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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Mar. 05, 2020	Jun. 30, 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	SYBX
Entity Registrant Name	SYNLOGIC, INC.
Entity Central Index Key	0001527599
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		32,250,814
Entity Public Float			$ 161.9
Title of 12(b) Security	Common Stock, par value $0.001 per share
Entity File Number	001-37566
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1824804
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity Address, Address Line One	301 Binney St
Entity Address, Address Line Two	Suite 402
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	401-9975
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE The following documents (or parts thereof) are incorporated by reference into the following parts of this Form 10-K: Certain information required in Part III of this Annual Report on Form 10-K is incorporated from the registrant’s definitive proxy statement for the 2020 annual meeting of stockholders to be filed pursuant to Regulation 14A with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2019.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 26,184	$ 11,252
Short-term marketable securities	93,387	111,477
Prepaid expenses and other current assets	13,675	1,609
Total current assets	133,246	124,338
Long-term marketable securities	7,502
Property and equipment, net	13,021	14,841
Right of use asset - operating lease	17,263
Restricted cash	1,097	1,097
Prepaid research and development, net of current portion	16,381
Other assets	64	64
Total assets	188,574	140,340
Current liabilities:
Accounts payable	2,165	2,421
Accrued expenses	3,946	4,993
Deferred revenue	544	268
Deferred rent		393
Lease liability - operating lease	2,000
Finance lease obligations	208	266
Total current liabilities	8,863	8,341
Long-term liabilities:
Deferred rent, net of current portion		7,691
Lease liability - operating lease, net of current portion	22,804
Finance lease obligations, net of current portion	2	210
Total long-term liabilities	22,806	7,901
Commitments and contingencies (Note 14)
Stockholders' Equity
Common stock, $0.001 par value 250,000,000 shares authorized as of December 31, 2019 and December 31, 2018. 32,266,814 shares issued and outstanding as of December 31, 2019 and 25,401,479 shares issued and outstanding as of December 31, 2018.	33	25
Additional paid-in capital	327,900	243,903
Accumulated other comprehensive loss	110	(65)
Accumulated deficit	(171,138)	(119,765)
Total stockholders' equity	156,905	124,098
Total liabilities and stockholders' equity	$ 188,574	$ 140,340

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	250,000,000	250,000,000
Common stock, Issued	32,266,814	25,401,479
Common stock, outstanding	32,266,814	25,401,479

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 2,224	$ 2,520
Operating expenses:
Research and development	41,905	38,034
General and administrative	14,728	15,716
Total operating expenses	56,633	53,750
Loss from operations	(54,409)	(51,230)
Other income (expense):
Interest and investment income	3,062	2,843
Interest expense	(21)	(43)
Other expense	(5)	(5)
Other income (expense), net	3,036	2,795
Net loss	$ (51,373)	$ (48,435)
Net loss per share - basic and diluted	$ (1.70)	$ (2.03)
Weighted-average common stock outstanding - basic and diluted	30,284,068	23,882,685
Comprehensive loss:
Net loss	$ (51,373)	$ (48,435)
Net unrealized gain (loss) on marketable securities	175	(56)
Comprehensive loss	$ (51,198)	$ (48,491)

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock $0.001 Par Value	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2017	$ 85,038	$ 16	$ 156,685	$ (9)	$ (71,654)
Balance (in Shares) at Dec. 31, 2017		16,272,617
Effect of adoption of ASU \| ASU 2014-09 (ASC 606)	324				324
Sale of common shares, net of issuance costs	82,666	$ 9	82,657
Sale of common shares, net of issuance costs, shares		9,179,500
Exercise of options	244		244
Exercise of options, shares		19,830
Cancellation of restricted stock		(70,468)
Equity-based compensation expense	4,317		4,317
Unrealized gain (loss) on securities	(56)			(56)
Net loss	(48,435)				(48,435)
Balance at Dec. 31, 2018	124,098	$ 25	243,903	(65)	(119,765)
Balance (in Shares) at Dec. 31, 2018		25,401,479
Sale of common shares, net of issuance costs	56,997	$ 7	56,990
Sale of common shares, net of issuance costs, shares		6,340,771
Proceeds from issuance of pre-funded common stock warrants, net of issuance costs	22,874		22,874
Issuance of restricted stock		$ 1	(1)
Issuance of restricted stock, shares		585,600
Cancellation of restricted stock		(61,036)
Equity-based compensation expense	4,134		4,134
Unrealized gain (loss) on securities	175			175
Net loss	(51,373)				(51,373)
Balance at Dec. 31, 2019	$ 156,905	$ 33	$ 327,900	$ 110	$ (171,138)
Balance (in Shares) at Dec. 31, 2019		32,266,814

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (51,373)	$ (48,435)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,702	2,421
Loss on disposal of property and equipment		8
Equity-based compensation expense	4,134	4,317
Accretion/amortization of investment securities	(1,282)	(1,401)
Reduction in carrying amount of operating lease right of use asset	1,370
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(12,263)	(45)
Prepaid research and development, net of current portion	(16,381)
Other assets		168
Accounts payable and accrued expenses	(935)	(257)
Deferred revenue	276	(520)
Deferred rent		1,274
Operating lease liabilities	(1,716)
Net cash, cash equivalents and restricted cash used in operating activities	(75,468)	(42,470)
Cash flows from investing activities:
Purchases of marketable securities	(145,418)	(172,887)
Proceeds from maturity of marketable securities	157,465	91,340
Purchases of property and equipment	(1,251)	(5,654)
Net cash, cash equivalents and restricted cash provided by (used in) investing activities	10,796	(87,201)
Cash flows from financing activities:
Payments on finance lease obligations	(266)	(427)
Proceeds from exercise of stock options		244
Proceeds from sale of common stock, net of issuance costs	56,996	82,666
Proceeds from sale of pre-funded warrants, net of issuance costs	22,874
Net cash, cash equivalents and restricted cash provided by financing activities	79,604	82,483
Net increase (decrease) in cash, cash equivalents and restricted cash	14,932	(47,188)
Cash, cash equivalents and restricted cash at beginning of period	12,349	59,537
Cash, cash equivalents and restricted cash at end of period	27,281	12,349
Supplemental disclosure of non-cash investing and financing activities:
Landlord funded allowance for tenant improvements		1,654
Property and equipment purchases included in accounts payable and accrued expenses	(369)	169
Assets acquired under operating lease obligation	2,714
Cash paid for interest	$ 21	43
Purchase under capital lease		$ 12

Nature of Business

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Business

(1)	Nature of Business

Organization

Synlogic, Inc., together with its wholly owned and consolidated subsidiaries (“Synlogic” or the “Company”), is a clinical-stage biopharmaceutical company focused on advancing its drug discovery and development platform for Synthetic Biotic™ medicines. Synthetic Biotic medicines are generated from Synlogic’s proprietary drug discovery and development platform applying the principles and tools of synthetic biology to engineer beneficial microbes to perform or deliver critical therapeutic functions to treat metabolic and inflammatory diseases and cancer. As living medicines, Synthetic Biotic medicines can be designed to sense a local disease context within a patient’s body and to respond by metabolizing a toxic substance, compensating for missing or damaged metabolic pathways in patients, or by delivering combinations of therapeutic factors. Synlogic’s goal is to lead in the discovery and development of Synthetic Biotic therapies as living medicines capable of robust and precise pathway complementation and delivery of therapeutic benefit. Since incorporation, the Company has devoted substantially all of its efforts to the research and development of its product candidates.

Synlogic, Inc. (“Private Synlogic” when referred to prior to the Merger (as defined below)) was founded and began operations on March 14, 2014, as TMC Therapeutics, Inc., located in Cambridge, Massachusetts. On July 15, 2014, TMC Therapeutics, Inc. changed its name to Synlogic, Inc. On July 2, 2015, the common and preferred stockholders of Private Synlogic executed the Synlogic, LLC Contribution Agreement (the “Contribution Agreement”), pursuant to which such common and preferred stockholders contributed such stockholders’ equity interests in Private Synlogic in exchange for common and preferred units in a newly formed parent company named Synlogic, LLC. In addition, Synlogic IBDCo, Inc. (“IBDCo”) was formed as a subsidiary of Synlogic, LLC (the “2015 Reorganization”). In conjunction with the 2015 Reorganization, Private Synlogic entered into a license, option and merger agreement with AbbVie S.à.r.l. (“AbbVie”), for the development of treatments for inflammatory bowel disease (“IBD”).

In May 2017, Private Synlogic completed a reorganization (“2017 Reorganization”) pursuant to which Synlogic, LLC merged with and into Private Synlogic, with Private Synlogic continuing as the surviving corporation. Pursuant to the 2017 Reorganization, the common units and preferred units of Synlogic, LLC, together consisting of Class A preferred units, contingently redeemable Class A preferred units and Class B preferred units, were exchanged for common stock and preferred stock of Private Synlogic, respectively. Additionally, Private Synlogic issued equity awards under the Synlogic 2017 Stock Incentive Plan (“2017 Plan”) to replace the canceled incentive units pursuant to the termination of the Synlogic, LLC 2015 Equity Incentive Plan (“2015 LLC Plan”).

On August 28, 2017, Synlogic, Inc., formerly known as Mirna Therapeutics, Inc. (NASDAQ: MIRN) (“Mirna”), completed its business combination with Private Synlogic pursuant to the Agreement and Plan of Merger and Reorganization, dated as of May 15, 2017, by and among Mirna, Meerkat Merger Sub, Inc. (“Merger Sub”), and Private Synlogic (the “Merger Agreement”), pursuant to which Merger Sub merged with and into Private Synlogic, with Private Synlogic surviving as a wholly owned subsidiary of Mirna (the “Merger”). Immediately after completion of the Merger, Mirna changed its name to “Synlogic, Inc.” (NASDAQ: SYBX).

Risks and Uncertainties

At December 31, 2019, the Company had approximately $119.6 million in cash, cash equivalents, and short-term marketable securities, $7.5 million of long-term marketable securities, $1.1 million of restricted cash and an accumulated deficit of approximately $171.1 million. Since its inception through December 31, 2019, the Company has primarily financed its operations through the issuance of preferred stock, units and warrants, the sale of its common stock, the AbbVie collaboration, and cash received in the Merger. In the absence of positive cash flows from operations, the Company is highly dependent on its ability to find additional sources of funding in the form of debt or equity financing. Management believes that the Company has sufficient cash to fund its operations through at least twelve months from the issuance of these financial statements.

As an early-stage company, the Company is subject to a number of risks common to other life science companies, including, but not limited to, raising additional capital, development by its competitors of new technological innovations, risk of failure in preclinical and clinical studies, safety and efficacy of its product candidates in clinical trials, the risk of relying on external parties such as contract research organizations (“CROs”) and contract manufacturing organizations (“CMOs”), the regulatory approval process, market acceptance of the Company’s products once approved, lack of marketing and sales history, dependence on key personnel and protection of proprietary technology. The Company’s therapeutic programs are currently pre-commercial, spanning discovery through early development and will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization of any product candidates. These efforts require significant amounts of additional capital, adequate personnel, infrastructure, and extensive compliance-reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales. The Company may never achieve profitability, and unless and until it does, it will continue to need to raise additional capital or obtain financing from other sources, such as strategic collaborations or partnerships.

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

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S.”) (“U.S. GAAP” or “GAAP”).

