Avidity Biosciences (RNA) 10-K15 Mar 212020 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2020	Feb. 26, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Registrant Name	AVIDITY BIOSCIENCES, INC.
Entity Central Index Key	0001599901
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		37,584,600
Entity File Number	001-39321
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-1336960
Entity Address, Address Line One	10975 N. Torrey Pines Road
Entity Address, Address Line Two	Suite 150
Entity Address, City or Town	La Jolla
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92037
City Area Code	(858)
Local Phone Number	401-7900
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	RNA
Security Exchange Name	NASDAQ
Document Annual Report	true
Document Transition Report	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 887.4
ICFR Auditor Attestation Flag	false

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 321,462	$ 94,578
Marketable securities	6,679
Prepaid and other assets	3,537	1,098
Total current assets	331,678	95,676
Property and equipment, net	1,468	631
Restricted cash	251
Other assets	501	600
Total assets	333,898	96,907
Current liabilities:
Accounts payable and accrued liabilities	7,745	2,308
Accrued compensation	3,152	1,314
Deferred revenue, current portion	3,690	3,840
Long-term debt, current portion		2,774
Total current liabilities	14,587	10,236
Lease liabilities, net of current portion	938	393
Deferred revenue, net of current portion	12,150	15,100
Long-term debt, net of current portion		1,770
Other long-term liabilities		45
Total liabilities	27,675	27,544
Commitments and contingencies (Note 9)
Convertible preferred stock, $0.0001 par value; authorized shares – none and 38,055 at December 31, 2020 and 2019, respectively; issued and outstanding shares – none and 37,267 at December 31, 2020 and 2019, respectively		134,720
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; authorized shares – 40,000 and none at December 31, 2020 and 2019, respectively; issued and outstanding shares – none
Common stock, $0.0001 par value; authorized shares – 400,000 and 52,042 at December 31, 2020 and 2019, respectively; issued and outstanding shares – 37,569 and 2,989 at December 31, 2020 and 2019, respectively	4
Additional paid-in capital	372,764	(43,172)
Accumulated other comprehensive loss	(5)
Accumulated deficit	(66,540)	(22,185)
Total stockholders’ equity (deficit)	306,223	(65,357)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 333,898	$ 96,907

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized	0	38,055,000
Convertible preferred stock, issued	0	37,267,000
Convertible preferred stock, outstanding	0	37,267,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	40,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	52,042,000
Common stock, shares issued	37,569,000	2,989,000
Common stock, shares outstanding	37,569,000	2,989,000

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Collaboration and contract research revenue	$ 6,787	$ 2,319	$ 379
Revenue from Contract with Customer, Product and Service [Extensible List]	rna:CollaborationAndContractResearchRevenueMember	rna:CollaborationAndContractResearchRevenueMember	rna:CollaborationAndContractResearchRevenueMember
Operating expenses:
Research and development	$ 37,602	$ 14,539	$ 8,436
General and administrative	13,462	5,112	2,441
Total operating expenses	51,064	19,651	10,877
Loss from operations	(44,277)	(17,332)	(10,498)
Other income (expense):
Interest income	206
Interest and other expense	(209)	(7,387)	(718)
Change in fair value of preferred warrant liability	(75)	(15)	0
Total other income (expense)	(78)	(7,402)	(718)
Net loss	(44,355)	(24,734)	(11,216)
Other comprehensive income (loss):
Net unrealized losses on marketable securities	(5)
Comprehensive loss	$ (44,360)	$ (24,734)	$ (11,216)
Net loss per share/unit, basic and diluted	$ (2.05)	$ (9.12)	$ (4.53)
Weighted-average shares/units outstanding, basic and diluted	21,663	2,713	2,477

Statements of Convertible Prefe

Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	Preferred Units	Common Units	Predecessor's Deficit	Convertible Preferred Stock	Common Stock	Common StockIPO	Additional Paid-in Capital	Additional Paid-in CapitalIPO	Accumulated Other Comprehensive Loss	Accumulated Deficit
Preferred Units, balance, Units at Dec. 31, 2017			12,459,000
Preferred Units, balance at Dec. 31, 2017			$ 32,693
Members' equity, balance, Units at Dec. 31, 2017				2,531,000
Members' equity, balance at Dec. 31, 2017				$ 267
Balance at Dec. 31, 2017	$ (30,072)				$ (30,339)
Issuance of common units upon exercise of unit options	67			$ 67
Issuance of common units upon exercise of unit options, Units				311,000
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	0
Vesting of early exercise options	32			$ 32
Stock-based compensation	60			$ 60
Net loss	(11,216)				(11,216)
Balance at Dec. 31, 2018	(41,129)				(41,555)
Preferred Units, balance, Units at Dec. 31, 2018			12,459,000
Preferred Units, balance at Dec. 31, 2018			$ 32,693
Members' equity, balance, Units at Dec. 31, 2018				2,842,000
Members' equity, balance at Dec. 31, 2018				$ 426
Distribution to members			$ (106)
Issuance of common units upon exercise of unit options	38			$ 38
Issuance of common units upon exercise of unit options, Units				78,000
Net loss to date of conversion	(2,549)				(2,549)
Conversion from LLC to C corporation				$ (481)	$ 44,104				$ (43,623)
Conversion from LLC to C corporation, Temporary equity, Shares			(12,459,000)			12,459,000
Conversion from LLC to C corporation, Temporary equity			$ (32,587)			$ 32,587
Conversion from LLC to C corporation, Shares				(2,920,000)			2,920,000
Issuance of Series C convertible preferred stock, net of issuance costs						$ 72,623
Issuance of Series C convertible preferred stock, net of issuance costs, Shares						17,915,000
Issuance of Series C convertible preferred stock upon conversion of convertible notes						$ 29,510
Issuance of Series C convertible preferred stock upon conversion of convertible notes, Shares						6,893,000
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	0
Issuance of common stock upon exercise of stock options, net of repurchases	26								26
Issuance of common stock upon exercise of stock options, net of repurchases, Shares							69,000
Vesting of early exercise options	36								36
Stock-based compensation	17			$ 17
Stock-based compensation	389								389
Net loss	(24,734)
Net loss	$ (22,185)											$ (22,185)
Temporary equity, balance, Shares at Dec. 31, 2019	37,267,000					37,267,000
Temporary equity, balance at Dec. 31, 2019	$ 134,720					$ 134,720
Balance, Shares at Dec. 31, 2019							2,989,000
Balance at Dec. 31, 2019	(65,357)								(43,172)			(22,185)
Issuance of Series C convertible preferred stock, net of issuance costs						$ 2,200
Issuance of Series C convertible preferred stock, net of issuance costs, Shares						538,000
Issuance of stock, net of issuance costs, Value		$ 274,054						$ 2		$ 274,052
Issuance of stock, net of issuance costs, Shares								16,560,000
Conversion of convertible preferred stock into common stock upon completion of initial public offering	136,920					$ (136,920)	$ 2		136,918
Conversion of convertible preferred stock into common stock upon completion of initial public offering, Shares						(37,805,000)	17,921,000
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	120								120
Cashless exercise of common stock warrants, Shares							16,000
Issuance of common stock upon exercise of stock options, net of repurchases	22								22
Issuance of common stock upon exercise of stock options, net of repurchases, Shares							54,000
Issuance of common stock under employee stock purchase plan	444								444
Issuance of common stock under employee stock purchase plan, Shares							29,000
Vesting of early exercise options	70								70
Stock-based compensation	4,310								4,310
Net loss	(44,355)											(44,355)
Other comprehensive loss	$ (5)										$ (5)
Temporary equity, balance, Shares at Dec. 31, 2020	0
Balance, Shares at Dec. 31, 2020							37,569,000
Balance at Dec. 31, 2020	$ 306,223						$ 4		$ 372,764		$ (5)	$ (66,540)

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock/Units and Stockholders'/Members' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Convertible Preferred Stock
Stock issuance costs	$ 100	$ 4,100
IPO \| Common Stock
Stock issuance costs	$ 24,026

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (44,355)	$ (24,734)	$ (11,216)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation	373	348	383
Stock-based compensation expense	4,310	406	60
Amortization of premiums and discounts on marketable securities, net	9	0	0
Amortization of discounts and loan issuance costs	29	71	73
Noncash interest expense	110	7,027	374
Change in fair value of preferred warrant liability	75	15	0
Changes in operating assets and liabilities:
Prepaid and other assets	(2,444)	(949)	12
Accounts payable and accrued liabilities	5,749	436	780
Accrued compensation	1,838	1,010	127
Operating lease right-of-use assets and liabilities, net	289	(80)	0
Deferred rent	0	0	(7)
Deferred revenue	(3,100)	18,940	(241)
Net cash (used in) provided by operating activities	(37,117)	2,490	(9,655)
Cash flows from investing activities
Purchases of marketable securities	(6,693)	0	0
Purchases of property and equipment	(1,092)	(235)	(49)
Net cash used in investing activities	(7,785)	(235)	(49)
Cash flows from financing activities
Proceeds from issuance of common stock in initial public offering, gross	298,080	0	0
Payment of issuance costs related to initial public offering	(24,026)	0	0
Proceeds from exercise of stock/unit options, net of repurchases	22	65	162
Proceeds from issuance of common stock under employee stock purchase plan	444	0	0
Proceeds from long-term debt, net of issuance costs	0	0	1,994
Payments on long-term debt	(4,683)	(2,800)	0
Distributions to members	0	(106)	0
Proceeds from issuance of Series C convertible preferred stock, net of issuance costs	2,200	72,623	0
Proceeds from issuance of convertible notes, net of issuance costs	0	19,451	2,988
Net cash provided by financing activities	272,037	89,233	5,144
Net increase (decrease) in cash, cash equivalents and restricted cash	227,135	91,488	(4,560)
Cash, cash equivalents and restricted cash at beginning of period	94,578	3,090	7,650
Cash, cash equivalents and restricted cash at end of period	321,713	94,578	3,090
Supplemental disclosure of cash flow information:
Cash paid for interest	571	322	291
Supplemental schedule of noncash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	936	807	0
Costs incurred, but not paid, in connection with purchases of property and equipment included in accounts payable and accrued liabilities	118	43	0
Conversion of convertible preferred stock into common stock upon completion of initial public offering	136,920	0	0
Issuance of Series C convertible preferred stock upon conversion of outstanding convertible notes	0	29,510	0
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	$ 120	$ 0	$ 0

