0001193125-21-085777 | 10-K | XBRL Viewer

Nature of Business and Basis of Presentation

1. Nature of Business and Basis of Presentation

Foghorn Therapeutics Inc. (the “Company”) is a clinical-stage biopharmaceutical company discovering and developing a new class of medicines targeting genetically determined dependencies within the chromatin regulatory system. The Company uses its proprietary Gene Traffic Control platform to identify, validate and potentially drug targets within the system. The Company was founded in

October 2015

as a Delaware corporation. The Company is headquartered in Cambridge, Massachusetts.

The Company is subject to risks similar to those of other early-stage companies in the biopharmaceutical industry, including dependence on key individuals, the need to develop commercially viable products, competition from other companies, many of whom are larger and better capitalized, the impact of the

COVID-19

pandemic and the need to obtain adequate additional financing to fund the development of its products. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be maintained, that any products developed will obtain required regulatory approval or that any approved products will be commercially viable. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from the sale of its products.

In March 2020, the World Health Organization declared the global novel coronavirus disease 2019

(“COVID-19”) outbreak

a pandemic. The Company’s operations have not been significantly impacted by

the COVID-19 pandemic.

However, the Company cannot at this time predict the specific extent, duration, or full impact that

the COVID-19 pandemic

will have on its financial condition and operations, including ongoing and planned clinical trials. The impact of

the COVID-19 outbreak

on the Company’s financial performance will depend on future developments, including the duration and spread of the pandemic and related governmental advisories and restrictions. These developments and the impact

of COVID-19 on

the financial markets and the overall economy are highly uncertain and cannot be predicted. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be materially adversely affected.

On October

2020

, the Company completed its initial public offering (“IPO”) pursuant to which it issued and sold

7,500,000

shares of its common stock at a public offering price of $

16.00

per share, resulting in net proceeds of $

107.9

million, after deducting underwriting discounts and commissions and other offering expenses. On November

2020

, the Company issued and sold an additional

951,837

shares of common stock at the IPO price of $

16.00

per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $

14.2

million after deducting underwriting discounts and commissions. Upon the closing of the IPO, all of the Company’s outstanding convertible preferred stock automatically converted into shares of

common stock and the Company’s outstanding

warrants to purchase Series A Preferred Stock automatically became warrants to purchase an aggregate of

7,608

shares of common stock (see Note 7).

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 primarily with proceeds from sales of preferred stock, debt financing and an upfront payment of $15.0 million the Company received in July 2020 under a collaboration agreement with Merck Sharp &

Dohme Corp. (see Note 10), and most recently,

with proceeds from the sale of common stock in the IPO completed in October 2020. The Company has incurred recurring losses, including net losses of $68.8 million and $51.1 million for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, the Company had an accumulated deficit of $162.9 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of these consolidated financial statements 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.

The Company will need to obtain additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and/or licensing arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborative or strategic alliances or licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Arrangements with collaborators or others may require the Company to relinquish rights to certain of its technologies or programs. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, pipeline expansion or commercialization efforts, 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.

Basis of presentation

The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. 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 Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

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 expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition, the valuation of stock-based awards and the accrual of research and development expenses. 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. 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. As of December 31, 2020, the Company maintained cash, cash equivalents and marketable securities at financial institutions in excess of federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company relies, and expects to continue to rely, on a small number of vendors to provide services, supplies and materials for certain activities related to its programs. These programs could be adversely affected by a significant interruption in these services or the availability of materials.

Cash equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Marketable Securities

The Company’s marketable securities are classified as available-for-sale and are carried at fair value with the unrealized gains and losses reported as a component of accumulated other comprehensive loss in stockholders’ equity (deficit). Realized gains and losses and declines in value judged to be other than temporary are included as a component of interest income and other income (expense), net based on the specific identification method. The Company classifies its marketable securities with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities are available for current operations.

Restricted cash

Amounts included in restricted cash represent amounts pledged as collateral for letters of credit required for security deposits on the Company’s leased facilities and credit cards. These amounts are classified as restricted cash (current and

non-current)

in the Company’s consolidated balance sheets.

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 as follows:


		Estimated Useful Life
Laboratory equipment		5 years
Furniture and fixtures		5 years
Computer equipment and software		3 years
Leasehold improvements		Shorter of useful life or remaining term of lease

Costs for capital assets not yet placed into service are 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 are charged to expense as incurred.

Impairment of long-lived assets

The Company evaluates its long-lived assets, which consist primarily of property and equipment and operating lease

right-of-use

assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2020 or 2019.

Fair value measurements

Certain assets and liabilities are carried at fair value under GAAP. 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 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—Quoted prices in active markets for identical assets or liabilities.

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the Company’s long-term debt approximates its fair value (a level 2 measurement) due to its variable interest rate.

Revenue recognition

The Company accounts for its one collaboration arrangement, entered into in July 2020, under ASC Topic 606,

Revenue From Contracts With Customers

(ASC 606). For additional information on the Company’s collaboration agreement, see Note 10, Collaboration Agreement, to these consolidated financial statements. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

The Company assesses the goods or services promised within each contract and determines those that are performance obligations. The promised goods or services in the Company’s arrangements would likely consist of licenses, rights to the Company’s intellectual property, research and development services and related supporting activities. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.

The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the

Company re-evaluates the

estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a

cumulative catch-up basis

in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded for deferred revenue.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between the transfer of the promised goods or services to the customer and the payment by the customer will be one year or less. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method.

Classification of convertible preferred stock

The Company classified its convertible preferred stock outstanding prior to the IPO outside of stockholders’ equity (deficit) on the consolidated balance sheet because the holders of such shares had redemption rights in the event of a deemed liquidation that, in certain situations, is not solely within the control of the Company.

Research and development costs

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 external costs of vendors engaged to conduct research, preclinical and clinical 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 over the period to which they relate. Costs for research and development activities are expensed in the period in which they are incurred. Payments for such activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense. Determining the prepaid and accrued balances at the end of any reporting period incorporate certain judgments and estimates by management that are based on information available to the Company including information provided by vendors regarding the progress to completion of specific tasks or costs incurred.

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.

Leases

In accordance with ASC 842,

Leases,

the Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset’s economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its

right-of-use

asset and lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. The Company’s policy is to not record leases with an original term of twelve months or less on its consolidated balance sheets and recognizes those lease payments in the income statement on a straight-line basis over the lease term. The Company’s existing leases are for office and laboratory space and an equipment lease.

In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as

non-lease

components. The Company has elected to not separate lease and

non-lease

components. Only the fixed costs for lease components and their associated

non-lease

components are accounted for as a single lease component and recognized as part of a

right-of-use

asset and liability. Rent expense for operating leases is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expense in the consolidated statements of operations and comprehensive loss.

Stock-based compensation

The Company measures stock options with service-based vesting or performance-based vesting granted to employees,

non-employees

and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model. The Company measures restricted common stock awards using the difference between the purchase price per share of the award, if any, and the fair value of the Company’s common stock at the date of grant. Compensation expense for the awards is recognized over the requisite service period for employees and directors and as services are delivered for

non-employees,

both of which are generally the vesting period of the respective award. The Company uses the straight-line method to record the expense of awards with only service-based vesting conditions. The Company uses the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing once achievement of the performance condition becomes probable. The Company accounts for forfeitures of share-based awards as they occur.

The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Net loss per share

In October 2020, upon the closing of the IPO, all outstanding shares of the Company’s convertible preferred stock automatically converted into 21,958,588 shares of the Company’s common stock. Prior to this conversion, the Company followed

the two-class method

when computing net income (loss) per share as the Company had issued shares that meet the definition of participating securities.

The two-class method

determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings.

The two-class method

requires income (loss) available to common stockholders for the period to be allocated between common stock and participating securities based upon their respective rights to share in the earnings as if all income (loss) for the period had been distributed.

Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares.

The Company’s participating securities contractually entitled the holders of such shares to participate in dividends but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reported a net loss, such losses were not allocated to such participating securities. In periods in which the Company reported a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2020 and 2019.