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Synlogic and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. On an on-going basis, the Company’s management evaluates its estimates, including those related to revenue recognition, income taxes including the valuation allowance for deferred tax assets, research and development accruals and prepaids, accrued expenses, investments, contingencies and equity-based compensation. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.

Cash Equivalents

The Company considers all highly liquid investment instruments with a remaining maturity when purchased of three months or less to be cash equivalents. Investments qualifying as cash equivalents primarily consist of money market funds, corporate debt securities and commercial paper. Cash equivalents are stated at cost plus accrued interest, which approximates fair value. The amount of cash equivalents included in cash and cash equivalents was approximately $13.5 million and $0.3 million at December 31, 2019 and 2018, respectively.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk include amounts held as cash, cash equivalents, marketable securities and restricted cash. The Company uses high quality, accredited financial institutions to maintain its balances, and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. The Company has no financial instruments with off-balance sheet risk of loss.

Restricted Cash

The Company held cash of approximately $1.0 million at December 31, 2019 and 2018 in a letter of credit to secure its lease at the 301 Binney Street facility. In addition, the Company held cash of $50,000 at December 31, 2019 and 2018 in a separate restricted bank account as collateral for the Company’s credit cards. The Company has classified these deposits as long-term restricted cash on its balance sheet.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the statement of financial position that sum to the total of the same such amounts shown in the statement of cash flows (in thousands).

	December 31,		December 31,
	2019		2018
Cash and cash equivalents	$	26,184	$	11,252
Restricted cash included in other long-term assets		1,097		1,097
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$	27,281	$	12,349

Fair Value

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. Accounting Standards Codification (“ASC”) Topic 820, Fair Value Measurements and Disclosures, establishes a fair value hierarchy for those instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). The hierarchy consists of three levels:

•

Level 1 – Utilize observable inputs such as quoted prices in active markets for identical assets or liabilities;

•

Level 2 – Utilize data points that are either directly or indirectly observable, such as quoted prices, interest rates and yield curves;

•

Level 3 – Utilize unobservable data points in which there is little or no market data, which require the Company to develop its own assumptions for the asset or liability.

The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1, Level 2 or Level 3 during the years ended December 31, 2019 and 2018.

Available-for-Sale Securities

The Company classifies all short-term investments with an original maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in other comprehensive income (loss). The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest and investment income. Realized gains and losses, and declines in value judged to be other than temporary on available-for-sale securities, are included in interest and investment income.

The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest and investment income. To determine whether an other-than-temporary impairment exists, the Company considers whether it has the ability and intent to hold the investment until a market price recovery, and whether evidence indicating the recoverability of the cost of the investment outweighs evidence to the contrary.

Property and Equipment

Property and equipment, including leasehold improvements, are recorded at cost and depreciated over their estimated useful lives using the straight‑line method. Repairs and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment.

Depreciation begins at the time the asset is placed in service. Depreciation is provided over the following estimated useful lives:

Asset classification		Useful life
Computer and office equipment		3 years
Furniture and fixtures		5 years
Laboratory equipment		5 years
Leasehold improvements		Lesser of useful life or remaining lease term

Impairment of Long‑Lived Assets

Long‑lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. When such events occur, the Company compares the carrying amounts of the assets to their undiscounted expected future cash flows. If this comparison indicates that there is impairment, the amount of impairment is calculated as the difference between the carrying value and fair value of the asset. To date, no such impairments have been recognized.

Research and Development Costs

Costs incurred in the research and development of the Company’s product candidates are expensed as incurred. The Company defers and capitalizes nonrefundable advance payments made by the Company for research and development activities until the related goods are received or the related services are performed.

Research and development expenses are comprised of costs incurred in performing research and development activities, including salary and benefits, equity-based compensation expense, laboratory supplies and other direct expenses, facilities expenses, overhead expenses, contractual services and other outside expenses.

When third-party service providers’ billing terms do not coincide with the Company’s period-end, the Company is required to make estimates of its obligations to those third parties, including clinical trial costs, contractual services costs and costs for supply of its drug candidates, incurred in a given accounting period and record accruals at the end of the period. The Company bases its estimates on its knowledge of the research and development programs, services performed for the period and the expected duration of the third-party service contract, where applicable.

Revenue recognition

The Company generates revenue through a collaboration and license arrangement with a strategic partner for the development and commercialization of product candidates.

The Company evaluates collaboration agreements with respect to FASB ASC Topic 808, Collaborative Arrangements, considering the nature and contractual terms of the arrangement and the nature of its business operations to determine the classification of the transactions. When the Company is an active participant in the activity and exposed to significant risks and rewards dependent on the commercial success of the collaboration, it will record its transactions on a gross basis in the consolidated financial statements and describe the rights and obligations under the collaborative arrangement in the notes to the consolidated financial statements.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the entity performs the following five-step analysis: (i) identify the contract(s) with a 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 entity satisfies a performance obligation. The Company only applies the five-step analysis to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

The Company may enter into collaboration agreements for research and development services, under which the Company may license certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, upfront license fees; reimbursement of certain costs; customer option exercise fees; development, regulatory and commercial milestone payments; and royalties on net sales of licensed products. Variable consideration is constrained until it is deemed not be at significant risk of reversal.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements for which the collaboration partner is also a customer, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use significant judgment to determine: a) the number of performance obligations based on the determination under step (ii) above; b) the transaction price under step (iii) above; and c) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses significant judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to the goods and services the Company expects to provide. The Company uses estimates to determine the timing of satisfaction of performance obligations, which may include the use of full time equivalent time as a measure of satisfaction of performance obligations.

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion.

Licenses of Intellectual Property

In assessing whether a promise or performance obligation is distinct from the other promises, the Company considers factors such as the research, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the customer can benefit from a promise for its intended purpose without the receipt of the remaining promises, whether the value of the promise is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise, and whether it is separately identifiable from the remaining promise. 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. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Research and Development Services

If an arrangement is determined to contain a promise or obligation for the Company to perform research and development services, the Company must determine whether these services are distinct from the other promises in the arrangement. In assessing whether the services are distinct from the other promises, the Company considers the capabilities of the customer to perform these same services. In addition, the Company considers whether the customer can benefit from a promise for its intended purpose without the receipt of the remaining promise, whether the value of the promise is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise, and whether it is separately identifiable from the remaining promise. For research and development services 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. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Customer Options

If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the goods and services underlying the customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon option exercise. The Company evaluates the customer options for material rights, that is, the option to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on an alternative approach when the goods or services are both (i) similar to the original goods and services in the contract and (ii) provided in accordance with the terms of the original contract. Under this alternative, the Company allocates the total amount of consideration expected to be received from the customer to the total goods or services expected to be provided to the customer. Amounts allocated to a material right are not recognized as revenue until the option is exercised and the performance obligation is satisfied.

Milestone Payments

At the inception of each arrangement that includes milestone payments, the Company evaluates whether a significant reversal of cumulative revenue provided in conjunction with achieving the milestones is probable and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, 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. For other milestones, the Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant reversal of cumulative revenue would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to 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 revenues and earnings in the period of adjustment.

Royalties

For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and 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 licensing arrangements.

Contract Costs

The Company recognizes as an asset the incremental costs of obtaining a contract with a customer if the costs are expected to be recovered. As a practical expedient, the Company recognizes the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that we otherwise would have recognized is one year or less. To date, the Company has not incurred any incremental costs of obtaining a contract with a customer.

Equity‑Based Compensation

The Company measures equity-based compensation to employees, nonemployees and directors based on the grant date fair value of the awards and recognizes the associated expense in the financial statements over the requisite service period of the award, which is generally the vesting period. The fair value of each option was estimated on the date of grant or remeasurement using the Black‑Scholes option‑pricing model. Expected volatility for the Company’s common stock was determined based on an average of the historical volatility of the Company and the historical volatility of a peer‑group of similar public companies. The expected term of options granted for employees was calculated using the simplified method, which represented the average of the contractual term of the option and the weighted-average vesting period of the option. The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future. The risk‑free interest rate is based upon the U.S. Treasury yield curve commensurate with the expected term at the time of grant or remeasurement. Forfeitures are recognized as they occur.

The Company records the expense for equity grants subject to performance-based milestone vesting over the remaining service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the relative satisfaction of the performance conditions as of the reporting date.

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

Income Taxes

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

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

Net Loss Per Share

Basic net loss per share is computed using the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed using the sum of the weighted-average number of shares of common stock outstanding during the period and if dilutive, the weighted-average number of potential shares of common stock, including unvested restricted common stock and outstanding stock options.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company operates in one operating segment: discovery and development of synthetic biology therapeutics for the treatment of rare, infectious and other diseases. The Company’s chief executive officer, as chief operating decision maker, manages and allocates resources to the operations of the Company on a total company basis. All of the Company’s equipment, leasehold improvements and other fixed assets are physically located within the United States, and all agreements with its partners are denominated in U.S. dollars, except where noted.

Recently Adopted Accounting Pronouncements

Leases

In February 2016, the FASB issued ASU 2016-02 – Leases (Topic 842), which replaces the existing accounting guidance for leases. This standard requires entities that lease assets to recognize the assets and liabilities for the rights and obligations created by those leases on the balance sheet. The standard is effective for fiscal years and the interim periods within those fiscal years beginning after December 15, 2018. The guidance is required to be applied by the modified retrospective transition approach and early adoption is permitted. In July 2018, the FASB issued ASU 2018-11 Leases – Targeted Improvements, intended to ease the implementation of the new lease standard for financial statement preparers by, among other things, allowing for an additional transition method. In lieu of presenting transition requirements to comparative periods, as previously required, an entity may now elect to show a cumulative effect adjustment on the date of adoption without the requirement to recast prior period financial statements or disclosures presented in accordance with Topic 842. The Company adopted the new standard using the cumulative effect adjustment transition option effective January 1, 2019, which is the initial date of application per ASU 2018-11.

The Company elected the available package of practical expedients which allows the Company to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of our leases, and the treatment of initial direct costs. The Company made an accounting policy election to keep leases with an initial term of 12 months or less off of the balance sheet.

The Company adopted Topic 842 as of January 1, 2019. The Company uses judgement to assess if an arrangement is a lease at contract inception. An arrangement is a lease if the contract involves the use of a distinct identified asset, the lessor does not have substantive substitution rights and the Company obtains control of the asset throughout the period by obtaining substantially all of the economic benefit of the asset and the right to direct the use of the asset. Leases classified as operating leases are included in operating lease right-of-use (“ROU”) assets, current operating lease liabilities and noncurrent operating lease liabilities in our consolidated balance sheet. Finance leases are included in property and equipment and finance lease obligations, in our consolidated balance sheet.

ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the estimated present value of lease payments over the lease term. The Company utilizes its incremental borrowing rate to determine the present value of lease payments. The incremental borrowing rate is the rate incurred to borrow similar funds, on a collateralized basis, over a comparable term in a similar economic environment.

For new and amended leases beginning in 2019 and after, the Company has elected to account for the lease and non-lease components for leases as a single component for classes of all underlying assets and allocate all of the contract consideration to the lease component only. Lease cost for operating leases is recognized on a straight-line basis over the lease term and is included in operating expenses on the statements of operations and comprehensive loss. Variable lease payments are included in lease operating expenses.

The lease term includes options to extend the lease when it is reasonably certain that option will be exercised. Leases with a term of 12 months or less are not recorded on the Company’s consolidated balance sheet.

The adoption had a material impact on the consolidated balance sheet related to the recognition of a transition adjustment on January 1, 2019 of a right-of-use asset of $15.9 million and lease liability of $24.0 million for an operating lease and the derecognition of deferred rent originally accounted for under legacy guidance. The adoption did not have a material impact on the consolidated statement of operations. Refer to Note 13, “Leases” for further information on the adoption of this standard and the Company’s accounting for leases.

Recently Issued Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13 - Measurement of Credit Losses on Financial Statements. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. In November 2019, the FASB issued ASU 2019-10 – Financial Instruments – Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842): Effective Dates, which amended the effective date for certain companies. The standard is effective for public companies eligible to be smaller reporting companies for annual and interim periods beginning after December 15, 2022. Early adoption is available. The Company is currently evaluating the potential impact ASU 2016-13, and related updates, will have on its consolidated financial statements and disclosures.

In August 2018, the FASB issued ASU 2018-13 - Fair Value Measurement - Disclosure Framework (Topic 820). The standard modifies the disclosure requirements for fair value measurements. The standard is effective for public companies for annual and interim periods beginning after December 15, 2019. Early adoption is permitted for any removed or modified disclosures. Management is currently assessing the impact adoption will have on the Company, but it is not expected to have a material impact on the Company’s financial statement disclosures.

In August 2018, the FASB issued ASU 2018-15 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract. The standard requires implementation costs incurred by customers in cloud computing arrangements to be deferred over the noncancelable term of the cloud computing arrangements plus any optional renewal periods (1) that are reasonably certain to be exercised by the customer or (2) for which exercise of the renewal option is controlled by the cloud service provider. The effective date of this pronouncement is for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, and early adoption is permitted. The standard can be adopted either using the prospective or retrospective transition approach. The Company is currently evaluating the impact of this pronouncement on the Company's consolidated financial statements and disclosures.

In November 2018, the FASB issued ASU 2018-18 - Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606, which, among other things, provides guidance on how to assess whether certain collaborative arrangement transactions should be accounted for under Topic 606. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. The Company is in the process of evaluating the impact the standard will have on its financial statements.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

(3)	Fair Value of Financial Instruments

The tables below present information about the Company’s assets that are measured at fair value on a recurring basis as of December 31, 2019 and 2018 and indicate the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value, as described under Note 2, Summary of Significant Accounting Policies.

The Company’s investment portfolio includes many fixed income securities that do not always trade on a daily basis. As a result, the pricing services used by the Company applied other available information as applicable through processes such as benchmark yields, benchmarking of like securities, sector groupings and matrix pricing to prepare evaluations. In addition, model processes were used to assess interest rate impact and develop prepayment scenarios. These models take into consideration relevant credit information, perceived market movements, sector news and economic events. The inputs into these models may include benchmark yields, reported trades, broker-dealer quotes, issuer spreads and other relevant data.

At December 31, 2019 and 2018, the Company has classified assets measured at fair value on a recurring basis as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	2019		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	3,240	$	3,240	$	—	$	—
Commercial paper (included in cash and cash equivalents)		4,249		—		4,249		—
Commercial paper (included in marketable securities)		20,501		—		20,501		—
Corporate debt securities (included in cash and cash equivalents)		6,005		—		6,005		—
Corporate debt securities (included in marketable securities)		71,383		—		71,383		—
U.S. government agency securities and treasuries		9,005		—		9,005		—
Total	$	114,383	$	3,240	$	111,143	$	—

	Fair Value Measurements at Reporting Date Using
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	2018		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	265	$	265	$	—	$	—
Commercial paper (included in short-term investments)		57,453		—		57,453		—
Corporate debt securities (included in short-term investments)		50,052		—		50,052		—
U.S. government agency securities and treasuries		3,972		1,987		1,985		—
Total	$	111,742	$	2,252	$	109,490	$	—

Cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses at December 31, 2019 and December 31, 2018 are carried at amounts that approximate fair value due to their short-term maturities. Finance lease obligations at December 31, 2019 and December 31, 2018 approximate fair value as they bear interest at a rate approximating a market interest rate.

- 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

Available-for-Sale Investments

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Investments

(4)	Available-for-Sale Investments

The following tables summarize the available-for-sale securities held at December 31, 2019 and 2018 (in thousands):

December 31, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Commercial paper	$	20,484	$	18	$	(1	)	$	20,501
Corporate debt securities		71,288		96		(1	)		71,383
U.S. government agency securities		9,005		2		(2	)		9,005
Total	$	100,777	$	116	$	(4	)	$	100,889

December 31, 2018	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Commercial paper	$	53,549	$	—	$	(47	)	$	53,502
Corporate debt securities		54,022		4		(23	)		54,003
U.S. government agency securities		3,971		1		—			3,972
Total	$	111,542	$	5	$	(70	)	$	111,477

The contractual maturity of all securities held at December 31, 2019 was 14 months or less. There were 9 investments in an unrealized loss position at December 31, 2019, none of which had been in an unrealized loss position for more than twelve months. The aggregate fair value of the securities in an unrealized loss position at December 31, 2019 and 2018 was $24.8 million and $96.5 million, respectively. The Company reviews its investments for other-than-temporary impairment whenever the fair value of an investment is less than amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. To determine whether an impairment is other-than-temporary, the Company considers whether it has the ability and intent to hold the investment until a market price recovery and considers whether evidence indicating the cost of the investment is recoverable outweighs evidence to the contrary. The Company did not hold any securities with an other-than-temporary impairment at December 31, 2019.

Gross realized gains and losses on the sales of investments have not been material to the Company’s consolidated statement of operations.

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2019

Text Block [Abstract]

Prepaid Expenses and Other Current Assets

(5)	Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31,		December 31,
	2019		2018
Prepaid insurance	$	648	$	502
Prepaid research and development		11,989		122
Other prepaid		390		597
Other current assets		648		388
	$	13,675	$	1,609

Property and Equipment, Net

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Property and Equipment, Net

(6)	Property and Equipment, net

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

	December 31,			December 31,
	2019			2018
Laboratory equipment	$	7,523		$	7,111
Computer and office equipment		782			781
Furniture and fixtures		421			413
Leasehold improvements		9,514			9,484
Construction in progress		412			39
		18,652			17,828
Less accumulated depreciation		(5,631	)		(2,987	)
	$	13,021		$	14,841

At December 31, 2019 and 2018, leasehold improvements include $6.6 million of lessor-paid tenant improvements for which the Company was deemed to be the accounting owner of the tenant improvements primarily because it was responsible for project cost overruns. Depreciation expense on property and equipment was $2.7 million and $2.4 million in 2019 and 2018, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2019

Payables And Accruals [Abstract]

Accrued Expenses

(7)	Accrued Expenses

Accrued expenses consists of the following (in thousands):

	December 31,		December 31,
	2019		2018
Payroll related	$	2,372	$	2,906
Professional fees		444		306
Research and development		1,005		1,585
Other		125		196
	$	3,946	$	4,993

Common Stock

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Common Stock

(8)	Common Stock

The Company’s common stock has the following characteristics:

•

The holders of shares of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders.

•

The holders of shares of common stock are entitled to receive dividends, if and when, declared by the Company’s board of directors. Since inception, no cash dividends have been declared.

The Company holds forfeiture rights relating to 586,929 shares of common stock. The forfeiture right lapses over time and is triggered when a holder ceases providing services to the Company. As of December 31, 2019, 147,617 shares of common stock have been forfeited back to the Company.

The Company holds repurchase rights which are at a price equal to the initial purchase price by the founders of Private Synlogic, adjusted by the Merger Exchange Ratio. The repurchase right lapses over time and is exercisable should the founders cease providing services to the Company prior to the end of a four-year period which began in April or May 2014, as the case may be. All repurchase rights terminated during 2018. As of December 31, 2018, the Company had exercised its repurchase right on 41,819 shares of common stock.

In January 2018, the Company sold 5,899,500 shares of its common stock through a firm commitment, underwritten public offering at a price to the public of $9.75 per share. As a result of the offering, including the exercise of the overallotment option, the Company received aggregate net proceeds, after underwriting discounts and commissions and other estimated offering expenses, of approximately $53.8 million.

In April 2018, the Company sold 3,280,000 shares of its common stock at a price of $9.15 per share in a registered direct offering. After fees and other offering expenses, the Company received approximately $28.9 million in net proceeds from the offering.

In June 2019, the Company issued to Ginkgo Bioworks (“Ginkgo”) 6,340,771 shares of common stock and accompanying Pre-Funded warrants (the “Pre-Funded Warrants”) to purchase up to an aggregate of 2,548,117 shares of common stock, at a combined purchase price per share and Pre-Funded Warrant of $9.00. The Pre-Funded Warrants have an exercise price of $9.00 per share, with $8.99 of such exercise price paid at the closing of the offering. The proceeds, net of issuance costs, were approximately $79.9 million, $57.0 million related to the proceeds from sale of the common stock and $22.9 million related to the proceeds from sale of the Pre-Funded warrants. The Pre-Funded Warrants may be exercised at any time until all of the Pre-Funded Warrants are exercised in full to the extent that, after giving effect to such issuance after exercise, Ginkgo would not beneficially own in excess of 19.99% of the number of shares of common stock outstanding immediately after giving effect to the issuance. The Pre-Funded Warrants were classified as a component of permanent equity and were recorded at the issuance date using a relative fair value allocation method. The Pre-Funded Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, and permit the holders to receive a fixed number of common shares upon exercise. In addition, such warrants do not provide any guarantee of value or return. In addition, in connection with the issuance to Ginkgo of common stock and Pre-Funded warrants, the Company expanded its existing collaboration and entered into an agreement with Ginkgo for the research and development of engineered microbial therapeutic products. (See Note 10).

The Company has a sales agreement with Cowen and Company, LLC (“Cowen”) with respect to an at-the-market (“ATM”) offering program under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock through Cowen as its sales agent. In an ATM offering, exchange-listed companies incrementally sell newly issued shares into the secondary trading market through a designated broker-dealer at prevailing market prices. No sales of common stock were made pursuant to the ATM during 2018 and 2019.

Equity-based Compensation and Equity Incentive Plans

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity-based Compensation and Equity Incentive Plans

(9)	Equity‑based Compensation and Equity Incentive Plans

Equity Plans

The Company has a number of equity plans, two of which are currently active.

The 2015 Equity Incentive Award Plan (“2015 Plan”) was adopted by Mirna in 2015 and remains active after the Merger, now functioning as the primary equity plan for the Company. Following the Merger, there were 647,893 shares authorized under the 2015 Plan. The 2015 Plan includes an “evergreen provision” that allows for an annual increase in the number of shares of common stock available for issuance under the 2015 Plan, which annual increase will be added on the first day of each fiscal year from 2016 through 2025, inclusive, and will be equal to the lesser of (i) five percent of the shares outstanding on the last day of the immediately preceding fiscal year and (ii) such smaller number of shares as determined by the Board of Directors. The 2015 Plan provides for the granting of a variety of stock‑based compensation awards, including stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, deferred stock awards, dividend equivalent awards, stock payment awards, performance awards and other stock‑based awards.