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
Description of Business and Basis of Presentation	Dec. 31, 2020
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	1. Description of Basis of Description of Business Avidity Biosciences, Inc. (the Company or Avidity) is a biopharmaceutical company pioneering a new class of oligonucleotide-based therapies called Antibody Oligonucleotide Conjugates (AOCs) designed to overcome the current limitations of oligonucleotide-based therapies in order to treat a wide range of serious diseases. The Company utilizes its proprietary AOC platform to design, engineer and develop therapeutics that combine the tissue selectivity of monoclonal antibodies (mAbs) and the precision of oligonucleotide-based therapies. Formation and Conversion The Company was formed under the laws of the State of Delaware in November 2012 as a Delaware limited liability company. In April 2019, pursuant to an Agreement and Plan of Conversion, Avidity Biosciences LLC (Avidity LLC) was converted into Avidity Biosciences, Inc., a Delaware corporation. The entire membership interests of Avidity LLC were converted into securities of Avidity Biosciences, Inc. as follows: (i) each outstanding common unit of Avidity LLC was converted into one share of Avidity Biosciences, Inc.’s common stock; (ii) each outstanding Series A convertible preferred unit of Avidity LLC converted into one share of Avidity Biosciences, Inc.’s Series A convertible preferred stock; and (iii) each outstanding Series B convertible preferred unit of Avidity LLC converted into one share of Avidity Biosciences, Inc.’s Series B convertible preferred stock. All the property, rights, privileges, powers and franchises of Avidity LLC vested in Avidity Biosciences, Inc., and all debts, liabilities and duties of Avidity LLC became debts, liabilities and duties of Avidity Biosciences, Inc. Outstanding convertible notes, warrants and stock awards under Avidity LLC’s employee benefit and incentive compensation plans continued on the same terms and conditions and became binding upon Avidity Biosciences, Inc. Initial Public Offering On June 16, 2020, the Company completed its initial public offering (IPO) in which it sold 16,560,000 shares of common stock at an offering price of $18.00 per share. Proceeds from the IPO, net of underwriting discounts, commissions and offering costs, were $274.1 million. In addition, each of the following occurred in connection with the completion of the IPO: • the conversion of all outstanding shares of convertible preferred stock into 17,921,069 shares of the Company’s common stock; • the adjustment of an outstanding warrant to purchase convertible preferred stock into a warrant to purchase 7,809 shares of the Company’s common stock; and • the amendment and restatement of the Company’s certificate of incorporation, authorizing 400,000,000 shares of common stock and 40,000,000 shares of undesignated preferred stock. Reverse Stock Split On June 4, 2020, the Company effected a one-for-2.1095 reverse stock split of its common stock (the Reverse Stock Split). The par value and the authorized shares of the common stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock and the conversion ratio of the convertible preferred stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. Liquidity As of December 31, 2020, the Company has devoted substantially all of its resources to organizing and staffing the company, business planning, raising capital, developing its proprietary AOC platform, identifying potential product candidates, establishing its intellectual property portfolio and conducting research and preclinical studies, and providing other general and administrative support for these operations. In addition, the Company has a limited operating history, has incurred operating losses since inception and expects that it will continue to incur net losses into the foreseeable future as it continues the development of its product candidates and development programs. As of December 31, 2020, the Company had an accumulated deficit of $66.5 million and cash, cash equivalents and marketable securities of $328.1 million. The Company believes that existing cash, cash equivalents and marketable securities, including the net proceeds from the IPO, will be sufficient to fund the Company’s operations for at least 12 months from the date of the filing of this Form 10-K. The Company plans to finance its future cash needs through equity offerings, debt financings or other capital sources, including potential collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, it may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, and/or delay or reduce the scope of its planned development programs. Any of these actions could materially harm the Company’s business, results of operations and future prospects. Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and the rules and regulations of the Securities and Exchange Commission (SEC). The financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair statement of the results for the periods presented. All such adjustments are of a normal and recurring nature. The operating results presented in these financial statements are not necessarily indicative of the results that may be expected for any future periods.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Policies Use of Estimates The Company’s financial statements accordance GAAP, which the Company and assumptions that impact the amounts of liabilities, revenues and expenses and the disclosure of contingent and liabilities in the financial statements and accompanying notes. The most significant estimates in the Company’s financial statements to Although these on the Company’s knowledge of events and actions undertake the actual ultimately these and assumptions. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts. Restricted cash represents cash held as collateral for the letter of credit required under the Company’s facility lease and is reported as a long-term asset in the accompanying balance sheets. Marketable Securities The Company’s marketable securities consist of corporate debt securities. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets because such marketable securities are available to fund the Company’s current operations. Realized gains and losses are calculated on the specific identification method and recorded as interest income. There were no realized gains and losses for the years ended December 31, 2020, 2019 and 2018. At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the unrealized loss is other-than-temporary. When the Company determines that a decline in the fair value below its cost basis is other-than-temporary, the Company recognizes an impairment loss in the period in which the other-than-temporary decline occurred. There have been no other-than-temporary impairments recognized for the years ended December 31, 2020, 2019 and 2018. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments, credit quality, diversification, liquidity and maturities of investments, which are designed to maintain safety and liquidity. Fair Value of Financial Instruments Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities • Level 2—Observable inputs, such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. None of the Company’s non-financial assets are recorded at fair value on a non-recurring basis. The carrying amounts reflected in the Company’s balance sheets for prepaid and other assets and accounts payable and accrued liabilities approximate their fair values due to their short-term nature. The carrying value of the Company’s previously outstanding debt approximated fair value due to the interest being reflective of then-current market rates for debt with similar terms and conditions. during the periods presented See Note 3 (Fair Value Measurements) for information on assets and liabilities measured at fair value. Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the related assets, which ranges from three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Repairs and maintenance charges that do not increase the useful life of the assets are charged to operating expenses as incurred. Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. The Company has not recognized any impairment losses in any of the periods presented in these financial statements. Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by management in making decisions regarding resource allocation and assessing performance. The Company manages its operations as a single operating segment in the United States for the purposes of assessing performance and making operating decisions. Revenue Recognition To date, all the Company’s revenue has been derived from collaboration and research agreements. The terms of these arrangements include the following types of payments to the Company: non-refundable, upfront license fees; development, regulatory and commercial milestone payments; payments for research and development services provided by the Company or for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. Effective January 1, 2019, the Company adopted Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606), In accordance with Topic 606, the Company performs the following steps in determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of these agreements: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. Prior to January 1, 2019, the Company recognized revenues when all four of the following criteria were met: (i) persuasive evidence that an arrangement exists, (ii) delivery of the products and/or services has occurred, (iii) the selling price is fixed or determinable, and (iv) collectability is reasonably assured. The Company’s research evaluation agreements in existence prior to January 1, 2019 contained multiple elements, including payments for reimbursement of internal and third parties’ development costs. The Company considered a variety of factors in determining the appropriate method of revenue recognition under these arrangements. The Company receives payments from its collaborators based on billing schedules established in each contract. Upfront and other payments may require deferral of revenue recognition to a future period until the Company performs its obligations under its research and collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. See Note 5 (Collaboration, License and Research Agreements) for further information. Research and Development Costs Research and development costs are expensed as incurred and include salaries, benefits and stock-based compensation associated with research and development personnel, third-party research and development expenses, license fees, laboratory supplies, facilities, overhead costs, and consultants. Nonrefundable advance payments for goods and services that will be used in future research and development activities are capitalized and recorded as expense in the period that the Company receives the goods or when services are performed. Upfront and milestone payments to acquire contractual rights to licensed technology are recorded when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights. Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain. Income Taxes The Company accounts for income taxes in accordance with Accounting Standards Codification (ASC) 740, Income Taxes When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company is subject to taxation in the United States and state jurisdictions. As of December 31, 2020, the Company’s tax years since conversion are subject to examination by taxing authorities. Stock-Based Compensation Stock-based compensation expense for employee and non-employee stock option grants is recorded at the estimated fair value of the award as of the grant date and is recognized as expense on a straight-line basis over the requisite service period (usually the vesting period) of the stock-based award, net of actual forfeitures during the period. Stock-based compensation expense for employee stock purchases under the Company’s Employee Stock Purchase Plan (the ESPP) is recorded at the estimated fair value of the purchase as of the plan enrollment date and is recognized as expense on a straight-line basis over the applicable six-month ESPP offering period. The estimation of fair value for stock-based compensation requires management to make estimates and judgments about, among other things, the estimated life of options and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized. Comprehensive Loss Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on marketable securities. Comprehensive gains (losses) have been reflected in the statements of operations and comprehensive loss for all periods presented. Net Loss Per Share/Unit Basic net loss per share/unit is computed by dividing the net loss by the weighted-average number of common shares/units outstanding for the period, adjusted for the weighted-average number of common shares/units outstanding that are subject to repurchase or forfeiture. The Company has excluded 123,285, 217,524 and 231,810 weighted-average shares/units subject to repurchase or forfeiture from the weighted-average number of common shares/units outstanding for the years ended December 31, 2020, 2019 and 2018, respectively. Diluted net loss per share/unit is computed by dividing the net loss by the weighted-average number of common shares/units and dilutive common stock/unit equivalents outstanding for the period determined using the treasury-stock and if-converted methods. For all periods presented, there is no difference in the number of shares/units used to calculate basic and diluted shares/units outstanding as inclusion of the potentially dilutive securities would be antidilutive due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per share/unit, because to do so would be anti-dilutive, are as follows (in common stock/unit equivalents; in thousands): December 31, 2020 2019 2018 Convertible preferred stock/units — 17,666 5,906 Warrant to purchase convertible preferred stock/units — 8 8 Warrant to purchase common stock/units — 9 9 Common stock/unit options issued and outstanding 3,788 1,667 300 Common stock/units subject to repurchase or forfeiture 69 195 263 ESPP shares pending issuance 1 — — Total 3,858 19,545 6,486 Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that are adopted by the Company as of the specified effective date. The Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company determines the fair value of its cash equivalents and marketable securities based on one or more valuations from its investment accounting and reporting service provider. The investment service provider values the securities using a hierarchical security pricing model that relies primarily on valuations provided by an industry-recognized valuation service. Such valuations may be based on trade prices in active markets for identical assets (Level 1 inputs) or valuation models using inputs that are observable either directly or indirectly (Level 2 inputs), such as quoted prices for similar assets, yield curves, volatility factors, credit spreads, default rates, loss severity, current market and contractual prices for the underlying instruments or debt, and broker and dealer quotes, as well as other relevant economic measures. As of December 31, 2020, cash equivalents and marketable securities measured at fair value were as follows (in thousands): Fair Value Measurements Using As of December 31, 2020 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Negotiable certificates of deposit $ 720 $ — $ 720 $ — Marketable securities: Corporate debt securities 6,679 — 6,679 — Total $ 7,399 $ — $ 7,399 $ — As of December 31, 2019, the Company had no cash equivalents or marketable securities measured at fair value. Prior to completion of the IPO in June 2020, the Company had an outstanding warrant to purchase shares of its Series A convertible preferred stock. Since the underlying Series A convertible preferred stock was classified outside of permanent equity, the preferred stock warrant was classified as other long-term liabilities in the accompanying balance sheet. The preferred stock warrant liability was recorded at fair value utilizing the Black-Scholes model using significant unobservable inputs adjusted for the preferred stock warrant’s expected life and the fair value of the underlying convertible preferred stock. The Company adjusted the carrying value of the preferred stock warrant to its estimated fair value at each reporting date, with any related increase or decrease in the fair value recorded as an increase or decrease to other income (expense) in the statements of operations and comprehensive loss. In connection with the IPO, the preferred stock warrant was adjusted to become a warrant to purchase shares of the Company’s common stock and met the criteria to be classified within stockholders’ equity. Accordingly, the fair value of the warrant liability was reclassified to stockholders’ equity. The following table provides a reconciliation of the preferred stock warrant liability measured at fair value using Level 3 unobservable inputs (in thousands): Balance at December 31, 2017 and 2018 $ 30 Change in fair value 15 Balance at December 31, 2019 45 Change in fair value 75 Reclassification of warrant liability to stockholders’ equity (120 ) Balance at December 31, 2020 $ —