The following common stock equivalents presented based on amounts outstanding at each period end, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact:


	December 31,
	2020		2019
Stock options to purchase common stock		5,016,460		3,886,489
Warrants to purchase common stock		18,445		—
Convertible preferred stock (as converted to common stock)		—		15,467,863
Unvested restricted common stock		—		891,894
Warrants to purchase convertible preferred stock (as converted to common stock)		—		7,608

		5,034,905		20,253,854

Segments

Operating segments are defined as components of an entity for which separate discrete financial information is made available and that is regularly evaluated by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s CODM is its chief executive officer and the Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is focused on pioneering the discovery and development of a new class of medicines targeting genetically determined dependencies within the chromatin regulatory system.

Comprehensive loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the year ended December 31, 2020, the Company’s only element of other comprehensive loss was unrealized losses on available for sale debt securities. For the year ended December 31, 2019, there was no difference between net loss and comprehensive loss.

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 consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year 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 the provision for income taxes. 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 consolidated 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 consolidated 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. Any resulting unrecognized tax benefits are recorded within the provision for income taxes.

Recently issued accounting pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to “opt out” of such extended transition period or (ii) no longer qualifies as an emerging growth company.

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326)

. The new standard adjusts the accounting for assets held at amortized costs basis, including marketable securities accounted for as available for sale. The standard eliminates the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For public entities, the guidance was effective for annual reporting periods beginning after December 15, 2019 and for interim periods within those fiscal years. For nonpublic entities and emerging growth companies that choose to take advantage of the extended transition period, the guidance is effective for annual reporting periods beginning after December 15, 2020. Early adoption is permitted for all entities. In November 2019, the FASB issued ASU

No. 2019-10,

which deferred the effective date for nonpublic entities to annual reporting periods beginning after December 15, 2022, including interim periods within those fiscal years. The Company is evaluating when to adopt this standard and the effect the adoption will have on its consolidated financial statements.

Marketable Securities and Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Marketable Securities and Fair Value Measurements

3.	Marketable Securities and Fair Value Measurements

As of December 31, 2020, available for sale marketable securities by security type consisted of (in thousands):


				Gross		Gross			Estimated
		Amortized		Unrealized		Unrealized			Fair
		Cost		Gains		Losses			Value
U . S . treasury notes (due within one year)	$	92,982	$	—	$	(7	)	$	92,975

Total	$	92,982	$	—	$	(7	)	$	92,975

The Company had no marketable securities as of December 31, 2019.

The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands):


	Fair Value Measurements at December 31, 2020 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	48,770	$	—	$	—	$	48,770
U .S . treasury notes		—		42,997		—		42,997
Marketable securities:
U . S . treasury notes		—		92,975		—		92,975

Total	$	48,770	$	135,972	$	—	$	184,742


	Fair Value Measurements at December 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	14,951	$	—	$	—	$	14,951

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	45	$	45

The preferred stock warrant liability as of December 31, 2019 consisted of the fair value of warrants to purchase 14,076 shares of

Series A-1

convertible preferred stock at $1.00

per share and was based on significant inputs not observable in the market, which represented a Level 3 measurement within the fair value hierarchy. The Company’s valuation of the preferred stock warrants utilized the Black-Scholes option-pricing model, which incorporated assumptions and estimates to value the preferred stock warrants. The Company assessed these assumptions and estimates at the end of each reporting period. Changes in the fair value of the preferred stock warrants were recognized within other income (expense) in the consolidated statements of operations and comprehensive loss and were not material during the years ended December 31, 2020 and 2019.

In October 2020, upon closing of the IPO, the warrants to purchase 14,076 shares of Series

A-1

convertible preferred stock automatically became warrants to purchase an aggregate of 7,608

shares of common stock. The Company remeasured the warrants as of the IPO date and reclassified the carrying value of the warrants from a non-current liability to additional paid-in capital in its consolidated balance sheet. During the year ended December 31, 2020, these warrants were exercised in full.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2020			2019
Laboratory equipment	$	3,740		$	3,202
Furniture and fixtures		815			337
Computer equipment and software		100			81
Leasehold improvements		16,961			75
Assets not yet placed in service		15			280

		21,631			3,975
Less: Accumulated depreciation and amortization		(2,103	)		(1,292	)

	$	19,528		$	2,683

Depreciation and amortization expense was $1.3 million and $0.7 million for the years ended December 31, 2020 and 2019, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Accrued Expenses

5. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2020		2019
Accrued employee compensation and benefits	$	3,513	$	1,867
Accrued construction in progress		2,385		119
Accrued external research and development expenses		2,146		1,384
Accrued professional fee s		979		274
Other		138		57

	$	9,161	$	3,701

Notes Payable

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Notes Payable

6. Notes Payable

Long-term debt consisted of the following (in thousands):


	December 31,
	2020			2019
Principal amount of long-term debt	$	20,000		$	15,000
Less: Current portion of long-term debt		—			(4,152	)

Long-term debt, net of current portion		20,000			10,848
Final payment fee		1,000			530
Debt discount, net of accretion		(1,346	)		(418	)

Long-term debt, net of discount and current portion	$	19,654		$	10,960

Loan and Security Agreements

As of December 31, 2019, the Company had outstanding loans under its amended loan and security agreement with Comerica Bank (the “Loan”) of

$7.0 million (“Term Loan A”) and $8.0 million (“Term Loan B”). Borrowings under both Term Loan A and Term Loan B were repayable in monthly payments of interest-only through February 2020, to be followed by monthly payments of equal principal plus interest until the loan maturity date of February 1, 2023. In April 2020, the Company amended the Loan to extend the interest only period through May 31, 2020 and in June 2020 the Loan was further amended to extend the interest-only period through August 31, 2020. Interest for Term Loan A was the greater of 1) Comerica’s Prime Rate or 2) LIBOR plus 2.5%, and for Term Loan B, 1.0% plus the greater of 1) Comerica’s Prime Rate or 2) LIBOR plus 2.5%.

A final payment fee of 3.0% of the aggregate amounts drawn under Term Loan A and 4.0% under Term Loan B was due upon the earlier of the maturity date, the repayment date if paid early, whether voluntary or upon acceleration due to default, the sale of substantially all of the Company’s assets, or the Company’s IPO. The Company may repay the Loan at any time by paying the outstanding principal balance in full, along with any unpaid accrued interest and the final payment fee. The final payment fee of $0.5 million was being amortized to interest expense over the term of the debt using the effective interest method. Upon closing of the Company’s IPO in October 2020, the final payment fee became due. In November 2020, the Company used a portion of the proceeds from its new loan and security agreement described below to repay the outstanding principal balance under Term Loan A and Term Loan B plus unpaid accrued interest and the final payment fee.

The Company recorded a loss

on debt extinguishment of $0.2 million related to this repayment.

On November 19, 2020, the Company entered into a new loan and security agreement, or the Oxford Loan, with Oxford Finance LLC, or Oxford, for an aggregate principal amount of $20.0 million (Oxford Term Loan A) and up to an additional $5.0 million (Oxford Term Loan B).

On November 19, 2020, the Company borrowed $20.0 million under the Oxford Term Loan A.

The Term Loan bears interest at a floating per annum rate equal to the greater of (i) 8.0% and (ii) the sum of

(a) thirty-day

LIBOR rate plus (b) 7.84%. In addition, upon loan maturity or prepayment, the Company is reqired to make a final payment fee equal to 5.0% of the aggregate principal amount borrowed which is being amortized to interest expense over the term of the debt using the effective interest method.

The Company is required to make monthly interest only payments under the Oxford Loan each month beginning on January 1, 2021. Beginning on December 1, 2023, the Company is required to make consecutive equal monthly payments of principal, together with applicable interest, in arrears, based upon a repayment schedule equal to 24 months, with a final maturity date of November 1, 2025 (the “Maturity Date”).

At the Company’s option, the Company may elect to prepay the loans subject to a prepayment fee equal to the following percentage of the principal amount being prepaid: 2% if an advance is prepaid during the first 12 months following the applicable advance date, 1% if an advance is prepaid after 12 months but prior to 24 months following the applicable advance date, and 0.5% if an advance is prepaid any time after 24 months following the applicable advance date but prior to the Maturity Date.

