Atreca Inc - Ordinary Shares (BCEL) 10-K 11 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Mar. 11, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity Registrant Name	ATRECA, INC.
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001532346
Amendment Flag	false
Entity Public Float			$ 210.9
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		22,136,897
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		5,934,191

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 157,954	$ 114,504
Investments	14,663
Prepaid expenses and other current assets	3,502	2,721
Total current assets	176,119	117,225
Property and equipment, net	5,771	4,143
Long-term Investments	10,799
Deposits and other	3,026	316
Total assets	195,715	121,684
Current Liabilities
Accounts payable	2,133	1,307
Accrued expenses	5,395	3,008
Other current liabilities	419	247
Total current liabilities	7,947	4,562
Capital lease obligations, net of current portion	53	100
Deferred rent	763	6
Preferred stock warrant liability		380
Total liabilities	8,763	5,048
Commitments and contingencies (Note 8)
Stockholders’ equity (deficit)
Additional paid-in capital	351,039	3,593
Accumulated other comprehensive income (loss)	16	(4)
Accumulated deficit	(164,106)	(96,622)
Total stockholders’ equity (deficit)	186,952	(93,033)
Total liabilities and stockholders’ equity (deficit)	195,715	121,684
Series A convertible preferred stock
Current Liabilities
Convertible preferred stock		55,030
Series B convertible preferred stock
Current Liabilities
Convertible preferred stock		34,333
Series C1 convertible preferred stock
Current Liabilities
Convertible preferred stock		65,691
Series C2 convertible preferred stock
Current Liabilities
Convertible preferred stock		$ 54,615
Class A common stock
Stockholders’ equity (deficit)
Common stock	2
Class B common stock
Stockholders’ equity (deficit)
Common stock	$ 1

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Series A convertible preferred stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	100,000,000	32,133,287
Convertible preferred stock, shares issued	0	5,305,513
Convertible preferred stock, shares outstanding	0	5,305,513
Convertible preferred stock, aggregate liquidation preference	$ 58,892	$ 58,892
Series B convertible preferred stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	100,000,000	18,008,749
Convertible preferred stock, shares issued	0	3,001,421
Convertible preferred stock, shares outstanding	0	3,001,421
Convertible preferred stock, aggregate liquidation preference	$ 35,000	$ 35,000
Series C1 convertible preferred stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	50,000,000	54,184,549
Convertible preferred stock, shares issued	0	5,007,134
Convertible preferred stock, shares outstanding	0	5,007,134
Convertible preferred stock, aggregate liquidation preference	$ 70,000	$ 70,000
Series C2 convertible preferred stock
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	50,000,000	23,605,150
Convertible preferred stock, shares issued	0	3,934,191
Convertible preferred stock, shares outstanding	0	3,934,191
Convertible preferred stock, aggregate liquidation preference	$ 55,000	$ 55,000
Class A common stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	650,000,000	191,398,492
Common stock, shares issued	22,035,976	2,119,872
Common stock, shares outstanding	22,035,976	2,119,872
Class B common stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	23,605,150
Common stock, shares issued	5,934,191	0
Common stock, shares outstanding	5,934,191	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Expenses
Research and development	$ 54,726	$ 32,513
General and administrative	17,845	7,060
Total expenses	72,571	39,573
Interest and other income (expense)
Other income	2,134	961
Interest income	3,213	714
Interest expense	(6)	(9)
Preferred stock warrant liability revaluation	(123)	(33)
Foreign exchange loss	(8)
Loss on disposal of property and equipment	(122)	(1)
Loss before income tax expense	(67,483)	(37,941)
Income tax benefit (expense)	(1)	1
Net loss	$ (67,484)	$ (37,940)
Net loss per share, basic and diluted	$ (4.26)	$ (18.02)
Weighted-average shares used in computing net loss per share, basic and diluted	15,834,175	2,104,861

Consolidated Statements of Loss

Consolidated Statements of Loss and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (67,484)	$ (37,940)
Other comprehensive income (loss);
Unrealized gain on fair value of investments	16	26
Unrealized gain (loss) on currency translation	4	(16)
Comprehensive loss	$ (67,464)	$ (37,930)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible preferred stock (as converted)	Total
Balances at beginning at Dec. 31, 2017					$ 89,362
Balances at beginning (in shares) at Dec. 31, 2017					8,306,934
Balances at beginning at Dec. 31, 2017		$ 2,130	$ (14)	$ (58,682)		$ (56,566)
Balances at beginning (in shares) at Dec. 31, 2017	2,092,040
Issuance of convertible preferred stock					$ 120,306
Issuance of convertible preferred stock (in shares)					8,941,325
Issuance of common stock upon exercise of options		44				44
Issuance of common stock upon exercise of options (in shares)	27,832
Stock-based compensation		1,419				1,419
Unrealized gain on fair value of investments			26			26
Unrealized currency exchange gain (loss)			(16)			(16)
Net loss				(37,940)		(37,940)
Balances at end at Dec. 31, 2018					$ 209,668
Balances at end (in shares) at Dec. 31, 2018					17,248,259
Balances at end at Dec. 31, 2018		3,593	(4)	(96,622)		(93,033)
Balances at end (in shares) at Dec. 31, 2018	2,119,872
Conversion of convertible preferred stock					$ (209,668)	209,668
Conversion of convertible preferred stock (in shares)					(17,248,259)
Conversion of convertible preferred stock	$ 2	209,666				209,668
Conversion of convertible preferred stock (in shares)	17,248,259
Issuance of common stock upon initial public offering, net	$ 1	130,785				130,786
Issuance of common stock upon initial public offering, net (in shares)	8,452,500
Exercise of warrants (in shares)	62,936
Issuance of common stock upon exercise of options		288				288
Issuance of common stock upon exercise of options (in shares)	77,368
Vesting of early exercised stock options		15				15
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital		503				503
Issuance of common stock under the Employee Stock Purchase Plan		133				133
Issuance of common stock under the Employee Stock Purchase Plan (shares)	9,232
Stock-based compensation		6,056				6,056
Unrealized gain on fair value of investments			16			16
Unrealized currency exchange gain (loss)			4			4
Net loss				(67,484)		(67,484)
Balances at end at Dec. 31, 2019	$ 3	$ 351,039	$ 16	$ (164,106)		$ 186,952
Balances at end (in shares) at Dec. 31, 2019	27,970,167

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities
Net loss	$ (67,484)	$ (37,940)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,697	1,409
Loss on disposal of property and equipment	122	1
Stock-based compensation	6,056	1,419
Preferred stock warrant liability revaluation	123	33
Accretion of discount on investments	(800)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,394)	(1,370)
Accounts payable	826	698
Accrued expenses	2,465	1,085
Other current liabilities	160
Deferred rent	691	(35)
Net cash used in operating activities	(58,538)	(34,700)
Cash Flows from Investing Activities
Purchase of property and equipment	(3,447)	(1,764)
Purchase of investments	(99,646)
Proceeds from maturities of investments	75,000	22,398
Change in deposits	189	24
Net cash provided by (used in) investing activities	(27,904)	20,658
Cash Flows from Financing Activities
Proceeds from issuance of convertible preferred stock, net		120,306
Proceeds from the issuance of common stock under the Employee Stock Purchase Plan	133
Proceeds from exercise of stock options	303	46
Proceeds from initial public offering, net	133,633
Principal payments on capital lease obligations	(47)	(48)
Payments of initial offering costs	(2,848)
Net cash provided by financing activities	131,174	120,304
Net change in cash, cash equivalents and restricted cash	44,732	106,262
Cash, cash equivalents and restricted cash, beginning of period	114,504	8,242
Cash, cash equivalents and restricted cash, end of period	159,236	114,504
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	6	9
Cash paid for income taxes	1	$ (1)
Supplemental Schedule of Non-Cash Investing and Financing Activities
Conversion of redeemable convertible preferred stock to common stock	209,668
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	503
Vesting of early exercised common stock options	$ 15