Marketable Securities

Marketable Securities	12 Months Ended
Marketable Securities	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Marketable Securities	3. Marketable Securities The Company’s marketable securities, which consist of highly liquid, investment grade debt securities, are classified as available-for-sale and are stated at fair value. As of December 31, 2020, marketable securities consisted of the following (in thousands): As of December 31, 2020 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 3,612 $ — $ (2 ) $ 3,610 Corporate debt securities 1 - 2 3,072 — (3 ) 3,069 Total $ 6,684 $ — $ (5 ) $ 6,679 As of December 31, 2019, the Company had no investments in marketable securities.

Collaboration, License and Rese

Collaboration, License and Research Agreements	12 Months Ended
Collaboration, License and Research Agreements	Dec. 31, 2020
Collaboration License And Research Agreements [Abstract]
Collaboration, License and Research Agreements	3. Collaboration, License and Research Agreements Research Collaboration and License Agreement with Eli Lilly and Company In April 2019, the Company entered into a Research Collaboration and License Agreement (the Lilly Agreement) with Eli Lilly and Company (Lilly) for the discovery, development and commercialization of AOC products directed against certain targets in immunology and other select indications on a worldwide basis. Under the Lilly Agreement, the Company granted Lilly an exclusive, worldwide, royalty-bearing license, with the right to sublicense (subject to certain conditions), under the Company’s technology to research, develop, manufacture and sell products containing AOCs that are directed to up to six mRNA targets. The Company retains the right to use its technology to perform its obligations under the Lilly Agreement and for all purposes not granted to Lilly. The Company agreed that it will not, itself or with a third party, research, develop, manufacture or commercialize or otherwise exploit any compound or product directed against targets subject to the Lilly Agreement. In consideration of the rights granted to Lilly under the Lilly Agreement, the Company received a one-time upfront fee of $20.0 million and is eligible to receive up to $60.0 million in development milestone payments, up to $140.0 million in regulatory milestone payments and up to $205.0 million in commercialization milestone payments per target. In addition, Lilly is obligated to reimburse the Company for research expenses, as defined in and incurred under the Lilly Agreement. Lilly is obligated to pay the Company a tiered royalty ranging from the mid-single to low-double digits on worldwide annual net sales of licensed products, subject to specified and capped reductions for the market entry of biosimilar products, loss of patent coverage of licensed products and for payments owed to third parties for additional rights necessary to commercialize licensed products in the territory. Lilly’s royalty obligations and the Lilly Agreement will expire on a licensed product-by-licensed product and country-by-country basis on the later of ten years from the date of the first commercial sale or when there is no longer a valid patent claim covering such licensed product in such country. The Company has identified multiple promises to deliver goods and services, which include at inception of the agreement: (i) a license to technology and patents, information and know-how; and (ii) collaboration, including research services, technical and regulatory support provided by the Company. At inception and through December 31, 2020, the Company has identified one performance obligation for all the deliverables under the Lilly Agreement since the delivered elements are either not capable of being distinct or are not distinct within the context of the contract. Accordingly, the Company will recognize revenue for the fixed or determinable collaboration in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses A reconciliation of the closing balance of deferred revenue related to the Lilly Agreement is as follows (in thousands): Balance at December 31, 2018 $ — Upfront payment 20,000 Revenue recognized (1,060 ) Balance at December 31, 2019 18,940 Revenue recognized (3,100 ) Balance at December 31, 2020 $ 15,840 Concurrently with the execution of the Lilly Agreement, the Company issued a convertible promissory note to Lilly (the Lilly Note). In connection with the Series C financing in November 2019, all outstanding principal and interest accrued under the Lilly Note converted into 4,576,342 shares of Series C convertible preferred stock. See Note 8 (Convertible Notes) for further discussion. Other Agreements In December 2020, the Company entered into a research collaboration (the MyoKardia Agreement) with MyoKardia, Inc. (MyoKardia), In 2016 and 2017, the Company entered into agreements with pharmaceutical companies under which the Company was contracted to perform certain research and development activities, as defined in work plans. All work under the agreements was completed in early 2018 with the Company recognizing revenue totaling $0.4 million for the year ended December 31, 2018.

Property and Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	6 . Property and Equipment Property and equipment consist of the following (in thousands): December 31, 2020 2019 Laboratory equipment $ 2,928 $ 1,755 Computers and software 58 65 Office furniture and equipment 44 37 Leasehold improvements 417 417 Property and equipment, gross 3,447 2,274 Less accumulated depreciation (1,979 ) (1,643 ) Total property and equipment, net $ 1,468 $ 631 Depreciation expense related to property and equipment was $0.4 million, $0.3 million and $0.4 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Debt

Debt	12 Months Ended
Debt	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	7 . Debt The Company’s debt consisted of the following (in thousands): December 31, 2020 2019 Current liabilities: Term loans $ — $ 2,800 Unamortized debt issuance costs — (25 ) Unamortized debt discount — (1 ) Loans payable, net of issuance costs and discount — 2,774 Non-current liabilities: Term loans — 1,400 Accrued end of term fees — 374 Unamortized debt issuance costs — (4 ) Loans payable, net of issuance costs and discount — 1,770 Total loans payable, net of issuance costs and discount $ — $ 4,544 Term Loan In June 2017, the Company entered into an amendment (the LSA Amendment) to the Amended and Restated Loan and Security Agreement (as amended, the LSA) with Silicon Valley Bank (SVB). Pursuant to the LSA Amendment, SVB agreed to make loans of up to $7.0 million, comprising (i) a $5.0 million term loan, funded at the closing date (the Term C Loan), and (ii) subject to the achievement of a specified milestone relating to the Company’s research, an additional term loan totaling up to $2.0 million (the Term D Loan), of which $4.1 million was used to repay the Company’s existing loan with SVB, in addition to the final payments totaling $0.4 million. The Term C Loan was scheduled to mature on June 1, 2021 and bore interest at an adjustable annual rate of the prime rate per the Wall Street Journal plus one-fifth of one percent (0.20%). The LSA Amendment provided an extension of the interest only period through June 1, 2019, upon the Term D Loan advance. Beginning July 1, 2019, the Company was required to repay the principal amount in 36 equal monthly installments, in addition to the monthly interest payment. In addition, a final payment of 6.5% of the funded amount, or $0.3 million, was due on the maturity date. The final payment fee was accrued as interest expense over the term of the loan and recorded in long-term debt, net of current portion. In August 2018, the Company entered into a second amendment to the LSA (the LSA Second Amendment). Pursuant to the LSA Second Amendment, SVB provided the Term D Loan of $2.0 million, upon the Company’s receipt of $3.0 million in convertible note financing. In addition, a final payment of 6.5% of the funded amount, or $0.1 million, was due on the maturity date. The Company accounted for the financing prospectively as a debt modification. On June 30, 2020, the Company voluntarily prepaid the aggregate outstanding principal balance of $2.8 million and final payments and accrued interest of $0.5 million related to the Term C and Term D Loans, and the LSA was terminated. In conjunction with the Term A and Term B Loans, the Company issued a warrant to SVB to purchase up to 16,474 shares of Series A convertible preferred stock at an exercise price of $2.2615 per share, exercisable at any time following the issuance, with a term of ten years. In connection with the completion of the IPO in June 2020, the preferred stock warrant was adjusted to become a warrant exercisable for 7,809 shares of common stock at an exercise price of $4.77 per share. In conjunction with the Term C Loan entered into in June 2017, the Company issued a warrant to SVB to purchase up to 9,442 shares of common stock at an exercise price of $0.53 per share, exercisable at any time following the issuance, with a term of seven years. The Company estimated the fair value of the warrants granted using the Black-Scholes model and recorded the fair value as debt discounts, which were being amortized to interest expense using the effective interest method over the term of the loans. On June 17, 2020, the warrants were cashless exercised for an aggregate of 15,833 shares of common stock.