The 2017 Stock Incentive Plan was adopted by Private Synlogic in 2017 at the time of the 2017 Reorganization and provides for the grant of incentive stock options, non-qualified stock options, restricted and unrestricted stock awards and other stock-based awards. Under the 2017 Plan, 1,753,061 shares were initially authorized and reserved for issuance. Pursuant to the 2017 Reorganization, Private Synlogic issued restricted common stock awards under the 2017 Plan to replace the canceled incentive units pursuant to the termination of the 2015 LLC Plan (“2015 LLC Plan”). In addition, Private Synlogic also issued stock options to certain employees prior to the Merger. Pursuant to the Merger Agreement, each restricted common stock award of Private Synlogic under the 2017 Plan that was outstanding immediately prior to the Merger and each option to purchase common stock of Private Synlogic under the 2017 Plan that was outstanding and unexercised immediately prior to the Merger was converted into and became restricted common stock and options to purchase shares of the Company’s common stock, respectively, based on the Exchange Ratio of 0.5532 and the Company assumed the 2017 Plan.

The 2015 Employee Stock Purchase Plan (“ESPP”) was adopted by Mirna in 2015 and allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP generally provides for set offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. The Company suspended the ESPP in 2017. On December 19, 2019, the board of directors (the “Board”) of the Company resolved by written consent to reactivate the 2015 ESPP and approved an amendment to the ESPP to (i) reduce the permitted payroll deduction and number of shares of the Company’s common stock that a participant may purchase per calendar year and offering period under the ESPP and (ii) establish a period for enrollment for eligible participants. The reactivation of the 2015 ESPP was effective immediately. The Company’s executive officers are eligible to participate in the 2015 ESPP.

As of December 31, 2019, there were 676,388 shares available for future grant under the Company’s two active equity incentive plans, the 2017 Plan and the 2015 Plan.

Stock Options

The weighted average assumptions used in the Black-Scholes option-pricing model for stock options issued to employees and non-employees under its two active equity plans, the 2015 Plan and the 2017 Plan, during the years ended December 31, 2019 and 2018 were:

	Year ended December 31,
Employees:	2019			2018
Expected term	6.2 years			6.2 years
Weighted-average, risk-free interest rate		2.2	%		2.8	%
Expected volatility		71.1	%		70.8	%
Dividend yield		—			—

The following table summarizes stock option activity, as adjusted for the Exchange Ratio under the 2015 and 2017 Plans.

	Stock options outstanding
						Weighted
						average
				Weighted		remaining		Aggregate
				average		contractual		intrinsic
	Number of			exercise		term		value^(a)
	options			price		(in years)		(in thousands)
Outstanding at December 31, 2018		1,739,884		$	11.92		9.0	$	—
Granted		1,427,030			7.07				—
Cancelled or Forfeited		(880,495	)		11.02				25
Outstanding at December 31, 2019		2,286,419			9.24		8.7	$	43

Vested or expected to vest at December 31, 2019		2,286,419			9.24		8.7	$	43
Exercisable at December 31, 2019		845,102			11.43		8.1	$	—

^(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the options and the fair market value of the underlying common stock for the options that were in the money at December 31, 2019. 132,500 options were in the money at December 31, 2019.

The weighted average grant date fair value per share of options granted during the years ended December 31, 2019 and 2018 was approximately $4.59 and $6.35, respectively. The total fair value of awards that vested during the years ended December 31, 2019 and 2018 was $3.9 million and $3.3 million, respectively.

As of December 31, 2019, there was approximately $6.8 million of unrecognized share-based compensation for unvested stock option grants which is expected to be recognized over a weighted average period of 2.4 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur.

Restricted Common Stock

During the year ended December 31, 2019, 585,600 shares of restricted common stock were granted. During the year ended December 31, 2018, no shares of restricted common stock were granted.

The following table shows restricted common stock activity:

	Restricted stock awards
				Weighted average grant date
	Number of			fair value
	shares			(per share)
Unvested at December 31, 2018		118,679		$	13.54
Granted		585,600			2.49
Vested		(56,314	)		13.55
Forfeited		(61,036	)		9.19
Unvested at December 31, 2019		586,929		$	2.97

The total fair value of shares that vested during the years ended December 31, 2019 and 2018 was $0.1 million and $1.3 million, respectively.

As of December 31, 2019, there was approximately $1.2 million of unrecognized share-based compensation related to restricted stock awards granted, which is expected to be recognized over a weighted average period of 1.2 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur.

Equity Compensation

The Company has recorded total equity‑based compensation expense of approximately $4.1 million and $4.3 million, during the years ended December 31, 2019 and 2018, respectively. Equity compensation during the years ended December 31, 2019 and 2018 is derived from stock options and restricted stock awards. Equity-based compensation during the year ended December 31, 2018 also includes $0.7 million related to modifications in equity awards in connection with the separation of the Company’s former Chief Executive Officer.

The following table summarizes equity‑based compensation expense within the Company’s consolidated statements of operations and comprehensive loss for the years ended December 31, 2019 and 2018 (in thousands):

	Years ended December 31,
	2019		2018
Research and development	$	1,377	$	1,333
General and administrative		2,757		2,984
	$	4,134	$	4,317

The following table summarizes equity‑based compensation expense by type of award for the years ended December 31, 2019 and 2018 (in thousands):

	Years ended December 31,
	2019		2018
Stock options	$	3,789	$	3,361
Restricted stock awards		345		956
	$	4,134	$	4,317

Collaboration Agreements

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration Agreements

(10)	Collaboration Agreements

Ginkgo Collaboration

In 2017, the Company established a technology collaboration with Ginkgo. In June 2019, in connection with the issuance to Ginkgo of an aggregate of 6,340,771 shares of common stock and Pre-Funded warrants to purchase an aggregate of 2,548,117 common stock (See Note 9), the Company expanded its collaboration and entered into an agreement with Ginkgo for the research and development of engineered microbial therapeutic products. Under the 2019 expanded agreement, the Company made a prepayment to Ginkgo of $30.0 million for its foundry services that will be provided to the Company over an initial term of five years. The prepayment of foundry services is recorded in Prepaid expenses and other current assets and Prepaid research and development, net of current portion on the December 31, 2019 consolidated balance sheet. Upon the expiration of such initial term and, if applicable, an additional period, any portion of the prepayment that has not been used to purchase services from Ginkgo will be retained by Ginkgo.

AbbVie Collaboration Agreement

In July 2015, the Company entered into the AbbVie Agreement under which the Company granted AbbVie an exclusive option to purchase IBDCo and, in exchange, agreed to collaborate in researching and developing an Investigational New Drug (“IND”) candidate for the treatment of IBD. The AbbVie Agreement sets forth the Company’s and AbbVie’s respective obligations for development and delivery of an IND candidate package using reasonable commercial efforts.

In exchange for the exclusive option to acquire IBDCo, initial research and development services for drug discovery and pre-clinical development, and participation on the joint research committee (“JRC”), AbbVie agreed to pay IBDCo an upfront, nonrefundable cash payment of $2.0 million, which IBDCo received in December 2015. AbbVie also agreed to pay IBDCo up to $16.5 million in milestone payments associated with specified research and pre-clinical events, which were determined to represent customer options for accounting purposes, as well as an option exercise fee upon the execution of their option to buy IBDCo and other royalty and milestone payments. The upfront cash payment and any payments for option fees and royalties are non-refundable, non-creditable and not subject to set-off.

The research and development will be performed by the Company over four phases of research defined in the research plan. The Company is eligible to receive payments from AbbVie upon the election to continue the research and development at the achievement of certain milestone events. The JRC will make a determination as to the continuation of the collaboration at the achievement of research and pre-clinical milestones, except for the final milestone, which AbbVie has the discretion to determine achievement without the approval of the JRC. If the parties make the determination to continue on with the AbbVie Agreement upon achievement of each milestone event, then AbbVie will pay the consideration associated with that milestone and the collaboration will continue through the remaining term of the option to purchase IBDCo, which was initially considered to be approximately 54 months. However, AbbVie has the right to terminate the contract at any time with 90 days’ notice.

The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, AbbVie, is a customer. The Company identified the following material promises at the outset of the arrangement: (1) a non-exclusive royalty-free research and development license; (2) research and development services for pre-clinical activities under the research plan through to the first research and development phase (or an estimated 17 months); (3) three option rights for AbbVie to continue the collaboration as related to three phases of research and development; (4) participation on the JRC; and (5) the transfer of ownership of IBDCo upon exercise of the option to buy IBDCo. The Company determined that the license and research and development activities were not distinct from one another. Participation on the JRC to oversee the research and development activities was determined to be quantitatively and qualitatively immaterial and therefore is excluded from performance obligations. As such, the Company determined that the license and research and development services should be combined into a single performance obligation.

The Company evaluated the milestone payments, which represent customer options as described above, and the option to purchase IBDCo, to determine whether they provide AbbVie with any material rights. The Company concluded that the options were not issued at a significant and incremental discount, and therefore do not provide material rights. As such, they were excluded as performance obligations at the outset of the arrangement. If AbbVie elects to exercise the options, the additional consideration will be added to the transaction price and allocated to the resulting performance obligations.

Based on these assessments, the Company identified one performance obligation at the outset of the AbbVie Agreement, which consists of: (1) the non-exclusive license and (2) the research and development activities through the first research and development phase.

At the outset of the arrangement, the transaction price included only the $2.0 million up-front consideration received which was allocated to the single performance obligation. The option exercise fees ($16.5 million for the milestones and the IBDCo purchase option exercise fee) that may be received are excluded from the transaction price until each customer option is exercised. The Company reevaluates the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust its estimate of the transaction price.

In May 2017, the Company completed the research and development services for the first phase of the research plan and was paid $2.0 million to commence the second phase of the research plan. At this time, the $2.0 million was added to the transaction price and allocated to a new performance obligation consisting of the underlying license and research and development services to be performed over the second phase of the research plan.

On September 27, 2018, AbbVie and the Company signed an amendment (the “Second Amendment”) to the AbbVie Agreement. The Amendment clarified the requirements necessary to complete the second phase which resulted in additional time and effort in the second phase of the research plan. Additionally, the Amendment split the next milestone payment under the AbbVie Agreement into two payments: a milestone payment of $2.0 million earned by the Company upon execution of the Amendment and the remaining milestone payment of the balance due upon the successful achievement of specified research and pre-clinical events and the advancement to the third phase of the research plan.

On December 18, 2018, AbbVie and the Company signed an amendment (the “Third Amendment”) to the AbbVie Agreement. The Third Amendment provides that in the event AbbVie determines that it is necessary to enter into license agreements with certain third parties in a particular country or other jurisdiction which, but for such license, would be infringed by the manufacture, use or sale of any product governed by the AbbVie Agreement, AbbVie would be entitled to deduct certain expenses related to such license agreements from particular payments made to the Company.

The Company determined that the Amendment represented a modification to the AbbVie Agreement. The additional research and development services are not distinct from the remaining research and development services under the second phase of the research plan of the AbbVie Agreement. The Amendment was accounted for as part of the original AbbVie Agreement and the services form part of the single performance obligation that was partially satisfied as of the date of the contract modification. As a result, the transaction price for the current performance obligation associated with the second phase of the research plan increased by $2.0 million. The impact of the contract modification on the transaction price and the measure of progress toward completion of the performance obligation was recognized as an adjustment to revenue upon execution of the Amendment on a cumulative catch-up basis. The cumulative catch-up adjustment to revenue, as a result of the contract modification, was $1.8 million during 2018.

Revenue associated with performance obligations under the AbbVie Agreement are recognized as the research and development services are provided using an input method, according to the full-time equivalents incurred. The research and development activities are expected to be performed over a period of approximately 54 months. The transfer of control occurs over time and, in management’s judgment, is the best measure of progress towards satisfying the performance obligation. The amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet.

On February 28, 2019, the JRC concluded that the remaining milestone of $2.5 million under the Second Amendment was achieved upon the achievement of specified research and pre-clinical events under the second phase of the research plan and the advancement to the third phase of the research plan. Revenue associated with performance obligations under the AbbVie Agreement is recognized as the research and development services are provided using an input method, according to the full-time equivalents incurred. The transfer of control occurs over time and, in management’s judgment, is the best measure of progress towards satisfying the performance obligation. The amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet.

For the years ended December 31, 2019 and 2018, the Company recognized $ 2.2 million and $2.5 million, respectively, as collaboration revenue in the Company’s consolidated statements of operations and comprehensive loss. Deferred revenue amounted to $0.5 million as of December 31, 2019, all of which is included in current liabilities.

Net Loss per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net Loss per Share

(11)	Net Loss per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except for share and per share amounts):

	2019			2018
Numerator:
Net loss	$	(51,373	)	$	(48,435	)
Denominator:
Weighted-average common shares outstanding - basic and diluted		30,284,068			23,882,685
Net loss per share - basic and diluted	$	(1.70	)	$	(2.03	)

The Company’s potentially dilutive shares, which include outstanding stock options and unvested restricted common stock, are considered to be common share equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of the diluted net loss per share attributable to common stockholders for the period indicated because including them would have had an anti-dilutive effect.

	As of December 31,
	2019		2018
Unvested restricted common stock awards		586,929		118,679
Outstanding options to purchase common stock		2,286,419		1,739,884

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

(12)	Income Taxes

During the years ended December 31, 2019 and 2018, the Company recorded no income tax benefits for the net operating losses incurred due to its uncertainty of reclaiming a benefit for those losses.

Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. Deferred tax assets consist of the following (in thousands):

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	46,362		$	33,275
Tax credit carryforwards		4,262			4,365
Accrued expenses		37			103
Deferred rent		—			2,209
Lease liabilities		6,776			—
Equity compensation		1,481			784
Amortizable intangibles		1,214			1,339
Other		138			78
Gross deferred tax assets		60,270			42,153
Deferred tax liabilities:
Property and equipment		(1,720	)		(1,863	)
Right of use assets		(4,716	)		—
Gross deferred tax liabilities		(6,436	)		(1,863	)
Valuation allowance		(53,834	)		(40,290	)
Net deferred tax assets	$	—		$	—

Management of the Company has evaluated the positive and negative evidence bearing upon the realizability of the Company’s deferred tax assets, which are comprised principally of net operating loss carryforwards, and determined that it is more likely than not that the Company will not recognize the benefits of the deferred tax assets. As a result, a full valuation allowance of approximately $53.8 million and $40.3 million was established at December 31, 2019 and 2018, respectively.

A reconciliation of the statutory federal income tax rate to the Company’s effective income tax rate is as follows (dollars in thousands):

	Years ended December 31,
	2019			2018
	Tax Rate			Tax Rate
U.S. federal statutory rate		21	%		21	%
State income taxes, net of federal benefit		6	%		6	%
Other permanent differences		(1	)%		(1	)%
Tax credits		0	%		3	%
Other items		0	%		(1	)%
Net change in valuation allowance		(26	)%		(28	)%
Effective income tax rate		—			—

A roll-forward of the valuation allowance for the years ended December 31, 2019 and 2018 is as follows (in thousands):

	Years ended December 31,
	2019			2018
Balance at beginning of year	$	(40,290	)	$	(26,515	)
Increase in valuation allowance		(13,544	)		(13,775	)
Balance at end of year	$	(53,834	)	$	(40,290	)

As of December 31, 2019 and 2018, the Company had federal net operating loss carryforwards that may be available to reduce future taxable income of approximately $172.9 million and $125.5 million, respectively. Of the $172.9 million of federal net operating loss carryforwards, $79.4 million begin to expire in 2034. The remaining $93.5 of federal net operating loss carryforwards do not expire. The Company also had state net operating loss carryforwards that may be available to reduce future taxable income of approximately $159.0 million and $109.4 million, for the periods ended December 31, 2019 and 2018, respectively. The state net operating loss carryforwards begin to expire in 2029. In addition, at December 31, 2019, the Company had federal and state research and development tax credit carryforwards available to reduce future tax liabilities of approximately $2.5 million and $1.8 million, respectively.

Pursuant to Section 382 of the Internal Revenue Code of 1986 (“IRC”), certain substantial changes in the Company’s ownership may result in a limitation on the amount of net operating loss (“NOL”) carryforwards and research and development credit (“R&D credit”) carryforwards that may be used in future years. Utilization of the NOL and R&D credit carryforwards may be subject to a substantial annual limitation under Section 382 of the IRC due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL and R&D credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company has not completed a study to assess whether an ownership change has occurred, or whether there have been multiple ownership changes since its formation, due to a significant complexity and related costs associated with such a study. There could be additional ownership changes in the future that may result in additional limitations on the utilization of NOL carryforwards and credits.

The Company is required to determine whether a tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals of litigation processes, based on the technical merits of the position. For tax positions meeting the more likely than not threshold, the tax amount recognized in the financial statements is reduced by the largest benefit that has a greater than fifty percent likelihood of being realized upon the ultimate settlement with the relevant taxing authority. The Company has not recognized any liability for unrecognized tax benefits as of December 31, 2019.

The Company files tax returns, on an entity-level basis, as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. Tax years from 2016 to the present are open to examination under the statute. The Company’s policy is to record interest and penalties related to income taxes as part of the tax provision. There are no interest or penalties accrued at December 31, 2019 and 2018.

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

(13)

Leases

Operating Leases

In July 2017, the Company entered into an agreement to lease approximately 41,346 square feet of laboratory and office space at 301 Binney Street in Cambridge, Massachusetts. Annual rent is approximately $3.1 million. The ten-year lease commenced in January 2018 and contains provisions for a free-rent period, annual rent increases and an allowance for tenant improvements. The Company is responsible for real estate taxes, maintenance, and other operating expenses applicable to the leased premises. The Company has paid for tenant improvements of approximately $2.9 million. Additionally, the Company has capitalized approximately $6.6 million of landlord-funded tenant improvements. The Company was deemed to be the accounting owner of the tenant improvements primarily because it was responsible for project cost overruns, and as such, the amounts were recorded as a leasehold improvement. The landlord-funded tenant improvement allowance is being amortized as a reduction to lease expense ratably over the lease term. In conjunction with the lease, the Company established a letter of credit of approximately $1.0 million secured by cash balances included in restricted cash. Variable payments based on our portion of the operating expenses, including real estate taxes and insurance, are recorded as a period expense when incurred. The Company has an option to extend the term by five years and an option to terminate the agreement if a similar agreement is executed with the landlord or an affiliate of the landlord. Neither option is reasonably certain of exercise and both are excluded from the lease liability calculation.

On December 7, 2018, Synlogic Operating Company, Inc., a wholly-owned subsidiary of Synlogic, Inc., entered into a Statement of Work (the “SOW”) with Azzur Group, LLC (“Azzur”) pursuant to a Master Contract Services Agreement (the “Master Services Agreement”), dated September 8, 2018, between the Company and Azzur.

Pursuant to the SOW, Azzur has agreed to provide the Company with access to, and the use of, an approximately 700 square foot cleanroom space to be constructed in Waltham, Massachusetts (the “Azzur Suite”), for a period of 44 months, from May 1, 2019 to December 31, 2022 (the “Term”). Azzur has also agreed to provide the Company with storage space and personnel support at the Azzur Suite. The total estimated project cost during the Term for access to, and use of, the cleanroom and storage space, and the personnel support and other services, is up to $4.8 million.

The Company may terminate the SOW on four months’ prior written notice at any time during the Term. In addition, either party may terminate the Master Services Agreement (including the SOW) due to a breach by the other party and failure to cure. The Company is reasonably certain not to exercise the termination option through December 31, 2022. Therefore, the Company used a term of May 1, 2019 through December 31, 2022 for purposes of the calculation of the ROU asset and lease liability.

The Company adopted Topic 842 as of January 1, 2019. Leases classified as operating leases are included in operating lease ROU assets, current operating lease liabilities and noncurrent operating lease liabilities in our December 31, 2019 consolidated balance sheet. The operating lease right-of-use asset and operating lease liability represents the Binney Street lease and the Azzur Suite lease. Finance leases are made up of laboratory and office equipment. Cash paid for amounts included in the present value of operating lease liabilities was $3.7 million during the year ended December 31, 2019 which is included in operating cash flows.

The components of lease cost for operating and finance leases for the year ended December 31, 2019 were:


Operating leases	$ (in thousands)
Operating lease cost	$	3,344
Short-term lease cost		330
Variable lease cost		1,092
		4,766
Finance leases
Depreciation on finance leases		188
Interest on finance leases		21
		209
Total lease cost	$	4,975

The right-of-use asset for the operating lease is disclosed on the consolidated balance sheet. The right-of-use asset for finance leases are classified within property and equipment, net, the total right-of-use asset for finance leases is $0.9 million.

The weighted average remaining lease term and the weighted average discount rate for operating and finance leases at December 31, 2019 was:

	Operating Lease			Finance Leases
Weighted average discount rate		8.0	%		6.1	%
Weighted average remaining lease term (years)		8.2			0.8

The following table reconciles the undiscounted cash flows for the operating and finance leases at December 31, 2019 to the operating and finance lease liabilities recorded on the balance sheet: December 31, 2019

Maturity of lease liabilities	Operating Leases		Finance Leases
	(in thousands)
2020	$	3,892	$	214
2021		4,236		2
2022		4,389		—
2023		3,574		—
2024		3,681		—
Thereafter		14,386		—
Total lease payments		34,158		216
Less: imputed interest		9,354		6
Total lease liabilities	$	24,804	$	210
Current lease liabilities		2,000		208
Long-term lease liabilities		22,804		2

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

(14)	Commitments and Contingencies

In the ordinary course of business, the Company may be subject to legal proceedings, claims and litigation as the Company operates in an industry susceptible to patent legal claims. The Company accounts for estimated losses with respect to legal proceedings and claims when such losses are probable and estimable. Legal costs associated with these matters are expensed when incurred. The Company is not currently a party to any material legal proceedings.

Employee Benefits

12 Months Ended

Dec. 31, 2019

Compensation And Retirement Disclosure [Abstract]

Employee Benefits

(15)	Employee Benefits

The Company has a defined contribution 401(k) plan for eligible employees. Employees are eligible to participate in the plan beginning on their date of hire. Under the terms of the plan, employees may make voluntary contributions as a percentage of compensation. The Company started to match employee contributions effective January 1, 2019. The Company matched 50% of the employee contributions to the 401(k) plan up to a maximum of 4% of the participating employee’s eligible earnings, resulting in a maximum company match of 2% of the participating employee’s eligible earnings, and subject to certain additional statutory dollar limitations.

Related-Party Transactions

12 Months Ended

Dec. 31, 2019

Related-Party Transactions

(16)	Related-Party Transactions

In June 2019, the Company expanded its collaboration and entered into an agreement with Ginkgo for the research and development of engineered microbial therapeutic products. See Note 10, Gingko Collaboration.

Under the agreement the Company made a prepayment to Ginkgo of $30.0 million for its foundry services that will be provided to the Company over an initial term of five years. At December 31, 2019, the Company had remaining balances of $11.5 million and $15.7 million of current and non-current pre-paid research and development costs related to this transaction, respectively. For the year ended December 31, 2019, the Company used $2.8 million of the pre-paid research and development expenses.

Selected Quarterly Data (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Data (Unaudited)

(17)	Selected Quarterly Data (Unaudited)

The following tables contain quarterly financial information for 2019 and 2018 (in thousands). The Company believes that the following information reflects all normal recurring adjustments necessary for a fair presentation of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period.

	2019 Quarter Ended
	March 31			June 30			September 30			December 31
Revenue	$	338		$	350		$	305		$	1,231
Operating expenses		14,035			13,445			14,443			14,710
Loss from operations		(13,697	)		(13,095	)		(14,138	)		(13,479	)
Net loss		(12,946	)		(12,344	)		(13,285	)		(12,798	)
Net loss per share - basic and diluted	$	(0.51	)	$	(0.45	)	$	(0.39	)	$	(0.37	)

	2018 Quarter Ended
	March 31			June 30			September 30			December 31
Revenue	$	354		$	254		$	1,801		$	111
Operating expenses		11,990			15,606			13,335			12,819
Loss from operations		(11,636	)		(15,352	)		(11,534	)		(12,708	)
Net loss		(11,165	)		(14,591	)		(10,748	)		(11,931	)
Net loss per share - basic and diluted	$	(0.55	)	$	(0.59	)	$	(0.43	)	$	(0.47	)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S.”) (“U.S. GAAP” or “GAAP”).

Principles of Consolidation

Use of Estimates

Cash Equivalents

Concentration of Credit Risk

Restricted Cash

	December 31,		December 31,
	2019		2018
Cash and cash equivalents	$	26,184	$	11,252
Restricted cash included in other long-term assets		1,097		1,097
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$	27,281	$	12,349

Fair Value

•

Level 1 – Utilize observable inputs such as quoted prices in active markets for identical assets or liabilities;

•

Level 2 – Utilize data points that are either directly or indirectly observable, such as quoted prices, interest rates and yield curves;

•

Level 3 – Utilize unobservable data points in which there is little or no market data, which require the Company to develop its own assumptions for the asset or liability.

Available-for-Sale Securities

Property and Equipment

Depreciation begins at the time the asset is placed in service. Depreciation is provided over the following estimated useful lives:

Asset classification		Useful life
Computer and office equipment		3 years
Furniture and fixtures		5 years
Laboratory equipment		5 years
Leasehold improvements		Lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

Impairment of Long‑Lived Assets

Research and Development Costs

Revenue recognition

The Company generates revenue through a collaboration and license arrangement with a strategic partner for the development and commercialization of product candidates.

Licenses of Intellectual Property

Research and Development Services

Customer Options

Milestone Payments

Royalties

Contract Costs

Equity-Based Compensation

Equity‑Based Compensation

Income Taxes

Net Loss Per Share

Segment Information

Recently Adopted Accounting Pronouncements

Leases

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash

	December 31,		December 31,
	2019		2018
Cash and cash equivalents	$	26,184	$	11,252
Restricted cash included in other long-term assets		1,097		1,097
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$	27,281	$	12,349

Schedule of Useful Life of Property and Equipment

Depreciation begins at the time the asset is placed in service. Depreciation is provided over the following estimated useful lives:

Asset classification		Useful life
Computer and office equipment		3 years
Furniture and fixtures		5 years
Laboratory equipment		5 years
Leasehold improvements		Lesser of useful life or remaining lease term

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Company's Classified Assets Measured at Fair Value on Recurring Basis

At December 31, 2019 and 2018, the Company has classified assets measured at fair value on a recurring basis as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	2019		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	3,240	$	3,240	$	—	$	—
Commercial paper (included in cash and cash equivalents)		4,249		—		4,249		—
Commercial paper (included in marketable securities)		20,501		—		20,501		—
Corporate debt securities (included in cash and cash equivalents)		6,005		—		6,005		—
Corporate debt securities (included in marketable securities)		71,383		—		71,383		—
U.S. government agency securities and treasuries		9,005		—		9,005		—
Total	$	114,383	$	3,240	$	111,143	$	—

	Fair Value Measurements at Reporting Date Using
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
Description	2018		(Level 1)		(Level 2)		(Level 3)
Money market funds	$	265	$	265	$	—	$	—
Commercial paper (included in short-term investments)		57,453		—		57,453		—
Corporate debt securities (included in short-term investments)		50,052		—		50,052		—
U.S. government agency securities and treasuries		3,972		1,987		1,985		—
Total	$	111,742	$	2,252	$	109,490	$	—

Available-for-Sale Investments (Tables)

12 Months Ended

Dec. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Available-for-Sale Securities Held

The following tables summarize the available-for-sale securities held at December 31, 2019 and 2018 (in thousands):

December 31, 2019	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Commercial paper	$	20,484	$	18	$	(1	)	$	20,501
Corporate debt securities		71,288		96		(1	)		71,383
U.S. government agency securities		9,005		2		(2	)		9,005
Total	$	100,777	$	116	$	(4	)	$	100,889

December 31, 2018	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Commercial paper	$	53,549	$	—	$	(47	)	$	53,502
Corporate debt securities		54,022		4		(23	)		54,003
U.S. government agency securities		3,971		1		—			3,972
Total	$	111,542	$	5	$	(70	)	$	111,477

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2019

Text Block [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	December 31,		December 31,
	2019		2018
Prepaid insurance	$	648	$	502
Prepaid research and development		11,989		122
Other prepaid		390		597
Other current assets		648		388
	$	13,675	$	1,609

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

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

	December 31,			December 31,
	2019			2018
Laboratory equipment	$	7,523		$	7,111
Computer and office equipment		782			781
Furniture and fixtures		421			413
Leasehold improvements		9,514			9,484
Construction in progress		412			39
		18,652			17,828
Less accumulated depreciation		(5,631	)		(2,987	)
	$	13,021		$	14,841

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2019

Payables And Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consists of the following (in thousands):

	December 31,		December 31,
	2019		2018
Payroll related	$	2,372	$	2,906
Professional fees		444		306
Research and development		1,005		1,585
Other		125		196
	$	3,946	$	4,993

Equity-based Compensation and Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of Restricted Common Stock Activity

The following table shows restricted common stock activity:

	Restricted stock awards
				Weighted average grant date
	Number of			fair value
	shares			(per share)
Unvested at December 31, 2018		118,679		$	13.54
Granted		585,600			2.49
Vested		(56,314	)		13.55
Forfeited		(61,036	)		9.19
Unvested at December 31, 2019		586,929		$	2.97

Schedule of Equity-based Compensation Expenses

	Years ended December 31,
	2019		2018
Research and development	$	1,377	$	1,333
General and administrative		2,757		2,984
	$	4,134	$	4,317

Schedule of Equity-based Compensation Expenses by Award Type

The following table summarizes equity‑based compensation expense by type of award for the years ended December 31, 2019 and 2018 (in thousands):

	Years ended December 31,
	2019		2018
Stock options	$	3,789	$	3,361
Restricted stock awards		345		956
	$	4,134	$	4,317

2015 and 2017 Plan

Schedule of Weighted Average Assumption Used Black-Scholes Option-pricing Model for Stock Options Issued to Employees and Non-employees

	Year ended December 31,
Employees:	2019			2018
Expected term	6.2 years			6.2 years
Weighted-average, risk-free interest rate		2.2	%		2.8	%
Expected volatility		71.1	%		70.8	%
Dividend yield		—			—

Schedule of Stock Option Activity

The following table summarizes stock option activity, as adjusted for the Exchange Ratio under the 2015 and 2017 Plans.

	Stock options outstanding
						Weighted
						average
				Weighted		remaining		Aggregate
				average		contractual		intrinsic
	Number of			exercise		term		value^(a)
	options			price		(in years)		(in thousands)
Outstanding at December 31, 2018		1,739,884		$	11.92		9.0	$	—
Granted		1,427,030			7.07				—
Cancelled or Forfeited		(880,495	)		11.02				25
Outstanding at December 31, 2019		2,286,419			9.24		8.7	$	43

Vested or expected to vest at December 31, 2019		2,286,419			9.24		8.7	$	43
Exercisable at December 31, 2019		845,102			11.43		8.1	$	—

^(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the options and the fair market value of the underlying common stock for the options that were in the money at December 31, 2019. 132,500 options were in the money at December 31, 2019.

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except for share and per share amounts):

	2019			2018
Numerator:
Net loss	$	(51,373	)	$	(48,435	)
Denominator:
Weighted-average common shares outstanding - basic and diluted		30,284,068			23,882,685
Net loss per share - basic and diluted	$	(1.70	)	$	(2.03	)

Schedule of Potentially Common Shares Excluded from Calculation of Net Loss Per share

	As of December 31,
	2019		2018
Unvested restricted common stock awards		586,929		118,679
Outstanding options to purchase common stock		2,286,419		1,739,884

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Temporary Differences Between Basis of Deferred Tax Assets and Liabilities

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	46,362		$	33,275
Tax credit carryforwards		4,262			4,365
Accrued expenses		37			103
Deferred rent		—			2,209
Lease liabilities		6,776			—
Equity compensation		1,481			784
Amortizable intangibles		1,214			1,339
Other		138			78
Gross deferred tax assets		60,270			42,153
Deferred tax liabilities:
Property and equipment		(1,720	)		(1,863	)
Right of use assets		(4,716	)		—
Gross deferred tax liabilities		(6,436	)		(1,863	)
Valuation allowance		(53,834	)		(40,290	)
Net deferred tax assets	$	—		$	—

Reconciliation of Statutory Federal Income Tax Rate to Company's Effective Income Tax Rate

A reconciliation of the statutory federal income tax rate to the Company’s effective income tax rate is as follows (dollars in thousands):

	Years ended December 31,
	2019			2018
	Tax Rate			Tax Rate
U.S. federal statutory rate		21	%		21	%
State income taxes, net of federal benefit		6	%		6	%
Other permanent differences		(1	)%		(1	)%
Tax credits		0	%		3	%
Other items		0	%		(1	)%
Net change in valuation allowance		(26	)%		(28	)%
Effective income tax rate		—			—

Schedule of Valuation Allowance

A roll-forward of the valuation allowance for the years ended December 31, 2019 and 2018 is as follows (in thousands):

	Years ended December 31,
	2019			2018
Balance at beginning of year	$	(40,290	)	$	(26,515	)
Increase in valuation allowance		(13,544	)		(13,775	)
Balance at end of year	$	(53,834	)	$	(40,290	)

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Components of Lease Cost for Operating and Finance Leases

The components of lease cost for operating and finance leases for the year ended December 31, 2019 were:


Operating leases	$ (in thousands)
Operating lease cost	$	3,344
Short-term lease cost		330
Variable lease cost		1,092
		4,766
Finance leases
Depreciation on finance leases		188
Interest on finance leases		21
		209
Total lease cost	$	4,975

Summary of Weighted Average Remaining Lease Term and Weighted Average Discount Rate for Operating and Finance Leases

The weighted average remaining lease term and the weighted average discount rate for operating and finance leases at December 31, 2019 was:

	Operating Lease			Finance Leases
Weighted average discount rate		8.0	%		6.1	%
Weighted average remaining lease term (years)		8.2			0.8

Summary of Maturity of Lease Liabilities for Operating and Finance Leases

Maturity of lease liabilities	Operating Leases		Finance Leases
	(in thousands)
2020	$	3,892	$	214
2021		4,236		2
2022		4,389		—
2023		3,574		—
2024		3,681		—
Thereafter		14,386		—
Total lease payments		34,158		216
Less: imputed interest		9,354		6
Total lease liabilities	$	24,804	$	210
Current lease liabilities		2,000		208
Long-term lease liabilities		22,804		2

Selected Quarterly Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Data (unaudited)

	2019 Quarter Ended
	March 31			June 30			September 30			December 31
Revenue	$	338		$	350		$	305		$	1,231
Operating expenses		14,035			13,445			14,443			14,710
Loss from operations		(13,697	)		(13,095	)		(14,138	)		(13,479	)
Net loss		(12,946	)		(12,344	)		(13,285	)		(12,798	)
Net loss per share - basic and diluted	$	(0.51	)	$	(0.45	)	$	(0.39	)	$	(0.37	)

	2018 Quarter Ended
	March 31			June 30			September 30			December 31
Revenue	$	354		$	254		$	1,801		$	111
Operating expenses		11,990			15,606			13,335			12,819
Loss from operations		(11,636	)		(15,352	)		(11,534	)		(12,708	)
Net loss		(11,165	)		(14,591	)		(10,748	)		(11,931	)
Net loss per share - basic and diluted	$	(0.55	)	$	(0.59	)	$	(0.43	)	$	(0.47	)

Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash, cash equivalents, and short-term marketable securities	$ 119,600
Long-term marketable securities	7,500
Restricted cash	1,097	$ 1,097
Accumulated deficit	$ (171,138)	$ (119,765)

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents maturity		three months or less
Cash equivalents		$ 13,500,000	$ 300,000
Cash held in a separate restricted bank account		1,097,000	1,097,000
Transfers of assets and liabilities between Level 1, Level 2, or Level 3		0	0
Impairment charge		$ 0
Revenue, practical expedient, incremental cost of obtaining contract [true/false]		true
Revenue, practical expedient, remaining performance obligation, description		The Company recognizes as an asset the incremental costs of obtaining a contract with a customer if the costs are expected to be recovered. As a practical expedient, the Company recognizes the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that we otherwise would have recognized is one year or less. To date, the Company has not incurred any incremental costs of obtaining a contract with a customer
Description of tax benefit likely to be realized upon settlement		greater than 50%
Number of operating segment \| Segment		1
Lease, practical expedients, package		true
Lessee, operating lease, existence of option to extend	true	true
Lessee, operating lease, option to extend		options to extend the lease when it is reasonably certain that option will be exercised
Operating lease, right-of-use asset		$ 17,263,000		$ 15,900,000
Operating lease, lease liability		24,804,000		$ 24,000,000
Bank Account
Summary Of Significant Accounting Policies [Line Items]
Cash held in a separate restricted bank account		50,000	50,000
Letter of Credit
Summary Of Significant Accounting Policies [Line Items]
Cash		$ 1,000,000	$ 1,000,000

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 26,184	$ 11,252
Restricted cash included in other long-term assets	1,097	1,097
Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows	$ 27,281	$ 12,349	$ 59,537

Summary of Significant Accounting Policies - Schedule of Useful Life of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2019
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Useful life	3 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Useful life	5 years
Laboratory Equipment
Property Plant And Equipment [Line Items]
Useful life	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Useful life	Lesser of useful life or remaining lease term

Fair Value of Financial Instruments - Schedule of Company's Classified Assets Measured at Fair Value on Recurring Basis (Detail) - Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value Asset Measured On Recurring Basis [Line Items]
Total assets	$ 114,383	$ 111,742
Money market funds
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	3,240	265
Commercial paper
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	4,249
Marketable securities	20,501
Short-term investments		57,453
U.S. Government Agency Securities and Treasuries
Fair Value Asset Measured On Recurring Basis [Line Items]
Short-term investments	9,005	3,972
Corporate debt securities
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	6,005
Marketable securities	71,383
Short-term investments		50,052
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Asset Measured On Recurring Basis [Line Items]
Total assets	3,240	2,252
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money market funds
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	3,240	265
Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. Government Agency Securities and Treasuries
Fair Value Asset Measured On Recurring Basis [Line Items]
Short-term investments		1,987
Significant Other Observable Inputs (Level 2)
Fair Value Asset Measured On Recurring Basis [Line Items]
Total assets	111,143	109,490
Significant Other Observable Inputs (Level 2) \| Commercial paper
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	4,249
Marketable securities	20,501
Short-term investments		57,453
Significant Other Observable Inputs (Level 2) \| U.S. Government Agency Securities and Treasuries
Fair Value Asset Measured On Recurring Basis [Line Items]
Short-term investments	9,005	1,985
Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	6,005
Marketable securities	71,383
Short-term investments		50,052
Significant Unobservable Inputs (Level 3)
Fair Value Asset Measured On Recurring Basis [Line Items]
Total assets	0	0
Significant Unobservable Inputs (Level 3) \| Money market funds
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	0	0
Significant Unobservable Inputs (Level 3) \| Commercial paper
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	0
Marketable securities	0
Short-term investments		0
Significant Unobservable Inputs (Level 3) \| U.S. Government Agency Securities and Treasuries
Fair Value Asset Measured On Recurring Basis [Line Items]
Short-term investments	0	0
Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Fair Value Asset Measured On Recurring Basis [Line Items]
Cash and Cash Equivalents	0
Marketable securities	$ 0
Short-term investments		$ 0

Available-for-Sale Investments - Summary of Available-for-Sale Securities Held (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 100,777	$ 111,542
Gross unrealized gains	116	5
Gross unrealized losses	(4)	(70)
Fair Value	100,889	111,477
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	20,484	53,549
Gross unrealized gains	18
Gross unrealized losses	(1)	(47)
Fair Value	20,501	53,502
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	71,288	54,022
Gross unrealized gains	96	4
Gross unrealized losses	(1)	(23)
Fair Value	71,383	54,003
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	9,005	3,971
Gross unrealized gains	2	1
Gross unrealized losses	(2)
Fair Value	$ 9,005	$ 3,972

Available-for-Sale Investments - Additional Information (Detail) $ in Millions	Dec. 31, 2019 USD ($) Investment Security	Dec. 31, 2018 USD ($)
Investments Debt And Equity Securities [Abstract]
Number of investments in unrealized loss position	9
Number of investments in unrealized loss position, more than twelve months	0
Aggregate fair value of securities in unrealized loss position \| $	$ 24.8	$ 96.5
Number of securities with other than temporary impairment \| Security	0

Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid insurance	$ 648	$ 502
Prepaid research and development	11,989	122
Other prepaid	390	597
Other current assets	648	388
Total	$ 13,675	$ 1,609

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 18,652	$ 17,828
Less accumulated depreciation	(5,631)	(2,987)
Property and equipment, net	13,021	14,841
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,523	7,111
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	782	781
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	421	413
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	9,514	9,484
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 412	$ 39

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Depreciation expense	$ 2,702	$ 2,421
Leasehold Improvements
Property Plant And Equipment [Line Items]
Lessor-paid tenant improvements	$ 6,600	$ 6,600

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Payroll related	$ 2,372	$ 2,906
Professional fees	444	306
Research and development	1,005	1,585
Other	125	196
Total accrued expenses	$ 3,946	$ 4,993

Common Stock - Additional Information (Detail)	1 Months Ended			12 Months Ended		20 Months Ended	32 Months Ended	145 Months Ended
Common Stock - Additional Information (Detail)	Jun. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2018 USD ($) $ / shares shares	Jan. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) Vote shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2018 shares	Dec. 31, 2019 shares	Dec. 31, 2019 USD ($)
Class Of Stock [Line Items]
Number of votes entitled to each share of common stock \| Vote				1
Cash dividends \| $								$ 0
Proceeds from sale of common stock, net of issuance costs \| $		$ 28,900,000	$ 53,800,000	$ 56,996,000	$ 82,666,000
Proceeds from sale of pre-funded warrants, net of issuance costs \| $				$ 22,874,000
Ginkgo Bioworks, Inc.
Class Of Stock [Line Items]
Proceeds from sale of common stock, net of issuance costs \| $	$ 57,000,000
Sale of stock, price per share \| $ / shares	$ 9.00
Proceeds, net of issuance costs, from issuance of common stock and pre-funded warrants \| $	$ 79,900,000
Ginkgo Bioworks, Inc. \| Pre-Funded Warrants
Class Of Stock [Line Items]
Warrants exercise price per share \| $ / shares	$ 9.00
Warrants exercise price per share paid at closing of offering \| $ / shares	$ 8.99
Proceeds from sale of pre-funded warrants, net of issuance costs \| $	$ 22,900,000
Ginkgo Bioworks, Inc. \| Pre-Funded Warrants \| Maximum
Class Of Stock [Line Items]
Warrants to purchase shares of common stock \| shares	2,548,117
Common Stock
Class Of Stock [Line Items]
Unvested shares of common stock \| shares					586,929	586,929
Number of shares forfeited \| shares							147,617
Repurchase option exercisable period				4 years
Repurchase options share exercised \| shares						41,819
Sale of common stock, shares \| shares		3,280,000	5,899,500	6,340,771	9,179,500
Stock sold and issued to investors, per share \| $ / shares		$ 9.15	$ 9.75
Common Stock \| Ginkgo Bioworks, Inc.
Class Of Stock [Line Items]
Sale of common stock, shares \| shares	6,340,771
Pre-Funded Warrants \| Ginkgo Bioworks, Inc. \| Maximum
Class Of Stock [Line Items]
Unbeneficial percentage of ownership after exercise of common stock outstanding effect to issuance	19.99%

Equity-based Compensation and Equity Incentive Plans - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Aug. 28, 2017 shares	Aug. 31, 2015 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exchange ratio of common stock			0.5532
Weighted average grant date fair value per share of options granted to employees \| $ / shares	$ 4.59	$ 6.35
Total fair value of awards vested	$ 3,900	$ 3,300
Employee unrecognized compensation expense	$ 6,800
Employee unrecognized compensation cost, period of recognition	2 years 4 months 24 days
Equity-based compensation expense	$ 4,134	4,317
Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of awards vested	100	$ 1,300
Employee unrecognized compensation expense	$ 1,200
Employee unrecognized compensation cost, period of recognition	1 year 2 months 12 days
Granted \| shares	585,600	0
Equity-based compensation expense	$ 345	$ 956
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of discount for employees under ESPP	15.00%
Purchase price as a percentage of fair value under ESPP	85.00%
Plan 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option and stock purchase rights available for grant (in shares) \| shares				647,893
Percentage of shares outstanding	5.00%
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock option and stock purchase rights available for grant (in shares) \| shares			1,753,061
2015 and 2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants \| shares	676,388
Modifications in Equity Awards \| Separation of Former Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation		$ 700

Equity-based Compensation and Equity Incentive Plans - Schedule of Weighted Average Assumption Used Black-Scholes Option-pricing Model for Stock Options Issued to Employees and Non-employees (Detail) - Employees and Nonemployees - 2015 and 2017 Plan	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 2 months 12 days	6 years 2 months 12 days
Weighted-average, risk-free interest rate	2.20%	2.80%
Expected volatility	71.10%	70.80%
Dividend yield	0.00%	0.00%

Equity-based Compensation and Equity Incentive Plans - Schedule of Stock Option Activity Under 2015 and 2017 Plan (Detail) - 2015 and 2017 Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Beginning balance, Number of options	1,739,884
Granted, Number of options	1,427,030
Cancelled or Forfeited, Number of options	(880,495)
Outstanding Ending balance, Number of options	2,286,419	1,739,884
Number of options, Vested or expected to vest	2,286,419
Number of options, Exercisable	845,102
Beginning balance, Weighted-average price	$ 11.92
Granted, Weighted-average price	7.07
Cancelled or Forfeited, Weighted-average price	11.02
Ending balance, Weighted-average price	9.24	$ 11.92
Weighted-average price Vested or expected to vest	9.24
Weighted-average price, Exercisable	$ 11.43
Outstanding, weighted average remaining contractual term (Year)	8 years 8 months 12 days	9 years
Weighted average remaining contractual term, Vested or expected to vest	8 years 8 months 12 days
Weighted average remaining contractual term, Exercisable	8 years 1 month 6 days
Cancelled or Forfeited, Aggregate Intrinsic value	$ 25
Ending balance, Aggregate Intrinsic value	43
Aggregate Intrinsic value, Vested or expected to vest at December 31, 2019	$ 43

Equity-based Compensation and Equity Incentive Plans - Schedule of Restricted Common Stock Activity (Detail) - Restricted Common Stock - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Beginning balance, Number of unvested shares/units	118,679
Granted, Number of shares/units	585,600	0
Vested, Number of shares/units	(56,314)
Forfeited, Number of shares/units	(61,036)
Ending balance, Number of unvested shares/units	586,929	118,679
Beginning balance, Unvested Grant date fair value	$ 13.54
Granted, Grant date fair value	2.49
Vested, Grant date fair value	13.55
Forfeited, Grant date fair value	9.19
Ending balance, Unvested Grant date fair value	$ 2.97	$ 13.54

Equity-based Compensation and Equity Incentive Plans - Schedule of Equity-based Compensation Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 4,134	$ 4,317
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	1,377	1,333
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 2,757	$ 2,984

Equity-based Compensation and Equity Incentive Plans - Schedule of Equity-based Compensation Expenses by Award Type (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 4,134	$ 4,317
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	3,789	3,361
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 345	$ 956

Collaboration Agreements - Additional Information (Detail) $ in Thousands		1 Months Ended					3 Months Ended								12 Months Ended
	Sep. 27, 2018 USD ($) Milestone	Jun. 30, 2019 USD ($) shares	Apr. 30, 2018 shares	Jan. 31, 2018 shares	May 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Feb. 28, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Recognition of revenue							$ 1,231	$ 305	$ 350	$ 338	$ 111	$ 1,801	$ 254	$ 354	$ 2,224	$ 2,520
Current deferred revenue							544				$ 268				$ 544	$ 268
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of shares sold \| shares			3,280,000	5,899,500											6,340,771	9,179,500
Ginkgo Collaboration
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Prepayment to related party for collaboration agreement		$ 30,000
Related party transaction collaboration agreement, initial term		5 years
Ginkgo Collaboration \| Pre-Funded Warrants
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Warrants to purchase shares of common stock \| shares		2,548,117							2,548,117
Ginkgo Collaboration \| Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of shares sold \| shares		6,340,771
AbbVie Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of mile stone payments under second phase \| Milestone	2
Initial milestone payment upon execution of amendment	$ 2,000
Increase in transaction price of performance obligation of second phase	$ 2,000
Cumulative catch-up adjustment to revenue, contract modification																$ 1,800
Remaining milestone achieved																	$ 2,500
Recognition of revenue															$ 2,200	$ 2,500
Current deferred revenue							$ 500								500
AbbVie Agreement \| IBDCo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront non-refundable payment						$ 2,000
Potential milestone payment															$ 16,500
Collaboration in research and development															54 months
Milestone payment					$ 2,000

Net Loss per Share - Schedule of Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ 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
Numerator:
Net loss	$ (12,798)	$ (13,285)	$ (12,344)	$ (12,946)	$ (11,931)	$ (10,748)	$ (14,591)	$ (11,165)	$ (51,373)	$ (48,435)
Denominator:
Weighted-average common shares outstanding - basic and diluted									30,284,068	23,882,685
Net loss per share - basic and diluted	$ (0.37)	$ (0.39)	$ (0.45)	$ (0.51)	$ (0.47)	$ (0.43)	$ (0.59)	$ (0.55)	$ (1.70)	$ (2.03)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss per Share - Schedule of Potentially Common Shares Excluded from Calculation of Net Loss Per share (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Unvested Restricted Common Stock Awards
Potentially Common Shares Excluded from Calculation of Net Loss Per share	586,929	118,679
Stock Options
Potentially Common Shares Excluded from Calculation of Net Loss Per share	2,286,419	1,739,884

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Income tax benefits for the net operating losses	$ 0	$ 0
Valuation allowance	$ 53,834,000	40,290,000	$ 26,515,000
Description of tax benefit likely to be realized upon settlement	greater than 50%
Unrecognized tax benefits	$ 0
Income tax examination description	In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. Tax years from 2016 to the present are open to examination under the statute.
Interest or penalties accrued	$ 0	0
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	172,900,000	125,500,000
Net operating loss carryforwards subject to expiration	79,400,000
Net operating loss carryforwards not subject to expiration	$ 93,500,000
Net operating loss carryforwards expiration year	2034
Federal \| Research and Development.
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 2,500,000
State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 159,000,000	$ 109,400,000
Net operating loss carryforwards expiration year	2029
State \| Research and Development.
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 1,800,000

Income Taxes - Schedule of Temporary Differences Between Basis of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 46,362	$ 33,275
Tax credit carryforwards	4,262	4,365
Accrued expenses	37	103
Deferred rent		2,209
Lease liabilities	6,776
Equity compensation	1,481	784
Amortizable intangibles	1,214	1,339
Other	138	78
Gross deferred tax assets	60,270	42,153
Deferred tax liabilities:
Property and equipment	(1,720)	(1,863)
Right of use assets	(4,716)
Gross deferred tax liabilities	(6,436)	(1,863)
Valuation allowance	$ (53,834)	$ (40,290)	$ (26,515)

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate to Company's Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	21.00%	21.00%
State income taxes, net of federal benefit, Tax Rate	6.00%	6.00%
Other permanent differences, Tax Rate	(1.00%)	(1.00%)
Tax credits, Tax Rate	0.00%	3.00%
Other items, Tax Rate	0.00%	(1.00%)
Net change in valuation allowance, Tax Rate	(26.00%)	(28.00%)

Income Taxes - Schedule of Valuation Allowance - (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ (40,290)	$ (26,515)
Increase in valuation allowance	(13,544)	(13,775)
Balance at end of year	$ (53,834)	$ (40,290)

Leases - Additional Information (Detail)		1 Months Ended	12 Months Ended
Leases - Additional Information (Detail)	Dec. 07, 2018 USD ($) ft²	Jul. 31, 2017 USD ($) ft²	Dec. 31, 2019 USD ($)
Lessee Lease Description [Line Items]
Laboratory and office space to be leased \| ft²		41,346
Operating lease annual rent		$ 3,100,000
Term of lease		10 years
Tenant improvement investment		$ 2,900,000
Letter of credit		$ 1,000,000
Lessee, operating lease, existence of option to extend		true	true
Renewal term of lease		5 years
Lessee, operating lease, existence of option to terminate		true
Agreement expiration date	Dec. 31, 2022
Cash paid included in operating cash flows			$ 3,700,000
Total right-of-use asset for finance leases			$ 900,000
Master Services Agreement \| Azzur Group, LLC
Lessee Lease Description [Line Items]
Access and use of space under agreement \| ft²	700
Term of agreement	44 months
Term of prior terminate written notice	4 months
Maximum
Lessee Lease Description [Line Items]
Tenant improvement investment		$ 6,600,000
Estimated project costs	$ 4,800,000

Leases - Components of Lease Cost for Operating and Finance Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Operating leases
Operating lease cost	$ 3,344
Short-term lease cost	330
Variable lease cost	1,092
Operating and variable lease cost	4,766
Finance leases
Depreciation on finance leases	188
Interest on finance leases	21
Finance lease cost	209
Total lease cost	$ 4,975

Leases - Summary of Weighted Average Remaining Lease Term and Weighted Average Discount Rate for Operating and Finance Leases (Detail)	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Weighted average discount rate	8.00%
Operating Lease, Weighted average remaining lease term (years)	8 years 2 months 12 days
Finance Leases, Weighted average discount rate	6.10%
Finance Leases, Weighted average remaining lease term (years)	9 months 18 days

Leases - Summary of Maturity of Lease Liabilities for Operating and Finance Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leases
2020	$ 3,892
2021	4,236
2022	4,389
2023	3,574
2024	3,681
Thereafter	14,386
Total lease payments	34,158
Less: imputed interest	9,354
Total lease liabilities	24,804	$ 24,000
Current lease liabilities	2,000
Long-term lease liabilities	22,804
Finance Leases
2020	214
2021	2
Total lease payments	216
Less: imputed interest	6
Total lease liabilities	210
Current lease liabilities	208		$ 266
Long-term lease liabilities	$ 2		$ 210

Employee Benefits - Additional Information (Detail)	12 Months Ended
Employee Benefits - Additional Information (Detail)	Dec. 31, 2019
Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract]
Eligible employees to contribute to 401(k) plan	50.00%
Employee contribution	4.00%
Maximum matching contributions as a percentage of eligible compensation	2.00%

Related-Party Transactions - Additional Information (Detail) - Ginkgo Bioworks, Inc. - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Prepayment to related party for collaboration agreement	$ 30.0
Related party transaction collaboration agreement, initial term	5 years
Current Pre-Paid Research and Development		$ 11.5
Non Current Pre-Paid Research and Development		15.7
Prepaid research and development expenses		$ 2.8

Selected Quarterly Data (unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,231	$ 305	$ 350	$ 338	$ 111	$ 1,801	$ 254	$ 354	$ 2,224	$ 2,520
Operating expenses	14,710	14,443	13,445	14,035	12,819	13,335	15,606	11,990	56,633	53,750
Loss from operations	(13,479)	(14,138)	(13,095)	(13,697)	(12,708)	(11,534)	(15,352)	(11,636)	(54,409)	(51,230)
Net loss	$ (12,798)	$ (13,285)	$ (12,344)	$ (12,946)	$ (11,931)	$ (10,748)	$ (14,591)	$ (11,165)	$ (51,373)	$ (48,435)
Net loss per share - basic and diluted	$ (0.37)	$ (0.39)	$ (0.45)	$ (0.51)	$ (0.47)	$ (0.43)	$ (0.59)	$ (0.55)	$ (1.70)	$ (2.03)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details