Business

Business	12 Months Ended
	Dec. 31, 2019
Business
Business	1. Business Nature of Business Atreca, Inc. (the “Company”) was incorporated in the State of Delaware on June 11, 2010 (“inception date”), and is located in South San Francisco, California. In April 2016, the Company formed a wholly owned subsidiary, Atreca Pte. Ltd., in Singapore. The Company is a biopharmaceutical company utilizing its differentiated platform to discover and develop novel antibody-based immunotherapeutics to treat a range of solid tumor types. The Company's lead product candidate, ATRC-101, is a monoclonal antibody in clinical development with a novel mechanism of action and a target derived from an antibody identified using its discovery platform. The Company operates in a single segment. Since inception, the Company has been primarily engaged in research and development, raising capital, building its management team and building its intellectual property portfolio. Reverse Stock Split On June 7, 2019, the Company effected a 1-for-6 reverse stock split of all classes of its capital stock. Upon the effectiveness of the reverse stock split, (i) every one share of the Company’s outstanding capital stock was combined into one-sixth of one share of the same class and series of capital stock, (ii) the number of shares of its Class A common stock and its Series A preferred stock for which each outstanding option or warrant, to purchase its Class A common stock and its Series A preferred stock is exercisable was proportionally decreased on a 1-for-6 basis and (iii) the exercise price of each outstanding option or warrant to purchase its Class A common stock and its Series A preferred stock was proportionately increased on a 1-for-6 basis. The par value per share of its common stock and preferred stock were not adjusted as a result of the reverse stock split. Initial Public Offering In June 2019, the Company closed its initial public offering (“IPO”) of 6,452,500 shares of its Class A common stock and 2,000,000 shares of its Class B common stock at an offering price of $17.00 per share, including 1,102,500 shares pursuant to the underwriters’ option to purchase additional shares of the Company’s Class A common stock. The Company received net proceeds of $130.8 million, after deducting underwriting discounts and commissions of $10.1 million and offering expenses of $2.8 million. Immediately prior to the closing of the IPO, all outstanding shares of the Company’s convertible Series A preferred stock, convertible Series B preferred stock and convertible Series C1 preferred stock automatically converted into 13,314,068 shares of the Company’s Class A common stock and all outstanding shares of the Company’s convertible Series C2 preferred stock automatically converted into 3,934,191 shares of the Company’s Class B common stock. Immediately prior to the closing of the IPO, the Company issued 62,936 shares of Class A common stock upon the exercise of an outstanding warrant. The Company reclassified $209.7 million from temporary equity to Class A common stock, Class B common stock, and additional paid-in-capital on its consolidated balance sheet. Deferred Offering Cost Deferred offering costs of $2.8 million, consisting of legal, accounting and other fees and costs related to the IPO, were reclassified to additional paid-in capital as a reduction of the proceeds upon the closing of the IPO in June 2019. During the year ended December 31, 2019, $2.8 million of the deferred offering costs were paid.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany transactions and accounts have been eliminated. Prior period reclassification An immaterial reclassification of prior period amounts has been made to conform to the current period presentation. Principles of Consolidation The consolidated financial statements include accounts of the Company and its wholly owned subsidiary. All significant intercompany accounts and transactions are eliminated upon consolidation. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of income and expenses in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates in the consolidated financial statements include estimated useful lives of property and equipment, impairment of long-lived assets, accrued expenses, valuation of deferred income tax assets, the fair value of warrants issued to purchasers of shares of preferred stock and common stock and fair value of options granted under the Company's stock option plan. Other Income Other income is comprised of amounts earned from services performed under service agreements. Beginning January 1, 2018, the Company follows the provisions of Accounting Standards Update 2014-09 Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“Topic 606”). The guidance provides a unified model to determine how income is recognized. In determining the appropriate amount of other income to be recognized as it fulfills its obligations under the agreements, the Company performs the following steps: (i) identifies the promised goods or services in the contract; (ii) determines whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on estimated selling prices; and (v) recognizes other income when (or as) the Company satisfies each performance obligation. Upon adoption of Topic 606, there was no change to the units of accounting previously identified with respect to existing service agreements under legacy Generally Accepted Accounting Principles (“GAAP”), which are now considered performance obligations under Topic 606, and there was no change to the revenue recognition pattern for the performance obligations. Accordingly, the adoption of the new standard resulted in no cumulative effect change to the Company's opening accumulated deficit balance. The Company generally allocates the transaction price to distinct performance obligations at their stand-alone selling prices, determined by their estimated costs plus some margin. Performance obligations are generally delivered over time and recognized based upon observable inputs as the related research services are performed, which are recorded as research and development expenses. Amounts due under service agreements are generally billed monthly as services are delivered and do not generally result in contract liabilities or assets. Receivables under service agreements of $237,000 and $282,000 are included in prepaid expenses and other current assets as of December 31, 2019 and 2018, respectively. Contract liabilities of zero and $200,000 are included in other current liabilities as of December 31, 2019 and 2018, respectively. Collaboration and Service Arrangements In March 2016, the Company entered into a research collaboration agreement with Genome Institute of Singapore (GIS) for the development of a high-throughput microfluidic droplet system for single cell phenotyping and genotyping. Under the agreement, the Company contributes reimbursement of research expenses and certain reagents and other consumables to GIS. The Company accounts for the collaboration agreement with GIS in accordance with ASC 808—Collaborative Arrangements. The Company recognized $36,000 and $522,000 of research and development expenses in 2019 and 2018, respectively, under the collaboration agreement, including wind-down costs. The Company exercised its right to early terminate the collaboration agreement in December 2018. Fair Value of Financial Instruments: The Company uses a three-level hierarchy, which prioritizes, within the measurement of fair value, the use of market-based information over entity-specific information for fair value measurements based on the nature of inputs used in the valuation of an asset or liability as of the measurement date. Fair value focuses on an exit price and is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The inputs or methodology used for valuing financial instruments are not necessarily an indication of the risk associated with those financial instruments. The three-level hierarchy for fair value measurements is defined as follows: Level 1: Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2: Level 3: An asset or liability's categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include all cash balances and highly liquid investments purchased with an original maturity of three months or less. The Company maintained restricted cash of $1.3 million and zero as of December 31, 2019 and 2018, respectively. This amount as of December 31, 2019 is included in deposits and other in the accompanying consolidated balance sheets and is comprised solely of letters of credit required pursuant to leases for Company facilities. The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows (in thousands): December 31, 2019 2018 Cash and cash equivalents $ 157,954 $ 114,504 Restricted cash 1,282 — Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows $ 159,236 $ 114,504 Investments The Company considers securities purchased with original maturities greater than three months to be investments. The Company’s policy is to protect the value of its investment portfolio and minimize principal risk by earning returns based on current interest rates. The Company’s intent is to convert all investments into cash to be used for operations and has classified them as available for sale. For purposes of determining realized gains and losses, the cost of securities sold is based on specific identification. Interest and dividends on securities classified as available-for-sale are included in interest income. Convertible Preferred Stock Warrants The Company issued convertible preferred stock warrants, which were exercisable into Series A preferred stock with liquidation preference. The conversion feature was evaluated under ASC Topic 480, Distinguishing liabilities from equity and the warrants were determined to be debt instruments and classified prior to the IPO as liabilities on the consolidated balance sheets. The Company recorded these warrant liabilities at fair value and adjusted the carrying value to their estimated fair value at each reporting date with the increases or decreases in the fair value recorded as a gain (loss) on revaluation of the warrant liability in the consolidated statements of operations. Upon the IPO, t he 49,997 preferred stock warrants were converted to common stock warrants of Class A shares and the warrant liability of $0.5 million was reclassified to additional paid-in capital as a result of the conversion. The warrants were not subject to further remeasurement for fair value. Risks and Uncertainties The Company is subject to a number of risks associated with companies at a similar stage, including dependence on key individuals, competition from similar services and larger companies, volatility of the industry, ability to obtain regulatory clearance, ability to obtain adequate financing to support growth, the ability to attract and retain additional qualified personnel to manage the anticipated growth of the Company and general economic conditions. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents, investments and other receivables. Cash and cash equivalents are held at three financial institution and were in excess of the Federal Deposit Insurance Corporation insurable limit at December 31, 2019, and 2018. Additionally, cash and cash equivalents and investments are maintained at a brokerage firm for which amounts are insured by the Securities Investor Protection Corporation subject to legal limits. The Company has not experienced any losses on its deposits to date. The Company does not require collateral or other security for other receivables; however, credit risk is mitigated by the Company’s ongoing evaluations of its debtors’ credit worthiness. Property and Equipment Property and equipment are stated at cost less depreciation. Depreciation is computed using the straight-line method with the estimated useful lives of the assets ranging from two to five years. Leasehold improvements are amortized over the estimated useful life of the asset, or the remaining lease term, whichever is shorter. Expenditures for repairs and maintenance, which do not extend the useful life of the property and equipment, are expensed as incurred. Accounting for Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. The Company has not recorded any impairment of long-lived assets in 2019 or 2018. Intellectual Property The legal and professional costs incurred by the Company to maintain its patent rights have been expensed as part of research and development costs since inception. As of December 31, 2019, and 2018, the Company has determined that these expenses have not met the criteria to be capitalized. Intellectual property-related expenses for the years ended December 31, 2019 and 2018 were $1.3 million and $1.1 million, respectively. Deferred Rent The Company has entered into lease agreements for its laboratory and office facilities. These leases qualify as and are accounted for as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. Research and Development Costs Research and development costs are expensed as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, stock-based compensation, certain facility costs, legal costs and other costs associated with preclinical development. A substantial portion of the Company’s ongoing research and development activities are conducted by third-party service providers in connection with preclinical development activities and contract manufacturing organizations in connection with the production of materials for clinical trials. At the end of the reporting period, the Company compares payments made to third-party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Stock‑Based Compensation The Company generally grants stock options to its employees for a fixed number of shares with an exercise price equal to the fair value of the underlying shares at the date of grant. The Company accounts for stock option grants using the fair value method. The fair value of options is calculated using the Black‑Scholes option pricing model. Stock‑based compensation is recognized as the underlying options vest using the straight‑line attribution approach, and forfeitures are recorded as they occur. Emerging Growth Company Status The Company is an “emerging growth company,” (“EGC”) as defined in the Jumpstart Our Business Startups Act, (“JOBS Act”), and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. The Company may take advantage of these exemptions until it is no longer an EGC under Section 107 of the JOBS Act, which provides that an EGC can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards, and as a result of this election, the Company’s consolidated financial statements may not be comparable to companies that comply with public company Financial Accounting Standards Board (“FASB”) standards’ effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of the IPO or such earlier time that the Company is no longer an EGC. Income Taxes The Company applies the provisions set forth in FASB ASC Topic 740, Income Taxes, to account for the uncertainty in income taxes. In the preparation of income tax returns in federal, foreign and state jurisdictions, the Company asserts certain income tax positions based on its understanding and interpretation of income tax laws. The taxing authorities may challenge such positions, and the resolution of such matters could result in recognition of income tax expense in the Company's consolidated financial statements. Management believes it has used reasonable judgments and conclusions in the preparation of its income tax returns. The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the financial statement and income tax basis of existing assets and liabilities. A valuation allowance is provided against the Company's deferred income tax assets when realization is not reasonably assured. Net Loss Per Share The Company computes basic loss per share by dividing the net loss available to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss assumes the conversion, exercise or issuance of all potential common stock equivalents, unless the effect of inclusion would be anti-dilutive. For purposes of this calculation, common stock equivalents include the Company's stock options, common stock warrants, convertible preferred stock warrants and convertible preferred stock, which are convertible into shares of the Company's common stock. No shares related to the convertible preferred stock were included in the diluted net loss calculation for the years ended December 31, 2019 or 2018 because the inclusion of such shares would have had an anti-dilutive effect. The shares to be issued upon exercise of certain outstanding stock options were also excluded from the diluted net loss calculation for the years ended December 31, 2019 and 2018 because such shares are anti-dilutive. Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016‑02 and subsequent amendments to the initial guidance under ASU 2017-13, ASU 2018-10, ASU 2018-11, and ASU 2019-01 (collectively, “Topic 842” ), which modifies the accounting by lessees for all leases with a term greater than 12 months. This standard will require lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Topic 842 is effective for the Company as of January 1, 2021. Early adoption is permitted. The Company’s most significant lease is its operating lease for its corporate headquarters, and, while the Company has not yet estimated the amounts by which its financial statements will be affected by the adoption of this guidance, it expects that the overall recognition of expense will be similar to current guidance, but that there will be a significant change in the balance sheet due to the recognition of right of use assets and the corresponding lease liabilities. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses ( “Topic 326” ): Measurement of Credit Losses on Financial Instruments and subsequent amendments to the initial guidance under ASU 2018-19, ASU 2019-04 and ASU 2019-05, which amends the current approach to estimate credit losses on certain financial assets, including trade and other receivables. The amendment replaces the existing incurred loss impairment model with an expected loss methodology, which will result in more timely recognition of credit losses. For available-for-sale debt securities, credit losses should be recorded through an allowance for credit losses. Topic 326 is effective for the Company as of January 1, 2023. Early adoption is permitted. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures. In August 2016, the FASB issued ASU 2016‑15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments ( “Topic 230” ). The standard clarifies how certain cash receipts and cash payments will be presented and classified in the statement of cash flows. Topic 230 is effective for the Company as of January 1, 2019. The adoption of this update had no material effect on the Company’s consolidated financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2019
Fair Value of Financial Instruments
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used for such measurements were as follows (in thousands): December 31, 2019 Level 1 Level 2 Level 3 Total Assets Money market funds $ 152,770 $ — $ — $ 152,770 Certificates of deposit 1,950 — — 1,950 Corporate debt securities — — 3,459 U.S. Treasury securities 20,052 — — 20,052 $ 174,772 $ 3,459 $ — $ 178,231 December 31, 2018 Level 1 Level 2 Level 3 Total Assets Money market funds $ 109,630 $ — $ — $ 109,630 Total $ 109,630 $ — $ — $ 109,630 Liabilities Warrant liability $ — $ — $ $ Total $ — $ — $ $ The Company utilized the market approach and Level 1 valuation inputs to value its money market funds and U.S. government treasury securities because published net asset values were readily available. The Company measured the fair value of the corporate debt securities using Level 2 valuation inputs, which are based on quoted prices and market observable data of similar instruments. As of December 31, 2019 and 2018, gross unrealized gains and unrealized losses for cash equivalents and short-term investments were not material, and the contractual maturity of all marketable securities was less than two years. The fair value of the warrants was calculated using the Black-Scholes option pricing model and was revalued to fair value at the end of each reporting period until the warrants were converted to common stock warrants effective with the closing of the IPO on June 24, 2019. The liability was valued using the following assumptions: December 31, 2018 Exercise price (1) $ 14.46 Stock price (2) $ 13.20 Time to maturity (in years) 3.64 Volatility (3) 83.7 % Risk-free interest rate (4) 2.50 % Expected dividend $ — (1) Based upon terms provided in the warrant agreement. (2) Based upon an independently prepared valuation as of December 31, 2018, adjusted for the one-for-six reverse stock split . (3) Based upon the historical daily volatility of a group of peer public company closing prices. (4) Based upon interest rate for U.S. Treasury Bonds, as published by the U.S. Federal Reserve. The preferred stock warrants were previously valued at Level 3 as there were no observable inputs supported by market activity. The Company estimated the fair value of the preferred stock warrants using the Black-Scholes model which considers various potential liquidity outcomes and assigned probabilities to each to arrive at the weighted equity value. Upon the IPO, t he 49,997 preferred stock warrants were revalued and converted to common stock warrants of Class A shares and the warrant liability of $0.5 million was reclassified to additional paid-in capital as a result of the conversion. Revaluation upon IPO was performed using the following assumptions: expected life of 3.17 years; fair value of Series A of $17.00 per share; risk-free interest rate of 1.69%; volatility of 83.61% and no expected dividends. For further information regarding convertible preferred stock warrants, refer to Note 9, Capital Stock .

