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Unaudited Quarterly Results (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Results of Operations on Quarterly Basis

The results of operations on a quarterly basis for the years ended December 31, 2019 and 2018 are set forth below:

	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	(Amounts in thousands except per share data)
Collaboration revenue	$	10,433		$	11,118		$	10,616		$	10,936
Operating expenses:
Research and development		23,709			25,460			27,513			31,731
General and administrative		10,533			13,118			8,431			8,976
Total operating expenses		34,242			38,578			35,944			40,707
Operating loss		(23,809	)		(27,460	)		(25,328	)		(29,771	)
Interest income		1,869			1,777			1,694			1,495
Net loss	$	(21,940	)	$	(25,683	)	$	(23,634	)	$	(28,276	)
Net loss per share, basic and diluted	$	(0.49	)	$	(0.56	)	$	(0.49	)	$	(0.57	)
Weighted average shares outstanding, basic and diluted		45,234			45,814			48,554			49,350

	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	(Amounts in thousands except per share data)
Collaboration revenue	$	7,469		$	7,677		$	7,408		$	7,880
Operating expenses:
Research and development		22,493			23,467			23,237			19,918
General and administrative		7,406			7,805			8,270			8,708
Total operating expenses		29,899			31,272			31,507			28,626
Operating loss		(22,430	)		(23,595	)		(24,099	)		(20,746	)
Interest income		1,074			1,376			1,397			1,680
Net loss	$	(21,356	)	$	(22,219	)	$	(22,702	)	$	(19,066	)
Net loss per share, basic and diluted	$	(0.51	)	$	(0.52	)	$	(0.53	)	$	(0.43	)
Weighted average shares outstanding, basic and diluted		42,043			42,836			43,161			44,215

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 57,226	$ 58,856
Marketable securities	222,500	255,203
Accounts receivable	4,620	7,547
Prepaid expenses and other current assets	5,135	3,371
Total current assets	289,481	324,977
Marketable securities - noncurrent	4,746
Property and equipment, net	17,996	17,061
Operating lease right-of-use assets	19,137
Other assets	2,920	5,277
Total Assets	334,280	347,315
Current Liabilities:
Accounts payable	3,941	2,708
Accrued expenses	13,273	10,742
Current portion of operating lease liability	5,745
Current portion of deferred revenue	12,674	27,122
Total current liabilities	35,633	40,572
Deferred revenue, net of current portion	16,136	28,810
Long-term operating lease liability	12,630
Other long-term liabilities		13
Commitments and contingencies (Note 8)
Stockholders’ Equity:
Common stock, $0.0001 par value; 120,000,000 shares authorized; 50,198,044 and 45,224,480 shares issued and outstanding at December 31, 2019 and 2018, respectively	5	5
Additional paid-in capital	570,493	478,968
Accumulated other comprehensive income (loss)	261	(28)
Accumulated deficit	(300,878)	(201,025)
Total stockholders’ equity	269,881	277,920
Total Liabilities and Stockholders’ Equity	$ 334,280	$ 347,315

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At-the-market offerings [Member]	Common Stock [Member]	Common Stock [Member] At-the-market offerings [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] At-the-market offerings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2016	$ 209,837		$ 4		$ 263,403			$ (53,570)
Beginning balance, shares at Dec. 31, 2016			36,018,540
Issuance of common stock	141,000				141,000
Issuance of common stock, shares			6,250,000
Exercise of stock options	1,156				1,156
Exercise of stock options, shares			141,759
Issuance of shares under employee stock purchase plan	825				825
Issuance of shares under employee stock purchase plan, shares			64,786
Equity-based compensation	15,322				15,322
Equity-based compensation, shares			(90,462)
Net loss	(67,543)							(67,543)
Ending balance at Dec. 31, 2017	300,597		$ 4		421,706			(121,113)
Ending balance, shares at Dec. 31, 2017			42,384,623
Retroactive adjustment to beginning accumulated deficit (ASU 2014-09 [Member]) at Dec. 31, 2018	5,431							5,431
Issuance of common stock		$ 28,548		$ 1		$ 28,547
Issuance of common stock, shares				1,659,300
Exercise of stock options	10,651				10,651
Exercise of stock options, shares			1,142,944
Issuance of shares under employee stock purchase plan	1,018				1,018
Issuance of shares under employee stock purchase plan, shares			68,865
Equity-based compensation	17,046				17,046
Equity-based compensation, shares			(31,252)
Other comprehensive income (loss)	(28)						$ (28)
Net loss	(85,343)							(85,343)
Ending balance at Dec. 31, 2018	$ 277,920		$ 5		478,968		(28)	(201,025)
Ending balance, shares at Dec. 31, 2018	45,224,480		45,224,480
Retroactive adjustment to beginning accumulated deficit (ASC 842 [Member]) at Dec. 31, 2019	$ (320)							(320)
Issuance of common stock		$ 72,256				$ 72,256
Issuance of common stock, shares				4,518,579
Exercise of stock options	$ 3,086				3,086
Exercise of stock options, shares	364,404		364,404
Issuance of shares under employee stock purchase plan	$ 1,092				1,092
Issuance of shares under employee stock purchase plan, shares			90,581
Equity-based compensation	15,091				15,091
Other comprehensive income (loss)	289						289
Net loss	(99,533)							(99,533)
Ending balance at Dec. 31, 2019	$ 269,881		$ 5		$ 570,493		$ 261	$ (300,878)
Ending balance, shares at Dec. 31, 2019	50,198,044		50,198,044

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

The consolidated financial statements include the accounts of Intellia Therapeutics, Inc. and its wholly owned, controlled subsidiary, Intellia Securities Corp. All intercompany balances and transactions have been eliminated in consolidation. Comprehensive loss is comprised of net loss and gain/loss on marketable securities.

Use of Estimates

The preparation of the Company’s consolidated financial statements in accordance with accounting principles generally accepted (“GAAP”) in the United States of America (“U.S.”) requires management to make estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of collaboration revenue and expenses during the reporting periods. Significant estimates in these consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses and equity-based compensation expense. The Company bases its estimates on historical experience and various other assumptions that management believes to be reasonable. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.

Fair Value Measurements

The Company’s financial instruments include cash equivalents, marketable securities, accounts receivable, accounts payable and accrued expenses. The Company’s financial assets, which include cash equivalents and marketable securities, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models and observable market inputs to determine value.

Refer to Note 4 for further information regarding the Company’s fair value measurements.

Other financial instruments, including accounts receivable, accounts payable and accrued expenses, are carried at cost, which approximate fair value due to the short duration and term to maturity.

Cash Equivalents

The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. As of December 31, 2019 and 2018, cash equivalents consisted of interest-bearing money market accounts.

Marketable Securities

The Company’s marketable securities are accounted for as available-for-sale and recorded at fair value with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of stockholders’ equity. Refer to Note 3 for further information regarding the Company’s marketable securities.

Concentrations of Credit Risk

The Company’s cash, cash equivalents and marketable securities may potentially be subject to concentrations of credit risk. The Company generally maintains balances in various accounts in excess of federally insured limits with financial institutions that management believes to be of high credit quality.

Accounts receivable represent amounts due from collaboration partners. The Company monitors economic conditions to identify facts or circumstances that may indicate that any of its accounts receivable are at risk of collection. As of December 31, 2019 and 2018, the Company’s two collaboration partners, Regeneron Pharmaceuticals, Inc. (“Regeneron”) and Novartis Institutes for BioMedical Research, Inc. (“Novartis”), accounted for all of the Company’s accounts receivable.

Property and Equipment

The Company records property and equipment at cost and recognizes depreciation and amortization using the straight-line method over the following estimated useful lives of the respective assets:

Asset Category		Useful Life
Laboratory equipment		5 years
Office furniture and equipment		5 years
Computer software		3 years
Computer equipment		3 years
Leasehold improvements		5 years or term of respective lease, if shorter

Expenditures for repairs and maintenance of assets are expensed as incurred. Upon retirement or sale, the cost of assets disposed and the corresponding accumulated depreciation are removed from the related accounts and any resulting gain or loss is reflected in the results of operations.

Impairment of Long-Lived Assets

The Company tests long-lived assets to be held and used, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of assets or asset groups may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets.

Evaluation of recoverability of the asset or asset group is based on an estimate of undiscounted future cash flows resulting from the use of the asset or asset group and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the asset or asset group, the assets are written down to their estimated fair values. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. To date, the Company has not recorded any material impairment losses on long-lived assets.

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 attributable to differences between carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax reporting purposes and for operating loss and tax credit carryforwards. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes.

The Company’s deferred tax assets and liabilities are measured using enacted tax rates expected to apply in the years in which these temporary differences are expected to be recovered or settled. A valuation allowance is recorded to reduce deferred tax assets if it is determined that it is more likely than not that all or a portion of the deferred tax asset will not be realized. The Company considers many factors when assessing the likelihood of future realization of deferred tax assets, including recent earnings results, expectations of future taxable income, carryforward periods available and other relevant factors. The Company records changes in the required valuation allowance in the period that the determination is made.

The Company assesses its income tax positions and records tax benefits for all years subject to examination based upon management’s evaluation of the facts, circumstances and information available as of the reporting date. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority having full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, the Company does not recognize a tax benefit in the financial statements. The Company records interest and penalties related to uncertain tax positions, if applicable, as a component of income tax expense.

Revenue Recognition

The Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) and its related amendments (collectively known as Accounting Standard Codification (“ASC”) 606 “ASC 606”) on January 1, 2018 using the modified retrospective method. The reported results for 2019 and 2018 reflect the application of ASC 606 guidance while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (“ASC 605” or “legacy GAAP”). The adoption of ASC 606 represented a change in accounting principle that more closely aligns revenue recognition with the delivery of the Company’s goods and services and provides financial statement readers with enhanced disclosures.

At inception, the Company determines whether contracts are within the scope of ASC 606 or other topics. For contracts that are determined to be within the scope of ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration.

Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, the Company applies judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation.

The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for each of the Company’s collaboration agreements in Note 9. In addition, none of the Company’s contracts as of December 31, 2019 contained a significant financing component.

If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. The Company typically determines standalone selling prices using an adjusted market assessment approach model.

The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, (ii) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or (iii) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

As of December 31, 2019, the Company’s only revenue recognized is related to collaboration agreements with third parties which are either within the scope of ASC 606, under which the Company licenses certain rights to its product candidates to third parties, or within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) if it involves a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement. For the collaboration arrangements under the scope of ASC 606, as discussed in further detail in Note 9, the terms of these arrangements typically include payment to the Company of one or more of the following: nonrefundable, upfront fees; development, regulatory, and commercial milestone payments; research and development funding payments; and royalties on the net sales of licensed products. Each of these payments results in collaboration revenues, except for revenues from royalties on the net sales of licensed products, which are classified as royalty revenues. For arrangements within the scope of ASC 808, the terms of these arrangements typically include payments received or made under the cost sharing provisions which are recognized as a component of revenues in the consolidated statements of operations and comprehensive loss.

Licenses of intellectual property: If the license to the Company’s IP is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the licenses. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue.

Milestone payments: At the inception of each arrangement that includes development milestone payments, the Company evaluates the probability of reaching the milestones 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 in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received and therefore revenue recognized is constrained as management is unable to assert that a reversal of revenue would not be possible. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones 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, which would affect collaboration revenues and earnings in the period of adjustment.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on levels of sales, if the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaboration agreements.