Convertible Notes

Convertible Notes	12 Months Ended
Convertible Notes	Dec. 31, 2020
Debt Disclosure [Abstract]
Convertible Notes	8. Convertible Notes In 2018 and 2019, the Company issued convertible promissory notes in the aggregate principal amount of $3.0 million and $4.5 million, respectively (the 2018 Notes and 2019 Notes, respectively). The 2018 Notes and the 2019 Notes accrued interest at 8% and 10% per annum, respectively, and automatically converted into preferred equity in the next qualified financing of at least $10 million at 85% and 80%, respectively, of the per share price paid by the investors in such financing. Concurrently with the execution of the Lilly Agreement in April 2019, the Company issued the Lilly Note and received cash proceeds of $15.0 million. The Lilly Note accrued simple interest of 8.0% per annum and, if not converted, would have matured in October 2020. All unpaid principal and interest were due at maturity. The 2018 Notes, 2019 Notes and the Lilly Note (collectively, the Notes) represented share settled debt that were accounted for at amortized cost by accreting the Notes to their redemption value over the life of the debt using the effective interest method. In connection with the Series C financing in November 2019, all outstanding principal and interest accrued under the Notes converted into 6,893,036 shares of Series C convertible preferred stock. The Company recorded interest expense of $6.9 million and $0.2 million for the years ended December 31, 2019 and 2018, respectively, for the stated interest rate and the discount at which the Notes converted.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9 . Commitments and Contingencies Lease Agreements The Company adopted ASC 842, Leases, as of January 1, 2019. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historic accounting under ASC 840, Leases. In accordance with ASC 842, the Company determines if an arrangement is a finance lease, operating lease or short-term lease at inception, or as applicable, and accounts for the arrangement under the relevant accounting literature. Currently, the Company is only party to non-cancellable office and laboratory space operating leases and a short-term office lease. Under the relevant guidance, the Company recognizes operating lease right-of-use (ROU) assets and liabilities based on the present value of the future minimum lease payments over the lease term at the commencement date, using the Company’s assumed incremental borrowing rate of 5.5%, and amortizes the ROU assets and liabilities over the lease term. Lease expense for operating leases is recognized on a straight-line basis over the lease term. The Company’s short-term lease is not subject to recognition of an ROU asset or liability or straight-line lease expense requirements. In March 2014, the Company entered into a non-cancellable operating lease for office and laboratory space with a lease term through November 2017. In July 2017, the Company entered into an amendment to this lease to extend the lease term through December 2021. On June 1, 2020, the Company entered into a second amendment to its existing operating lease (as amended, the 2014 Lease) and entered into a new non-cancellable temporary operating lease in connection with a newly executed non-cancellable operating lease for its new headquarters location, with a projected commencement date of July 1, 2021. On December 18, 2020, the Company entered into an amendment to the non-cancellable operating lease for its new headquarters location (as amended, the New Lease), which increased the square footage by adding adjacent space and extended the projected commencement date to November 1, 2021. Additionally, the non-cancellable temporary operating lease was amended (as amended, the Temporary Lease) to accommodate the projected commencement date of the New Lease. The lease term under both the 2014 Lease and the Temporary Lease ends 15 days after the commencement date of the New Lease in November 2021. The remaining monthly rental payments under the 2014 Lease and the rent under the Temporary Lease were abated beginning on June 1, 2020, given the execution of the New Lease. The New Lease has a five-year term upon commencement in November 2021 and a renewal option for an additional five years. Under the terms of the New Lease, the initial monthly base rent of approximately $251,000 will increase to approximately $282,000 during the last year of the New Lease's initial term, and the first year includes five months of rent abatement. The total lease payments under the initial term of the New Lease of $14.7 million were allocated amongst the 2014 Lease, Temporary Lease and New Lease based on the relative standalone price of the separate lease components. Furthermore, pursuant to the terms of the New Lease, the Company is required to maintain a letter of credit totaling $251,000 throughout the lease term. In June 2020, in accordance with the lease terms applicable at that time, the Company adjusted the ROU asset and liability of the 2014 Lease to conform to the modification terms and recorded an ROU asset and liability for the Temporary Lease upon occupancy. In December 2020, in connection with the lease amendments described above, the Company adjusted the ROU asset and liability of the 2014 Lease and Temporary Lease to conform to the modification terms. The Company will recognize an ROU asset and liability related to the New Lease upon obtaining control of the asset, which is expected to be upon occupancy of the new space in November 2021. As of December 31, 2020, the Company’s ROU assets and liabilities related to the 2014 Lease and the Temporary Lease are as follows (in thousands): ROU assets (included in other assets) $ 454 Lease liabilities, current portion (included in accounts payable and accrued liabilities) $ — Lease liabilities, net of current portion 938 Total lease liabilities $ 938 As of December 31, 2020, maturities of the lease liabilities due under the 2014 Lease and the Temporary Lease are as follows (in thousands): Year ending December 31, 2021 $ 17 2022 135 2023 208 2024 214 2025 220 2026 188 Total lease payments 982 Less imputed interest (44 ) Total operating lease liabilities 938 Less lease liabilities, current portion — Lease liabilities, net of current portion $ 938 Supplemental cash flow information related to cash paid for amounts included in the measurement of operating lease liabilities was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Cash paid included in operating cash flows $ 163 $ 382 N/A Rent expense was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Operating leases $ 453 $ 302 $ 302 Short-term lease 36 6 — Total rent expense $ 489 $ 308 $ 302 As of December 31, 2020, the weighted-average remaining term of the Company’s operating leases was 0.8 years. Litigation Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding for which any liabilities have been accrued. Contractual Obligations The Company enters into contracts in the normal course of business for contract research services, contract manufacturing services, professional services, and other services and products for operating purposes. These contracts may include certain provisions that could require payments for early termination. The amount of the termination payments vary depending on the timing of the termination and the specific terms of the contract.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
Stockholders' Equity (Deficit)	Dec. 31, 2020
Equity [Abstract]
Stockholders’ Equity (Deficit)	10 . Stockholders’ Equity (Deficit) Amended and Restated Certificate of Incorporation On June 16, 2020, the Company’s certificate of incorporation was amended and restated to authorize 400,000,000 shares of common stock and 40,000,000 shares of undesignated preferred stock, each with a par value of $0.0001 per share. Initial Public Offering On June 16, 2020, the Company completed its IPO in which it sold 16,560,000 shares of common stock at an offering price of $18.00 per share. Proceeds from the IPO, net of underwriting discounts, commissions and offering costs, were $274.1 million. Conversion On April 1, 2019, Avidity LLC, a Delaware limited liability company, was converted into Avidity Biosciences, Inc., a Delaware corporation. The entire membership interests of Avidity LLC were converted into securities of Avidity Biosciences, Inc. as follows: (i) each outstanding common unit of Avidity LLC was converted into one share of Avidity Biosciences, Inc.’s common stock; (ii) each outstanding Series A convertible preferred unit of Avidity LLC converted into one share of Avidity Biosciences, Inc.’s Series A convertible preferred stock; and (iii) each outstanding Series B convertible preferred unit of Avidity LLC converted into one share of Avidity Biosciences, Inc.’s Series B convertible preferred stock. All the property, rights, privileges, powers and franchises of Avidity LLC vested in Avidity Biosciences, Inc., and all debts, liabilities and duties of Avidity LLC became debts, liabilities and duties of Avidity Biosciences, Inc. All references to the former members’ equity accounts in Avidity LLC have been adjusted to reflect the equivalent number of Avidity Biosciences, Inc.’s shares of common stock. Upon completion of the conversion, the Company reclassified an accumulated deficit of $44.1 million from predecessor deficit to additional paid-in capital. Convertible Preferred Stock In November 2019, the Company issued 17,915,525 shares of Series C convertible preferred stock, for cash, at a price of $4.2812 per share, for net proceeds of $72.6 million, net of issuance costs of $4.1 million. In addition, all outstanding principal and accrued interest under the Notes were automatically converted into 6,893,036 shares of Series C convertible preferred stock, at a stated discount pursuant to the original terms of the notes at issuance. In January 2020, the Company issued an additional 537,232 shares of Series C convertible preferred stock, for cash, at a price of $4.2812 per share, for net proceeds of $2.2 million, net of issuance costs of $100,000. In connection with the completion of the IPO in June 2020, all of the outstanding shares of convertible preferred stock were converted into 17,921,069 shares of the Company’s common stock. As of December 31, 2019, the Company’s convertible preferred stock was classified as temporary equity on the accompanying balance sheet in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities whose redemption is based upon certain change in control events outside of the Company’s control. As of December 31, 2019, convertible preferred stock consisted of the following (in thousands, except per share data): Series Shares Authorized Shares Issued and Outstanding Per Share Original Issue Price and Conversion Price Liquidation Preference Carrying Value Series A 4,367 4,350 $ 2.2615 $ 9,838 $ 9,773 Series B 8,108 8,108 2.8269 22,922 22,814 Series C 25,580 24,809 4.2812 106,210 102,133 Total 38,055 37,267 $ 138,970 $ 134,720 Equity Incentive Plans In January 2013, the Company adopted the 2013 Equity Incentive Plan (the 2013 Plan). The 2013 Plan provided for the issuance of incentive units to employees and nonemployees of the Company and non‑statutory unit options, restricted unit awards, unit appreciation rights, and unit bonuses to directors, employees and consultants of the Company. Under the 2013 Plan, 2,127,013 units were initially reserved for issuance. Upon the conversion of the Company to a C corporation, the 2013 Plan continued on the same terms and conditions. In 2019, the number of shares reserved under the 2013 Plan was increased to 4,771,615 shares. In June 2020, the Board of Directors adopted, and the Company’s stockholders approved, the 2020 Incentive Award Plan (the 2020 Plan), which became effective in connection with the IPO. Pursuant to the 2020 Plan, the Company ceased granting awards under the 2013 Plan. Under the 2020 Plan, the Company may grant stock options, restricted stock, dividend equivalents, restricted stock units, stock appreciation rights, and other stock or cash-based awards to individuals who are then employees, officers, non-employee directors or consultants of the Company. A total of 3,900,000 shares of common stock were initially reserved for issuance under the 2020 Plan. In addition, the number of shares of common stock available for issuance under the 2020 Plan will be increased annually on the first day of each fiscal year during the term of the 2020 Plan, beginning with the 2021 fiscal year, by an amount equal to the lesser of (a) 5% of the shares of common stock outstanding on the final day of the immediately preceding calendar year or (b) such smaller number of shares as determined by the Company’s board of directors. At December 31, 2020, 2,851,824 shares remain available for issuance under the 2020 Plan. Stock Options Options granted from the 2013 Plan and 2020 Plan are exercisable at various dates and will expire no more than ten years from their date of grant. Options generally vest over a two- to four-year period. Prior to the IPO, the exercise price of options was determined by the Company’s board of directors. Following the IPO, the Company grants options with an exercise price equal to the fair market value of the Company’s stock on the date of the option grant. Stock option activity for employee and nonemployee awards and related information is as follows (in thousands, except per share and contractual term data): Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2019 1,667 $ 1.08 Granted 2,291 14.24 Exercised (119 ) 0.45 Forfeited (51 ) 1.24 Outstanding at December 31, 2020 3,788 $ 9.06 9.1 $ 65,082 Exercisable at December 31, 2020 556 $ 1.24 8.3 $ 13,491 The aggregate intrinsic values presented in the table above were calculated as the difference between the closing price of the Company’s common stock at December 31, 2020 and the exercise price of stock options that had strike prices below the closing price. The total intrinsic value of options exercised during the years ended December 31, 2020, 2019 and 2018 were $0.5 million, $7,000 and $0, respectively. The total intrinsic values of options exercised were calculated as the difference between the fair value of the Company’s common stock/units at the time of the option exercise and the exercise price of that stock/unit option. The weighted-average grant date fair value of options granted during the years ended December 31, 2020, 2019 and 2018 were $11.63, $3.46 and $0.30 per share/unit, respectively. As of December 31, 2020 and 2019, 69,359 and 194,729, respectively, of the stock options exercised were unvested and subject to repurchase. Employee Stock Purchase Plan In June 2020, the Company adopted the ESPP, which permits participants to contribute up to 15% of their eligible compensation during defined rolling six-month periods to purchase the Company’s common stock. The purchase price of the shares will be 85% of the lower of the fair market value of the Company’s common stock on the first day of trading of the offering period or on the applicable purchase date. A total of 325,000 shares of common stock was initially reserved for issuance under the ESPP. The Company issued 28,979 shares of common stock under the ESPP during the year ended December 31, 2020. The Company had an outstanding liability of $35,000 at December 31, 2020, which is included in accounts payable and accrued liabilities on the balance sheet, for employee contributions to the ESPP for shares pending issuance at the end of the offering period. Stock-Based Compensation Expense The assumptions used in the Black-Scholes model to determine the fair value of the stock/unit option grants and the shares purchasable under the ESPP were as follows: Year Ended December 31, Stock/Unit Option Grants 2020 2019 2018 Risk-free interest rate 0.3% - 1.5% 1.4% - 2.7% 2.4% - 2.9% Expected volatility 88% - 92% 84% - 88% 83% - 84% Expected term (in years) 5.4 - 6.1 2.0 - 6.1 2.0 - 6.1 Expected dividend yield —% —% —% Year Ended December 31, ESPP 2020 2019 2018 Risk-free interest rate 0.1% - 0.2% N/A N/A Expected volatility 75% - 96% N/A N/A Expected term (in years) 0.5 N/A N/A Expected dividend yield —% N/A N/A Risk-Free Interest Rate. The Company bases the risk-free interest rate assumption for equity awards on the rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. Expected Volatility. Due to the limited trading history of the Company’s common stock, the expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the biotechnology industry. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Expected Term. The Company has estimated the expected life of its stock options using the simplified method, whereby the expected life equals the average of the vesting term and the original contractual term of the option. The expected life assumption for employee stock purchases under the ESPP is six months to conform with the six-month ESPP offering period. Expected Dividend Yield. The Company’s expected dividend yield assumption is zero as it has never paid dividends and has no present intention to do so in the future. The allocation of stock-based compensation expense was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Research and development expense $ 1,895 $ 84 $ 26 General and administrative expense 2,415 322 34 Total stock-based compensation expense $ 4,310 $ 406 $ 60 As of December 31, 2020, the unrecognized compensation cost related to outstanding time-based options was $27.2 million, which is expected to be recognized over a weighted-average period of 3.2 years. As of December 31, 2020, the unrecognized compensation cost related to stock purchase rights under the ESPP was $0.2 million, which is expected to be recognized over a weighted-average period of 0.5 years. Common Stock Reserved for Future Issuance Common stock reserved for future issuance consisted of the following (in thousands): December 31, 2020 2019 Conversion of convertible preferred stock — 17,666 Common stock options issued and outstanding 3,788 1,667 Equity awards available for future issuance under equity plans 2,852 1,601 Preferred and common stock warrants outstanding — 17 Common stock authorized under the ESPP 296 — Total 6,936 20,951

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	11 . Income Taxes The Company operated as a nontaxable partnership until its conversion on March 31, 2019. The Company had deferred tax assets in existence on March 31, 2019 when the Company became a taxable entity. Deferred tax assets were not recognized due to the uncertainty that such assets will be realized. The Company retained the valuation allowance on the deferred tax assets at December 31, 2019. No provision for income taxes was recorded for the years ended December 31, 2020 and 2019. A reconciliation of income taxes to the amount computed by applying the statutory federal income tax rate to the net loss is summarized as follows (in thousands): Year Ended December 31, 2020 2019 Income tax expense (benefit) at statutory rates $ (9,315 ) $ (5,194 ) State income tax, net of federal benefit (3,004 ) (1,057 ) Permanent items 1 14 Book income for pre-conversion period — 527 Interest on convertible notes — 445 Realized gain on conversion of convertible notes — 958 Reserve for uncertain tax positions 398 140 Research and development tax credits (1,639 ) (584 ) Deferred taxes recognized upon conversion — (3,076 ) Valuation allowance 13,488 7,827 Other 71 — Income tax expense (benefit) $ — $ — Significant components of the Company’s deferred tax assets as of December 31, 2020 and 2019 are shown below (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 11,277 $ 4,275 Research and development tax credits 1,855 438 Deferred revenue 4,443 — Accrued expenses 153 179 Intangibles and fixed assets 2,483 2,721 Lease liability 263 265 Stock-based compensation 969 160 Total deferred tax assets 21,443 8,038 Less valuation allowance (21,316 ) (7,827 ) Net deferred tax assets 127 211 Deferred tax liabilities: Right-of-use asset (127 ) (211 ) Total deferred tax liabilities (127 ) (211 ) Net deferred tax assets $ — $ — The Company has established a full valuation allowance against its net deferred tax assets due to the uncertainty that such assets will be realized. The Company periodically evaluates the recoverability of the deferred tax assets. At such time as it is determined that it is more likely than not that the deferred tax assets will be realizable, the valuation allowance will be released. The change in the valuation allowance was an increase of $13.5 million for the year ended December 31, 2020. At December 31, 2020, the Company had federal and state net operating loss (NOL) carryforwards of $40.2 million and $40.0 million, respectively. On March 27, 2020, the CARES Act was signed into law in response to the economic challenges facing U.S. businesses. At December 31, 2020, the Company had federal and state research and development tax credits of $1.7 million and $1.0 million, respectively. The federal research and development tax credits begin to expire in 2039 unless previously utilized, and the state credits carry forward indefinitely. Pursuant to IRC Section 382 and Section 383, the Company’s ability to use NOL and R&D tax credit carryforwards (tax attribute carryforwards) to offset future taxable income is limited if the Company experiences a cumulative change in ownership of more than 50% within a three-year testing period. The Company has not completed an ownership change analysis pursuant to IRC Section 382 and therefore has established a valuation allowance as the realization of such deferred tax assets has not met the more likely than not threshold requirement The following table summarizes the activity related to the Company’s gross unrecognized tax benefits for the years ended December 31, 2020 and 2019 (in thousands): Year Ended December 31, 2020 2019 Gross unrecognized tax benefits at the beginning of the year $ 156 $ — Increases related to current year positions 446 156 Increases related to prior year positions 62 — Other true up 7 — Gross unrecognized tax benefits at the end of the year $ 671 $ 156 The unrecognized tax benefit amounts are reflected in the determination of the Company’s deferred tax assets. If recognized, none of these amounts would affect the Company’s effective tax rate, since it would be offset by a corresponding adjustment to the deferred tax asset valuation allowance. The Company does not foresee material changes to its liability for uncertain tax benefits within the next twelve months. The Company’s policy is to recognize interest and/or penalties related to income tax matters in income tax expense. The Company had no accrual for interest or penalties as of December 31, 2020 or 2019. As of December 31, 2020, the Company’s tax years since conversion are subject to examination by taxing authorities.

Quarterly Financial Data (unaud

Quarterly Financial Data (unaudited)	12 Months Ended
Quarterly Financial Data (unaudited)	Dec. 31, 2020
Selected Quarterly Financial Information [Abstract]
Quarterly Financial Data (unaudited)	12 . Quarterly Financial Data (unaudited) The following tables summarize the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share/unit data): 2020 First Quarter Second Quarter Third Quarter Fourth Quarter Revenue $ 1,358 $ 1,541 $ 1,746 $ 2,142 Operating expenses 7,508 11,909 13,212 18,435 Other income (expense) 65 (188 ) 27 18 Net loss (6,085 ) (10,556 ) (11,439 ) (16,275 ) Net loss per share, basic and diluted (1) (2.14 ) (1.23 ) (0.31 ) (0.43 ) 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Revenue $ — $ 224 $ 650 $ 1,445 Operating expenses 2,174 4,129 5,856 7,492 Other income (expense) (375 ) (1,211 ) (1,462 ) (4,354 ) Net loss (2,549 ) (5,116 ) (6,668 ) (10,401 ) Net loss per share/unit, basic and diluted (1) (0.97 ) (1.89 ) (2.43 ) (3.75 ) (1) Net loss per share/unit is computed independently for each quarter and the full year based upon respective shares/units outstanding; therefore, the sum of the quarterly net loss per share/unit amounts may not equal the annual amounts reported.

COVID-19

COVID-19	12 Months Ended
COVID-19	Dec. 31, 2020
Extraordinary And Unusual Items [Abstract]
COVID-19	1 3 . COVID-19 The COVID-19 outbreak in the United States has caused significant business disruption. The extent of the impact of COVID-19 on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the outbreak, and its impact on the Company’s preclinical studies and clinical trials, employees and vendors, all of which are uncertain and cannot be predicted. In response to the COVID-19 outbreak, the Company has closed its executive offices with its administrative employees continuing their work remotely and limited the number of staff in its research and development laboratories. To date, the Company has not experienced material disruptions in its business operations. However, a prolonged outbreak could have a material adverse impact on the financial results and business operations of the Company, including the timing and ability of the Company to complete certain clinical trials and other efforts required to advance the development of its product candidates and raise additional capital. In response to the pandemic, the Coronavirus Aid, Relief and Economic Security Act (the CARES Act) was signed into law on March 27, 2020. The CARES Act, among other things, includes tax provisions relating to refundable payroll tax credits, deferment of employer’s social security payments, net operating loss utilization and carryback periods, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. The CARES Act had no impact on the Company’s income tax provision for the year ended December 31, 2020. The Company currently does not expect to apply for loans or grants under the CARES Act.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and the rules and regulations of the Securities and Exchange Commission (SEC). The financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair statement of the results for the periods presented. All such adjustments are of a normal and recurring nature. The operating results presented in these financial statements are not necessarily indicative of the results that may be expected for any future periods.
Use of Estimates	Use of Estimates The Company’s financial statements accordance GAAP, which the Company and assumptions that impact the amounts of liabilities, revenues and expenses and the disclosure of contingent and liabilities in the financial statements and accompanying notes. The most significant estimates in the Company’s financial statements to Although these on the Company’s knowledge of events and actions undertake the actual ultimately these and assumptions.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts. Restricted cash represents cash held as collateral for the letter of credit required under the Company’s facility lease and is reported as a long-term asset in the accompanying balance sheets.
Marketable Securities	Marketable Securities The Company’s marketable securities consist of corporate debt securities. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets because such marketable securities are available to fund the Company’s current operations. Realized gains and losses are calculated on the specific identification method and recorded as interest income. There were no realized gains and losses for the years ended December 31, 2020, 2019 and 2018. At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the unrealized loss is other-than-temporary. When the Company determines that a decline in the fair value below its cost basis is other-than-temporary, the Company recognizes an impairment loss in the period in which the other-than-temporary decline occurred. There have been no other-than-temporary impairments recognized for the years ended December 31, 2020, 2019 and 2018.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments, credit quality, diversification, liquidity and maturities of investments, which are designed to maintain safety and liquidity.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities • Level 2—Observable inputs, such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. None of the Company’s non-financial assets are recorded at fair value on a non-recurring basis. The carrying amounts reflected in the Company’s balance sheets for prepaid and other assets and accounts payable and accrued liabilities approximate their fair values due to their short-term nature. The carrying value of the Company’s previously outstanding debt approximated fair value due to the interest being reflective of then-current market rates for debt with similar terms and conditions. during the periods presented See Note 3 (Fair Value Measurements) for information on assets and liabilities measured at fair value.
Property and Equipment	Property and Equipment Property and equipment, including leasehold improvements, are stated at cost less accumulated depreciation and amortization. Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the related assets, which ranges from three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Repairs and maintenance charges that do not increase the useful life of the assets are charged to operating expenses as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. The Company has not recognized any impairment losses in any of the periods presented in these financial statements.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by management in making decisions regarding resource allocation and assessing performance. The Company manages its operations as a single operating segment in the United States for the purposes of assessing performance and making operating decisions.
Revenue Recognition	Revenue Recognition To date, all the Company’s revenue has been derived from collaboration and research agreements. The terms of these arrangements include the following types of payments to the Company: non-refundable, upfront license fees; development, regulatory and commercial milestone payments; payments for research and development services provided by the Company or for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. Effective January 1, 2019, the Company adopted Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606), In accordance with Topic 606, the Company performs the following steps in determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of these agreements: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when, or as, the Company satisfies each performance obligation. Prior to January 1, 2019, the Company recognized revenues when all four of the following criteria were met: (i) persuasive evidence that an arrangement exists, (ii) delivery of the products and/or services has occurred, (iii) the selling price is fixed or determinable, and (iv) collectability is reasonably assured. The Company’s research evaluation agreements in existence prior to January 1, 2019 contained multiple elements, including payments for reimbursement of internal and third parties’ development costs. The Company considered a variety of factors in determining the appropriate method of revenue recognition under these arrangements. The Company receives payments from its collaborators based on billing schedules established in each contract. Upfront and other payments may require deferral of revenue recognition to a future period until the Company performs its obligations under its research and collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. See Note 5 (Collaboration, License and Research Agreements) for further information.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred and include salaries, benefits and stock-based compensation associated with research and development personnel, third-party research and development expenses, license fees, laboratory supplies, facilities, overhead costs, and consultants. Nonrefundable advance payments for goods and services that will be used in future research and development activities are capitalized and recorded as expense in the period that the Company receives the goods or when services are performed. Upfront and milestone payments to acquire contractual rights to licensed technology are recorded when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with Accounting Standards Codification (ASC) 740, Income Taxes When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit would more likely than not be realized assuming examination by the taxing authority. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company is subject to taxation in the United States and state jurisdictions. As of December 31, 2020, the Company’s tax years since conversion are subject to examination by taxing authorities.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense for employee and non-employee stock option grants is recorded at the estimated fair value of the award as of the grant date and is recognized as expense on a straight-line basis over the requisite service period (usually the vesting period) of the stock-based award, net of actual forfeitures during the period. Stock-based compensation expense for employee stock purchases under the Company’s Employee Stock Purchase Plan (the ESPP) is recorded at the estimated fair value of the purchase as of the plan enrollment date and is recognized as expense on a straight-line basis over the applicable six-month ESPP offering period. The estimation of fair value for stock-based compensation requires management to make estimates and judgments about, among other things, the estimated life of options and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on marketable securities. Comprehensive gains (losses) have been reflected in the statements of operations and comprehensive loss for all periods presented.
Net Loss Per Share/Unit	Net Loss Per Share/Unit Basic net loss per share/unit is computed by dividing the net loss by the weighted-average number of common shares/units outstanding for the period, adjusted for the weighted-average number of common shares/units outstanding that are subject to repurchase or forfeiture. The Company has excluded 123,285, 217,524 and 231,810 weighted-average shares/units subject to repurchase or forfeiture from the weighted-average number of common shares/units outstanding for the years ended December 31, 2020, 2019 and 2018, respectively. Diluted net loss per share/unit is computed by dividing the net loss by the weighted-average number of common shares/units and dilutive common stock/unit equivalents outstanding for the period determined using the treasury-stock and if-converted methods. For all periods presented, there is no difference in the number of shares/units used to calculate basic and diluted shares/units outstanding as inclusion of the potentially dilutive securities would be antidilutive due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per share/unit, because to do so would be anti-dilutive, are as follows (in common stock/unit equivalents; in thousands): December 31, 2020 2019 2018 Convertible preferred stock/units — 17,666 5,906 Warrant to purchase convertible preferred stock/units — 8 8 Warrant to purchase common stock/units — 9 9 Common stock/unit options issued and outstanding 3,788 1,667 300 Common stock/units subject to repurchase or forfeiture 69 195 263 ESPP shares pending issuance 1 — — Total 3,858 19,545 6,486
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that are adopted by the Company as of the specified effective date. The Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share/Unit	Potentially dilutive securities not included in the calculation of diluted net loss per share/unit, because to do so would be anti-dilutive, are as follows (in common stock/unit equivalents; in thousands): December 31, 2020 2019 2018 Convertible preferred stock/units — 17,666 5,906 Warrant to purchase convertible preferred stock/units — 8 8 Warrant to purchase common stock/units — 9 9 Common stock/unit options issued and outstanding 3,788 1,667 300 Common stock/units subject to repurchase or forfeiture 69 195 263 ESPP shares pending issuance 1 — — Total 3,858 19,545 6,486

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Summary of Cash Equivalents and Marketable Securities Measured at Fair Value	As of December 31, 2020, cash equivalents and marketable securities measured at fair value were as follows (in thousands): Fair Value Measurements Using As of December 31, 2020 Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents: Negotiable certificates of deposit $ 720 $ — $ 720 $ — Marketable securities: Corporate debt securities 6,679 — 6,679 — Total $ 7,399 $ — $ 7,399 $ —
Schedule of Reconciliation of Preferred Stock Warrant Liability Measured at Fair Value Using Level 3 Unobservable Inputs	The following table provides a reconciliation of the preferred stock warrant liability measured at fair value using Level 3 unobservable inputs (in thousands): Balance at December 31, 2017 and 2018 $ 30 Change in fair value 15 Balance at December 31, 2019 45 Change in fair value 75 Reclassification of warrant liability to stockholders’ equity (120 ) Balance at December 31, 2020 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
Marketable Securities (Tables)	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities	The Company’s marketable securities, which consist of highly liquid, investment grade debt securities, are classified as available-for-sale and are stated at fair value. As of December 31, 2020, marketable securities consisted of the following (in thousands): As of December 31, 2020 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 3,612 $ — $ (2 ) $ 3,610 Corporate debt securities 1 - 2 3,072 — (3 ) 3,069 Total $ 6,684 $ — $ (5 ) $ 6,679

Collaboration, License and Re_2

Collaboration, License and Research Agreements (Tables)	12 Months Ended
Collaboration, License and Research Agreements (Tables)	Dec. 31, 2020
Collaboration License And Research Agreements [Abstract]
Summary of Reconciliation of Deferred Revenue Related to Lilly Agreement	A reconciliation of the closing balance of deferred revenue related to the Lilly Agreement is as follows (in thousands): Balance at December 31, 2018 $ — Upfront payment 20,000 Revenue recognized (1,060 ) Balance at December 31, 2019 18,940 Revenue recognized (3,100 ) Balance at December 31, 2020 $ 15,840

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): December 31, 2020 2019 Laboratory equipment $ 2,928 $ 1,755 Computers and software 58 65 Office furniture and equipment 44 37 Leasehold improvements 417 417 Property and equipment, gross 3,447 2,274 Less accumulated depreciation (1,979 ) (1,643 ) Total property and equipment, net $ 1,468 $ 631

Debt (Tables)

Debt (Tables)	12 Months Ended
Debt (Tables)	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Debt	The Company’s debt consisted of the following (in thousands): December 31, 2020 2019 Current liabilities: Term loans $ — $ 2,800 Unamortized debt issuance costs — (25 ) Unamortized debt discount — (1 ) Loans payable, net of issuance costs and discount — 2,774 Non-current liabilities: Term loans — 1,400 Accrued end of term fees — 374 Unamortized debt issuance costs — (4 ) Loans payable, net of issuance costs and discount — 1,770 Total loans payable, net of issuance costs and discount $ — $ 4,544

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of ROU Assets and Liabilities Related to 2014 Lease and Temporary Lease	As of December 31, 2020, the Company’s ROU assets and liabilities related to the 2014 Lease and the Temporary Lease are as follows (in thousands): ROU assets (included in other assets) $ 454 Lease liabilities, current portion (included in accounts payable and accrued liabilities) $ — Lease liabilities, net of current portion 938 Total lease liabilities $ 938
Schedule of Maturities of Lease Liabilities due under 2014 Lease and Temporary Lease	As of December 31, 2020, maturities of the lease liabilities due under the 2014 Lease and the Temporary Lease are as follows (in thousands): Year ending December 31, 2021 $ 17 2022 135 2023 208 2024 214 2025 220 2026 188 Total lease payments 982 Less imputed interest (44 ) Total operating lease liabilities 938 Less lease liabilities, current portion — Lease liabilities, net of current portion $ 938
Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in Measurement of Operating Lease Liabilities	Supplemental cash flow information related to cash paid for amounts included in the measurement of operating lease liabilities was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Cash paid included in operating cash flows $ 163 $ 382 N/A
Schedule of Rent Expense	Rent expense was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Operating leases $ 453 $ 302 $ 302 Short-term lease 36 6 — Total rent expense $ 489 $ 308 $ 302

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
Stockholders' Equity (Deficit) (Tables)	Dec. 31, 2020
Equity [Abstract]
Summary of Convertible Preferred Stock	As of December 31, 2019, convertible preferred stock consisted of the following (in thousands, except per share data): Series Shares Authorized Shares Issued and Outstanding Per Share Original Issue Price and Conversion Price Liquidation Preference Carrying Value Series A 4,367 4,350 $ 2.2615 $ 9,838 $ 9,773 Series B 8,108 8,108 2.8269 22,922 22,814 Series C 25,580 24,809 4.2812 106,210 102,133 Total 38,055 37,267 $ 138,970 $ 134,720
Summary of Stock Option Activity	Stock option activity for employee and nonemployee awards and related information is as follows (in thousands, except per share and contractual term data): Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2019 1,667 $ 1.08 Granted 2,291 14.24 Exercised (119 ) 0.45 Forfeited (51 ) 1.24 Outstanding at December 31, 2020 3,788 $ 9.06 9.1 $ 65,082 Exercisable at December 31, 2020 556 $ 1.24 8.3 $ 13,491
Schedule of Assumptions used in Black-Scholes Model to Determine Fair Value of Stock/Unit Option Grants and Shares Purchasable under ESPP	The assumptions used in the Black-Scholes model to determine the fair value of the stock/unit option grants and the shares purchasable under the ESPP were as follows: Year Ended December 31, Stock/Unit Option Grants 2020 2019 2018 Risk-free interest rate 0.3% - 1.5% 1.4% - 2.7% 2.4% - 2.9% Expected volatility 88% - 92% 84% - 88% 83% - 84% Expected term (in years) 5.4 - 6.1 2.0 - 6.1 2.0 - 6.1 Expected dividend yield —% —% —% Year Ended December 31, ESPP 2020 2019 2018 Risk-free interest rate 0.1% - 0.2% N/A N/A Expected volatility 75% - 96% N/A N/A Expected term (in years) 0.5 N/A N/A Expected dividend yield —% N/A N/A
Schedule of Allocated Stock-based Compensation Expense	The allocation of stock-based compensation expense was as follows (in thousands): Year Ended December 31, 2020 2019 2018 Research and development expense $ 1,895 $ 84 $ 26 General and administrative expense 2,415 322 34 Total stock-based compensation expense $ 4,310 $ 406 $ 60
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance consisted of the following (in thousands): December 31, 2020 2019 Conversion of convertible preferred stock — 17,666 Common stock options issued and outstanding 3,788 1,667 Equity awards available for future issuance under equity plans 2,852 1,601 Preferred and common stock warrants outstanding — 17 Common stock authorized under the ESPP 296 — Total 6,936 20,951

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Reconciliation of Income Taxes Computed by Applying Statutory Federal Income Tax Rate	A reconciliation of income taxes to the amount computed by applying the statutory federal income tax rate to the net loss is summarized as follows (in thousands): Year Ended December 31, 2020 2019 Income tax expense (benefit) at statutory rates $ (9,315 ) $ (5,194 ) State income tax, net of federal benefit (3,004 ) (1,057 ) Permanent items 1 14 Book income for pre-conversion period — 527 Interest on convertible notes — 445 Realized gain on conversion of convertible notes — 958 Reserve for uncertain tax positions 398 140 Research and development tax credits (1,639 ) (584 ) Deferred taxes recognized upon conversion — (3,076 ) Valuation allowance 13,488 7,827 Other 71 — Income tax expense (benefit) $ — $ —
Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets as of December 31, 2020 and 2019 are shown below (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 11,277 $ 4,275 Research and development tax credits 1,855 438 Deferred revenue 4,443 — Accrued expenses 153 179 Intangibles and fixed assets 2,483 2,721 Lease liability 263 265 Stock-based compensation 969 160 Total deferred tax assets 21,443 8,038 Less valuation allowance (21,316 ) (7,827 ) Net deferred tax assets 127 211 Deferred tax liabilities: Right-of-use asset (127 ) (211 ) Total deferred tax liabilities (127 ) (211 ) Net deferred tax assets $ — $ —
Summarizes of Activity Related to Gross Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s gross unrecognized tax benefits for the years ended December 31, 2020 and 2019 (in thousands): Year Ended December 31, 2020 2019 Gross unrecognized tax benefits at the beginning of the year $ 156 $ — Increases related to current year positions 446 156 Increases related to prior year positions 62 — Other true up 7 — Gross unrecognized tax benefits at the end of the year $ 671 $ 156

Quarterly Financial Data (una_2

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
Quarterly Financial Data (unaudited) (Tables)	Dec. 31, 2020
Selected Quarterly Financial Information [Abstract]
Summary of Unaudited Quarterly Financial Data	The following tables summarize the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share/unit data): 2020 First Quarter Second Quarter Third Quarter Fourth Quarter Revenue $ 1,358 $ 1,541 $ 1,746 $ 2,142 Operating expenses 7,508 11,909 13,212 18,435 Other income (expense) 65 (188 ) 27 18 Net loss (6,085 ) (10,556 ) (11,439 ) (16,275 ) Net loss per share, basic and diluted (1) (2.14 ) (1.23 ) (0.31 ) (0.43 ) 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Revenue $ — $ 224 $ 650 $ 1,445 Operating expenses 2,174 4,129 5,856 7,492 Other income (expense) (375 ) (1,211 ) (1,462 ) (4,354 ) Net loss (2,549 ) (5,116 ) (6,668 ) (10,401 ) Net loss per share/unit, basic and diluted (1) (0.97 ) (1.89 ) (2.43 ) (3.75 ) (1) Net loss per share/unit is computed independently for each quarter and the full year based upon respective shares/units outstanding; therefore, the sum of the quarterly net loss per share/unit amounts may not equal the annual amounts reported.

Description of Business and B_2

Description of Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Jun. 16, 2020USD ($)$ / sharesshares	Jun. 04, 2020	Apr. 01, 2019shares	Jun. 30, 2020shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)shares
Description Of Business And Basis Of Presentation [Line Items]
Common stock, shares authorized	400,000,000				400,000,000	52,042,000
Preferred stock, shares authorized	40,000,000				40,000,000	0
Reverse stock split, description					On June 4, 2020, the Company effected a one-for-2.1095 reverse stock split of its common stock (the Reverse Stock Split).
Stockholders' equity note, stock split, conversion ratio		2.1095
Accumulated deficit \| $					$ 66,540	$ 22,185
Cash, cash equivalents and marketable securities \| $					$ 328,100
Initial Public Offering
Description Of Business And Basis Of Presentation [Line Items]
Sale of stock number of shares issued in transaction	16,560,000
Sale of stock, price per share \| $ / shares	$ 18
Proceeds from the IPO, net of underwriting discounts, commissions and offering costs \| $	$ 274,100
Outstanding shares of convertible preferred stock converted into common stock	17,921,069
Series A Convertible Preferred Stock
Description Of Business And Basis Of Presentation [Line Items]
Preferred unit converted into convertible preferred stock			1
Series B Convertible Preferred Stock
Description Of Business And Basis Of Presentation [Line Items]
Preferred unit converted into convertible preferred stock			1
Undesignated Preferred Stock \| Initial Public Offering
Description Of Business And Basis Of Presentation [Line Items]
Preferred stock, shares authorized	40,000,000
Common Stock
Description Of Business And Basis Of Presentation [Line Items]
Common unit converted into common stock			1
Outstanding shares of convertible preferred stock converted into common stock					17,921,000
Common Stock \| Initial Public Offering
Description Of Business And Basis Of Presentation [Line Items]
Outstanding shares of convertible preferred stock converted into common stock				17,921,069
Warrant to purchase of common stock	7,809
Common stock, shares authorized	400,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)Segmentshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)shares
Summary Of Significant Accounting Policies [Line Items]
Realized gains and losses on marketable securities	$ 0	$ 0	$ 0
Other-than-temporary impairments on marketable securities	0	$ 0	$ 0
Transfers of assets measured on recurring basis out of Level 1 into Level 2	0
Transfers of assets measured on recurring basis out of Level 2 into Level 1	0
Transfers of liabilities measured on recurring basis out of Level 1 into Level 2	0
Transfers of liabilities measured on recurring basis out of Level 2 into Level 1	0
Transfers of financial instrument classified as liability into level 3	0
Transfers of financial instrument classified as liability out of level 3	0
Transfers of financial instrument classified as asset into level 3	0
Transfers of financial instrument classified as asset out of level 3	$ 0
Number of operating segment \| Segment	1
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2019
Weighted-average shares/units subject to repurchase or forfeiture \| shares	123,285	217,524	231,810
Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of assets	5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share/Unit (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	3,858	19,545	6,486
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		17,666	5,906
Warrant \| Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		9	9
Warrant \| Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		8	8
Common Stock/Unit Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	3,788	1,667	300
Common Stock/Units Subject to Repurchase or Forfeiture
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	69	195	263
ESPP Shares Pending Issuance
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	1	0	0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Cash Equivalents and Marketable Securities Measured at Fair Value (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents:		$ 0
Marketable securities:	$ 6,679,000	$ 0
Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	7,399,000
Recurring \| Negotiable certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents:	720,000
Recurring \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities:	6,679,000
Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	7,399,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Negotiable certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents:	720,000
Recurring \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities:	$ 6,679,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Cash equivalents at fair value		$ 0
Marketable securities at fair value	$ 6,679,000	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Reconciliation of Preferred Stock Warrant Liability Measured at Fair Value Using Level 3 Unobservable Inputs (Details) - Significant Unobservable Inputs (Level 3) - Recurring - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 45	$ 30
Change in fair value	75	15
Reclassification of warrant liability to stockholders’ equity	$ (120)
Ending Balance		$ 45

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 6,684,000
Unrealized Gains	0
Unrealized Losses	(5,000)
Marketable securities:	6,679,000	$ 0
Corporate Debt Securities with 1 Year or Less Maturity
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,612,000
Unrealized Gains	0
Unrealized Losses	(2,000)
Marketable securities:	3,610,000
Corporate Debt Securities with 1 to 2 Years Maturity
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,072,000
Unrealized Gains	0
Unrealized Losses	(3,000)
Marketable securities:	$ 3,069,000

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Investments Debt And Equity Securities [Abstract]
Investments in marketable securities	$ 6,679,000	$ 0

Collaboration, License and Re_3

Collaboration, License and Research Agreements - Additional Information (Details)

1 Months Ended

3 Months Ended

12 Months Ended

Nov. 30, 2019shares

Apr. 30, 2019USD ($)Product

Dec. 31, 2020USD ($)

Sep. 30, 2020USD ($)

Jun. 30, 2020USD ($)

Mar. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Dec. 31, 2020USD ($)Obligation

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 2,142,000

$ 1,746,000

$ 1,541,000

$ 1,358,000

$ 1,445,000

$ 650,000

$ 224,000

$ 0

$ 6,787,000

$ 2,319,000

$ 379,000

Lilly Note | Series C Convertible Preferred Stock

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Conversion of convertible note payable to preferred stock | shares

4,576,342

Research Collaboration and License Agreement with Eli Lilly

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront fees received

$ 20,000,000

License agreement expiry period

10 years

Number of performance obligation | Obligation

Period for expects performance obligation

5 years

Revenue recognized

$ 6,800,000

2,300,000

Deferred revenue

15,840,000

18,940,000

15,840,000

18,940,000

Research Collaboration and License Agreement with Eli Lilly | Prepaid and Other Assets

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration receivables

$ 1,200,000

$ 800,000

1,200,000

$ 800,000

Research Collaboration and License Agreement with Eli Lilly | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Rights to antibody oligonucleotide conjugates for messengers RNA targets. | Product

Development milestone payment eligible to receive per target

$ 60,000,000

Regulatory milestone payment eligible to receive per target

140,000,000

Commercialization milestone payment eligible to receive

$ 205,000,000

Research Collaboration with MyoKardia, Inc.

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 0

Agreements with Pharmaceutical Companies

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized

$ 400,000

Collaboration, License and Re_4

Collaboration, License and Research Agreements - Reconciliation of Deferred Revenue Related to Lilly Agreement (Details) - Research Collaboration and License Agreement with Eli Lilly - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance	$ 18,940
Upfront payment		$ 20,000
Revenue recognized	(3,100)	(1,060)
Balance	$ 15,840	$ 18,940

Property,and Equipment - Schedu

Property,and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 3,447	$ 2,274
Less accumulated depreciation	1,979	1,643
Total property and equipment, net	1,468	631
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,928	1,755
Computers and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	58	65
Office Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	44	37
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 417	$ 417

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation expenses related to property and equipment	$ 373	$ 348	$ 383

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) $ in Thousands	Dec. 31, 2019USD ($)
Current liabilities:
Term loans	$ 2,800
Unamortized debt issuance costs	(25)
Unamortized debt discount	(1)
Loans payable, net of issuance costs and discount	2,774
Non-current liabilities:
Term loans	1,400
Accrued end of term fees	374
Unamortized debt issuance costs	(4)
Loans payable, net of issuance costs and discount	1,770
Total loans payable, net of issuance costs and discount	$ 4,544

Debt - Additional Information (

Debt - Additional Information (Details)	Jun. 17, 2020shares	Jun. 30, 2020USD ($)$ / sharesshares	Aug. 31, 2018USD ($)	Jun. 30, 2017USD ($)Installment$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Repayment of existing loan					$ 4,683,000	$ 2,800,000	$ 0
Proceeds from notes					$ 0	$ 19,451,000	$ 2,988,000
Common Stock
Debt Instrument [Line Items]
Warrant exercisable \| shares		7,809
Exercise price of warrant \| $ / shares		$ 4.77
Cashless exercise of warrants \| shares	15,833
SVB
Debt Instrument [Line Items]
Repayment of existing loan				$ 4,100,000
Debt instrument final payments				$ 400,000
SVB \| Convertible Notes
Debt Instrument [Line Items]
Proceeds from notes			$ 3,000,000
SVB \| Term C Loan \| Common Stock
Debt Instrument [Line Items]
Warrant term					7 years
Exercise price of warrant \| $ / shares				$ 0.53
SVB \| Term C Loan \| Common Stock \| Maximum
Debt Instrument [Line Items]
Warrant to purchase common stock \| shares				9,442
SVB \| Term A And Term B Loans \| Series A Convertible Preferred Stock
Debt Instrument [Line Items]
Exercise price of warrant \| $ / shares					$ 2.2615
Warrant term					10 years
SVB \| Term A And Term B Loans \| Series A Convertible Preferred Stock \| Maximum
Debt Instrument [Line Items]
Warrant to purchase convertible preferred stock \| shares					16,474
SVB \| LSA Amendment
Debt Instrument [Line Items]
Loan facility maximum borrowing capacity				$ 7,000,000
SVB \| LSA Amendment \| Term C Loan
Debt Instrument [Line Items]
Face amount of loans				5,000,000
Debt instrument final payments				$ 300,000
Maturity date				Jun. 1, 2021
Basis spread on variable rate				0.20%
Frequency of periodic payment principal					36 equal monthly
Number of equal monthly installments of principal \| Installment				36
Frequency of periodic payment interest					monthly
Debt instrument final payment percentage				6.50%
SVB \| LSA Amendment \| Term D Loan
Debt Instrument [Line Items]
Face amount of loans				$ 2,000,000
SVB \| LSA Second Amendment \| Term D Loan
Debt Instrument [Line Items]
Debt instrument final payments			$ 100,000
Debt instrument final payment percentage			6.50%
Proceeds from issuance of long-term debt			$ 2,000,000
SVB \| LSA \| Term C And D Loans
Debt Instrument [Line Items]
Loans prepaid amount		$ 2,800,000
Payment of final payment and accrued interest		$ 500,000

Convertible Notes - Additional

Convertible Notes - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Nov. 30, 2019	Apr. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Proceeds from issuance of convertible notes			$ 0	$ 19,451,000	$ 2,988,000
Interest expense			$ 209,000	7,387,000	718,000
Convertible Notes \| Series C Convertible Preferred Stock
Debt Instrument [Line Items]
Conversion of convertible notes payable to preferred stock	6,893,036
Interest expense				6,900,000	200,000
2018 Notes
Debt Instrument [Line Items]
Face amount of loans					$ 3,000,000
Convertible promissory notes accrued interest rate					8.00%
Convertible promissory notes conversion percentage on per share price paid by investors					85.00%
Qualified financing of convertible promissory notes converted into preferred equity					$ 10,000,000
2019 Notes
Debt Instrument [Line Items]
Face amount of loans				$ 4,500,000
Convertible promissory notes accrued interest rate				10.00%
Convertible promissory notes conversion percentage on per share price paid by investors				80.00%
Qualified financing of convertible promissory notes converted into preferred equity				$ 10,000,000
Lilly Note
Debt Instrument [Line Items]
Convertible promissory notes accrued interest rate		8.00%
Proceeds from issuance of convertible notes		$ 15,000,000
Maturity date		2020-10
Lilly Note \| