the agreement in its entirety upon certain insolvency events involving the other party. The Company has the right to terminate the license agreement with CAMP4 for any or no reason upon prior written notice to CAMP4.

The Company recognizes development and regulatory milestone payments when the underlying contingency is resolved and the consideration is paid or becomes payable. The milestone payments are capitalized or expensed depending on the nature of the associated asset as of the date of recognition.

11. Leases

Operating Leases

26 Landsdowne Street

In November 2017, the Company entered into a lease agreement for its current corporate headquarters comprising approximately 28,731square feet of office and laboratory space at 26 Landsdowne Street in Cambridge, Massachusetts, commencing December 2017. The Company began to occupy and use the leased space for its intended purpose in June 2018. The lease ends on June 30, 2028. The Company has the option to extend the term of the lease for an additional five-yearperiod, at the market rate, by giving the landlord written notice of its election to exercise the extension at least nine months prior to the original expiration of the lease term. The lease has a total commitment of $25.1million over the ten yearterm, and includes escalating rent payments. The lease provides the Company with an allowance for normal leasehold improvements of $5.0million. The lease agreement requires the Company to either pay a security deposit or maintain a letter of credit of $1.1million. The Company maintains a letter of credit for this lease and has recorded the cash held to secure the letter of credit as restricted cash on the consolidated balance sheet as of September 30, 2024 and December 31, 2023. Operating lease expense associated with this lease for the three and nine months ended September 30, 2024was approximately $0.5million and $1.4million, respectively. Variable lease expense associated with this lease for the three and nine months ended September 30, 2024was approximately $0.2million and $0.7million, respectively.

125 Sidney Street

In November 2021, the Company entered into a lease agreement comprising approximately 12,196square feet of office space at 125 Sidney Street in Cambridge, Massachusetts, commencing November 2021. The Company began recognizing rent expense associated with this lease during November 2021. The lease ended on March 31, 2024. The Company had the option to extend the term of the lease for two successive one-year periods, at the market rate, by giving the landlord written notice of its election to exercise the extension at least nine months prior to the original expiration of the lease term. The lease had a total commitment of $1.7million over the initial term, and included escalating rent payments. Operating lease expense associated with this lease for the three and nine months ended September 30, 2024was approximately zeroand $0.2million, respectively. Novariable lease expense was recorded associated with this lease for the three and nine months ended September 30, 2024.

There are nofuture minimum lease payments associated with this lease as of September 30, 2024.

12. Commitments and Contingencies

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters arising out of the relationship between such parties and the Company. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior

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management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations as of September 30, 2024 or December 31, 2023.

Legal Proceedings

On April 28, 2023, a class action complaint was filed in the United States District Court for the District of New Jersey against the Company and current and former officers (the "Securities Action"). On May 19, 2023, the Securities Action was transferred to the United States District Court for the District of Massachusetts, captioned Celano v. Fulcrum Therapeutics, Inc., et al., Case No. 1:23-cv-11125-IT. On July 31, 2023, the court appointed a lead plaintiff, who filed an amended complaint on September 29, 2023. The Securities Action alleges violations of Section 10(b) of the Securities Exchange Act of 1934, as amended, and Rule 10b-5 promulgated thereunder against all defendants and control person violations of Section 20(a) against the individuals, related to the Company's February 2023 announcement that the U.S. Food and Drug Administration issued a clinical hold regarding the investigational new drug application for pociredir for the potential treatment of sickle cell disease. The Securities Action alleges that the defendants made misleading statements and omitted to disclose material information related to the clinical hold and seeks, among other things, compensatory damages in connection with an allegedly inflated stock price between March 3, 2022, and March 8, 2023, as well as attorneys' fees and costs. On November 28, 2023, all defendants filed a motion to dismiss the Securities Action. Briefing was completed on the motion in February 2024, and the motion is currently pending. The Company intends to defend vigorously against this litigation.

At each reporting date, the Company evaluates whether or not 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 the costs related to its legal proceedings as they are incurred. Other than attorneys' fees and costs related to the defense of the Securities Action, nosuch costs have been incurred during the three and nine months ended September 30, 2024.

13. Defined Contribution Plan

The Company has a defined contribution savings plan under Section 401(k) of the Internal Revenue Code (the "401(k)Plan"). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants the option to elect to defer a portion of their annual compensation on a pretax basis. As currently established, the Company is not required to make contributions to the 401(k) Plan. The Company made $0.2million and $0.6million, respectively, in contributions to the 401(k) Plan for the three and nine months ended September 30, 2024 and 2023.

14. Net Income (Loss) per Share

Basic net income per share is calculated by dividing net income (loss) by the weighted average number of shares of common stock outstanding during the period. Shares of the Company's common stock underlying pre-funded warrants are included in the calculation of basic and diluted net income per share. Diluted net income per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period. For purposes of the diluted net income per share calculation, the effect of stock options and unvested restricted stock units on the weighted average number of shares is calculated using the treasury stock method. In periods with reported net operating losses, all common stock equivalents are deemed anti-dilutive such that basic net loss per share and diluted net loss per share are equal.