The Company receives payments from its customers based on billing schedules established in each contract. The Company’s contract liabilities consist of deferred revenue. Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company satisfies its obligations under these arrangements.

The Company also considers the nature and contractual terms of an arrangement and assesses whether the arrangement involves a joint operating activity pursuant to which the Company is an active participant and is exposed to significant risks and rewards with respect to the arrangement. If the Company is an active participant and is exposed to the significant risks and rewards with respect to the arrangement, the Company accounts for the arrangement under ASC 808. Based on this consideration, the Company accounts for its Co-Development and Co-Promotion (“Co/Co”) Agreement with Regeneron under ASC 808. Because ASC 808 does not provide recognition and measurement guidance for collaborative arrangements, the Company has analogized to ASC 606. Refer to Note 9 for additional information regarding the Company’s collaboration agreements.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development expenses consist of salaries, equity-based compensation and benefits of employees, lab supplies and materials, facilities expenses, overhead expenses, fees paid to subcontractors and contract research organizations and other external expenses.

The Company records payments made for research and development services prior to the services being rendered as prepaid expense on the consolidated balance sheet and expenses them as the services are provided. Contracts for multi-year research and development services are recorded on a straight-line basis over each annual contractual period based on the total contractual fee when the services rendered are expected to be substantially equivalent over the term of the arrangement. The cost of obtaining licenses for certain technology or IP is recorded to research and development expense when incurred if the licensed technology or IP has not yet reached technological feasibility and has no alternative future use.

Equity-Based Compensation

The Company measures employee equity-based compensation based on the grant date fair value of the equity awards using the Black-Scholes option pricing model. Equity-based compensation expense is recognized on a straight-line basis over the requisite service period of the awards and is adjusted for pre-vesting forfeitures in the period in which the forfeitures occur. For equity awards that have a performance condition, the Company recognizes compensation expense based on its assessment of the probability that the performance condition will be achieved.

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

(Loss) Earnings per Share

The Company calculates basic (loss) earnings per share by dividing (loss) income by the weighted average number of common shares outstanding. The Company computes diluted (loss) earnings per share after giving consideration to the dilutive effect of stock options and unvested restricted stock that are outstanding during the period, except where such non-participating securities would be anti-dilutive.

Segment Information

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s one business segment is the development of genome editing-based therapies. All of the Company’s assets are held in the U.S. and all of the Company’s revenue has been generated in the U.S.

Recent Accounting Pronouncements - Adopted

Recent Accounting Pronouncements – Adopted

Leases

Effective January 1, 2019, the Company adopted ASC 842, Leases (“ASC 842”), using the required modified retrospective approach and utilizing the effective date as its date of initial application. As a result, prior periods are presented in accordance with the previous guidance in ASC Topic 840, Leases.

At the inception of an arrangement, the Company determines whether an arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Most leases with a term greater than one year are recognized on the consolidated balance sheet as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company has elected not to recognize leases with terms of 12 months or less on the consolidated balance sheets. The Company typically only includes an initial lease term in its assessment of a lease arrangement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis.

Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in the Company’s leases is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate to discount lease payments, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. In its transition to ASC 842, the Company utilized the remaining lease term of its leases in determining the appropriate incremental borrowing rates.

In accordance with ASC 842, components of a lease should be allocated between lease components (e.g., land, building, etc.) and non-lease components (e.g., common area maintenance, consumables, etc.). The fixed and in-substance fixed contract consideration must be allocated based on the respective relative fair values to the lease components and non-lease components.

Although separation of lease and non-lease components is otherwise required, an expedient is available whereby the entity may account for each lease component and related non-lease component together as a single lease component. For new and amended leases for office and laboratory space beginning in 2019 and after, the Company has elected to account for the lease and non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only.

ASC 842 provides several optional practical expedients in transition. The Company elected the package of practical expedients which allows the Company to not reassess its existing conclusions on lease identification, classification, and initial direct costs. Further, the Company elected the hindsight practical expedient and utilized the short-term lease exemption for all leases with an original term of 12 months or less, for purposes of applying the recognition and measurement requirements of the new standard. The Company also elected the practical expedient which allows it to not separate lease and non-lease components for all its current office and laboratory leases.

The adoption of the new standard on January 1, 2019 resulted in the recognition of operating lease liabilities of $20.6 million, and right-of-use assets of $22.3 million on the Company’s consolidated balance sheet relating to its leases. Further, an adjustment to retained earnings of $0.3 million was recognized due to the use of hindsight being applied in updating the lease term for the Company’s property leases. The adoption of the standard did not have a material effect on the Company’s consolidated statements of operations and comprehensive loss or consolidated statements of cash flows.

Refer to Note 10 for the Company’s current lease commitments.

In June 2018, the Financial Accounting Standards Board (“FASB”) issued ASU 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which simplified the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. The Company’s adoption of the new standard on January 1, 2019 did not have a material effect on the Company’s consolidated financial statements.

Recent Accounting Pronouncements – Issued but not yet adopted

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The amendments in ASU 2019-12 are effective for fiscal years beginning after December 15, 2020, including interim periods therein. Early adoption of the standard is permitted. The Company does not anticipate that the adoption of ASU 2019-12 will have a material effect on the Company’s consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”). The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The new standard was effective beginning January 1, 2020 and early adoption is permitted. The Company does not anticipate that the adoption of ASU 2018-13 will have a material effect on its disclosures upon adoption.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). The standard changes how credit losses are measured for most financial assets and certain other instruments. For trade and other receivables, the standard requires the use of a new forward-looking “expected credit loss” model that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. The new standard also requires new disclosures and was effective beginning January 1, 2020. With certain exceptions, the guidance is applied using a modified retrospective approach by reflecting adjustments through a cumulative-effect impact to retained earnings as of the beginning of the fiscal year of adoption. The Company does not anticipate that the adoption of ASU 2016-13 will have a material effect on the Company’s consolidated financial statements.

Unaudited Quarterly Results

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Unaudited Quarterly Results

16.	Unaudited Quarterly Results

The results of operations on a quarterly basis for the years ended December 31, 2019 and 2018 are set forth below:

	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	(Amounts in thousands except per share data)
Collaboration revenue	$	10,433		$	11,118		$	10,616		$	10,936
Operating expenses:
Research and development		23,709			25,460			27,513			31,731
General and administrative		10,533			13,118			8,431			8,976
Total operating expenses		34,242			38,578			35,944			40,707
Operating loss		(23,809	)		(27,460	)		(25,328	)		(29,771	)
Interest income		1,869			1,777			1,694			1,495
Net loss	$	(21,940	)	$	(25,683	)	$	(23,634	)	$	(28,276	)
Net loss per share, basic and diluted	$	(0.49	)	$	(0.56	)	$	(0.49	)	$	(0.57	)
Weighted average shares outstanding, basic and diluted		45,234			45,814			48,554			49,350

	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	(Amounts in thousands except per share data)
Collaboration revenue	$	7,469		$	7,677		$	7,408		$	7,880
Operating expenses:
Research and development		22,493			23,467			23,237			19,918
General and administrative		7,406			7,805			8,270			8,708
Total operating expenses		29,899			31,272			31,507			28,626
Operating loss		(22,430	)		(23,595	)		(24,099	)		(20,746	)
Interest income		1,074			1,376			1,397			1,680
Net loss	$	(21,356	)	$	(22,219	)	$	(22,702	)	$	(19,066	)
Net loss per share, basic and diluted	$	(0.51	)	$	(0.52	)	$	(0.53	)	$	(0.43	)
Weighted average shares outstanding, basic and diluted		42,043			42,836			43,161			44,215

Collaborations - Additional Information (Detail)			1 Months Ended			3 Months Ended								12 Months Ended			45 Months Ended	60 Months Ended
Collaborations - Additional Information (Detail)	Dec. 13, 2019	Dec. 12, 2019	Jul. 31, 2018 USD ($) shares	Apr. 30, 2016 USD ($)	Jan. 31, 2015 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) PerformanceObligation	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expenses incurred to obtain collaboration agreements and costs to fulfill contracts														$ 0
Costs to obtain or fulfill contract capitalized						$ 0								0			$ 0	$ 0
Collaboration revenue						10,936,000	$ 10,616,000	$ 11,118,000	$ 10,433,000	$ 7,880,000	$ 7,408,000	$ 7,677,000	$ 7,469,000	43,103,000	$ 30,434,000	$ 26,117,000
Deferred revenue						28,810,000				55,932,000				$ 28,810,000	55,932,000	59,868,000	28,810,000	28,810,000
Novartis [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Strategic collaboration agreement amended date														2018-12
Regulatory based milestone payments under agreement														$ 5,000,000.0
Estimated fair value of units					$ 11,600,000
Difference between cash proceeds received and estimated fair value of preferred units					2,600,000
Novartis [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development based milestone payments under agreement					30,300,000
Regulatory based milestone payments for first indication					50,000,000.0
Regulatory based milestone payments for second indication					50,000,000.0
Sales based milestone payments under agreement					100,000,000.0
Novartis [Member] \| 2014 Novartis Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions					10,000,000.0									10,000,000.0
Technology access fees					20,000,000.0	20,000,000.0								20,000,000.0			20,000,000.0	20,000,000.0
Quarterly research payments					$ 1,000,000.0	20,000,000.0								20,000,000.0			20,000,000.0	20,000,000.0
Research Payments						19,000,000.0								19,000,000.0			19,000,000.0	19,000,000.0
Research term					5 years
Proceeds from issuance of preferred stock														$ 9,000,000.0
One time collaboration payment										10,000,000.0					10,000,000.0
Termination period of agreement														90 days
Number of performance obligations \| PerformanceObligation														2
Transaction price														$ 59,000,000.0
Transaction price allocated to preferred units purchased at fair value														11,600,000
Novartis [Member] \| 2014 Novartis Agreement [Member] \| HSC and CAR-T Cell Products [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Remaining transaction price allocated to combined performance obligation of licenses and associated research activities														$ 47,400,000
Combined performance obligation of licenses and associated research activities, revenue recognition period														5 years
Novartis [Member] \| 2014 Novartis Agreement [Member] \| LSCs [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of performance obligations \| PerformanceObligation														1
Transaction price														$ 10,000,000.0
Combined performance obligation of licenses and associated research activities, revenue recognition period														1 year
Novartis [Member] \| 2014 Novartis Agreement [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total research funding					$ 20,000,000.0
Novartis [Member] \| Unit Purchase Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from issuance of preferred stock					$ 9,000,000.0
Novartis [Member] \| Novartis Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions																		57,400,000
Collaboration revenue														$ 18,500,000	10,300,000	9,300,000		57,400,000
Aggregate transaction price remaining to be recognized, period														Through December 31, 2019
Accounts receivable						1,000,000.0				6,000,000.0				$ 1,000,000.0	6,000,000.0		1,000,000.0	1,000,000.0
Deferred revenue						0				14,500,000				0	14,500,000		0	0
Regeneron Pharmaceuticals Inc. [Member] \| Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions				$ 75,000,000.0										$ 75,000,000.0
One time collaboration payment				$ 25,000,000.0
Termination period of agreement				180 days
Number of performance obligations \| PerformanceObligation														3
Transaction price														$ 125,000,000.0
Purchase of common stock through private placement														50,000,000.0
Collaboration term extension period				2 years
Royalty payment obligation expiration period				12 years
Transaction price allocated to common stock														50,000,000.0
Remaining transaction price allocated to combined performance obligation														75,000,000.0
Amount allocated to licenses to targets and associated research activities and evaluation plans														63,800,000
Amount allocated to technology collaboration and associated research activities														$ 11,200,000
Licenses to targets and associated research activities and evaluation plans performance period														6 years
Regeneron Pharmaceuticals Inc. [Member] \| Regeneron Agreement [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Regulatory based milestone payments under agreement				$ 110,000,000.0
Development based milestone payments under agreement				25,000,000.0
Sales based milestone payments under agreement				185,000,000.0
Regeneron Pharmaceuticals Inc. [Member] \| Stock Purchase Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase of common stock through private placement				$ 50,000,000.0
Regeneron Pharmaceuticals Inc. [Member] \| Co-Development and Co-Promotion Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Termination period of agreement			180 days
Compensation for prior work			$ 1,500,000
Payment of royalty percentage on net product sales	25.00%	50.00%	50.00%
Regeneron Pharmaceuticals Inc. [Member] \| Co-Development and Co-Promotion Agreement [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Options exercisable, number of shares exercisable \| shares			5
Collaborative arrangement obligation to be fund in development costs			$ 5,000,000
Regeneron Pharmaceuticals Inc. [Member] \| Regeneron Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions																	75,000,000.0
Collaboration revenue														$ 24,600,000	20,100,000	16,800,000	70,300,000
Aggregate transaction price remaining to be recognized, period														through April 2022
Deferred revenue						28,800,000				41,400,000				$ 28,800,000	41,400,000		28,800,000	28,800,000
Payments due														12,000,000.0	7,500,000	$ 4,100,000
Aggregate transaction price remaining to be recognized						28,800,000								28,800,000			28,800,000	28,800,000
Accounts receivable						$ 3,600,000				$ 1,500,000				$ 3,600,000	$ 1,500,000		3,600,000	$ 3,600,000
Regeneron Pharmaceuticals Inc. [Member] \| Regeneron Arrangement [Member] \| Research and Development Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue																	$ 24,100,000

Equity-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity-Based Compensation

11.	Equity-Based Compensation

In April 2016, the Company adopted the Amended and Restated 2015 Stock Option and Incentive Plan (the “2015 Plan”). The 2015 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Recipients of incentive stock options and non-qualified stock options are eligible to purchase shares of the Company’s common stock at an exercise price equal to the fair value of such stock on the grant date. Stock options granted under the 2015 Plan generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, unless they contain specific performance-based vesting provisions. The maximum term of stock options granted under the 2015 Plan is ten years.

As of December 31, 2019, there were 2,655,673 shares available for future issuance. The number of shares reserved for issuance under the 2015 Plan shall be cumulatively increased by four percent of the number of shares of stock issued and outstanding on the immediately preceding December 31 or such lesser number of shares of stock as determined by the board of directors.

Equity-based compensation expense is classified in the consolidated statements of operations and comprehensive loss as follows:

	Year Ended December 31,
	2019		2018		2017
	(In thousands)
Research and development	$	6,986	$	8,994	$	7,280
General and administrative		8,105		8,052		8,042
Total	$	15,091	$	17,046	$	15,322

Restricted Stock

Restricted stock is measured at fair value based on the quoted price of the Company’s common stock.

The following table summarizes the Company’s restricted stock activity for the year ended December 31, 2019:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock as of December 31, 2018		109,073		$	15.53
Granted		-			-
Vested		(37,198	)		1.34
Cancelled		-			-
Unvested restricted stock as of December 31, 2019		71,875		$	22.88

The weighted average grant date fair value of restricted stock, was $22.98 for restricted stock granted during 2018. There was no restricted stock granted in 2017 or 2019. As of December 31, 2019, there was $0.2 million of unrecognized equity-based compensation expense related to restricted stock that is expected to vest. These costs are expected to be recognized over a weighted average remaining vesting period of 1.0 year. All of the unvested restricted stock outstanding as of December 31, 2019 are performance-based restricted stock units that vest upon obtaining certain scientific, financial and regulatory milestones through 2020. These 71,875 restricted stock units are not included in computing the diluted (loss) earnings per share because the performance criteria had not been met as of the end of the reporting period.

Stock Options

The weighted average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $9.21 per option for options granted during the year ended December 31, 2019, $15.05 per option for options granted during the year ended December 31, 2018 and $12.43 per option for options granted during the year ended December 31, 2017. The total intrinsic value (the amount by which the fair market value exceeded the exercise price) of stock options exercised during the year ended December 31, 2019, 2018 and 2017 was $2.3 million, $18.0 million, and $1.6 million, respectively. Key assumptions used to apply this pricing model were as follows:

	Year Ended December 31,
	2019			2018			2017
Risk-free interest rate		2.1	%		2.7	%		2.0	%
Expected life of options	6.0 years			6.0 years			6.0 years
Expected volatility of underlying stock		68.1	%		87.1	%		93.9	%
Expected dividend yield		0.0	%		0.0	%		0.0	%

Risk-free Interest Rate. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant with maturities approximately equal to the option’s expected term.

Expected Dividend Yield. The expected dividend yield assumption is based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends.

Expected Volatility. The expected volatility was derived from a blend of average historical stock volatilities of several unrelated public companies within the Company’s industry and the Company’s historical volatility, both over a period equivalent to the expected term of the stock option grants.

Expected Term. The expected term represents the period that stock options awards are expected to be outstanding. For option grants that are considered to be “plain vanilla,” the Company determines the expected term using the simplified method. The simplified method deems the term to be the average of the time-to-vesting and the contractual life of the options. The Company uses the simplified method because it does not have sufficient historical option exercise data to provide a reasonable basis upon which to estimate the expected term.

The Company uses the market closing price of its common stock as reported on the Nasdaq Global Select Market to determine the fair value of the shares of common stock underlying stock options. The following is a summary of stock option activity for the year ended December 31, 2019:

	Number of Options			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding at December 31, 2018		5,037,663		$	15.63
Granted		1,220,613			14.90
Exercised		(364,404	)		8.47
Forfeited		(527,901	)		18.50
Outstanding at December 31, 2019		5,365,971		$	15.67		7.86	$	9,082
Exercisable at December 31, 2019		2,578,717		$	14.11		6.92	$	8,017

As of December 31, 2019, there was $28.2 million of unrecognized compensation cost related to stock options that have not yet vested. These costs are expected to be recognized over a weighted average remaining vesting period of 2.5 years.

Of the unvested stock options outstanding as of December 31, 2019, 213,750 are performance-based stock options that vest upon obtaining certain scientific, financial and regulatory milestones through 2020. At December 31, 2019, 188,750 performance-based options are not included in computing the diluted (loss) earnings per share because the performance criteria had not been met as of the end of the reporting period.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

7.	Income Taxes

The Company did not record net income tax benefits for the operating losses incurred during the periods presented due to the uncertainty of realizing a tax benefit from those losses. Accordingly, any benefit recorded related to these deferred tax assets was offset by a valuation allowance reflecting management’s conclusion that realization of those assets was not more likely than not.

A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2019			2018			2017
Federal statutory income tax rate		(21.0	)%		(21.0	)%		(34.0	)%
State income taxes		(8.9	)		(8.6	)		(6.9	)
Research and development tax credits		(5.1	)		(4.7	)		(3.4	)
Stock-based compensation		1.2			(0.6	)		3.6
Change in U.S. tax rate		-			-			18.7
Change in valuation allowance		33.8			34.9			22.0
Effective income tax rate		-	%		-	%		-	%

The Company’s net deferred tax assets (liabilities) consisted of the following:

	December 31,
	2019			2018
	(in thousands)
Deferred tax assets:
Intangibles, including acquired in-process research and development	$	1,091		$	1,201
Capitalized start-up costs		421			463
Net operating loss carryforwards		63,245			34,234
Research and development credit carryforwards		19,417			11,766
Operating lease liability		5,008			-
Deferred revenue		7,843			12,199
Equity-based compensation		7,092			4,064
Accruals and allowances		1,245			1,359
Gross deferred tax assets		105,362			65,286
Deferred tax asset valuation allowance		(98,513	)		(64,046	)
Total deferred tax assets		6,849			1,240
Deferred tax liabilities:
Fixed assets		(1,633	)		(1,240	)
Operating lease right-of-use assets		(5,216	)		-
Total deferred tax liabilities		(6,849	)		(1,240	)
Net deferred tax asset (liability)	$	-		$	-

As of December 31, 2019, the Company had federal and state net operating loss carryforwards of $229.9 million and $236.8 million, respectively. As of December 31, 2019, approximately $193.0 million of the Company’s federal net operating loss carryforward can be carried forward indefinitely while the remaining federal net operating loss of $36.9 million begins to expire in 2034. As of December 31, 2019, the Company had federal and state research and development and other credit carryforwards of approximately $12.6 million and $8.7 million, which begin to expire in 2035 and 2031, respectively.

The Company evaluated the expected realizability of its net deferred tax assets and determined that there was significant negative evidence due to its net operating loss position and insufficient positive evidence to support the realizability of these net deferred tax assets. The Company concluded it is more likely than not that its net deferred tax assets would not be realized in the future; therefore, the Company has provided a full valuation allowance against its net deferred tax asset balance as of December 31, 2019 and 2018. The valuation allowance increased by $34.5 million in 2019, $28.7 million in 2018 and $14.8 million in 2017.

Utilization of the net operating loss and research and development credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss and research and development credit carryforwards that can be utilized annually to offset future taxable income and tax expense, respectively. The Company has not yet conducted a study to assess whether a change of control, as defined in Section 382, has occurred or whether there have been multiple changes in control since inception.

As of December 31, 2019, the Company had not identified any unrecognized tax benefits. The Company files income tax returns in the U.S. federal tax jurisdiction and Massachusetts and various other state tax jurisdictions. The Company is subject to examination by the Internal Revenue Service and Massachusetts taxing authorities. The returns in these jurisdictions since inception remain open for examination; however, there are currently no pending tax examinations.

Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation expense related to restricted stock	$ 0.2
Potential dilutive securities excluded from computation of diluted net loss per common share	5,438,000	5,147,000	5,185,000
Weighted average grant date fair value per share	$ 9.21	$ 15.05	$ 12.43
Total intrinsic value of stock options exercised	$ 2.3	$ 18.0	$ 1.6
Unrecognized compensation cost related to stock options	$ 28.2
Stock options outstanding	5,365,971	5,037,663
Vesting description	performance-based stock options that vest upon obtaining certain scientific, financial and regulatory milestones through 2020.
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of restricted stock, granted		$ 22.98
Restricted stock granted	0		0
Weighted average period of unrecognized compensation costs	1 year
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	71,875
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unrecognized compensation costs	2 years 6 months
Performance Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	188,750
Stock options outstanding	213,750
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period	3 years
Description of stock options granted under the Plan	Stock options granted under the 2015 Plan generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, unless they contain specific performance-based vesting provisions. The maximum term of stock options granted under the 2015 Plan is ten years.
Shares available for future issuance	2,655,673
Percentage of cumulative increase in number of shares for future issuance	4.00%
2015 Plan [Member] \| First Anniversary of Original Vesting Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest percentage on the first anniversary	25.00%
Maximum [Member] \| 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of stock options granted	10 years

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Feb. 21, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	NTLA
Entity Registrant Name	INTELLIA THERAPEUTICS, INC.
Entity Central Index Key	0001652130
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	No
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Entity File Number	001-37766
Entity Tax Identification Number	36-4785571
Entity Address, Address Line One	40 Erie Street
Entity Address, Address Line Two	Suite 130
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	285-6200
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Document Annual Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		50,507,681
Entity Public Float			$ 741,046,311
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Part III of this Annual Report on Form 10-K incorporates by reference certain information from the registrant’s definitive Proxy Statement for its 2020 annual meeting of shareholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year end of December 31, 2019. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.

Collaborations (Tables)

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of Changes in Accounts Receivable and Contract Liabilities

The following table presents changes in the Company’s accounts receivable and contract liabilities during the years ended December 31, 2019 and 2018 (in thousands):

	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2019
Accounts receivable	$	7,547	$	15,999	$	(18,926	)	$	4,620
Contract liabilities:
Deferred revenue	$	55,932	$	4,000	$	(31,122	)	$	28,810

	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2018
Accounts receivable	$	10,471	$	16,498	$	(19,422	)	$	7,547
Contract liabilities:
Deferred revenue	$	59,868	$	19,000	$	(22,936	)	$	55,932

Summary of Revenues Recognized Resulting From Changes in Contract Liability Balance

During the years ended December 31, 2019 and 2018, the Company recognized the following revenues as a result of changes in the contract liability balance (in thousands):

Revenue recognized in the period from:

Year Ended

December 31, 2019

Year Ended

December 31, 2018

Amounts included in the contract liability at the beginning of the period

27,122

22,936

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (99,533)	$ (85,343)	$ (67,543)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,587	4,464	2,994
Loss on disposal of property and equipment	1	75	166
Equity-based compensation	15,091	17,046	15,322
Accretion of investment discounts	(3,725)	(676)
Changes in operating assets and liabilities:
Accounts receivable	2,927	2,924	(4,017)
Prepaid expenses and other current assets	(1,763)	310	(1,893)
Operating right-of-use assets	5,728
Other assets	153	1,022	902
Accounts payable	1,880	232	(488)
Accrued expenses	2,310	2,780	2,394
Deferred revenue	(27,122)	(3,936)	(12,988)
Operating lease liabilities	(4,774)
Other long-term liabilities		(155)	(125)
Net cash used in operating activities	(103,240)	(61,257)	(65,276)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(6,794)	(6,358)	(10,091)
Proceeds from sale of property and equipment		131
Purchases of marketable securities	(297,030)	(254,555)
Maturities of marketable securities	329,000
Net cash provided by (used in) investing activities	25,176	(260,782)	(10,091)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from common stock offerings, net of offering costs	72,256	28,547	141,000
Proceeds from options exercised	3,086	10,652	1,156
Issuance of shares through employee stock purchase plan	1,092	1,018	825
Net cash provided by financing activities	76,434	40,217	142,981
Net (decrease) increase in cash and cash equivalents	(1,630)	(281,822)	67,614
Cash and cash equivalents, beginning of period	58,856	340,678	273,064
Cash and cash equivalents, end of period	57,226	58,856	340,678
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Purchases of property and equipment unpaid at period end	800	$ 1,071	$ 805
Right-of-use assets acquired under operating leases	$ 2,554

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Equity-Based Compensation Expense

Equity-based compensation expense is classified in the consolidated statements of operations and comprehensive loss as follows:

	Year Ended December 31,
	2019		2018		2017
	(In thousands)
Research and development	$	6,986	$	8,994	$	7,280
General and administrative		8,105		8,052		8,042
Total	$	15,091	$	17,046	$	15,322

Summary of Restricted Stock Activity

The following table summarizes the Company’s restricted stock activity for the year ended December 31, 2019:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock as of December 31, 2018		109,073		$	15.53
Granted		-			-
Vested		(37,198	)		1.34
Cancelled		-			-
Unvested restricted stock as of December 31, 2019		71,875		$	22.88

Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted

Key assumptions used to apply this pricing model were as follows:

	Year Ended December 31,
	2019			2018			2017
Risk-free interest rate		2.1	%		2.7	%		2.0	%
Expected life of options	6.0 years			6.0 years			6.0 years
Expected volatility of underlying stock		68.1	%		87.1	%		93.9	%
Expected dividend yield		0.0	%		0.0	%		0.0	%

Summary of Stock Option Activity

The following is a summary of stock option activity for the year ended December 31, 2019:

	Number of Options			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding at December 31, 2018		5,037,663		$	15.63
Granted		1,220,613			14.90
Exercised		(364,404	)		8.47
Forfeited		(527,901	)		18.50
Outstanding at December 31, 2019		5,365,971		$	15.67		7.86	$	9,082
Exercisable at December 31, 2019		2,578,717		$	14.11		6.92	$	8,017

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

10.

Leases

In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025. Upon the execution of the original lease, the Company provided a $0.3 million security deposit. The Company has recorded this security deposit in other assets on the consolidated balance sheets.

In applying the ASC 842 transition guidance, the Company retained the classification of this lease as operating and recorded a lease liability and a right-of-use asset on the ASC 842 effective date with the five-year extension included in the lease term, based on the Company’s election of the hindsight practical expedient as the Company was reasonably certain to exercise this option term.

In March 2019, the Company entered into a separate agreement to sublease additional office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating sublease agreement with a term through April

2021, with two options to extend the agreement by one year each, for a total option period of up to two years. Upon commencement of the lease in April 2019, the Company recognized a right-of-use asset and lease liability of approximately $1.3 million.

In January 2016, the Company entered into a ten-year agreement to lease office and laboratory space at 40 Erie Street in Cambridge, Massachusetts under an operating lease agreement, with an option to terminate the lease at the end of the sixth year and an option to extend the term of the lease for an additional three years. Upon the execution of this lease, the Company provided a $2.2 million security deposit, which has been recorded in other assets on the consolidated balance sheets.

Throughout the term of its leases, the Company is responsible for paying certain costs and expenses, in addition to the rent, as specified in the lease, including a proportionate share of applicable taxes, operating expenses and utilities. The variable portion of these costs are expensed as incurred and are disclosed as variable lease cost.

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the year ended December 31, 2019:

	Year Ended
	December 31, 2019
	(in thousands)
Lease cost
Operating lease cost	$	7,431
Short-term lease cost		53
Variable lease cost	2,218
Total lease cost	$	9,702

	Year Ended
	December 31, 2019
	(in thousands)
Other information
Operating cash flows used for operating leases	$	6,476
Operating lease liabilities arising from obtaining right-of-use assets	2,554

	As of December 31, 2019
Lease term and discount rate
Weighted average remaining lease term	3.0 years
Weighted average discount rate	9.00%

The table below reconciles the undiscounted cash flows for each of the first five years and total of the remaining years to the operating lease liabilities recorded in the consolidated balance sheet as of December 31, 2019:

Future Operating Lease Payments
Year Ending December 31,	(in thousands)
2020	$	7,113
2021		7,350
2022		4,733
2023		871
2024		871
Thereafter		73
Total lease payments	$	21,011
Less: imputed interest		(2,636	)
Total operating lease liabilities at December 31, 2019	$	18,375

Future minimum lease payments under the Company’s non-cancelable operating leases as of December 31, 2018, are as follows:

Year Ending December 31,	(In thousands)
2019	$	5,616
2020		4,963
2021		5,507
2022		3,861
	$	19,947

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Available-for-sale Marketable Securities

The following table summarizes the Company’s available-for-sale marketable securities as of December 31, 2019 and 2018 at net book value:

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	159,361	$	142	$	(1	)	$	159,502
Financial institution debt securities		40,173		105		-			40,278
Corporate debt securities		18,966		1		-			18,967
Other asset-backed securities		8,485		14		-			8,499
Total	$	226,985	$	262	$	(1	)	$	227,246

	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	165,959	$	2	$	(13	)	$	165,948
Financial institution debt securities		65,436		1		(17	)		65,420
Corporate debt securities		23,836		-		(1	)		23,835
Total	$	255,231	$	3	$	(31	)	$	255,203

Collaborations

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaborations

9.	Collaborations

To accelerate the development and commercialization of CRISPR/Cas9-based products in multiple therapeutic areas, the Company has formed, and intends to seek other opportunities to form, strategic alliances with collaborators who can augment its leadership in CRISPR/Cas9 therapeutic development. As of December 31, 2019 and December 31, 2018, the Company’s accounts receivable and contract liabilities were primarily related to the Company’s collaborations with Novartis and Regeneron.

The following table presents changes in the Company’s accounts receivable and contract liabilities during the years ended December 31, 2019 and 2018 (in thousands):

	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2019
Accounts receivable	$	7,547	$	15,999	$	(18,926	)	$	4,620
Contract liabilities:
Deferred revenue	$	55,932	$	4,000	$	(31,122	)	$	28,810

	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
Year Ended December 31, 2018
Accounts receivable	$	10,471	$	16,498	$	(19,422	)	$	7,547
Contract liabilities:
Deferred revenue	$	59,868	$	19,000	$	(22,936	)	$	55,932

During the years ended December 31, 2019 and 2018, the Company recognized the following revenues as a result of changes in the contract liability balance (in thousands):

Revenue recognized in the period from:

Year Ended

December 31, 2019

Year Ended

December 31, 2018

Amounts included in the contract liability at the beginning of the period

27,122

22,936

Costs to obtain and fulfill a contract

The Company did not incur any expenses to obtain collaboration agreements and costs to fulfill those contracts do not generate or enhance resources of the Company. As such, no costs to obtain or fulfill a contract have been capitalized in any period.

Novartis Institutes for BioMedical Research, Inc.

In December 2014, the Company entered into a strategic collaboration agreement with Novartis (the “2014 Novartis Agreement”), primarily focused on the research of new ex vivo CRISPR/Cas9-edited therapies using CAR-T cells and hematopoietic stem cells (“HSCs”). The agreement was amended in December 2018 to also include research on ocular stem cells (“OSCs”). In December 2019, per the terms of the 2014 Novartis Agreement, the research term ended, although the 2014 Novartis Agreement remains in effect. As provided in the agreement, Novartis has selected various CAR-T, HSC and OSC targets for continued development, for which the Company will be eligible to receive milestone and royalty payments in the future.

Agreement Structure. Under the 2014 Novartis Agreement, the parties agreed to engage in collaborative research activities using the Company’s CRISPR/CAS9 platform to identify and research therapeutic, prophylactic and palliative products and services relating to the following applications: a) ex vivo HSCs and b) ex vivo CAR-T cells. In addition, in the last two years of the collaboration term, Novartis was permitted to engage in research and development of a limited number of in vivo targets using the Company’s platform.

Scope of Collaboration. During the five-year research term, the parties researched potential therapeutic, prophylactic and palliative ex vivo applications of CRISPR/Cas9 technology in HSCs and CAR-T cells. Research expenses incurred by the Company in support of the collaboration were reimbursed by Novartis.

HSC Program. The Company and Novartis agreed to collaborate exclusively with each other during the research term to conduct research on ex vivo applications of CRISPR/Cas9 technology for HSC targets under a research plan agreed upon by both parties. At the end of the research term in December 2019, this exclusive HSC research collaboration ended. Within the ex vivo HSC therapeutic space, Novartis obtained exclusive rights to research and develop human therapeutics for a limited number of HSC targets, which were selected by Novartis in a series of selection windows.

During the research term, the Company had the right to choose a limited number of HSC targets for its exclusive development and commercialization per the specified selection schedule. Following these selections by Novartis and the Company, Novartis had the right to research an additional limited number of non-selected HSC targets on a non-exclusive basis, but Novartis did not exercise this right. Because the research term has ended, the parties can no longer select additional exclusive HSC targets, and Novartis has an exclusive license to research, develop and commercialize human therapeutic products directed to its selected HSC targets. Novartis assumed sole responsibility for developing and commercializing human therapeutic products for the HSC targets it selected arising from the Company’s collaboration and is solely responsible for the costs and expenses of developing, manufacturing and commercializing its HSC products. To maintain its exclusive license on a target-by-target basis, Novartis is required to use commercially reasonable efforts to research, develop and commercialize at least one HSC product directed to each of their selected HSC targets. In 2019, Novartis announced that it had completed investigational new drug (“IND”)-enabling studies in support of a potential IND on a program targeting sickle cell disease that leveraged the Company’s CRISPR/Cas 9 technology. The Company is entitled to receive a $5.0 million payment related to this regulatory milestone upon filing the IND.

CAR-T Program. The Company and Novartis also agreed to collaborate exclusively with each other during the research term on research directed to applying CRISPR/Cas9 technology to CAR-T cell targets under a research plan agreed upon by both parties. At the end of the research term in December 2019, this exclusive research collaboration ended. Under the 2014 Novartis Agreement, Novartis assumed sole responsibility for developing human therapeutic products for the limited number of CAR targets it selected arising from its collaboration with the Company and is solely responsible for the costs and expenses of developing, manufacturing and commercializing its selected targets. Novartis has an exclusive license to research, develop and commercialize CAR products directed to its selected CAR-T cell targets. To maintain its exclusive license on a target-by-target basis, Novartis is required to use commercially reasonable efforts to research, develop and commercialize at least one CAR-T cell product directed to each of its selected CAR targets.

Governance. The parties formed HSC and CAR-T cell steering committees with responsibility for oversight of these respective research programs and approval of the associated research plans. Beginning in December 2018, the HSC steering committee also became responsible for the OSC program (see the section below entitled “2018 Amendment to the Agreement”). These steering committees in turn were overseen by a joint steering committee and comprised an equal number of representatives from each party. The steering committees terminated upon completion of the research term in December 2019.

Financial Terms. The Company received an upfront technology access payment from Novartis of $10.0 million in January 2015 and was entitled to additional technology access fees of $20.0 million and quarterly research payments of $1.0 million, or up to $20.0 million in the aggregate, during the five-year research term. As of December 31, 2019, the Company has received $20.0 million in technology access fees and $19.0 million in research payments related to these programs. In addition, for each Novartis product under the collaboration (whether HSC or CAR-T cell product, and beginning as of December 2018, an OSC product), subject to certain conditions, the Company may be eligible to receive (i) up to $30.3 million in development milestones, including for the filing of an IND application and for the dosing of the first patient in each of Phase IIa, Phase IIb and Phase III clinical trials, (ii) up to $50.0 million in regulatory milestones for the product’s first indication, including regulatory approvals in the U.S. and the European Union (“EU”), (iii) up to $50.0 million in regulatory milestones for the product’s second indication, if any, including U.S. and EU regulatory approvals, (iv) royalties on net sales in the mid-single digits, and (v) net sales milestone payments of up to $100.0 million.

Equity Investments. Additionally, at the inception of the arrangement at which time the Company was a privately held company, Novartis invested $9.0 million to purchase the Company’s Class A-1 and Class A-2 Preferred Units (the “Preferred Units”). The difference between the cash proceeds received from Novartis for the units and the $11.6 million estimated fair value of those units at the date of issuance was determined to be $2.6 million. Accordingly, $2.6 million of the upfront technology access payment was allocated to record the Preferred Units purchased by Novartis at fair value.

License Grant to Novartis. In the 2014 Novartis Agreement, the Company granted to Novartis a license to its CRISPR/Cas9 platform technology, including a sublicense to certain platform rights licensed from Caribou, that is exclusive in the ex vivo HSC, CAR-T cell and in vivo fields with respect to each target selected by Novartis pursuant to the agreement and the research plan as long as Novartis continues to use commercially reasonable efforts to research, develop, and commercialize CRISPR-edited products directed to such targets.

License Grant to Intellia. In the 2014 Novartis Agreement, prior to the Novartis Amendment described below, Novartis granted the Company a non-exclusive license to its IP covering a small molecule for HSC expansion and to its lipid nanoparticle (“LNP”) platform technology to research, develop and commercialize HSC and in vivo genome editing products, respectively, in the 2014 Novartis Agreement.

Intellectual Property. IP that the Company develops within the collaboration related to the Company’s CRISPR/Cas9 platform will be owned solely by the Company, while all other IP developed within the collaboration, including IP covering products arising from the collaboration, will be jointly owned by the Company and Novartis.

2018 Amendment to the Agreement

In December 2018, the Company entered into an amendment to this agreement with Novartis (the “Novartis Amendment”) which expanded the scope of the 2014 Novartis Agreement to include the ex vivo development of CRISPR/Cas9-based cell therapies using limbal stem cells, a type of OSC, primarily against gene targets selected by Novartis in exchange for a one-time payment of $10.0 million which the Company received in December 2018. The governance, license rights and development responsibilities, as well as milestones and royalties, associated with any OSC program and product follow those for the HSC programs and products. Because the research term has ended, as with the HSC programs, the parties’ exclusive research collaboration for limbal stem cells has ended, and Novartis has an exclusive license to research, develop and commercialize OSC products directed to a limited number of OSC targets. As part of the Novartis Amendment, Intellia rights to Novartis’ LNP technology were expanded to include use in all genome editing applications in both in vivo and ex vivo settings.

Term and Termination. The term of the 2014 Novartis Agreement expires on the later of (i) the expiration of Novartis’ payment obligations under the agreement and (ii) the date of expiration of the last-to-expire of the patent rights licensed to the Company or Novartis under the agreement. Novartis’ royalty payment obligations expire on a country-by-country and product-by-product basis upon the later of (i) the expiration of the last valid claim of the royalty-bearing patents covering such product in such country or (ii) ten years after the first commercial sale of such product in such country. The Company may terminate the agreement if Novartis or its affiliates institute a patent challenge against its IP rights, and all improvements thereto, licensed to Novartis under the agreement. Novartis may terminate the agreement, without cause, upon 90 days’ written notice to the Company subject to certain conditions and continuing obligations. Either party may terminate the agreement in the event of the other party’s uncured material breach or bankruptcy - or insolvency-related events.

Accounting Analysis. The Company concluded that the 2014 Novartis Agreement and the Novartis Amendment are subject to ASC 606 and assessed its accounting for them accordingly. The Company evaluated the promised goods and services under the 2014 Novartis Agreement and determined that it had two performance obligations: (1) a combined performance obligation representing a series of distinct goods and services including the licenses to research, develop and commercialize HSC and LSC products and their associated research activities and the licenses to research, develop and commercialize CAR-T cell products and their associated research activities; and (2) the Preferred Units.

The Company determined that the transaction price of the 2014 Novartis Agreement was $59.0 million consisting of the following consideration: (1) the upfront technology access payment of $10.0 million; (2) the additional technology access fees of $20.0 million; (3) the Company’s estimate of variable consideration of $20.0 million related to the quarterly research payments; and (4) the payment for the Preferred Units of $9.0 million. None of the clinical or regulatory milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon future regulatory progress and the licensee’s efforts. Any consideration related to sales-based milestones and royalties will be recognized when the related sales occur as they were determined to relate predominantly to the licenses granted to Novartis and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and when events whose outcomes are resolved or other changes in circumstances occur.

The Company first allocated $11.6 million of the transaction price to the Preferred Units to record the Preferred Units purchased by Novartis at fair value. The Company then allocated the remaining $47.4 million of the transaction price to the remaining combined performance obligation of the licenses and associated research activities for HSC and CAR-T cell products. Revenue allocated to the combined performance obligation of the licenses and associated research activities for HSC and CAR-T cell products is being recognized using a time elapsed inputs method over a period of five years, which, in management’s judgment, is the best measure of progress towards satisfying the performance obligation as this method provides the most faithful depiction of the entity’s performance in transferring control of the goods and services promised to Novartis and represents the Company’s best estimate of the period of the obligation.

The Company determined that there is only one combined performance obligation identified under the Novartis Amendment, representing a series of distinct goods and services including the licenses to research, develop and commercialize products using LSCs and their associated research and development services related to the research, development and commercialization of products using LSCs, and allocated the $10.0 million transaction price accordingly. Revenue allocated to this performance obligation is being recognized using a time elapsed inputs method over a period of one year, which, in management’s judgment, is the best measure of progress towards satisfying the performance obligation as this method provides the most faithful depiction of the entity’s performance in transferring control of the goods and services promised to Novartis and represents the Company’s best estimate of the period of the obligation.

Revenue Recognition: Collaboration Revenue. Through December 31, 2019, excluding amounts allocated to Novartis’ purchase of the Company’s Preferred Units, the Company had recorded a total of $57.4 million in cash and accounts receivable under the 2014 Novartis Agreement and the Novartis Amendment. Through December 31, 2019, the Company has recognized $57.4 million of collaboration revenue, including $18.5 million in the year ended December 31, 2019, $10.3 million in the year ended December 31, 2018, and $9.3 million in the year ended December 31, 2017, in the consolidated statements of operations and comprehensive loss related to the 2014 Novartis Agreement and the Novartis Amendment. As of December 31, 2019, the aggregate transaction price had been recognized in full.

As of the periods ended December 31, 2019 and 2018, the Company had accounts receivable of $1.0 million and $6.0 million, respectively, related to this agreement. As of December 31, 2019, the Company had no deferred revenue related to this agreement. As of December 31, 2018, the Company had deferred revenue of $14.5 million related to this agreement.

Regeneron Pharmaceuticals, Inc.

In April 2016, the Company entered into a license and collaboration agreement with Regeneron (the “Regeneron Agreement”).

Agreement Structure. The Regeneron Agreement has two principal components: i) a product development component under which the parties will research, develop and commercialize CRISPR/Cas-based therapeutic products primarily focused on genome editing in the liver, and ii) a technology collaboration component, pursuant to which the Company and Regeneron will engage in research and development activities aimed at discovering and developing novel technologies and improvements to CRISPR/Cas technology to enhance the Company’s genome editing platform. Under this agreement, the Company also may access the Regeneron Genetics Center and proprietary mouse models to be provided by Regeneron for a limited number of the Company’s liver programs.

Scope of Collaboration. Under the terms of the six-year collaboration, Regeneron may obtain exclusive rights for up to ten targets to be chosen by Regeneron during the collaboration term, subject to a target selection process and various adjustments and limitations set forth in the agreement. Of these ten total targets, Regeneron may select up to five non-liver targets, while the remaining targets must be focused in the liver. Certain non-liver targets from the Company’s ongoing and planned research at the time, as well as any targets included in another of the Company’s collaborations, are excluded from this collaboration. At the inception of the agreement, Regeneron selected the first of its ten targets, transthyretin amyloidosis (“ATTR”), which is subject to a Co/Co agreement between the Company and Regeneron, the general terms and conditions for which were outlined within the Regeneron Agreement.

Research Collaboration. Research activities under the collaboration will be governed by evaluation and research and development plans that will outline the parties’ responsibilities under, anticipated timelines of and budgets for, the various programs. The Company will assist Regeneron with the preliminary evaluation of its selected liver targets, and Regeneron will be responsible for preclinical research and conducting clinical development, manufacturing and commercialization of products directed to each of its exclusive targets. The Company may assist, as requested by Regeneron, with the later discovery and research of product candidates directed to any selected target. For each selected target, Regeneron is required to use commercially reasonable efforts to submit regulatory filings necessary to achieve IND acceptance for at least one product directed to each applicable target, and following IND acceptance for at least one product, to develop and commercialize such product.

Reserved Liver Targets. The Company retains the exclusive right to solely develop products via CRISPR/Cas genome editing directed against certain specified genetic targets. During the collaboration term and subject to a target selection process, the Company has the right to choose additional liver targets for its own development using commercially reasonable efforts. Certain targets that either the Company or Regeneron select during the term may be subject to further Co/Co agreements at the Company or Regeneron’s option, as applicable, which either can exercise pursuant to defined conditions.

Governance. Under the Regeneron Agreement, the parties formed a joint steering committee, which is responsible for setting research objectives and overseeing the general strategies and research and development activities undertaken by the parties. Additionally, under the Co/Co agreement directed to ATTR (the “ATTR Co/Co”), the parties formed a Joint Development and Commercialization Committee (“JDCC”) to oversee all profit share products under the Co/Co agreement as discussed below. The JDCC has responsibility for overseeing the development, manufacture, regulatory matters, and commercialization (including pricing and reimbursement) of ATTR, as the first profit share product under the Regeneron agreement.

Financial Terms. The Company received a nonrefundable upfront payment of $75.0 million. In addition, on Regeneron programs that are not subject to Co/Co agreements the Company may be eligible to earn, on a per-licensed target basis, (i) up to $25.0 million in development milestones, including for the dosing of the first patient in each of Phase I, Phase II and Phase III clinical trials, (ii) up to $110.0 million in regulatory milestones, including for the acceptance of a regulatory filing in the U.S., and for obtaining regulatory approval in the U.S. and in certain other identified countries, and (iii) up to $185.0 million in sales-based milestone payments. The Company is also eligible to earn royalties ranging from the high single digits to low teens, in each case, on a per-product basis, which royalties are potentially subject to various reductions and offsets and incorporate the Company’s existing low- to mid-single-digit royalty obligations under a license agreement with Caribou.

Equity Investments. In connection with this collaboration, Regeneron purchased $50.0 million of the Company’s common stock in a private placement under a Stock Purchase Agreement concurrent with the Company’s initial public offering (“IPO”).

Term and Termination. The research collaboration term ends in April 2022, except that Regeneron may make a one-time payment of $25.0 million to extend the term for an additional two-year period. The Regeneron Agreement will continue until the date when no royalty or other payment obligations are due, unless earlier terminated in accordance with the terms of the agreement. Regeneron’s royalty payment obligations expire on a country-by-country and product-by-product basis upon the later of (i) the expiration of the last valid claim of the royalty-bearing patents covering such product in such country, (ii) 12 years from the first commercial sale of such product in such country, or (iii) the expiration of regulatory exclusivity for such product. The Company may terminate the Regeneron Agreement on a target-by-target basis if Regeneron or any of its affiliates institutes a patent challenge against the Company’s CRISPR/Cas or certain other background patent rights or does not proceed with the development of a product directed to a selected target within specified periods of time. Regeneron may terminate the agreement, without cause, upon 180 days written notice to the Company, either in its entirety or on a target-by-target basis, in which event, certain rights in the terminated targets and associated IP revert to the Company, as described in the agreement. Following such termination, the Company may owe Regeneron royalties, in certain circumstances, up to mid-single digits on any terminated targets that the Company subsequently commercializes on a product-by-product basis for a period of 12 years after the first commercial sale of any such products. Either party may terminate the Regeneron Agreement either in its entirety or with respect to the research collaboration or one or more of the targets selected by Regeneron, in the event of the other party’s uncured material breach.

Co-Development and Co-Promotion Agreement. In July 2018, the Company and Regeneron finalized the form of the Co/Co agreement that will be used as the basis for each Co/Co agreement directed to a target. Simultaneously, the Company and Regeneron executed the Co/Co agreement directed to the first collaboration target, ATTR, for which the Company is the clinical and commercial Lead Party (see below) and Regeneron is the Participating Party (see below).

Co-Development and Co-Promotion: Agreement Structure Under the Regeneron Agreement, Regeneron has the right to exercise at least five options to enter into a Co/Co agreement for the Company’s liver targets (other than the Company’s reserved liver targets), while the Company may exercise at least one option to enter into a Co/Co agreement for Regeneron’s liver targets, the exact number of options being subject to certain conditions of the target selection process. Each option to enter into a Co/Co agreement must be exercised (or forfeited) once a target reaches a defined preclinical stage. Within 15 days of exercising the option, the party exercising the option must pay $1.5 million to the other party as compensation for prior work. The ATTR program was exempted from this payment. One party will be the “Lead Party” and the other party the “Participating Party”. The Lead Party shall have control and primary responsibility for the development, manufacturing, regulatory and commercial activities. The Participating Party shall have the right to consult on these activities through its participation on the JDCC and will have the right to co-fund development and commercialization activities in exchange for a share of profits. In general, under each Co/Co agreement, the parties will share equally in worldwide development costs and profits of any future products. Prior to reaching a specific development milestone, the Participating Party may elect to reduce its share of worldwide development costs and profits by 50%. Pursuant to the ATTR Co/Co, on December 13, 2019, Regeneron informed the Company that it would exercise its rights under the ATTR Co/Co agreement to modify its share of worldwide development costs and profits from 50% to 25%, effective six months after its notice.

Co-Development and Co-Promotion: Termination. Either party may terminate by providing 180 days written notice. If the Company terminates, the product becomes a Regeneron product, and is subject to all future milestone and royalty payment obligations under the Regeneron Agreement. If Regeneron terminates and has contributed at least $5 million in development costs under the Co/Co agreement, the Company will pay low- to mid-single digit royalties on the net sales of the product, depending on co-funding percentage, stage at termination and, if any, Regeneron IP incorporated into the product.

Accounting Analysis. The Company determined that the Regeneron Agreement is within the scope of ASC 606. The Company evaluated the promised goods and services under the Regeneron Agreement and determined that the Regeneron Agreement included three performance obligations: (1) a combined performance obligation including the licenses to targets and the associated research activities and evaluation plans; (2) a combined performance obligation including the technology collaboration and associated research activities; and (3) the common stock.

The Company also concluded that the ATTR Co/Co agreement meets the definition of a collaborative arrangement per ASC 808, which is outside of the scope of ASC 606. Since ASC 808 does not provide recognition and measurement guidance for collaborative arrangements, the Company has analogized to ASC 606. As such, the Company classifies payments received or made under the cost sharing provisions of the ATTR Co/Co agreement as a component of revenues in the consolidated statements of operations and comprehensive loss.

Under the Regeneron Agreement, the Company determined that the transaction price was $125.0 million, consisting of the following consideration: (1) the nonrefundable upfront payment of $75.0 million; and (2) the payment for the common stock of $50.0 million. None of the clinical or regulatory milestones were included in the transaction price, as all milestone amounts were fully constrained. As part its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future regulatory progress and the licensee’s efforts. Any consideration related to sales-based milestones and royalties will be recognized when the related sales occur as they were determined to relate predominantly to the licenses granted to Regeneron and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and when events whose outcome are resolved or other changes in circumstances occur.

The Company first allocated $50.0 million of the transaction price to the common stock. The common stock was sold at its standalone selling price and the Company concluded that the total discount inherent in the arrangement is entirely attributable to the combined performance obligation including the licenses to targets and associated research activities and evaluation plans and the combined performance obligation including the technology collaboration and associated research activities. As such, the remaining $75.0 million of the transaction price was allocated to the combined performance obligation including the licenses to targets and associated research activities and evaluation plans and the combined performance obligation including the technology collaboration and associated research activities on a relative standalone selling price basis. The Company estimated the standalone selling price of each combined performance obligation by taking into consideration internal estimates of research and development personnel needed to perform the research and development services, estimates of expected cash outflows to third parties for services and supplies, selling prices of comparable transactions and typical gross profit margins. As a result of this evaluation, the Company allocated $63.8 million to the combined performance obligation including the licenses to targets and associated research activities and evaluation plans and $11.2 million to the combined performance obligation including the technology collaboration and associated research activities. The $63.8 million allocated to the combined performance obligation including the licenses to targets and associated research activities and evaluation plans is being recognized using a time elapsed inputs method over a period of six years, which, in management’s judgment, is the best measure of progress towards satisfying the performance obligation as this method provides the most faithful depiction of the entity’s performance in transferring control of the goods and services promised to Regeneron and represents the Company’s best estimate of the period of the obligation. The $11.2 million allocated to the combined performance obligation including the technology collaboration and associated research activities is being recognized using a time elapsed inputs method over a period beginning with the inception of the technology collaboration in September 2016 through the end of the arrangement, which, in management’s judgment, is the best measure of progress towards satisfying the performance obligation as this method provides the most faithful depiction of the entity’s performance in transferring control of the goods and services promised to Regeneron and represents the Company’s best estimate of the period of the obligation.

Revenue Recognition: Collaboration Revenue. Through December 31, 2019, excluding the amounts allocated to Regeneron’s purchase of the Company’s common stock, the Company recorded a $75.0 million upfront payment and $24.1 million for research and development services under the Regeneron Agreement. As of December 31, 2019, there was approximately $28.8 million of the aggregate transaction price remaining to be recognized, which will be recognized ratably through April 2022. As of December 31, 2019 and 2018, the Company had deferred revenue of $28.8 million and $41.4 million, respectively, and accounts receivable of $3.6 million and $1.5 million, respectively, related to this arrangement.

Through December 31, 2019, the Company has recognized $70.3 million, including $24.6 million, $20.1 million and $16.8 million of collaboration revenue in the years ended December 31, 2019, 2018 and 2017, respectively, in the consolidated statements of operations and comprehensive loss related to this arrangement. This includes $12.0 million, $7.5 million, and $4.1 million representing payments from Regeneron pursuant to the ATTR Co/Co agreement, which is accounted for under ASC 808.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Collaboration revenue	$ 43,103	$ 30,434	$ 26,117
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 108,413	$ 89,115	$ 67,647
General and administrative	41,058	32,189	28,025
Total operating expenses	149,471	121,304	95,672
Operating loss	(106,368)	(90,870)	(69,555)
Interest income	6,835	5,527	2,012
Net loss	$ (99,533)	$ (85,343)	$ (67,543)
Net loss per share, basic and diluted	$ (2.11)	$ (1.98)	$ (1.88)
Weighted average shares outstanding, basic and diluted	47,247	43,069	36,006
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	$ 289	$ (28)
Comprehensive loss	$ (99,244)	$ (85,371)	$ (67,543)

Equity-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding, Beginning Balance \| shares	5,037,663
Number of options, Granted \| shares	1,220,613
Number of options, Exercised \| shares	(364,404)
Number of options, Forfeited \| shares	(527,901)
Number of Options, Outstanding, Ending Balance \| shares	5,365,971
Number of Options, Exercisable \| shares	2,578,717
Weighted Average Exercise Price per Share, Outstanding, Beginning Balance \| $ / shares	$ 15.63
Weighted Average Exercise Price per Share, Granted \| $ / shares	14.90
Weighted Average Exercise Price per Share, Exercised \| $ / shares	8.47
Weighted Average Exercise Price per Share, Forfeited \| $ / shares	18.50
Weighted Average Exercise Price per Share, Outstanding, Ending Balance \| $ / shares	15.67
Weighted Average Exercise Price per Share, Exercisable \| $ / shares	$ 14.11
Weighted Average Remaining Contractual Term, Outstanding	7 years 10 months 9 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 11 months 1 day
Aggregate Intrinsic Value, Outstanding \| $	$ 9,082
Aggregate Intrinsic Value, Exercisable \| $	$ 8,017

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.Summary of Significant Accounting Policies

Basis of Presentation

Use of Estimates

Fair Value Measurements

Refer to Note 4 for further information regarding the Company’s fair value measurements.

Other financial instruments, including accounts receivable, accounts payable and accrued expenses, are carried at cost, which approximate fair value due to the short duration and term to maturity.

Cash Equivalents

Marketable Securities

Concentrations of Credit Risk

Property and Equipment

The Company records property and equipment at cost and recognizes depreciation and amortization using the straight-line method over the following estimated useful lives of the respective assets:

Asset Category		Useful Life
Laboratory equipment		5 years
Office furniture and equipment		5 years
Computer software		3 years
Computer equipment		3 years
Leasehold improvements		5 years or term of respective lease, if shorter

Impairment of Long-Lived Assets

Income Taxes

Revenue Recognition

Research and Development Expenses

Equity-Based Compensation

(Loss) Earnings per Share

Segment Information

Recent Accounting Pronouncements – Adopted

Leases

Refer to Note 10 for the Company’s current lease commitments.

Recent Accounting Pronouncements – Issued but not yet adopted

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.	Fair Value Measurements

The Company classifies fair value-based measurements using a three-level hierarchy that prioritizes the inputs used to measure fair value. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1, quoted market prices in active markets for identical assets or liabilities; Level 2, observable inputs other than quoted market prices included in Level 1, such as quoted market prices for markets that are not active or other inputs that are observable or can be corroborated by observable market data; and Level 3, unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities, including certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.

As of December 31, 2019 and 2018, the Company’s financial assets recognized at fair value on a recurring basis consisted of the following:

	Fair Value as of December 31, 2019
	Total		Level 1		Level 2		Level 3
	(In thousands)
Cash equivalents	$	46,917	$	46,917	$	-	$	-
Marketable securities:
U.S. Treasury securities		159,502		159,502		-		-
Financial institution debt securities		40,278		-		40,278		-
Corporate debt securities		18,967		-		18,967		-
Other asset-backed securities		8,499		-		8,499		-
Total marketable securities		227,246		159,502		67,744		-
Total	$	274,163	$	206,419	$	67,744	$	-

	Fair Value as of December 31, 2018
	Total		Level 1		Level 2		Level 3
	(In thousands)
Cash equivalents	$	45,986	$	45,986	$	-	$	-
Marketable securities:
U.S. Treasury securities		165,948		165,948		-		-
Financial institution debt securities		65,420		-		65,420		-
Corporate debt securities		23,835		-		23,835		-
Total marketable securities		255,203		165,948		89,255		-
Total	$	301,189	$	211,934	$	89,255	$	-

The Company’s financial assets, which include cash equivalents and marketable securities, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models and observable market inputs to determine value. After completing its validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of December 31, 2019 or 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Income Taxes - Summary of Company's Net Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Intangibles, including acquired in-process research and development	$ 1,091	$ 1,201
Capitalized start-up costs	421	463
Net operating loss carryforwards	63,245	34,234
Research and development credit carryforwards	19,417	11,766
Operating lease liability	5,008
Deferred revenue	7,843	12,199
Equity-based compensation	7,092	4,064
Accruals and allowances	1,245	1,359
Gross deferred tax assets	105,362	65,286
Deferred tax asset valuation allowance	(98,513)	(64,046)
Total deferred tax assets	6,849	1,240
Deferred tax liabilities:
Fixed assets	(1,633)	(1,240)
Operating lease right-of-use assets	(5,216)
Total deferred tax liabilities	$ (6,849)	$ (1,240)

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets Recognized at Fair Value on Recurring Basis

As of December 31, 2019 and 2018, the Company’s financial assets recognized at fair value on a recurring basis consisted of the following:

	Fair Value as of December 31, 2019
	Total		Level 1		Level 2		Level 3
	(In thousands)
Cash equivalents	$	46,917	$	46,917	$	-	$	-
Marketable securities:
U.S. Treasury securities		159,502		159,502		-		-
Financial institution debt securities		40,278		-		40,278		-
Corporate debt securities		18,967		-		18,967		-
Other asset-backed securities		8,499		-		8,499		-
Total marketable securities		227,246		159,502		67,744		-
Total	$	274,163	$	206,419	$	67,744	$	-

	Fair Value as of December 31, 2018
	Total		Level 1		Level 2		Level 3
	(In thousands)
Cash equivalents	$	45,986	$	45,986	$	-	$	-
Marketable securities:
U.S. Treasury securities		165,948		165,948		-		-
Financial institution debt securities		65,420		-		65,420		-
Corporate debt securities		23,835		-		23,835		-
Total marketable securities		255,203		165,948		89,255		-
Total	$	301,189	$	211,934	$	89,255	$	-

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Summary of Lease Costs and Other Information

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the year ended December 31, 2019:

	Year Ended
	December 31, 2019
	(in thousands)
Lease cost
Operating lease cost	$	7,431
Short-term lease cost		53
Variable lease cost	2,218
Total lease cost	$	9,702

	Year Ended
	December 31, 2019
	(in thousands)
Other information
Operating cash flows used for operating leases	$	6,476
Operating lease liabilities arising from obtaining right-of-use assets	2,554

	As of December 31, 2019
Lease term and discount rate
Weighted average remaining lease term	3.0 years
Weighted average discount rate	9.00%

Schedule of Reconciliation of Undiscounted Cash Flows for Operating Lease Liabilities / Future Minimum Lease Payments

Future Operating Lease Payments
Year Ending December 31,	(in thousands)
2020	$	7,113
2021		7,350
2022		4,733
2023		871
2024		871
Thereafter		73
Total lease payments	$	21,011
Less: imputed interest		(2,636	)
Total operating lease liabilities at December 31, 2019	$	18,375

Future minimum lease payments under the Company’s non-cancelable operating leases as of December 31, 2018, are as follows:

Year Ending December 31,	(In thousands)
2019	$	5,616
2020		4,963
2021		5,507
2022		3,861
	$	19,947

Unaudited Quarterly Results - Schedule of Results of Operations on Quarterly Basis (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Collaboration revenue	$ 10,936	$ 10,616	$ 11,118	$ 10,433	$ 7,880	$ 7,408	$ 7,677	$ 7,469	$ 43,103	$ 30,434	$ 26,117
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 31,731	$ 27,513	$ 25,460	$ 23,709	$ 19,918	$ 23,237	$ 23,467	$ 22,493	$ 108,413	$ 89,115	$ 67,647
General and administrative	8,976	8,431	13,118	10,533	8,708	8,270	7,805	7,406	41,058	32,189	28,025
Total operating expenses	40,707	35,944	38,578	34,242	28,626	31,507	31,272	29,899	149,471	121,304	95,672
Operating loss	(29,771)	(25,328)	(27,460)	(23,809)	(20,746)	(24,099)	(23,595)	(22,430)	(106,368)	(90,870)	(69,555)
Interest income	1,495	1,694	1,777	1,869	1,680	1,397	1,376	1,074	6,835	5,527	2,012
Net loss	$ (28,276)	$ (23,634)	$ (25,683)	$ (21,940)	$ (19,066)	$ (22,702)	$ (22,219)	$ (21,356)	$ (99,533)	$ (85,343)	$ (67,543)
Net loss per share, basic and diluted	$ (0.57)	$ (0.49)	$ (0.56)	$ (0.49)	$ (0.43)	$ (0.53)	$ (0.52)	$ (0.51)	$ (2.11)	$ (1.98)	$ (1.88)
Weighted average shares outstanding, basic and diluted	49,350	48,554	45,814	45,234	44,215	43,161	42,836	42,043	47,247	43,069	36,006

Leases - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended				12 Months Ended
	Apr. 30, 2019	Mar. 31, 2019	Jan. 31, 2016	Oct. 31, 2014	Dec. 31, 2019
Lessee Lease Description [Line Items]
Operating lease right-of-use assets					$ 19,137
Operating lease, liability					$ 18,375
130 Brookline Street [Member]
Lessee Lease Description [Line Items]
Operating lease, description					In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025.
Operating lease expiration				2020-01
Lessee operating lease extended expiration date	Jan. 31, 2025
Operating lease, existence of option to extend				true
Operating lease, options to extend					option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025.
Operating lease, renewal term	5 years			5 years
Lessee operating sublease option to extend					two options to extend the agreement by one year each, for a total option period of up to two years.
Operating sublease expiration		2021-04
Operating sublease, existence of option to extend		true
Operating lease right-of-use assets	$ 1,300
Operating lease, liability	$ 1,300
130 Brookline Street [Member] \| Maximum [Member]
Lessee Lease Description [Line Items]
Operating sublease, renewal term		2 years
130 Brookline Street [Member] \| Other Assets [Member]
Lessee Lease Description [Line Items]
Lease security deposit				$ 300
40 Erie Street [Member]
Lessee Lease Description [Line Items]
Operating lease, description					In January 2016, the Company entered into a ten-year agreement to lease office and laboratory space at 40 Erie Street in Cambridge, Massachusetts under an operating lease agreement, with an option to terminate the lease at the end of the sixth year and an option to extend the term of the lease for an additional three years.
Operating lease, existence of option to extend			true
Operating lease, options to extend					option to extend the term of the lease for an additional three years.
Operating lease, renewal term			3 years
Operating lease, term of contract			10 years
Operating lease, existence of option to terminate			true
Operating lease, option to terminate					option to terminate the lease at the end of the sixth year
Operating lease, terminate term			6 years
40 Erie Street [Member] \| Other Assets [Member]
Lessee Lease Description [Line Items]
Lease security deposit			$ 2,200

Stockholders' Equity - Additional Information (Detail) - USD ($)						1 Months Ended	12 Months Ended
	Aug. 23, 2019	Oct. 12, 2018	Nov. 06, 2017	Nov. 01, 2017	May 11, 2016	Nov. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Number of common stock issued upon conversion of value									$ 141,000,000
Common stock par value per share							$ 0.0001	$ 0.0001
Proceeds from common stock offering							$ 72,256,000	$ 28,547,000	$ 141,000,000
2018 Sales Agreement [Member]
Class Of Stock [Line Items]
Number of common stock issued upon conversion of shares						1,659,300	4,231,348
Common stock price per share						$ 18.00	$ 16.57
Proceeds from common stock offering						$ 28,500,000	$ 67,800,000
Percentage of gross proceeds from common stock as sales agent cash commission		3.00%
Proceeds from common stock offering							0
2018 Sales Agreement [Member] \| General and Administrative Expenses [Member]
Class Of Stock [Line Items]
Legal accounting and other fees						$ 400,000	$ 200,000
2018 Sales Agreement [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering		$ 100,000,000.0
2019 Sales Agreement [Member]
Class Of Stock [Line Items]
Number of common stock issued upon conversion of shares							287,231
Common stock price per share							$ 16.48
Proceeds from common stock offering							$ 4,400,000
Percentage of gross proceeds from common stock as sales agent cash commission							3.00%
Proceeds from common stock offering							$ 145,300,000
2019 Sales Agreement [Member] \| General and Administrative Expenses [Member]
Class Of Stock [Line Items]
Legal accounting and other fees							$ 200,000
2019 Sales Agreement [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering	$ 150,000,000.0
IPO [Member]
Class Of Stock [Line Items]
Number of common stock issued upon conversion of shares					6,900,000
Common stock price per share					$ 18.00
Convertible preferred stock conversion ratio							one-for-0.6465903
Conversion of convertible preferred stock into common stock					23,481,956
Private Placement [Member]
Class Of Stock [Line Items]
Number of common stock issued upon conversion of shares					3,055,554
Number of common stock issued upon conversion of value					$ 55,000,000.0
Public Offering [Member] \| Underwriting Agreement [Member]
Class Of Stock [Line Items]
Number of common stock issued upon conversion of shares				6,250,000
Common stock par value per share				$ 0.0001
Proceeds from common stock offering			$ 141,000,000.0

Marketable Securities

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Marketable Securities

3.	Marketable Securities

The following table summarizes the Company’s available-for-sale marketable securities as of December 31, 2019 and 2018 at net book value:

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	159,361	$	142	$	(1	)	$	159,502
Financial institution debt securities		40,173		105		-			40,278
Corporate debt securities		18,966		1		-			18,967
Other asset-backed securities		8,485		14		-			8,499
Total	$	226,985	$	262	$	(1	)	$	227,246

	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	165,959	$	2	$	(13	)	$	165,948
Financial institution debt securities		65,436		1		(17	)		65,420
Corporate debt securities		23,836		-		(1	)		23,835
Total	$	255,231	$	3	$	(31	)	$	255,203

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At December 31, 2019 and 2018, the balance in the Company’s accumulated other comprehensive income (loss) was composed of activity related to the Company’s available-for-sale marketable securities. There were no material realized gains or losses in the years ended December 31, 2019, 2018 or 2017 and, as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income (loss) during these periods. The Company did not have any securities in a material unrealized loss position at December 31, 2019 or 2018.

The Company's available-for-sale securities that are classified as short term marketable securities in the consolidated balance sheet mature within one year or less as of the balance sheet date. Available-for-sale securities that are classified as noncurrent in the consolidated balance sheet mature after one year but within five years from the balance sheet date. At December 31, 2019 and 2018, the Company did not hold any investments that matured beyond five years.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of the Federal Statutory Income Tax Rate and the Company's Effective Income Tax Rate

A reconciliation of the federal statutory income tax rate and the Company’s effective income tax rate is as follows:

	Year Ended December 31,
	2019			2018			2017
Federal statutory income tax rate		(21.0	)%		(21.0	)%		(34.0	)%
State income taxes		(8.9	)		(8.6	)		(6.9	)
Research and development tax credits		(5.1	)		(4.7	)		(3.4	)
Stock-based compensation		1.2			(0.6	)		3.6
Change in U.S. tax rate		-			-			18.7
Change in valuation allowance		33.8			34.9			22.0
Effective income tax rate		-	%		-	%		-	%

Summary of Company's Net Deferred Tax Assets (Liabilities)

The Company’s net deferred tax assets (liabilities) consisted of the following:

	December 31,
	2019			2018
	(in thousands)
Deferred tax assets:
Intangibles, including acquired in-process research and development	$	1,091		$	1,201
Capitalized start-up costs		421			463
Net operating loss carryforwards		63,245			34,234
Research and development credit carryforwards		19,417			11,766
Operating lease liability		5,008			-
Deferred revenue		7,843			12,199
Equity-based compensation		7,092			4,064
Accruals and allowances		1,245			1,359
Gross deferred tax assets		105,362			65,286
Deferred tax asset valuation allowance		(98,513	)		(64,046	)
Total deferred tax assets		6,849			1,240
Deferred tax liabilities:
Fixed assets		(1,633	)		(1,240	)
Operating lease right-of-use assets		(5,216	)		-
Total deferred tax liabilities		(6,849	)		(1,240	)
Net deferred tax asset (liability)	$	-		$	-

Income Taxes - Schedule of Reconciliation of the Federal Statutory Income Tax Rate and the Company's Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	(21.00%)	(21.00%)	(34.00%)
State income taxes	(8.90%)	(8.60%)	(6.90%)
Research and development tax credits	(5.10%)	(4.70%)	(3.40%)
Stock-based compensation	1.20%	(0.60%)	3.60%
Change in U.S. tax rate			18.70%
Change in valuation allowance	33.80%	34.90%	22.00%

Equity-Based Compensation - Summary of Restricted Stock Activity (Detail)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested, Beginning balance \| shares	109,073
Number of Shares, Vested \| shares	(37,198)
Number of Shares, Unvested, Ending balance \| shares	71,875
Weighted Average Grant Date Fair Value per Share, Unvested, Beginning balance \| $ / shares	$ 15.53
Weighted Average Grant Date Fair Value per Share, Vested \| $ / shares	1.34
Weighted Average Grant Date Fair Value per Share, Unvested, Ending balance \| $ / shares	$ 22.88

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Benefit [Line Items]
Net operating loss carryforwards, federal	$ 229,900,000
Net operating loss carryforwards, state	$ 236,800,000
Net operating loss carryforwards, begins to expiring year	2034
Net operating loss carryforwards, expiration date description	begins to expire in 2034
Research and development and other credit	$ 19,417,000	$ 11,766,000
Research and development tax credits, expiration date description	begin to expire in 2035 and 2031
Increase in valuation allowance	$ 34,500,000	$ 28,700,000	$ 14,800,000
Unrecognized tax benefits	0
Operating Loss Carryforward Indefinitely [Member]
Income Tax Benefit [Line Items]
Net operating loss carryforwards, federal	193,000,000.0
Operating Loss Carryforward Indefinitely Begins to Expire in 2034 [Member]
Income Tax Benefit [Line Items]
Net operating loss carryforwards, federal	36,900,000
Federal [Member]
Income Tax Benefit [Line Items]
Research and development and other credit	$ 12,600,000
Research and development tax credits, expiration year	2035
State [Member]
Income Tax Benefit [Line Items]
Research and development and other credit	$ 8,700,000
Research and development tax credits, expiration year	2031

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 31,864	$ 25,673
Less: accumulated depreciation and amortization	(13,868)	(8,612)
Property and equipment, net	17,996	17,061
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	27,199	22,453
Office Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,121	960
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,051	929
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,474	898
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,019	$ 433

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 5,587	$ 4,464	$ 2,994

Leases - Summary of Lease Costs and Other Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease cost
Operating lease cost	$ 7,431
Short-term lease cost	53
Variable lease cost	2,218
Total lease cost	9,702
Other information
Operating cash flows used for operating leases	6,476
Operating lease liabilities arising from obtaining right-of-use assets	$ 2,554
Weighted average remaining lease term	3 years
Weighted average discount rate	9.00%

Collaborations - Summary of Revenues Recognized Resulting From Changes in Contract Liability Balance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Amounts included in the contract liability at the beginning of the period	$ 27,122	$ 22,936

Leases - Schedule of Reconciliation of Undiscounted Cash Flows for Operating Lease Liabilities / Future Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
2020	$ 7,113	$ 5,616
2021	7,350	4,963
2022	4,733	5,507
2023	871	3,861
2024	871
Thereafter	73
Total lease payments	21,011	$ 19,947
Less: imputed interest	(2,636)
Operating lease, liability	$ 18,375

Related Party Transactions - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended								12 Months Ended
	May 31, 2016	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Collaboration revenue		$ 10,936,000	$ 10,616,000	$ 11,118,000	$ 10,433,000	$ 7,880,000	$ 7,408,000	$ 7,677,000	$ 7,469,000	$ 43,103,000	$ 30,434,000	$ 26,117,000
Deferred revenue		28,810,000				55,932,000				28,810,000	55,932,000	59,868,000
Novartis [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Issuance of common stock through at-the-market offering, net of issuance costs, shares	277,777
Collaboration revenue										18,500,000	10,300,000	$ 9,300,000
Accounts receivable		1,000,000.0				6,000,000.0				1,000,000.0	6,000,000.0
Deferred revenue		$ 0				$ 14,500,000				$ 0	$ 14,500,000
Novartis [Member] \| Collaborative Arrangement [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Percentage of shares owned		10.00%								10.00%

Collaborations - Summary of Changes in Accounts Receivable and Contract Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable:
Accounts receivable, Balance at Beginning of Period	$ 7,547	$ 10,471
Accounts receivable, Additions	15,999	16,498
Accounts receivable, Deductions	(18,926)	(19,422)
Accounts receivable, Balance at End of Period	4,620	7,547
Contract liabilities:
Deferred revenue, Balance at Beginning of Period	55,932	59,868
Deferred revenue, Additions	4,000	19,000
Deferred revenue, Deductions	(31,122)	(22,936)
Deferred revenue, Balance at End of Period	$ 28,810	$ 55,932

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	50,198,044	45,224,480
Common stock, shares outstanding	50,198,044	45,224,480

Marketable Securities - Summary of Available -for-sale Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Amortized Cost	$ 226,985	$ 255,231
Gross Unrealized Gains	262	3
Gross Unrealized Losses	(1)	(31)
Estimated Fair Value	227,246	255,203
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	159,361	165,959
Gross Unrealized Gains	142	2
Gross Unrealized Losses	(1)	(13)
Estimated Fair Value	159,502	165,948
Financial Institution Debt Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	40,173	65,436
Gross Unrealized Gains	105	1
Gross Unrealized Losses		(17)
Estimated Fair Value	40,278	65,420
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	18,966	23,836
Gross Unrealized Gains	1
Gross Unrealized Losses		(1)
Estimated Fair Value	18,967	$ 23,835
Other Asset Backed Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	8,485
Gross Unrealized Gains	14
Estimated Fair Value	$ 8,499

Fair Value Measurements - Summary of Financial Assets Recognized at Fair Value on Recurring Basis (Detail) - Fair Value on Recurring Basis [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 46,917	$ 45,986
Marketable securities:
Marketable securities	227,246	255,203
Total	274,163	301,189
U.S. Treasury Securities [Member]
Marketable securities:
Marketable securities	159,502	165,948
Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	40,278	65,420
Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	18,967	23,835
Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	8,499
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	46,917	45,986
Marketable securities:
Marketable securities	159,502	165,948
Total	206,419	211,934
Level 1 [Member] \| U.S. Treasury Securities [Member]
Marketable securities:
Marketable securities	159,502	165,948
Level 2 [Member]
Marketable securities:
Marketable securities	67,744	89,255
Total	67,744	89,255
Level 2 [Member] \| Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	40,278	65,420
Level 2 [Member] \| Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	18,967	$ 23,835
Level 2 [Member] \| Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	$ 8,499

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Segment	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Percentage of likelihood of realization required to record tax benefit	50.00%
Number of reportable segment \| Segment	1
Operating lease, liability	$ 18,375
Operating lease right-of-use assets	19,137
Retained earnings	$ (300,878)		$ (201,025)
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease, liability		$ 20,600
Operating lease right-of-use assets		22,300
ASU 2016-02 [Member] \| Restatement Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Retained earnings		$ 300
Maximum [Member] \| ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Maximum lease term	12 months

401(k) Plan - Additional Information (Detail) - 401(k) plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution of employee contribution, percent	50.00%
Employer matching contribution, percent	6.00%
Employer discretionary contribution amount	$ 0.8	$ 0.6

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Employee compensation and benefits	$ 6,311	$ 6,175
Accrued research and development	4,208	2,328
Accrued legal and professional expenses	1,563	1,633
Accrued other	1,191	606
Total accrued expenses	$ 13,273	$ 10,742