The Company’s obligations under the Oxford Loan Agreement are secured by a security interest in all of its assets, other than its intellectual property. The Company is also subject to certain affirmative and negative covenants

including

limitations on dispositions, mergers or acquisitions; encumbering its intellectual property; incurring indebtedness or liens; paying dividends; making certain investments; and engaging in certain other business transactions. The obligations under the Loan are subject to acceleration upon the occurrence of specified events of default, including a material adverse change in the Company’s business, operations or financial or other condition. Upon the occurrence of an event of default and until such event of default is no longer continuing, the annual interest rate will be 5.0% above the otherwise applicable rate. As of December 31, 2020, the Company believes an event of default would be remote.

addition, in

connection with the Oxford Loan Agreement, the Company granted warrants to purchase 18,445 shares of the Company’s common stock at $16.26 per share. The issued warrants are exerciseable for 10 years. The Company valued the warrants using the Black-Scholes option pricing model and determined the fair value of the warrants to be $0.2 million. The Company determined the warrants met the criteria for equity classification, and, as such, the fair value of the warrants were recorded as additional

paid-in

capital and as a discount to the

debt which is being amortized to interest expense over the term of the Oxford Loan of five years. In addition, the Company incurred debt issuance costs of

$0.2 million.

As of December 31, 2020, the interest rate applicable to outstanding borrowings under the Oxford Loan was

8.0%. During the years ended December 31, 2020 and 2019, the weighted average effective interest rate on outstanding borrowings was approximately 6.4% and 6.9%, respectively.

As of December 31, 2020, future principal payments due are as follows (in thousands):


2021	$	—
2022		—
2023		833
2024		10,000
2025		9,167

	$	20,000

Convertible Preferred Stock and Preferred Stock Warrants

12 Months Ended

Dec. 31, 2020

Stockholders' Equity Note [Abstract]

Convertible Preferred Stock and Preferred Stock Warrants

7.	Convertible Preferred Stock and Preferred Stock Warrants

Convertible Preferred Stock

The Company

issued Series A-1 convertible

preferred stock

(the “Series A-1”), Series A-2 convertible

preferred stock (the

“Series A-2”) and

Series B convertible preferred stock (the “Series B”).

The Series A-1 and

Series A-2 are

collectively referred to as the “Series A” and the Series A and Series B are collectively referred to as the “Preferred Stock.”

In July and August 2020, in two separate closings, the Company sold 5,600,000 shares of Series B preferred stock at a purchase price of $7.50 per share resulting in gross proceeds to the Company of $42.0 million.

In April 2020, in two separate closings, the Company sold 6,407,867 shares of Series B preferred stock at a purchase price of $7.50 per share resulting in gross proceeds to the Company of $48.1 million.

As of December 31, 2019,

Preferred Stock consisted of the following (in thousands, except share amounts):


	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A-1 Preferred Stock		9,707,826		9,693,750	$	9,609	$	9,694		5,239,865
Series A-2 Preferred Stock		10,804,165		10,804,165		16,179		16,206		5,840,089
Series B Preferred Stock		8,117,631		8,117,631		60,756		60,882		4,387,909

		28,629,622		28,615,546	$	86,544	$	86,782		15,467,863

Upon the closing of the IPO in October 2020, the Company’s Preferred Stock automatically converted into 21,958,588 shares of common stock.

Warrants to Purchase Preferred Stock

n connection with the issuance of notes payable, the Company issued warrants to purchase 14,076 shares of Series

A-1

preferred stock at an exercise price of $1.00 per share. In October 2020, upon closing of the IPO, the warrants automatically became warrants to purchase an aggregate of 7,608 shares of common stock and were then cashless exercised in full for 6,728 shares of common stock.

Common Stock

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Common Stock

8. Common Stock

On October 27, 2020, the Company completed its initial public offering (“IPO”) pursuant to which it issued and sold 7,500,000 shares of its common stock at a public offering price of $16.00 per share, resulting in net proceeds of $107.9 million, after deducting underwriting discounts and commissions and other offering expenses. On November 19, 2020, the Company issued and sold an additional 951,837 shares of common stock at the IPO price of $16.00 per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $14.2 million after deducting underwriting discounts and commissions. Upon the closing of the IPO, all of the Company’s outstanding convertible preferred stock automatically converted into shares of common stock (see Note 7).

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

9. Stock-Based Compensation

2016 Stock incentive plan

The Company’s 2016 Stock Incentive Plan, (the “2016 Plan”) provided for the Company to grant incentive stock options or nonqualified stock options and other equity awards to employees, directors and consultants of the Company. Upon the effectiveness of the 2020 Equity Incentive Plan (the “2020 Plan”) in October 2020, the Company ceased granting additional awards under the 2016 Plan.

2020 Equity Incentive Plan

On October 21, 2020, the Company’s board of directors adopted and its stockholders approved the 2020 Plan, which became effective on October 21, 2020. The 2020 Plan provides for the grant of incentive stock

options, non-qualified options,

stock appreciation rights, restricted

stock awards, restricted stock units and other stock-based awards

The number of shares initially reserved for issuance under the 2020 Plan

s (i)

2,200,000

shares (the “share pool”), plus (ii) the number of shares of common stock available for issuance under the 2016 Plan as of the effective date of the 2020 Plan, plus the number of shares of common stock underlying awards under the 2016 Plan that on or after the date of adoption expire or become unexercisable without delivery of shares, are forfeited to, or repurchased for cash, are settled in cash, or otherwise become available again for grant under the 2016 Plan, in each case, in accordance with its terms (up to an aggregate of

5,078,295

shares). As of December 31, 2020,

2,213,094

shares remained available for future grants under the 2020 Plan.

The share pool will automatically increase on January 1 of each year from 2021 to 2030 by the lesser of (i) four percent of the number of shares of our common stock outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the board of directors on or prior to such date for such year. The number of shares reserved for issuance under the 2020 Plan was increased

by 1,471,576 shares effective January 1, 2021.

The 2020 Plan and 2016 Plan are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated. Stock options granted with service-based vesting conditions generally vest over

four

years and expire after

ten

years. The exercise price for stock options granted is not less than the fair value of common stock on the date of grant. The Company bases fair value of common stock on the quoted market price. Prior to the IPO, the board of directors determined the value the Company’s common stock, taking into consideration its most recently available valuation of common stock performed by third parties as well as additional relevant factors which may have changed since the date of the most recent contemporaneous valuation through the date of grant.

2020 Employee Stock Purchase Plan

On October 21, 2020, the Company’s board of directors adopted and its stockholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective on October 21, 2020. The aggregate number of shares of common stock available for purchase pursuant to the exercise of options under the ESPP is 360,000 shares, plus an automatic annual increase, as of January 1 of each year from 2021 to 2030, equal to the lesser of (i) one percent of the number of shares of common stock outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the board of directors on or prior to such date for such year (up to a maximum of 3,220,520 shares). The number of shares reserved for issuance under the ESPP was increased by 367,894 shares effective January 1, 2021.

As of December 31, 2020, no offering periods have commenced under the ESPP.

Stock option valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. Prior to the IPO, the Company was a private company and 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. 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 following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted in 2020 and 2019:


	Year Ended December 31,
	2020			2019
Risk-free interest rate		0.4	%		2.2	%
Expected volatility		78.5	%		78.2	%
Expected dividend yield		—			—
Expected term (in years)		6.1			6.0

The following table summarizes the Company’s option activity during the year ended December 31, 2020:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2019		3,886,489		$	2.39
Granted		1,922,377			8.87
Exercised		(611,048	)		1.99
Forfeited		(181,358	)		2.10

Outstanding as of December 31, 2020		5,016,460		$	4.93		8.5	$	76,941

Vested and expected to vest as of December 31, 2020		5,016,460		$	4.93		8.5	$	76,941
Options exercisable as of December 31, 2020		1,508,122		$	1.91		7.4	$	27,683

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 for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2020 and 2019 was $3.5 million and $1.2 million, respectively.

The weighted average grant-date fair value of stock options granted during the years ended December 31, 2020 and 2019 was $6.01 per share and $2.54 per share, respectively.

Restricted common stock

During 2015, the Company issued and sold 4,459,459 shares of restricted common stock at par value to the scientific founders of the Company. The shares were subject to vesting over a period of five years and began vesting upon the closing of the Series

A-1

Preferred Stock in April 2016

and were fully vested as of December 31, 2020.

The following table summarizes the Company’s restricted common stock activity during the year ended December 31, 2020:


	Shares
Unvested restricted common stock as of December 31, 2019		891,894
Issued		—
Vested		(891,894	)

Unvested restricted common stock as of December 31, 2020		—

The aggregate fair value of restricted stock that vested during the years ended December 2020 and 2019 was $4.8 million and $3.3 million, respectively.

Stock-based compensation

The Company recorded stock-based compensation expense related to common stock options and restricted common stock in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):


	Year Ended December 31,
	2020		2019
Research and development expenses	$	1,724	$	1,140
General and administrative expenses		1,237		554

		$2,961		$1,694

As of December 31, 2020, total unrecognized compensation cost was

$13.5 million, which is expected to be recognized over a weighted average period of 3.6 years.

Collaboration Agreement

12 Months Ended

Dec. 31, 2020

Disclosure Text Block [Abstract]

Collaboration Agreement

10. Collaboration Agreement

In July 2020, the Company entered into a research collaboration and license agreement (the “Collaboration Agreement”) with Merck Sharp & Dohme Corp. (“Merck”). The Company and Merck will apply Foghorn’s proprietary Gene Traffic Control platform to discover and develop novel therapeutics. Under the Collaboration Agreement, the Company granted Merck exclusive global rights to develop and commercialize drugs that target dysregulation of a single transcription factor. Under the terms of the Collaboration Agreement, the Company and Merck are each responsible to perform certain research activities in accordance with a mutually agreed upon research plan. Merck may substitute the selected transcription factor during certain stages of the research program, subject to certain limitations. Following completion of the research program, Merck is responsible for the development and commercialization of the compounds developed pursuant to the research program and any product containing such compounds. Pursuant to the Collaboration Agreement, the Company will also participate on a joint steering committee.

Under the terms of the agreement, Foghorn received a nonrefundable upfront payment of $15.0 million from Merck, and is eligible to receive up to $245.0 million upon achievement of specified research, development and regulatory milestones by any product candidate generated by the collaboration, and up to $165.0

million upon achievement of specified sales-based milestones per approved product from the collaboration, if any. The Company will be eligible to receive tiered royalties, calculated on a

product-by-product

and

country-by-country

basis, on net sales of approved products from the collaboration, if any, at royalty rates ranging from the

mid-single

digits to low tens, depending on whether the products are covered by patent rights it licenses to Merck.

Unless terminated earlier, the Collaboration Agreement will continue in full force and effect until one or more products has received marketing authorization and, thereafter, until expiration of all royalty obligations under the Collaboration Agreement. The Company or Merck may terminate the Collaboration Agreement upon an uncured material breach by the other party or insolvency of the other party. Merck may also terminate the Merck Collaboration Agreement for any reason upon certain notice to the Company.

The Company determined that the (1) research, development, manufacture and commercialization licenses, (2) the research activities performed by the Company and (3) service on the joint committees represent a single performance obligation under the Collaboration Agreement. The Company determined that Merck cannot benefit from licenses separately from the research activities and participation on the joint steering committee as these services are specialized and rely on the Company’s expertise such that these activities are highly interrelated and therefore not distinct. Accordingly, the promised goods and services represent one combined performance obligation and the entire transaction price was allocated to that single combined performance obligation. The performance obligation will be satisfied over the research term as the Company performs the research activities and participates in a joint steering committee to oversee research activities.

The upfront payment of

$15.0 million was initially recorded as deferred revenue and is being recognized as revenue as the performance obligation is satisfied. The Company recognizes revenue

using the cost-to-cost method, which

it believes best depicts the transfer of control to the customer over time.

Under the cost-to-cost method, the

extent of progress towards completion is measured based on the ratio of actual costs incurred to the total estimated costs expected upon satisfying the identified performance obligation. Under this method, revenue is recorded as a percentage of the estimated transaction price based on the extent of progress towards completion. As of December 31, 2020, the potential research, development and regulatory milestone payments that the Company is eligible to receive were excluded from the transaction price as they were fully constrained by uncertain events. The Company will reevaluate 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. Any additions to the transaction price would be reflected in the period as a cumulative

revenue catch-up

based on the ratio of costs incurred to the total estimated costs expected applied to the revised transaction price. Sales-based royalties and milestone payments, which predominantly relate to the license, will be recognized if and when the related sales occur.

As of December 31, 2020, the aggregate amount of the transaction price related to the unsatisfied portion of the performance obligation is $14.6 million, which is expected to be recognized as revenue through 2028. The Company does not expect collaboration revenue to be recognized evenly over this period as it will be recognized on a percentage of completion basis (using

cost-to-cost

method) as the Company performs the research activities and participates on the joint steering committee, which will likely vary from period to period. In estimating the total costs to satisfy its single performance obligation pursuant to the Collaboration Agreement, the Company is required to make significant estimates including an estimate of the number of transcription factor substitutions and the expected time and expected costs to fulfill the performance obligation. The cumulative effect of revisions to the total estimated costs to complete the Company’s single performance obligation will be recorded in the period in which the changes are identified, and amounts can be reasonably estimated. While such revisions will have no impact on the Company’s cash flows, a significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods.

The Company assessed the Collaboration Agreement to determine whether a significant financing component exists and concluded that a significant financing component does not exist. Through December 31, 2020, the Company had recorded $0.4 million of revenue under the Collaboration Agreement.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

During the years ended December 31, 20

and 2019, the Company recorded no

income tax benefits for the net deferred tax assets comprised primarily of net operating losses incurred and research and development tax credits generated in each year, due to its uncertainty of realizing a benefit from these items.

All of the Company’s operating losses since inception have been generated in the United States.

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,
	20 20			2019
Federal statutory income tax rate		(21.0	)%		(21.0	)%
State taxes, net of federal benefit		(6.4	)		(7.1	)
Federal and state research and development tax credits		(3.7	)		(2.2	)
Other		(0.5	)		0.4
Change in deferred tax asset valuation allowance		31.6			29.9

Effective income tax rate		0.0	%		0.0	%

Net deferred tax assets consisted of the following (in thousands):


	December 31,
	20 20			2019
Deferred tax assets:
Net operating loss carryforwards	$	39,289		$	23,769
Research and development tax credit carryforwards		4,955			2,415
Capitalized start-up costs		174			190
Accrued expenses		1,010			522
Stock-based compensation		436			74
Operating lease liabilities		17,032			414

Total deferred tax assets		62,896			27,384
Deferred tax liabilities:
Depreciation		(2,819	)		(482	)
Operating lease right-of-use assets		(11,694 )			(281	)

Total deferred tax liabilities		(14,513	)		(763	)

Valuation allowance		(48,383	)		(26,621	)

Net deferred tax assets	$	—		$	—

As of December 31, 20

, the Company had U.S. federal and state net operating loss carryforwards of $147.3 million and $132.3 million, respectively, which may be available to offset future taxable income. The federal net operating loss carryforwards include $12.5 million which expire at various dates beginning in 2035 and $134.8 million which carryforward indefinitely but in some circumstances may be limited to offset 80% of annual taxable income. The state net operating loss carryforwards expire at various dates beginning in 2036. As of December 31, 20

, the Company also had U.S. federal and state research and development tax credit carryforwards of $3.4 million and $2.0 million, respectively, which may be available to offset future tax liabilities and expire at various dates beginning in 2036 and 2031, respectively.

Utilization of the U.S. federal and state net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Sections 382 and 383 of the Internal Revenue Code of 1986, and corresponding provisions of state law, 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 or tax liabilities. 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 has not conducted a study to assess whether a change of control has occurred or whether there have been multiple changes of control since inception due to the significant complexity and cost associated with such a study. If the Company has experienced a change of control, as defined by Section 382, at any time since inception, utilization of the net operating loss carryforwards or research and development tax credit carryforwards would be subject to an annual limitation under Section 382. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and development tax credit carryforwards before utilization. Further, until a study is completed by the Company and any limitation is known, no amounts are

being recorded as an uncertain tax position.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products that would generate revenue from product sales and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 20

and 2019. Management reevaluates the positive and negative evidence at each reporting period.

The valuation allowance increased by $21.8 million and $15.3 million during the years ended December 31, 20

and 2019, respectively, primarily as a result of the increase in net operating loss carryforwards.

As of December 31, 20

and 2019, the Company had not

recorded any amounts for unrecognized tax benefits. The Company files income tax returns in the U.S. and Massachusetts, 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 federal and state jurisdictions, where applicable. There are currently no pending tax examinations. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

Commitments and Contingencies Disclosure [Abstract]

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Leases

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Leases

12. Leases

In October 2019, the Company entered into a lease for 81,441 square feet of office and laboratory space in Cambridge, Massachusetts, commencing in January 2020 (the “New Lease”). The initial term of the New Lease was eight years with a five-year option to extend at fair-market rent at the time of the extension. The base rent payments escalate annually over the eight-year lease term and totaled approximately $60.3 million. In connection with the New Lease, the landlord agreed to fund up to $3.0 million in tenant improvements to the leased facility as well as up to an additional $16.3 million, which resulted in additional rent payments to the landlord over the lease term. During the year ended December 31, 2020, $15.4 million of leasehold improvements were reimbursed by the landlord, which resulted in an increase to operating lease liabilities. The Company is obligated to pay its portion of real estate taxes and costs related to the premises, including costs of operations and management of the leased premises. The Company is required to maintain a cash balance of $1.7 million to secure a letter of credit associated with the lease. This amount was classified as restricted cash

(non-current)

on the consolidated balance sheet as of December 31, 2020 and 2019. On January 1, 2020, the lease commencement date, the Company recorded an operating lease asset of $38.6 million and corresponding lease liability of $38.3 million.

In June 2020, the Company amended the New Lease to defer payment of a portion of the base rent and operating expenses and to extend the lease term by nine months to September 2028. The amendment was accounted for as a lease modification and the

right-of-use

asset and lease liability were remeasured at the modification date of June 29, 2020 resulting in an increase of $7.4 million to both the

right-of-use

asset and lease liabilities.

The Company had a lease for office and laboratory facilities in Cambridge, Massachusetts under a noncancelable operating lease that began in August 2017 and expired in March 2025. In April 2020, this lease was assigned and assumed by a related party which became effective in October 2020.

The components of lease expense were as follows (in thousands):


	Year Ended December 31,
	2020		2019
Operating lease cost	$	7,032	$	1,671
Short-term lease cost		61		60
Variable lease cost		1,217		547

	$	8,310	$	2,278

Supplemental disclosure of cash flow information related to leases was as follows (in thousands):


	Year Ended December 31,
	2020		2019
Cash paid for amounts included in the measurement of operating lease liabilities	$	3,086	$	1,731
Operating lease liabilities arising from obtaining right-of-use assets	$	38,306	$	271
Increase in operating lease liabilities and right-of-use assets due to lease remeasurement	$	7,384	$	6,513

The weighted-average remaining lease term and discount rate were as follows:


	2020			2019
Weighted-average remaining lease term—operating leases (in years)		7.7			1.1
Weighted-average discount rate—operating leases		5.35	%		7.53	%

Future annual minimum lease payments under operating leases as of December 31, 20

were as follows (in thousands):


2021	$	9,814
2022		10,016
2023		10,107
2024		10,347
2025		10,595
Thereafter		30,500

Total future minimum lease payments		81,379
Less: imputed interest		(15,104	)
Less: estimated lease incentives		(3,933	)

Total operating lease liabilities	$	62,342



Included in the consolidated balance sheet (in thousands):	December 31, 2020
Current operating lease liabilities	$	3,981
Operating lease liabilities, net of current portion		58,361
Total operating lease liabilities	$	62,342

Sublease agreement

In April 2020, the Company entered into a

two-year

sublease of approximately 16,843 square feet of office space under the New Lease, as amended, which began in July 2020. As of December 31, 2020, the remaining base rent payments due to the Company under the subleases was $2.5 million. The Company recorded other income of $1.0 million during the year ended December 31, 2020 related to this sublease.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies

13. Commitments and Contingencies

Leases

The Company’s commitments under its leases are described in Note 1

License agreements

Dana-Farber Cancer Institute

In 2016, the Company entered into a license agreement with the Dana-Farber Cancer Institute, Inc. (“Dana Farber”) for an exclusive license for certain biological materials as well as patent rights to methods of identifying compounds to treat prostate cancer. In consideration for the right to develop, manufacture, and commercialize products based on certain of Dana Farber’s intellectual property, the Company is obligated to reimburse Dana Farber for patent expenses and pay low single-digit sales-based royalties upon the occurrence of specific events as outlined in the license agreement. Unless terminated earlier, in accordance with the provisions of the agreement, the agreement will terminate on the expiration date of the last to expire of the applicable Dana Farber patents. None of the Company’s product candidates utilize technology covered by this license.

Stanford

In July 2017, the Company entered into a license agreement with the Board of Trustees of the Leland Stanford Junior University (“Stanford”) for a

non-exclusive

license for patent rights to certain diseases associated with chromatin remodeling. In consideration for the right to develop, manufacture, and commercialize products based on certain of Stanford’s intellectual property, the Company paid a

one-time,

non-refundable

license fee of less than $0.1 million and reimbursed Stanford for $0.1 million of costs incurred related to the patented technology. The Company also issued 42,781 shares of the Company’s common stock upon execution of a share purchase agreement. In addition to annual license maintenance fees of less than $0.1 million, the Company will reimburse Stanford for patent expenses, pay low single-digit sales-based royalties, and pay up to $1.1 million in regulatory milestones on each licensed product upon the occurrence of specific events as outlined in the license agreement. None of the Company’s product candidates utilize technology covered by this license.

Indemnification agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers 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. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims.

Legal Proceedings

From time to time, the Company may become involved in litigation or other legal proceedings. The Company is not currently a party to any material litigation or legal proceedings.

Defined Contribution Plan

12 Months Ended

Dec. 31, 2020

Retirement Benefits [Abstract]

Defined Contribution Plan

14. Defined Contribution Plan

The Company has a 401(k) defined contribution plan (the “401(k) Plan”) for its employees. Eligible employees may make pretax contributions to the 401(k) Plan up to statutory limits. There was no discretionary match made under the 401(k) Plan as of December 31, 20

and 2019.

The entire disclosure for retirement benefits.

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Related Parties

12 Months Ended

Dec. 31, 2020

Related Parties

15. Related Parties

In October 2015, the Company entered into a five-year service agreement with Flagship Pioneering (“Flagship”),

an affiliate of one of its stockholders, to provide general and administrative services

to the Company, including certain consulting services and the provision of employee health and dental benefit plans for the Company’s employees. The Company made cash payments for services received under this agreement of $1.2 million and $0.9 million during the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020 and 2019, the Company had no accounts payable to Flagship for costs related to the service agreement.

This agreement expired in 2020.

In October 2015, the Company entered into a five-year consulting agreement with a scientific founder of the Company who is also a board member and a

shareholder. In October 2020, this agreement was extended to January 1, 2022, with an option to renew. During

the years ended December 31, 2020 and 2019, the Company paid the scientific founder $0.2 million and $0.2 million, respectively. As of December 31, 2020 the Company had less than $0.1 million in accounts payable to this scientific founder.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

Concentrations of credit risk and of significant suppliers

Basis of presentation

Use of estimates

Cash equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Marketable Securities

Restricted cash

non-current)

in the Company’s consolidated balance sheets.

Property and equipment


		Estimated Useful Life
Laboratory equipment		5 years
Furniture and fixtures		5 years
Computer equipment and software		3 years
Leasehold improvements		Shorter of useful life or remaining term of lease

Impairment of long-lived assets

The Company evaluates its long-lived assets, which consist primarily of property and equipment and operating lease

right-of-use

Fair value measurements

•

Level 1—Quoted prices in active markets for identical assets or liabilities.

•

Revenue recognition

The Company accounts for its one collaboration arrangement, entered into in July 2020, under ASC Topic 606,

Revenue From Contracts With Customers

Company re-evaluates the

cumulative catch-up basis

in the period of adjustment.

Classification of convertible preferred stock

Research and development costs

Patent costs

Leases

In accordance with ASC 842,

Leases,

right-of-use

In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as

non-lease

components. The Company has elected to not separate lease and

non-lease

components. Only the fixed costs for lease components and their associated

non-lease

components are accounted for as a single lease component and recognized as part of a

right-of-use

Stock-based compensation

The Company measures stock options with service-based vesting or performance-based vesting granted to employees,

non-employees

non-employees,

Net loss per share

the two-class method

when computing net income (loss) per share as the Company had issued shares that meet the definition of participating securities.

The two-class method

determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings.

The two-class method

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2020 and 2019.


	December 31,
	2020		2019
Stock options to purchase common stock		5,016,460		3,886,489
Warrants to purchase common stock		18,445		—
Convertible preferred stock (as converted to common stock)		—		15,467,863
Unvested restricted common stock		—		891,894
Warrants to purchase convertible preferred stock (as converted to common stock)		—		7,608

		5,034,905		20,253,854

Segments

Comprehensive loss

Income taxes

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a

two-step

more-likely-than-not

Recently issued accounting pronouncements

In June 2016, the FASB issued ASU

No. 2016-13,

Financial Instruments – Credit Losses (Topic 326)

No. 2019-10,

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Property and Equipment are Stated at Cost Less Accumulated Depreciation and Amortization


		Estimated Useful Life
Laboratory equipment		5 years
Furniture and fixtures		5 years
Computer equipment and software		3 years
Leasehold improvements		Shorter of useful life or remaining term of lease

Summary of Earnings Per Share Diluted Anti Dilutive Impact


	December 31,
	2020		2019
Stock options to purchase common stock		5,016,460		3,886,489
Warrants to purchase common stock		18,445		—
Convertible preferred stock (as converted to common stock)		—		15,467,863
Unvested restricted common stock		—		891,894
Warrants to purchase convertible preferred stock (as converted to common stock)		—		7,608

		5,034,905		20,253,854

Marketable Securities and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Available for Sale Marketable Securities By Security Type

As of December 31, 2020, available for sale marketable securities by security type consisted of (in thousands):


				Gross		Gross			Estimated
		Amortized		Unrealized		Unrealized			Fair
		Cost		Gains		Losses			Value
U . S . treasury notes (due within one year)	$	92,982	$	—	$	(7	)	$	92,975

Total	$	92,982	$	—	$	(7	)	$	92,975

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands):


	Fair Value Measurements at December 31, 2020 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	48,770	$	—	$	—	$	48,770
U .S . treasury notes		—		42,997		—		42,997
Marketable securities:
U . S . treasury notes		—		92,975		—		92,975

Total	$	48,770	$	135,972	$	—	$	184,742


	Fair Value Measurements at December 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	14,951	$	—	$	—	$	14,951

Liabilities:
Preferred stock warrant liability	$	—	$	—	$	45	$	45

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Sumary of Property and Equipment Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2020			2019
Laboratory equipment	$	3,740		$	3,202
Furniture and fixtures		815			337
Computer equipment and software		100			81
Leasehold improvements		16,961			75
Assets not yet placed in service		15			280

		21,631			3,975
Less: Accumulated depreciation and amortization		(2,103	)		(1,292	)

	$	19,528		$	2,683

Accrued Expenses (Table)

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2020		2019
Accrued employee compensation and benefits	$	3,513	$	1,867
Accrued construction in progress		2,385		119
Accrued external research and development expenses		2,146		1,384
Accrued professional fee s		979		274
Other		138		57

	$	9,161	$	3,701

Notes Payable (Tables)

12 Months Ended

Dec. 31, 2020

Long-term Debt, Unclassified [Abstract]

Summary of Long Term Debt

Long-term debt consisted of the following (in thousands):


	December 31,
	2020			2019
Principal amount of long-term debt	$	20,000		$	15,000
Less: Current portion of long-term debt		—			(4,152	)

Long-term debt, net of current portion		20,000			10,848
Final payment fee		1,000			530
Debt discount, net of accretion		(1,346	)		(418	)

Long-term debt, net of discount and current portion	$	19,654		$	10,960

Summary of Future Long Term Loan Principal Payments Due

As of December 31, 2020, future principal payments due are as follows (in thousands):


2021	$	—
2022		—
2023		833
2024		10,000
2025		9,167

	$	20,000

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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Stockholders' Equity Note [Abstract]

Convertible Preferred Stock and Preferred Stock Warrants (Tables)

12 Months Ended

Dec. 31, 2020

Schedule of stock by class

As of December 31, 2019,

Preferred Stock consisted of the following (in thousands, except share amounts):


	Preferred Stock Authorized		Preferred Stock Issued and Outstanding		Carrying Value		Liquidation Preference		Common Stock Issuable Upon Conversion
Series A-1 Preferred Stock		9,707,826		9,693,750	$	9,609	$	9,694		5,239,865
Series A-2 Preferred Stock		10,804,165		10,804,165		16,179		16,206		5,840,089
Series B Preferred Stock		8,117,631		8,117,631		60,756		60,882		4,387,909

		28,629,622		28,615,546	$	86,544	$	86,782		15,467,863

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

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Share-based Payment Arrangement [Abstract]

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Schedule of Weighted-Average Assumptions Used to Estimate Fair Value of Stock Options and Restricted Stock Awards using Black-Scholes Option Pricing Model


	Year Ended December 31,
	2020			2019
Risk-free interest rate		0.4	%		2.2	%
Expected volatility		78.5	%		78.2	%
Expected dividend yield		—			—
Expected term (in years)		6.1			6.0

Schedule of Share Option Activity

The following table summarizes the Company’s option activity during the year ended December 31, 2020:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2019		3,886,489		$	2.39
Granted		1,922,377			8.87
Exercised		(611,048	)		1.99
Forfeited		(181,358	)		2.10

Outstanding as of December 31, 2020		5,016,460		$	4.93		8.5	$	76,941

Vested and expected to vest as of December 31, 2020		5,016,460		$	4.93		8.5	$	76,941
Options exercisable as of December 31, 2020		1,508,122		$	1.91		7.4	$	27,683

Summary of Restricted common stock


	Shares
Unvested restricted common stock as of December 31, 2019		891,894
Issued		—
Vested		(891,894	)

Unvested restricted common stock as of December 31, 2020		—

Summary of Stock-Based Compensation Expense


	Year Ended December 31,
	2020		2019
Research and development expenses	$	1,724	$	1,140
General and administrative expenses		1,237		554

		$2,961		$1,694

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Summary of Reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate

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,
	20 20			2019
Federal statutory income tax rate		(21.0	)%		(21.0	)%
State taxes, net of federal benefit		(6.4	)		(7.1	)
Federal and state research and development tax credits		(3.7	)		(2.2	)
Other		(0.5	)		0.4
Change in deferred tax asset valuation allowance		31.6			29.9

Effective income tax rate		0.0	%		0.0	%

Summary of Net Deferred Tax Assets

Net deferred tax assets consisted of the following (in thousands):


	December 31,
	20 20			2019
Deferred tax assets:
Net operating loss carryforwards	$	39,289		$	23,769
Research and development tax credit carryforwards		4,955			2,415
Capitalized start-up costs		174			190
Accrued expenses		1,010			522
Stock-based compensation		436			74
Operating lease liabilities		17,032			414

Total deferred tax assets		62,896			27,384
Deferred tax liabilities:
Depreciation		(2,819	)		(482	)
Operating lease right-of-use assets		(11,694 )			(281	)

Total deferred tax liabilities		(14,513	)		(763	)

Valuation allowance		(48,383	)		(26,621	)

Net deferred tax assets	$	—		$	—

Leases (Tables)

12 Months Ended

Dec. 31, 2020

Leases [Abstract]

Summary of Lease Cost

The components of lease expense were as follows (in thousands):


	Year Ended December 31,
	2020		2019
Operating lease cost	$	7,032	$	1,671
Short-term lease cost		61		60
Variable lease cost		1,217		547

	$	8,310	$	2,278

Summary of Supplemental Cash Flow Information Related to Leases

Supplemental disclosure of cash flow information related to leases was as follows (in thousands):


	Year Ended December 31,
	2020		2019
Cash paid for amounts included in the measurement of operating lease liabilities	$	3,086	$	1,731
Operating lease liabilities arising from obtaining right-of-use assets	$	38,306	$	271
Increase in operating lease liabilities and right-of-use assets due to lease remeasurement	$	7,384	$	6,513

Summary of Weighted-Average Remaining Lease Term and Discount Rate Leases

The weighted-average remaining lease term and discount rate were as follows:


	2020			2019
Weighted-average remaining lease term—operating leases (in years)		7.7			1.1
Weighted-average discount rate—operating leases		5.35	%		7.53	%

Summary of Minimum Lease Payments

Future annual minimum lease payments under operating leases as of December 31, 2020 were as follows (in thousands):


2021	$	9,814
2022		10,016
2023		10,107
2024		10,347
2025		10,595
Thereafter		30,500

Total future minimum lease payments		81,379
Less: imputed interest		(15,104	)
Less: estimated lease incentives		(3,933	)

Total operating lease liabilities	$	62,342

Summary of Operating Lease Liabilities


Included in the consolidated balance sheet (in thousands):	December 31, 2020
Current operating lease liabilities	$	3,981
Operating lease liabilities, net of current portion		58,361

Total operating lease liabilities	$	62,342

Nature of Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Nov. 19, 2020	Oct. 27, 2020	Jul. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net income (loss)				$ 68,800	$ 51,128
Retained earnings accumulated deficit				162,936	$ 94,136
Upfront payment received from Merck			$ 15,000	$ 15,000
IPO [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Warrants granted to purchase common stock		7,608
IPO [Member] \| Common Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during the period shares new issues shares		7,500,000		8,451,837
Sale of stock issue price per share		$ 16.00
Sale of stock consideration received on the transaction		$ 107,900
Warrants granted to purchase common stock		7,608
Over-Allotment Option [Member] \| Common Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during the period shares new issues shares	951,837
Sale of stock issue price per share	$ 16.00
Sale of stock consideration received on the transaction	$ 14,200

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions			12 Months Ended
	Oct. 31, 2020	Oct. 27, 2020	Dec. 31, 2020	Dec. 31, 2019
Impairment losses on long-lived assets			$ 0	$ 0
IPO [Member]
Conversion of preferred stock, common shares issued	21,958,588	21,958,588

Summary of Significant Accounting Policies - Summary of Property and Equipment are Stated at Cost Less Accumulated Depreciation and Amortization (Detail)	12 Months Ended
	Dec. 31, 2020
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	Shorter of useful life or remaining term of lease

Summary of Significant Accounting Policies - Summary of Earnings Per Share Diluted Anti Dilutive Impact (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,034,905	20,253,854
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,016,460	3,886,489
Warrents to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	18,445
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		15,467,863
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		891,894
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		7,608

Marketable Securities and Fair Value Measurements - Summary of Available for Sale Markatable Securties By Security Type (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	$ 92,982
Gross Unrealized Losses	(7)
Estimated Fair Value	92,975
U.S. treasury notes (due within one year) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	92,982
Gross Unrealized Losses	(7)
Estimated Fair Value	$ 92,975

Marketable Securities and Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Marketable securities	$ 92,975
Total	184,742
Preferred Stock Warrant Liability [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Preferred stock warrant liability		$ 45
Money Market Funds [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Money market funds	48,770	14,951
US Treasury Securities [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Money market funds	42,997
Marketable securities	92,975
Level 1 [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Total	48,770
Level 1 [Member] \| Fair Value, Recurring [Member] \| Money Market Funds [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Money market funds	48,770	14,951
Level 2 [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Total	135,972
Level 2 [Member] \| Fair Value, Recurring [Member] \| US Treasury Securities [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Money market funds	42,997
Marketable securities	$ 92,975
Level 3 [Member] \| Fair Value, Recurring [Member] \| Preferred Stock Warrant Liability [Member]
FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Preferred stock warrant liability		$ 45

Marketable Securities and Fair Value Measurements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Oct. 27, 2020	Oct. 26, 2020
Marketable Securities	$ 0	$ 92,975
IPO [Member]
Class of warrant or right, number of securities called by warrants or rights			7,608
IPO [Member] \| Common Stock [Member]
Class of warrant or right, number of securities called by warrants or rights			7,608
Before IPO [Member] \| Series A one Preferred Stock [Member]
Class of warrant or right, number of securities called by warrants or rights				14,076
Preferred Stock Warrant Liability [Member]
Class of warrant or right, number of securities called by warrants or rights	14,076
Warrant issue price	$ 1.00

Property and Equipment, Net - Sumary of Property and Equipment Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 21,631	$ 3,975
Less: Accumulated depreciation and amortization	(2,103)	(1,292)
Property, Plant and Equipment, Net	19,528	2,683
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,740	3,202
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	815	337
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	100	81
Leaseholds and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,961	75
Assets Not Yet Placed In service [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 15	$ 280

Property and Equipment, Net - Sumary of Property and Equipment Net (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 1.3	$ 0.7

Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued employee compensation and benefits	$ 3,513	$ 1,867
Accrued construction in progress	2,385	119
Accrued external research and development expenses	2,146	1,384
Other	138	57
Accrued professional fees	979	274
Total	$ 9,161	$ 3,701

Notes Payable - Summary of Long Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]
Principal amount of long-term debt	$ 20,000	$ 15,000
Less: Current portion of long-term debt		(4,152)
Long-term debt, net of current portion	20,000	10,848
Final payment fee	1,000	530
Debt discount, net of accretion	(1,346)	(418)
Long-term debt, net of discount and current portion	$ 19,654	$ 10,960

Notes Payable - Summary of Future Principal Payments Due (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	$ 0
2022	0
2023	833
2024	10,000
2025	9,167
Long-term Debt, Gross	$ 20,000	$ 15,000

Notes Payable - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Nov. 19, 2020	Nov. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Debt instrument loan amount			$ 20,000	$ 15,000
Final payment fee			1,000	$ 530
Loss on Extinguishment of Debt			$ (222)
Oxford Finance LLC [Member]
Short-term Debt [Line Items]
Interest rate outstanding borrowings loan			8.00%
Debt, weighted average interest rate			6.40%	6.90%
Debt, final payment fee percentage	5.00%
Debt instrument interest terms	The Term Loan bears interest at a floating per annum rate equal to the greater of (i) 8.0% and (ii) the sum of (a) thirty-day LIBOR rate plus (b) 7.84%.
Debt instrument maturity date	Nov. 01, 2025
Debt instruments payment terms	The Company is required to make monthly interest only payments under the Oxford Loan each month beginning on January 1, 2021.
Debt instrument frequency of payment terms	monthly
Debt instrument, restrictive covenants	The Company’s obligations under the Oxford Loan Agreement are secured by a security interest in all of its assets, other than its intellectual property. The Company is also subject to certain affirmative and negative covenants
Class of warrant or right, number of securities called by warrants or rights			18,445
Warrants Issue price per share			$ 16.26
Warrants exercisable term			10 years
Warrants not settleable in cash, fair value disclosure	$ 200
Debt instrument terms			At the Company’s option, the Company may elect to prepay the loans subject to a prepayment fee equal to the following percentage of the principal amount being prepaid: 2% if an advance is prepaid during the first 12 months following the applicable advance date, 1% if an advance is prepaid after 12 months but prior to 24 months following the applicable advance date, and 0.5% if an advance is prepaid any time after 24 months following the applicable advance date but prior to the Maturity Date.
Payments of debt issuance costs			$ 200
Term of loan			5 years
Oxford Finance LLC [Member] \| Prepayment within First Twelve Months [Member]
Short-term Debt [Line Items]
Percentage of prepayment fee			2.00%
Oxford Finance LLC [Member] \| Prepayment After 12 months but prior to 24 months [Member]
Short-term Debt [Line Items]
Percentage of prepayment fee			1.00%
Oxford Finance LLC [Member] \| Prepayment After 24 Months [Member]
Short-term Debt [Line Items]
Percentage of prepayment fee			0.50%
Minimum [Member] \| Oxford Finance LLC [Member]
Short-term Debt [Line Items]
Debt instrument, description of variable rate basis	LIBOR
Debt instrument, basis spread on variable rate	7.84%
Debt instrument, interest rate, stated percentage	8.00%
Additional Rate In Event Of Default [Member]
Short-term Debt [Line Items]
Debt instrument, interest rate, effective percentage			5.00%
Term Loan A [Member]
Short-term Debt [Line Items]
Debt instrument loan amount				$ 7,000
Debt, final payment fee percentage			3.00%
Term Loan A [Member] \| Oxford Finance LLC [Member]
Short-term Debt [Line Items]
Debt instrument loan amount	$ 20,000
Proceeds from issuance of debt	20,000
Term Loan A [Member] \| Minimum [Member]
Short-term Debt [Line Items]
Debt instrument, description of variable rate basis			LIBOR
Debt instrument, basis spread on variable rate			2.50%
Term Loan B [Member]
Short-term Debt [Line Items]
Debt instrument loan amount				$ 8,000
Debt, final payment fee percentage			4.00%
Term Loan B [Member] \| Base Rate [Member]
Short-term Debt [Line Items]
Debt instrument, interest rate, stated percentage			1.00%
Term Loan B [Member] \| Maximum [Member] \| Oxford Finance LLC [Member]
Short-term Debt [Line Items]
Debt instrument loan amount	$ 5,000
Term Loan B [Member] \| Additional Over Base Rate [Member] \| Minimum [Member]
Short-term Debt [Line Items]
Debt instrument, description of variable rate basis			LIBOR
Debt instrument, basis spread on variable rate			2.50%
Term Loan A and B [Member]
Short-term Debt [Line Items]
Final payment fee			$ 500
Loss on Extinguishment of Debt		$ 200

Convertible Preferred Stock and Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended	2 Months Ended	12 Months Ended
	Oct. 31, 2020	Oct. 27, 2020	Apr. 30, 2020	Aug. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Common Stock [Member]
Issuance of common stock upon exercise of stock options , shares					6,728
IPO [Member]
Conversion of preferred stock, common shares issued	21,958,588	21,958,588
Class of warrant or right, number of securities called by warrants or rights		7,608
IPO [Member] \| Common Stock [Member]
Class of warrant or right, number of securities called by warrants or rights		7,608
Issuance of common stock upon exercise of stock options , shares		6,728
Series A-1 Preferred Stock [Member] \| Issuance of Notes Payable [Member]
Class of warrant or right, number of securities called by warrants or rights						14,076
Class of Warrant exercise price						$ 1.00
Series B [Member]
Sale of preferred stock			6,407,867	5,600,000
Preferred stock, par or stated value per share			$ 7.50	$ 7.50
Proceeds from issuance of convertible preferred stock			$ 48.1	$ 42.0

Convertible Preferred Stock and Preferred Stock Warrants - Schedule of stock by class (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Preferred Stock Authorized	25,000,000	28,629,622
Preferred Stock Issued and Outstanding	0	28,615,546
Carrying Value		$ 86,544
Liquidation Preference		$ 86,782
Common Stock Issuable Upon Conversion		15,467,863
Series A-1 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock Authorized		9,707,826
Preferred Stock Issued and Outstanding		9,693,750
Carrying Value		$ 9,609
Liquidation Preference		$ 9,694
Common Stock Issuable Upon Conversion		5,239,865
Series A-2 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock Authorized		10,804,165
Preferred Stock Issued and Outstanding		10,804,165
Carrying Value		$ 16,179
Liquidation Preference		$ 16,206
Common Stock Issuable Upon Conversion		5,840,089
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock Authorized		8,117,631
Preferred Stock Issued and Outstanding		8,117,631
Carrying Value		$ 60,756
Liquidation Preference		$ 60,882
Common Stock Issuable Upon Conversion		4,387,909

Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Nov. 19, 2020	Oct. 27, 2020	Dec. 31, 2020
Class of Stock [Line Items]
Common stock voting rights			Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors.
IPO [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Stock issued during the period shares new issues shares		7,500,000	8,451,837
Sale of stock issue price per share		$ 16.00
Sale of stock consideration received on the transaction		$ 107.9
Over-Allotment Option [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Stock issued during the period shares new issues shares	951,837
Sale of stock issue price per share	$ 16.00
Sale of stock consideration received on the transaction	$ 14.2

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		12 Months Ended
	Jan. 01, 2021	Oct. 21, 2020	Apr. 30, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2015
Share-based Payment Arrangement [Line Items]
Unrecognized compensation costs related to unvested options and unvested restricted stock				$ 13.5
Weighted average period of unrecognized compensation costs				3 years 7 months 6 days
Aggregate Intrinsic Value,Exercised				$ 3.5	$ 1.2
Weighted Average Grant Date Fair value,granted				$ 6.01	$ 2.54
Aggregate fair value of restricted stock that vested				$ 4.8	$ 3.3
Common Stock [Member]
Share-based Payment Arrangement [Line Items]
Sale of restricted common stock to scientific founders						4,459,459
Vesting period			5 years
2020 Incentive Plan [Member]
Share-based Payment Arrangement [Line Items]
Common stock shares available for grant				2,213,094
Number of additional shares authorized	1,471,576
2020 Incentive Plan [Member] \| Initial Amount [Member]
Share-based Payment Arrangement [Line Items]
Number of shares authorized		2,200,000
2020 Incentive Plan [Member] \| Initial Aggregate From 2016 And 2020 Plans [Member] \| Maximum [Member]
Share-based Payment Arrangement [Line Items]
Number of shares authorized		5,078,295
2020 Incentive Plan [Member] \| 2021 to 2030 [Member]
Share-based Payment Arrangement [Line Items]
Percentage of automatic annual increase in number of shares		4.00%
2020 Employee Stock Purchase Plan [Member]
Share-based Payment Arrangement [Line Items]
Number of additional shares authorized	367,894
Maximum aggregate number of shares added to plan		3,220,520
2020 Employee Stock Purchase Plan [Member] \| Initial Aggregate [Member]
Share-based Payment Arrangement [Line Items]
Number of shares authorized		360,000
2020 Employee Stock Purchase Plan [Member] \| 2021 to 2030 [Member]
Share-based Payment Arrangement [Line Items]
Percentage of automatic annual increase in number of shares		1.00%
2020 and 2016 Incentive Plans [Member] \| Service Based Vesting [Member]
Share-based Payment Arrangement [Line Items]
Vesting period				4 years
Stock option expiry period				10 years

Stock-Based Compensation - Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Stock Options and Restricted Stock Awards using Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Risk-free interest rate	0.40%	2.20%
Expected volatility	78.50%	78.20%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6 years 1 month 6 days	6 years

Stock-Based Compensation - Schedule of Share Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance \| shares	3,886,489
Number of shares, Granted \| shares	1,922,377
Number of shares, Exercised \| shares	(611,048)
Number of shares, Forfeited \| shares	(181,358)
Ending Balance \| shares	5,016,460
Number of shares, Vested \| shares	5,016,460
Number of shares, Exercisable \| shares	1,508,122
Weighted Average Exercise Price, Beginning balance \| $ / shares	$ 2.39
Weighted Average Exercise Price, Granted \| $ / shares	8.87
Weighted Average Exercise Price, Exercised \| $ / shares	1.99
Weighted Average Exercise Price, Forfeited \| $ / shares	2.10
Weighted Average Exercise Price, Ending Balance \| $ / shares	4.93
Weighted Average Exercise Price, Vested \| $ / shares	4.93
Weighted Average Exercise Price, Exercisable \| $ / shares	$ 1.91
Weighted Average Contractual Term, Ending Balance	8 years 6 months
Weighted Average Contractual Term, Vested	8 years 6 months
Weighted Average Contractual Term, Exercisable	7 years 4 months 24 days
Aggregate Intrinsic Value, Ending Balance \| $	$ 76,941
Aggregate Intrinsic Value, Vested \| $	76,941
Aggregate Intrinsic Value, Exercisable \| $	$ 27,683

Stock-Based Compensation - Summary of Restricted Common Stock (Detail) - Restricted Stock [Member] - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common stock as of December 31, 2019		891,894
Vested	(891,894)

Stock-Based Compensation - Summary of Stock-based compensation expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock-based compensation expense	$ 2,961	$ 1,694
Research and Development Expenses [Member]
Stock-based compensation expense	1,724	1,140
General and Administrative Expenses [Member]
Stock-based compensation expense	$ 1,237	$ 554

Collaboration Agreement - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2020	Dec. 31, 2020
Upfront payment received from Merck	$ 15,000	$ 15,000
Deferred revenue		15,000
Revenue		430
Unsatisfied portion of the performance obligation		14,600
Maximum [Member] \| Sales based [Member]
Amount receivable for achievement of milestones		165,000
Research Development And Regulatory [Member] \| Maximum [Member]
Amount receivable for achievement of milestones		245,000
Merck Collaboration Agreement [Member]
Revenue		$ 400

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856