Cash, Cash Equivalents and Inve

Cash, Cash Equivalents and Investments	12 Months Ended
	Dec. 31, 2019
Cash, Cash Equivalents and Investments
Cash, Cash Equivalents and Investments	4 . Cash, Cash Equivalents and Investments The fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type consist of the following (in thousands): As of December 31, 2019 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cash and cash equivalents and investments Cost Gains Losses Value Cash, cash equivalents and money market funds $ 157,954 $ — $ — $ 157,954 U.S. Treasury securities 20,037 16 — 20,053 Corporate debt securities 3,459 — — 3,459 Certificates of deposit 1,950 — — 1,950 Total 183,400 16 — 183,416 Less amounts classified as cash and cash equivalents (157,954) — — (157,954) Total available-for-sale investments $ 25,446 $ 16 $ — $ 25,462 As of December 31, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cash and cash equivalents and investments Cost Gains Losses Value Cash, cash equivalents and money market funds $ 114,504 $ — $ — $ 114,504 Total 114,504 — — 114,504 Less amounts classified as cash and cash equivalents (114,504) — — (114,504) Total available-for-sale investments $ — $ — $ — $ —

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2019
Prepaid Expenses and Other Current Assets
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, 2019 2018 Prepaid insurance $ 1,265 $ 36 Vendor prepayments and deposits 963 2,009 Prepaid rent 879 394 Non-trade receivables 242 282 Interest receivables and other current assets 153 — Total prepaid expenses and other current assets $ 3,502 $ 2,721

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2019
Property and Equipment, net
Property and Equipment, net	6. Property and Equipment, net Property and equipment consists of the following (in thousands): December 31, 2019 2018 Laboratory equipment $ 9,355 $ 7,561 Furniture and fixtures 225 386 Computer hardware and software 785 580 Leasehold improvements 765 236 11,130 8,763 Less accumulated depreciation and amortization (5,359) (4,620) Total property and equipment, net $ 5,771 $ 4,143 Depreciation and amortization expense was $1.7 million and $1.4 million for the years ended December 31, 2019 and 2018, respectively. The net book value of property and equipment under capital leases was $94,000 and $142,000 at December 31, 2019 and 2018, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Accrued Expenses	7. Accrued Expenses Accrued expenses consist of the following (in thousands): December 31, 2019 2018 Compensation and related benefits $ 4,435 $ 2,568 Professional fees 214 183 Contract research fees 563 43 Other 183 214 Total accrued expenses $ 5,395 $ 3,008

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Commitments and Contingencies	8. Commitments and Contingencies Leases The Company leases its office facilities under non-cancellable operating lease agreements that expire at various dates through May 2033. Under the terms of the leases, the Company is responsible for certain insurance, property taxes and maintenance expenses. The office facilities lease agreements contain scheduled increases over the lease term. The related rent expense is calculated on a straight-line basis with the difference recorded as deferred rent. Rent expense was $4,534,000 and $1,250,000 for the years ended December 31, 2019 and 2018, respectively. The Company leases certain property and equipment under capital leases. In 2017, the Company financed purchases of $226,000 under a capital lease agreement. Outstanding amounts under the capital lease agreements are generally secured by liens on the related property and equipment. Future minimum lease payments under non-cancelable operating and capital lease agreements consisted of the following at December 31, 2019 (in thousands): Capital Operating Leases Leases Years ending December 31: 2020 51 5,622 2021 51 6,697 2022 4 7,336 2023 — 7,037 2024 — 7,249 Thereafter — 69,091 Total minimum lease payments 106 $ 103,032 Less: amount representing interest (6) Present value of capital lease obligation 100 Less: current portion (47) Non-current portion $ 53 Litigation The Company is not aware of any asserted or unasserted claims against it where it believes that an unfavorable resolution would have an adverse material impact on the operations or financial position of the Company.

Capital Stock

Capital Stock	12 Months Ended
	Dec. 31, 2019
Capital Stock
Capital Stock	9. Capital Stock Class A and Class B Common Stock On June 2, 2019 the board of directors of the Company authorized the issuance of 650,000,000 shares of Class A common stock, $0.0001 par value per share, 50,000,000 shares of Class B common stock, $0.0001 par value per share and 300,000,000 shares of preferred stock, $0.0001 par value per share, upon the filing of the Company’s Amended and Restated Certificate of Incorporation in connection with the reverse stock split. Each holder of Class A common stock will be entitled to one vote and each holder of Class B common stock is not entitled to vote except as may be required by law and shall not be entitled to vote on the election of directors at any time. Convertible Preferred Stock Warrant Upon the IPO, t he 49,997 preferred stock warrants were revalued and converted to common stock warrants of Class A common stock shares and the warrant liability of $0.5 million was reclassified to additional paid-in capital as a result of the conversion. The warrants were not subject to further remeasurement for fair value. The balances of the preferred stock warrant liabilities were zero and $0.4 million, respectively, as of December 31, 2019 and 2018. Common Stock Warrant In connection with the issuance of Series A in August 2015, the Company issued a warrant to purchase an aggregate of 62,936 shares of common stock at $0.0001 per share. The warrant was immediately exercisable and expires, if not exercised, in August 2025. At issuance, the fair value of the warrant was determined to be $41,509, which was recorded as a Series A preferred stock issuance cost and additional paid-in capital. The warrant was exercised in full during the year ended December 31, 2019 and the Company issued 62,936 shares of Class A common stock upon such exercise.

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2019
Equity Incentive Plans
Equity Incentive Plans	10. Equity Incentive Plans 2019 Equity Incentive Plan The Company’s board of directors adopted and our stockholders approved our 2019 Equity Incentive Plan, (the “2019 Plan”), on June 2, 2019, and June 7, 2019, respectively. The 2019 Plan became effective on June 19, 2019, and no further grants will be made under the Company’s 2010 Equity Incentive Plan. The purpose of the 2019 Plan, through the grant of stock awards including stock options and other stock-based awards, including restricted stock units (“RSUs”) , is to help us secure and retain the services of eligible award recipients, provide incentives for such persons to exert maximum efforts for our success and that of our affiliates, and provide a means by which the eligible recipients may benefit from increases in the value of our Class A common stock. Under the 2019 Plan, 6,141,842 shares of the Company’s Class A common stock have been reserved for issuance to employees, directors and consultants. Additionally, the number of shares of our Class A common stock reserved for issuance under our 2019 Plan will automatically increase on January 1 of each year, beginning on January 1, 2020 and continuing through and including January 1, 2029, by 4% of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by our board of directors. Stock option activity under the Plan is as follow (in thousands, except share and per share data and years): Options Outstanding Weighted- Average Aggregate Weighted- Remaining Intrinsic Number Average Contractual Value of Shares Exercise Price Life (years) (in thousands) Balances, December 31, 2017 567,319 $ 3.96 $ 694 Granted 1,609,086 6.66 Exercised (27,832) 1.68 Cancelled (12,282) 4.92 Balances, December 31, 2018 2,136,291 $ 6.06 $ 12,881 Granted 1,764,713 13.63 Exercised (77,368) 3.94 Cancelled (81,492) 9.80 Balances, December 31, 2019 3,742,144 $ 9.58 $ 22,910 Vested and expected to vest at December 31, 2019 3,742,144 $ 9.58 $ 22,910 Exercisable at December 31, 2019 1,793,254 $ 5.87 $ 17,211 Vested at December 31, 2019 1,168,118 $ 6.27 $ 10,747 Additional information regarding the Company’s stock options outstanding and vested and exercisable as of December 31, 2019 is summarized below: Options Outstanding Options Exercisable Weighted- Average Weighted- Remaining Weighted- Average Number of Contractual Average Shares Subject Exercise Stock Options Life Exercise Price to Stock Price per Exercise Prices Outstanding (Years) per Share Options Share Up to $0.66 48,984 2.9 $ 0.17 48,984 $ 0.17 $4.56-$5.16 1,474,367 7.7 $ 5.00 1,450,561 $ 5.00 $9.94-$12.95 1,720,981 9.1 $ 11.56 293,709 $ 11.13 $16.10-$22.06 497,812 9.5 $ 17.18 — — 3,742,144 8.6 $ 9.58 1,793,254 $ 5.87 The weighted‑average grant date fair value of options granted to employees and non‑employees in the year ended December 31, 2019 and 2018 was $10.35 and $5.16, respectively. The fair value of each option is estimated on the date of grant using the Black‑Scholes option pricing model, assuming no expected dividends and the following weighted average assumptions: Year Ended December 31, 2019 2018 Expected life (in years) 6.02 6.01 Volatility 81.0 % 78.3 % Risk-free interest rate 2.16 % 2.88 % Expected volatility is based on volatilities of public companies operating in the Company’s industry. The expected life of the options is estimated using the simplified method detailed in SEC Staff Accounting Bulletin No. 107. The simplified method calculates the expected term as the mid-point between the weighted-average time to vesting and the contractual maturity. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant. The Company has elected to account for forfeitures as they occur, rather than estimate expected forfeitures. 2019 Employee Stock Purchase Plan The Company’s board of directors adopted the 2019 Employee Stock Purchase Plan, (“ESPP”), on June 2, 2019, and the Company’s stockholders approved the ESPP on June 7, 2019. The ESPP became effective on June 19, 2019. The Company’s board of directors authorized 283,333 shares of Class A common stock to be reserved for future issuance under the ESPP. The number of shares of our Class A common stock reserved for issuance will automatically increase on January 1 of each calendar year, from January 1, 2020 through January 1, 2029, by the lesser of (1) 1% of the total number of shares of our Class A common stock outstanding on December 31 of the preceding calendar year, and (2) 416,666 shares; provided, that prior to the date of any such increase, the Company’s board of directors may determine that such increase will be less than the amount set forth in clauses (1) and (2). During the year ended December 31, 2019, the expense related to the ESPP was $348,000. The fair value of each ESPP is estimated on the date of grant using the Black‑Scholes option pricing model, assuming no expected dividends and the following range of assumptions: Year Ended December 31, 2019 2018 Expected life (in years) 0.2 - 2.0 — Volatility 74.5 - 101.6 % — % Risk-free interest rate 1.50 - 2.15 % — % The Company recognized $6.1 million and $1.4 million of stock‑based compensation expense related to options and the ESPP granted to employees and non‑employees for the years ended December 31, 2019 and 2018, respectively. The compensation expense is allocated on a departmental basis, based on the classification of the option holder as follows (in thousands): Year Ended December 31, 2019 2018 Research and development $ 2,977 $ 631 General and administrative 3,079 788 $ 6,056 $ 1,419 No income tax benefits have been recognized in the statements of operations for stock‑based compensation arrangements and no stock‑based compensation costs have been capitalized as property and equipment as of December 31, 2019. Unrecognized estimated compensation expense as of December 31, 2019, totaled $20.0 million related to non‑vested stock options with a remaining requisite service period of 3.1 years.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2019
Net Loss Per Share
401 (k) Plan	11. 401(k) Plan The Company has a 401(k) plan that qualifies as a deferred compensation arrangement under Section 401 of the Internal Revenue Code of 1986, as amended, or the Code. Eligible employees may elect to defer a portion of their pretax earnings subject to certain statutory limits. The Company has not made any matching contributions to date.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Net Loss Per Share
Net Loss Per Share	12. Net Loss Per Share The Company calculates basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities. The Company considered all series of redeemable convertible preferred stock to have been participating securities as the holders were entitled to receive non-cumulative dividends on a pari passu basis in the event a dividend was paid on common stock. Under the two-class method, the net loss attributable to common stockholders is not allocated to the redeemable convertible preferred stock as the holders of redeemable convertible preferred stock do not have a contractual obligation to share in losses. Under the two-class method, basic net loss per share attributable to common stockholders is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less shares subject to repurchase. Diluted net loss per share attributable to common stockholders is computed by giving effect to all potentially dilutive common stock equivalents outstanding for the period. For purposes of this calculation, redeemable convertible preferred stock, stock options to purchase common stock, early exercised stock options, and warrants to purchase redeemable convertible preferred stock and common stock are considered common shares equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive. Basic and diluted net loss per share was the same for each period presented, as the inclusion of all potential common shares outstanding would have been antidilutive. The rights, including the liquidation and dividend rights, of the holders of Class A and Class B common stock are identical, except with respect to voting. As the liquidation and dividend rights are identical, the undistributed earnings are allocated on a proportionate basis and the resulting net loss per share attributed to common stockholders will, therefore, be the same for both Class A and Class B common stock on an individual or combined basis. The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2019 2018 Numerator: Net loss attributable to common stockholders for earnings per share, basic and diluted $ 67,484 $ 37,940 Denominator: Shares used to compute net loss per share, basic and diluted 15,834,175 2,104,861 Basic and diluted net loss attributable to common stockholders per share $ 4.26 $ 18.02 The following outstanding potentially dilutive common shares were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because the impact of including them would have been antidilutive: Year Ended December 31, 2019 2018 Convertible preferred stock (as converted) — 17,248,259 Common stock options 3,742,144 2,136,291 Common stock warrants 49,997 62,936 Convertible preferred stock warrants — 49,997 Early exercised stock options 913 — 3,793,054 19,497,483

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Taxes
Income Taxes	13. Income Taxes For the years ended December 31, 2019, and 2018, the Company recorded income tax provision related to state minimum taxes due. A reconciliation of the federal statutory income tax rate and the Company's effective income tax rate is as follows: December 31, 2019 2018 Tax computed at federal statutory rate % % State income taxes, net of federal benefit % % Other % % Tax reform rate change % % Change in valuation allowance % % Credits % Effective income tax rate % % Deferred income taxes result from the tax effect of transactions that are recognized in different periods for financial statement and income tax reporting purposes, as well as operating loss and tax credit carryforwards. Significant components of the Company's deferred income tax assets and liabilities are as follows (in thousands): As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforward $ 34,529 $ 18,636 Tax credits 7,459 4,121 Intangibles 1,914 1,554 Other 1,379 366 Total deferred tax assets 45,281 24,677 Deferred tax liabilities: Fixed assets 233 133 Total deferred tax liabilities 233 133 Valuation allowance (45,048) (24,544) Total $ — $ — The Company uses the "more likely than not" criterion for recognizing the income tax benefit of uncertain income tax positions and establishing measurement criteria for income tax benefits. The Company has evaluated the impact of these positions and has reserved an unrecognized tax benefit of $2.6 million and $1.4 million as of December 31, 2019 and 2018, respectively. The following table summarizes the changes in the Company’s unrecognized tax benefits during the periods presented (in thousands): As of December 31, 2019 2018 Beginning of period $ 1,396 $ 915 Current period tax position increases 1,097 457 Prior period tax position increases 90 24 End of period 2,583 1,396 The increase in the unrecognized tax benefit in 2019 is primarily additions based on tax positions related to 2019. In the event the Company should need to recognize interest and penalties related to unrecognized income tax liabilities, this amount will be recorded as an accrued liability and an increase to income tax expense. No amounts of interest or penalties were recognized in the Company's consolidated financial statements for 2019 or 2018. The Company is not currently under examination by income tax authorities in federal, state or other foreign jurisdictions. The Company does not anticipate any significant changes within 12 months of this reporting date of its uncertain tax positions. The net increase in the valuation allowance was $20.5 million and $9.2 million in 2019 and 2018, respectively. At December 31, 2019, the Company has federal and state net operating loss carryforwards of $46.5 million and $46.2 million, respectively, which begin to expire in 2030 and $98.5 million of federal net operating loss carryforwards which do not expire but are subject to the 80% taxable income limitation. Additionally, the Company had federal tax credits totaling $5.7 million and $3.2 million at December 31, 2019 and 2018, respectively, and state tax credits totaling $5.3 million and $2.9 million, at December 31, 2019 and 2018, respectively. The federal tax credits begin to expire in 2032. The state tax credits may be carried forward indefinitely. Section 382 of the Internal Revenue Code of 1986, as amended, limits the use of net operating losses and income tax credit carryforwards in certain situations where changes occur in stock ownership of a company. If the Company should have an ownership change of more than 50% of the value of the Company's capital stock, utilization of the carryforwards could be restricted. The Company files income tax returns in the U.S. federal jurisdiction, various state jurisdictions and Singapore. The U.S. federal and state tax years from 2010 to 2019 remain open to examination due to the carryover of unused net operating loss carryforwards and tax credits. In January 2018, the FASB released guidance on the accounting for tax on the global intangible low-taxed income (GILTI) provisions of the 2017 Tax Act. The GILTI provisions subject certain U.S. entities to current tax on GILTI earned by certain foreign subsidiaries. The Company has considered these new provisions as they are effective for tax years starting after December 31, 2017 and determined that none will likely apply for the year ended December 31, 2019 and 2018.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions
Related Party Transactions	1 The Company recorded other income of $611,000 and $892,000 for the years ended December 31, 2019, and 2018, respectively, under service contracts with a stockholder. The Company had a receivable from the stockholder as of December 31, 2019, and 2018 of $121,000 and $89,000, respectively. The Company recorded expense of $1.4 million and $1.1 million for the years ended December 31, 2019, and 2018, respectively, related to intellectual property and other legal services performed by a related party. The Company owed $69,000 and $134,000 to the related party at December 31, 2019, and 2018, respectively. The Company recorded expense of $2.7 million and $0.5 million for the years ended December 31, 2019, and 2018, respectively, related to legal services performed by a related party. The Company owed $186,000 and $40,000 to the related party at December 31, 2019, and 2018, respectively. The Company recorded research and development expenses of $400,000 for each of the years ended December 31, 2019, and 2018, respectively, under consulting agreements with two members of the Company’s board of directors. On August 22, 2019, one of the two members provided the Company with notice of his resignation from the Company’s Board of Directors. The Company owed $73,000 and zero to the member of the Company’s board of directors as of December 31, 2019, and 2018, respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events
Subsequent Events	15. Subsequent Events The Company has evaluated subsequent events that may require adjustments to or disclosure in the consolidated financial statements through March 11, 2020, the date on which the consolidated financial statements were available to be issued. In February, the Company entered into a research collaboration agreement with Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc. (“Merck”), to identify the antigenic targets of select antibodies discovered by Atreca with potential utility in oncology. Under the terms of the agreement, Atreca received a nominal upfront cash payment and following target identification, both companies will have freedom to advance therapeutic candidates against the targets identified under the collaboration, with development and commercial milestones payable by either party.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Principles of Consolidation	Basis of Presentation The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany transactions and accounts have been eliminated. Prior period reclassification An immaterial reclassification of prior period amounts has been made to conform to the current period presentation. Principles of Consolidation The consolidated financial statements include accounts of the Company and its wholly owned subsidiary. All significant intercompany accounts and transactions are eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and reported amounts of income and expenses in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Key estimates in the consolidated financial statements include estimated useful lives of property and equipment, impairment of long-lived assets, accrued expenses, valuation of deferred income tax assets, the fair value of warrants issued to purchasers of shares of preferred stock and common stock and fair value of options granted under the Company's stock option plan.
Other Income	Other Income Other income is comprised of amounts earned from services performed under service agreements. Beginning January 1, 2018, the Company follows the provisions of Accounting Standards Update 2014-09 Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“Topic 606”). The guidance provides a unified model to determine how income is recognized. In determining the appropriate amount of other income to be recognized as it fulfills its obligations under the agreements, the Company performs the following steps: (i) identifies the promised goods or services in the contract; (ii) determines whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measures the transaction price, including the constraint on variable consideration; (iv) allocates the transaction price to the performance obligations based on estimated selling prices; and (v) recognizes other income when (or as) the Company satisfies each performance obligation. Upon adoption of Topic 606, there was no change to the units of accounting previously identified with respect to existing service agreements under legacy Generally Accepted Accounting Principles (“GAAP”), which are now considered performance obligations under Topic 606, and there was no change to the revenue recognition pattern for the performance obligations. Accordingly, the adoption of the new standard resulted in no cumulative effect change to the Company's opening accumulated deficit balance. The Company generally allocates the transaction price to distinct performance obligations at their stand-alone selling prices, determined by their estimated costs plus some margin. Performance obligations are generally delivered over time and recognized based upon observable inputs as the related research services are performed, which are recorded as research and development expenses. Amounts due under service agreements are generally billed monthly as services are delivered and do not generally result in contract liabilities or assets. Receivables under service agreements of $237,000 and $282,000 are included in prepaid expenses and other current assets as of December 31, 2019 and 2018, respectively. Contract liabilities of zero and $200,000 are included in other current liabilities as of December 31, 2019 and 2018, respectively.
Collaboration and Service Arrangements	Collaboration and Service Arrangements In March 2016, the Company entered into a research collaboration agreement with Genome Institute of Singapore (GIS) for the development of a high-throughput microfluidic droplet system for single cell phenotyping and genotyping. Under the agreement, the Company contributes reimbursement of research expenses and certain reagents and other consumables to GIS. The Company accounts for the collaboration agreement with GIS in accordance with ASC 808—Collaborative Arrangements. The Company recognized $36,000 and $522,000 of research and development expenses in 2019 and 2018, respectively, under the collaboration agreement, including wind-down costs. The Company exercised its right to early terminate the collaboration agreement in December 2018.
Fair Value of Financial Instruments	Fair Value of Financial Instruments: The Company uses a three-level hierarchy, which prioritizes, within the measurement of fair value, the use of market-based information over entity-specific information for fair value measurements based on the nature of inputs used in the valuation of an asset or liability as of the measurement date. Fair value focuses on an exit price and is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The inputs or methodology used for valuing financial instruments are not necessarily an indication of the risk associated with those financial instruments. The three-level hierarchy for fair value measurements is defined as follows: Level 1: Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2: Level 3: An asset or liability's categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents include all cash balances and highly liquid investments purchased with an original maturity of three months or less. The Company maintained restricted cash of $1.3 million and zero as of December 31, 2019 and 2018, respectively. This amount as of December 31, 2019 is included in deposits and other in the accompanying consolidated balance sheets and is comprised solely of letters of credit required pursuant to leases for Company facilities.
Investments	Investments The Company considers securities purchased with original maturities greater than three months to be investments. The Company’s policy is to protect the value of its investment portfolio and minimize principal risk by earning returns based on current interest rates. The Company’s intent is to convert all investments into cash to be used for operations and has classified them as available for sale. For purposes of determining realized gains and losses, the cost of securities sold is based on specific identification. Interest and dividends on securities classified as available-for-sale are included in interest income. Convertible Preferred Stock Warrants The Company issued convertible preferred stock warrants, which were exercisable into Series A preferred stock with liquidation preference. The conversion feature was evaluated under ASC Topic 480, Distinguishing liabilities from equity and the warrants were determined to be debt instruments and classified prior to the IPO as liabilities on the consolidated balance sheets. The Company recorded these warrant liabilities at fair value and adjusted the carrying value to their estimated fair value at each reporting date with the increases or decreases in the fair value recorded as a gain (loss) on revaluation of the warrant liability in the consolidated statements of operations. Upon the IPO, t he 49,997 preferred stock warrants were converted to common stock warrants of Class A shares and the warrant liability of $0.5 million was reclassified to additional paid-in capital as a result of the conversion. The warrants were not subject to further remeasurement for fair value.
Risks and Uncertainties	Risks and Uncertainties The Company is subject to a number of risks associated with companies at a similar stage, including dependence on key individuals, competition from similar services and larger companies, volatility of the industry, ability to obtain regulatory clearance, ability to obtain adequate financing to support growth, the ability to attract and retain additional qualified personnel to manage the anticipated growth of the Company and general economic conditions.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents, investments and other receivables. Cash and cash equivalents are held at three financial institution and were in excess of the Federal Deposit Insurance Corporation insurable limit at December 31, 2019, and 2018. Additionally, cash and cash equivalents and investments are maintained at a brokerage firm for which amounts are insured by the Securities Investor Protection Corporation subject to legal limits. The Company has not experienced any losses on its deposits to date. The Company does not require collateral or other security for other receivables; however, credit risk is mitigated by the Company’s ongoing evaluations of its debtors’ credit worthiness.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less depreciation. Depreciation is computed using the straight-line method with the estimated useful lives of the assets ranging from two to five years. Leasehold improvements are amortized over the estimated useful life of the asset, or the remaining lease term, whichever is shorter. Expenditures for repairs and maintenance, which do not extend the useful life of the property and equipment, are expensed as incurred.
Accounting for Impairment of Long-Lived Assets	Accounting for Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset may not be recoverable. Recoverability of assets held and used is measured by comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. The Company has not recorded any impairment of long-lived assets in 2019 or 2018.
Intellectual Property	Intellectual Property The legal and professional costs incurred by the Company to maintain its patent rights have been expensed as part of research and development costs since inception. As of December 31, 2019, and 2018, the Company has determined that these expenses have not met the criteria to be capitalized. Intellectual property-related expenses for the years ended December 31, 2019 and 2018 were $1.3 million and $1.1 million, respectively.
Deferred Rent	Deferred Rent The Company has entered into lease agreements for its laboratory and office facilities. These leases qualify as and are accounted for as operating leases. Rent expense is recognized on a straight-line basis over the term of the lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development costs consist primarily of salaries and benefits, consultant fees, stock-based compensation, certain facility costs, legal costs and other costs associated with preclinical development. A substantial portion of the Company’s ongoing research and development activities are conducted by third-party service providers in connection with preclinical development activities and contract manufacturing organizations in connection with the production of materials for clinical trials. At the end of the reporting period, the Company compares payments made to third-party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs.
Stock Based Compensation	Stock‑Based Compensation The Company generally grants stock options to its employees for a fixed number of shares with an exercise price equal to the fair value of the underlying shares at the date of grant. The Company accounts for stock option grants using the fair value method. The fair value of options is calculated using the Black‑Scholes option pricing model. Stock‑based compensation is recognized as the underlying options vest using the straight‑line attribution approach, and forfeitures are recorded as they occur.
Emerging Growth Company Status	Emerging Growth Company Status The Company is an “emerging growth company,” (“EGC”) as defined in the Jumpstart Our Business Startups Act, (“JOBS Act”), and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. The Company may take advantage of these exemptions until it is no longer an EGC under Section 107 of the JOBS Act, which provides that an EGC can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards, and as a result of this election, the Company’s consolidated financial statements may not be comparable to companies that comply with public company Financial Accounting Standards Board (“FASB”) standards’ effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of the IPO or such earlier time that the Company is no longer an EGC.
Income Taxes	Income Taxes The Company applies the provisions set forth in FASB ASC Topic 740, Income Taxes, to account for the uncertainty in income taxes. In the preparation of income tax returns in federal, foreign and state jurisdictions, the Company asserts certain income tax positions based on its understanding and interpretation of income tax laws. The taxing authorities may challenge such positions, and the resolution of such matters could result in recognition of income tax expense in the Company's consolidated financial statements. Management believes it has used reasonable judgments and conclusions in the preparation of its income tax returns. The Company accounts for income taxes using the asset and liability method. Under this method, deferred income tax assets and liabilities are recorded based on the estimated future tax effects of differences between the financial statement and income tax basis of existing assets and liabilities. A valuation allowance is provided against the Company's deferred income tax assets when realization is not reasonably assured.
Net Loss Per Share	Net Loss Per Share The Company computes basic loss per share by dividing the net loss available to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss assumes the conversion, exercise or issuance of all potential common stock equivalents, unless the effect of inclusion would be anti-dilutive. For purposes of this calculation, common stock equivalents include the Company's stock options, common stock warrants, convertible preferred stock warrants and convertible preferred stock, which are convertible into shares of the Company's common stock. No shares related to the convertible preferred stock were included in the diluted net loss calculation for the years ended December 31, 2019 or 2018 because the inclusion of such shares would have had an anti-dilutive effect. The shares to be issued upon exercise of certain outstanding stock options were also excluded from the diluted net loss calculation for the years ended December 31, 2019 and 2018 because such shares are anti-dilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016‑02 and subsequent amendments to the initial guidance under ASU 2017-13, ASU 2018-10, ASU 2018-11, and ASU 2019-01 (collectively, “Topic 842” ), which modifies the accounting by lessees for all leases with a term greater than 12 months. This standard will require lessees to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Topic 842 is effective for the Company as of January 1, 2021. Early adoption is permitted. The Company’s most significant lease is its operating lease for its corporate headquarters, and, while the Company has not yet estimated the amounts by which its financial statements will be affected by the adoption of this guidance, it expects that the overall recognition of expense will be similar to current guidance, but that there will be a significant change in the balance sheet due to the recognition of right of use assets and the corresponding lease liabilities. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses ( “Topic 326” ): Measurement of Credit Losses on Financial Instruments and subsequent amendments to the initial guidance under ASU 2018-19, ASU 2019-04 and ASU 2019-05, which amends the current approach to estimate credit losses on certain financial assets, including trade and other receivables. The amendment replaces the existing incurred loss impairment model with an expected loss methodology, which will result in more timely recognition of credit losses. For available-for-sale debt securities, credit losses should be recorded through an allowance for credit losses. Topic 326 is effective for the Company as of January 1, 2023. Early adoption is permitted. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures. In August 2016, the FASB issued ASU 2016‑15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments ( “Topic 230” ). The standard clarifies how certain cash receipts and cash payments will be presented and classified in the statement of cash flows. Topic 230 is effective for the Company as of January 1, 2019. The adoption of this update had no material effect on the Company’s consolidated financial statements

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Schedule of reconciliation of cash and cash equivalents and restricted cash	December 31, 2019 2018 Cash and cash equivalents $ 157,954 $ 114,504 Restricted cash 1,282 — Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows $ 159,236 $ 114,504

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value of Financial Instruments
Summary of financial assets and liabilities subject to fair value measurements on a recurring basis	December 31, 2019 Level 1 Level 2 Level 3 Total Assets Money market funds $ 152,770 $ — $ — $ 152,770 Certificates of deposit 1,950 — — 1,950 Corporate debt securities — — 3,459 U.S. Treasury securities 20,052 — — 20,052 $ 174,772 $ 3,459 $ — $ 178,231 December 31, 2018 Level 1 Level 2 Level 3 Total Assets Money market funds $ 109,630 $ — $ — $ 109,630 Total $ 109,630 $ — $ — $ 109,630 Liabilities Warrant liability $ — $ — $ $ Total $ — $ — $ $
Summary of fair value of the warrants were calculated using the Black-Scholes option pricing model	December 31, 2018 Exercise price (1) $ 14.46 Stock price (2) $ 13.20 Time to maturity (in years) 3.64 Volatility (3) 83.7 % Risk-free interest rate (4) 2.50 % Expected dividend $ — (1) Based upon terms provided in the warrant agreement. (2) Based upon an independently prepared valuation as of December 31, 2018, adjusted for the one-for-six reverse stock split . (3) Based upon the historical daily volatility of a group of peer public company closing prices. (4) Based upon interest rate for U.S. Treasury Bonds, as published by the U.S. Federal Reserve.

Cash, Cash Equivalents and In_2

Cash, Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Cash, Cash Equivalents and Investments
Summary of fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type	The fair value and the amortized cost of cash, cash equivalents and available-for-sale investments by major security type consist of the following (in thousands): As of December 31, 2019 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cash and cash equivalents and investments Cost Gains Losses Value Cash, cash equivalents and money market funds $ 157,954 $ — $ — $ 157,954 U.S. Treasury securities 20,037 16 — 20,053 Corporate debt securities 3,459 — — 3,459 Certificates of deposit 1,950 — — 1,950 Total 183,400 16 — 183,416 Less amounts classified as cash and cash equivalents (157,954) — — (157,954) Total available-for-sale investments $ 25,446 $ 16 $ — $ 25,462 As of December 31, 2018 Gross Gross Estimated Amortized Unrealized Unrealized Fair Cash and cash equivalents and investments Cost Gains Losses Value Cash, cash equivalents and money market funds $ 114,504 $ — $ — $ 114,504 Total 114,504 — — 114,504 Less amounts classified as cash and cash equivalents (114,504) — — (114,504) Total available-for-sale investments $ — $ — $ — $ —

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Prepaid Expenses and Other Current Assets
Summary of Prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2019 2018 Prepaid insurance $ 1,265 $ 36 Vendor prepayments and deposits 963 2,009 Prepaid rent 879 394 Non-trade receivables 242 282 Interest receivables and other current assets 153 — Total prepaid expenses and other current assets $ 3,502 $ 2,721

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2019
Property and Equipment, net
Summary of property and equipment	Property and equipment consists of the following (in thousands): December 31, 2019 2018 Laboratory equipment $ 9,355 $ 7,561 Furniture and fixtures 225 386 Computer hardware and software 785 580 Leasehold improvements 765 236 11,130 8,763 Less accumulated depreciation and amortization (5,359) (4,620) Total property and equipment, net $ 5,771 $ 4,143

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Summary of accrued expenses	Accrued expenses consist of the following (in thousands): December 31, 2019 2018 Compensation and related benefits $ 4,435 $ 2,568 Professional fees 214 183 Contract research fees 563 43 Other 183 214 Total accrued expenses $ 5,395 $ 3,008

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Schedule of future minimum lease payments under non-cancelable operating and capital lease agreements	Future minimum lease payments under non-cancelable operating and capital lease agreements consisted of the following at December 31, 2019 (in thousands): Capital Operating Leases Leases Years ending December 31: 2020 51 5,622 2021 51 6,697 2022 4 7,336 2023 — 7,037 2024 — 7,249 Thereafter — 69,091 Total minimum lease payments 106 $ 103,032 Less: amount representing interest (6) Present value of capital lease obligation 100 Less: current portion (47) Non-current portion $ 53

Equity Incentive Plan (Tables)

Equity Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	Stock option activity under the Plan is as follow (in thousands, except share and per share data and years): Options Outstanding Weighted- Average Aggregate Weighted- Remaining Intrinsic Number Average Contractual Value of Shares Exercise Price Life (years) (in thousands) Balances, December 31, 2017 567,319 $ 3.96 $ 694 Granted 1,609,086 6.66 Exercised (27,832) 1.68 Cancelled (12,282) 4.92 Balances, December 31, 2018 2,136,291 $ 6.06 $ 12,881 Granted 1,764,713 13.63 Exercised (77,368) 3.94 Cancelled (81,492) 9.80 Balances, December 31, 2019 3,742,144 $ 9.58 $ 22,910 Vested and expected to vest at December 31, 2019 3,742,144 $ 9.58 $ 22,910 Exercisable at December 31, 2019 1,793,254 $ 5.87 $ 17,211 Vested at December 31, 2019 1,168,118 $ 6.27 $ 10,747
Schedule of Share-based Payment Arrangement, Option, Exercise Price Range	Options Outstanding Options Exercisable Weighted- Average Weighted- Remaining Weighted- Average Number of Contractual Average Shares Subject Exercise Stock Options Life Exercise Price to Stock Price per Exercise Prices Outstanding (Years) per Share Options Share Up to $0.66 48,984 2.9 $ 0.17 48,984 $ 0.17 $4.56-$5.16 1,474,367 7.7 $ 5.00 1,450,561 $ 5.00 $9.94-$12.95 1,720,981 9.1 $ 11.56 293,709 $ 11.13 $16.10-$22.06 497,812 9.5 $ 17.18 — — 3,742,144 8.6 $ 9.58 1,793,254 $ 5.87
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	Year Ended December 31, 2019 2018 Expected life (in years) 6.02 6.01 Volatility 81.0 % 78.3 % Risk-free interest rate 2.16 % 2.88 %
Schedule of stock-based compensation expense	The compensation expense is allocated on a departmental basis, based on the classification of the option holder as follows (in thousands): Year Ended December 31, 2019 2018 Research and development $ 2,977 $ 631 General and administrative 3,079 788 $ 6,056 $ 1,419
2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	Year Ended December 31, 2019 2018 Expected life (in years) 0.2 - 2.0 — Volatility 74.5 - 101.6 % — % Risk-free interest rate 1.50 - 2.15 % — %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Net Loss Per Share
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, 2019 2018 Numerator: Net loss attributable to common stockholders for earnings per share, basic and diluted $ 67,484 $ 37,940 Denominator: Shares used to compute net loss per share, basic and diluted 15,834,175 2,104,861 Basic and diluted net loss attributable to common stockholders per share $ 4.26 $ 18.02
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Year Ended December 31, 2019 2018 Convertible preferred stock (as converted) — 17,248,259 Common stock options 3,742,144 2,136,291 Common stock warrants 49,997 62,936 Convertible preferred stock warrants — 49,997 Early exercised stock options 913 — 3,793,054 19,497,483

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Taxes
Schedule of Effective Income Tax Rate Reconciliation	December 31, 2019 2018 Tax computed at federal statutory rate % % State income taxes, net of federal benefit % % Other % % Tax reform rate change % % Change in valuation allowance % % Credits % Effective income tax rate % %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company's deferred income tax assets and liabilities are as follows (in thousands): As of December 31, 2019 2018 Deferred tax assets: Net operating loss carryforward $ 34,529 $ 18,636 Tax credits 7,459 4,121 Intangibles 1,914 1,554 Other 1,379 366 Total deferred tax assets 45,281 24,677 Deferred tax liabilities: Fixed assets 233 133 Total deferred tax liabilities 233 133 Valuation allowance (45,048) (24,544) Total $ — $ —
Schedule of Unrecognized Tax Benefits Roll Forward	The following table summarizes the changes in the Company’s unrecognized tax benefits during the periods presented (in thousands): As of December 31, 2019 2018 Beginning of period $ 1,396 $ 915 Current period tax position increases 1,097 457 Prior period tax position increases 90 24 End of period 2,583 1,396

Business (Details)

Business (Details) $ / shares in Units, $ in Thousands	Jun. 07, 2019	Jun. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018
Business
Reverse stock split	0.167			0.167
Proceeds from Issuance Initial Public Offering | $			$ 133,633
Underwriting discounts and commissions | $		$ 10,100
Offering expenses | $		2,800
Warrants to purchase (in shares) | shares			49,997
Conversion of redeemable convertible preferred stock to common stock | $		209,700	$ 209,668
Deferred offering cost | $		$ 2,800
Payment of deferred offering cost | $			$ 2,848
IPO
Business
Offering price | $ / shares		$ 17
Proceeds from Issuance Initial Public Offering | $		$ 130,800
Class A common stock
Business
Number of shares issued up on conversion | shares		13,314,068
Warrants to purchase (in shares) | shares		62,936
Class A common stock | IPO
Business
Shares issued | shares		6,452,500
Class A common stock | Underwriters option
Business
Shares issued | shares		1,102,500
Class B common stock
Business
Number of shares issued up on conversion | shares		3,934,191
Class B common stock | IPO
Business
Shares issued | shares		2,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents and restricted cash reported within the condensed balance sheets
Cash and cash equivalents	$ 157,954,000	$ 114,504,000
Restricted cash	1,282,000	0
Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows	$ 159,236,000	114,504,000	$ 8,242,000
Convertible Preferred Stock Warrants
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 503,000
Prepaid expenses and other current assets
Other Income
Receivables under service agreements	237,000	282,000
Other current liabilities
Other Income
Contract liabilities	$ 0	$ 200,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Collaboration and Service Arrangements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and Development Expense	$ 54,726,000	$ 32,513,000
Research collaboration agreement | Genome Institute Of Singapore
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and Development Expense	$ 36,000	$ 522,000

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Minimum
Property and Equipment
Estimated useful lives	2 years
Maximum
Property and Equipment
Estimated useful lives	5 years

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Intellectual Property (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies
Intellectual property-related expenses	$ 1.3	$ 1.1

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Anti-dilutive securities not included in diluted net loss per share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	3,793,054	19,497,483
Convertible preferred stock (as converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation		17,248,259

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Financial assets and liabilities (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Total assets	$ 178,231	$ 109,630
Liabilities
Total liabilities		380
Common stock warrants
Liabilities
Total liabilities		380
Cash, cash equivalents and money market funds
Assets
Total assets	152,770	109,630
Certificates of Deposit
Assets
Total assets	1,950
Corporate Debt Securities
Assets
Total assets	3,459
U.S. Treasury securities
Assets
Total assets	20,052
Level 1
Assets
Total assets	174,772	109,630
Level 1 | Cash, cash equivalents and money market funds
Assets
Total assets	152,770	109,630
Level 1 | Certificates of Deposit
Assets
Total assets	1,950
Level 1 | U.S. Treasury securities
Assets
Total assets	20,052
Level 2
Assets
Total assets	3,459
Level 2 | Corporate Debt Securities
Assets
Total assets	$ 3,459
Level 3
Liabilities
Total liabilities		380
Level 3 | Common stock warrants
Liabilities
Total liabilities		$ 380

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Fair value of the warrants (Details) $ in Thousands	Jun. 07, 2019	Dec. 31, 2019USD ($)shares	Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Reverse stock split	0.167		0.167
Warrant liability, measurement input		17
Warrants to purchase (in shares) | shares		49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital | $		$ 503
Expected life		3 years 2 months 1 day	3 years 7 months 21 days
Exercise price (1)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input			14.46
Stock price (2)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input			13.20
Volatility (3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		83.61	83.7
Risk-free interest rate (4)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		1.69	2.50
Expected dividend
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0

Cash, Cash Equivalents and In_3

Cash, Cash Equivalents and Investments - Fair value and Amortized cost (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 157,954	$ 114,504
Cash, cash equivalents and money market funds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	157,954	114,504
Estimated Fair Value	157,954	114,504
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	20,037
Gross Unrealized Gains	16
Estimated Fair Value	20,053
Corporate Debt Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	3,459
Estimated Fair Value	3,459
Certificates of Deposit
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,950
Estimated Fair Value	1,950
Total
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	183,400	114,504
Gross Unrealized Gains	16
Estimated Fair Value	183,416	114,504
Less amounts classified as cash and cash equivalents
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	157,954	114,504
Estimated Fair Value	157,954	$ 114,504
Total available-for-sale investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	25,446
Gross Unrealized Gains	16
Estimated Fair Value	$ 25,462

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Prepaid Expenses and Other Current Assets
Prepaid Insurance	$ 1,265	$ 36
Vendor prepayments and deposits	963	2,009
Prepaid rent	879	394
Non-trade receivables	242	282
Interest receivables and other current assets	153
Total prepaid expenses and other current assets	$ 3,502	$ 2,721

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment, Net, by Type [Abstract]
Property, Plant and Equipment, Gross	$ 11,130,000	$ 8,763,000
Less accumulated depreciation and amortization	(5,359,000)	(4,620,000)
Total property and equipment, net	5,771,000	4,143,000
Depreciation expense	1,700,000	1,400,000
Net book value of property and equipment under capital leases	94,000	142,000
Laboratory equipment
Property, Plant and Equipment, Net, by Type [Abstract]
Property, Plant and Equipment, Gross	9,355,000	7,561,000
Furniture and fixtures
Property, Plant and Equipment, Net, by Type [Abstract]
Property, Plant and Equipment, Gross	225,000	386,000
Computer hardware and software
Property, Plant and Equipment, Net, by Type [Abstract]
Property, Plant and Equipment, Gross	785,000	580,000
Leasehold improvements
Property, Plant and Equipment, Net, by Type [Abstract]
Property, Plant and Equipment, Gross	$ 765,000	$ 236,000

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Compensation and related benefits	$ 4,435	$ 2,568
Professional fees	214	183
Contract research fees	563	43
Other	183	214
Total accrued expenses	$ 5,395	$ 3,008

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating leases
Rent expenses	$ 4,534,000	$ 1,250,000
Capital lease
Purchases under capital lease			$ 226,000

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Future minimum capital leases:
2020	$ 51
2021	51
2022	4
Total minimum lease payments	106
Less: amount representing interest	(6)
Present value of capital lease obligation	100
Less: current portion	(47)
Non-current portion	53	$ 100
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2020	5,622
2021	6,697
2022	7,336
2023	7,037
2024	7,249
Thereafter	69,091
Total minimum lease payments	$ 103,032

Capital Stock - Class A and Cla

Capital Stock - Class A and Class B Common Stock (Details)	Jun. 02, 2019Vote$ / sharesshares	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock [Line Items]
Preferred Stock, Shares Authorized | shares	300,000,000
Preferred stock par value | $ / shares	$ 0.0001
Class A common stock
Class of Stock [Line Items]
Common stock, shares authorized | shares	650,000,000	650,000,000	191,398,492
Common stock, par value | $ / shares	$ 0.0001	$ 0.0001	$ 0.0001
Number of votes entitled per share | Vote	1
Class B common stock
Class of Stock [Line Items]
Common stock, shares authorized | shares	50,000,000	50,000,000	23,605,150
Common stock, par value | $ / shares	$ 0.0001	$ 0.0001	$ 0.0001

Capital Stock - Convertible Pre

Capital Stock - Convertible Preferred Stock Warrant (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 503
Preferred stock warrant liability		$ 380
Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)	49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital	$ 500
Preferred stock warrant liability	$ 0	$ 400

Capital Stock - Common Stock Wa

Capital Stock - Common Stock Warrants (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2015	Dec. 31, 2019	Jun. 30, 2019
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)		49,997
Class A common stock
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)			62,936
Common Stock Warrants | Class A common stock
Class of Warrant or Right [Line Items]
Exercise of warrants		62,936
Common Stock Warrants | Series A convertible preferred stock
Class of Warrant or Right [Line Items]
Warrants to purchase (in shares)	62,936
Price per share (in dollars per share)	$ 0.0001
Fair value of warrants	$ 41,509

Equity Incentive Plan - Narrati

Equity Incentive Plan - Narrative (Details) - 2019 Equity Incentive Plan	Jun. 19, 2019shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	6,141,842
Percentage of additional number of shares authorized annually	4.00%

Equity Incentive Plan - Stock o

Equity Incentive Plan - Stock option (Details) - 2019 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Balance at beginning of period (in shares)	2,136,291	567,319
Granted (in shares)	1,764,713	1,609,086
Exercised (in shares)	(77,368)	(27,832)
Cancelled (in shares)	(81,492)	(12,282)
Balance at end of period (in shares)	3,742,144	2,136,291	567,319
Vested and expected to vest at end of period (in shares)	3,742,144
Exercisable at end of period (in shares)	1,793,254
Vested at end of period (in shares)	1,168,118
Weighted-Average Exercise Price
Balance at beginning of period (in dollars per share)	$ 6.06	$ 3.96
Granted (in dollars per share)	13.63	6.66
Exercised (in dollars per share)	3.94	1.68
Cancelled (in dollars per share)	9.80	4.92
Balance at end of period (in dollars per share)	9.58	$ 6.06	$ 3.96
Vested and expected to vest at end of period (in dollars per share)	9.58
Exercisable at end of period (in dollars per share)	5.87
Vested at end of period (in dollars per share)	$ 6.27
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life	8 years 7 months 6 days	8 years 10 months 24 days	8 years 1 month 6 days
Vested and expected to vest at end of period (in years)	8 years 7 months 6 days
Exercisable at end of period (in years)	7 years 8 months 12 days
Vested at end of period (in years)	7 years 6 months
Aggregate Intrinsic Value
Balance at beginning of period	$ 12,881	$ 694
Balance at end of period	22,910	$ 12,881	$ 694
Vested and expected to vest at end of period	22,910
Exercisable at end of period	17,211
Vested at end of period	$ 10,747

Equity Incentive Plan - Additio

Equity Incentive Plan - Additional information regarding stock option (Details) - 2019 Equity Incentive Plan - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Number of Stock options outstanding	3,742,144	2,136,291	567,319
Shares subject to stock options	1,793,254
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share	$ 9.58	$ 6.06	$ 3.96
Options Exercisable, weighted-average exercise Price per share	$ 5.87
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding	8 years 7 months 6 days	8 years 10 months 24 days	8 years 1 month 6 days
Up to $0.66
Number of Shares
Number of Stock options outstanding	48,984
Shares subject to stock options	48,984
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share	$ 0.17
Options Exercisable, weighted-average exercise Price per share	$ 0.17
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding	2 years 10 months 24 days
$4.56-$5.16
Number of Shares
Number of Stock options outstanding	1,474,367
Shares subject to stock options	1,450,561
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share	$ 5
Options Exercisable, weighted-average exercise Price per share	$ 5
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding	7 years 8 months 12 days
$9.94-$12.95
Number of Shares
Number of Stock options outstanding	1,720,981
Shares subject to stock options	293,709
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share	$ 11.56
Options Exercisable, weighted-average exercise Price per share	$ 11.13
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding	9 years 1 month 6 days
$16.10-$22.06
Number of Shares
Number of Stock options outstanding	497,812
Weighted-Average Exercise Price
Options Outstanding, weighted-Average Exercise Price per share	$ 17.18
Weighted-Average Remaining Contractual Life
Weighted-Average Remaining Contractual Life of options outstanding	9 years 6 months

Equity Incentive Plan - Weighte

Equity Incentive Plan - Weighted-average grant date fair value (Details) - 2019 Equity Incentive Plan - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value (in dollars per share)	$ 10.35	$ 5.16
Expected dividend	0.00%	0.00%

Equity Incentive Plan - Weigh_2

Equity Incentive Plan - Weighted average assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	6 years 7 days	6 years 4 days
Volatility	81.00%	78.30%
Risk-free interest rate	2.16%	2.88%
2019 Employee Stock Purchase Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	2 months 12 days
Volatility	74.50%
Risk-free interest rate	1.50%
2019 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life (in years)	2 years
Volatility	101.60%
Risk-free interest rate	2.15%

Equity Incentive Plan - 2019 Em

Equity Incentive Plan - 2019 Employee Stock Purchase Plan (Details) - USD ($)	Jun. 19, 2019	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 6,056,000	$ 1,419,000
Class A common stock | 2019 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	283,333
Stock-based compensation expense		$ 348,000
Expected dividend		0.00%
Class A common stock | 2019 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of additional number of shares authorized annually	1.00%
Additional number of shares authorized annually	416,666

Equity Incentive Plan - Stock-b

Equity Incentive Plan - Stock-based compensation expense (Details) - 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]
Stock-based compensation expense	$ 6,056	$ 1,419
Income tax benefits for stock-based compensation	0
Stock-based compensation costs capitalized	0
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,977	631
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,079	$ 788

Equity Incentive Plan - Unrecog

Equity Incentive Plan - Unrecognized compensation (Details) - 2019 Equity Incentive Plan $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized estimated compensation expense	$ 20
Remaining requisite service period	3 years 1 month 6 days

Net Loss Per Share - Basic and

Net Loss Per Share - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss attributable to common stockholders for earnings per share, basic and diluted	$ 67,484	$ 37,940
Denominator:
Shares used to compute net loss per share, basic and diluted	15,834,175	2,104,861
Basic and diluted net loss attributable to common stockholders per share	$ 4.26	$ 18.02

Net Loss Per Share - Antidiluti

Net Loss Per Share - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	3,793,054	19,497,483
Convertible preferred stock (as converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation		17,248,259
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	3,742,144	2,136,291
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	49,997	62,936
Convertible preferred stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation		49,997
Early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in the diluted net loss per share calculation	913

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Unrecognized Tax Benefits	$ 2,583	$ 1,396	$ 915
Interest or penalties	0	0
Net increase in valuation allowance	20,500	9,200
Federal
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	46,500
Operating Loss Carryforwards, Not Subject to Expiration	$ 98,500
Percentage of taxable income limitation of net operating loss carryforwards	80.00%
Tax Credit Carryforward	$ 5,700	3,200
State
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	46,200
Tax Credit Carryforward	$ 5,300	$ 2,900

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the federal statutory income tax rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of the federal statutory income tax rate
Tax computed at federal statutory rate	21.00%	21.00%
State income taxes, net of federal benefit	8.30%	2.00%
Other	(1.00%)	(1.50%)
Tax reform rate change	0.00%	0.40%
Change in valuation allowance	(30.40%)	(24.20%)
Credits	2.10%	2.30%
Effective income tax rate	0.00%	0.00%

Income Taxes - Deferred income

Income Taxes - Deferred income tax assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforward	$ 34,529	$ 18,636
Tax credits	7,459	4,121
Intangibles	1,914	1,554
Other	1,379	366
Total deferred tax assets	45,281	24,677
Fixed assets	233	133
Total deferred tax liabilities	233	133
Valuation allowance	(45,048)	(24,544)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized benefit - beginning of period	1,396	915
Current period tax position increases	1,097	457
Prior period tax position increases	90	24
Unrecognized benefit - end of period	$ 2,583	$ 1,396

Related Party Transactions (Det

Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2019USD ($)director	Dec. 31, 2018USD ($)director	Aug. 22, 2019director
Related Party Transaction [Line Items]
Other income	$ 611,000	$ 892,000
Receivable from stockholders	121,000	89,000
Due to related party	73,000	0
Research and development expense	$ 400,000	$ 400,000
Number of members under consulting agreements | director	2	2
Number of directors submitted resignation | director			1
Intellectual property related legal fees
Related Party Transaction [Line Items]
Legal fees	$ 1,400,000	$ 1,100,000
Due to related party	69,000	134,000
Other legal fees
Related Party Transaction [Line Items]
Legal fees	2,700,000	500,000
Due to related party	$ 186,000	$ 40,000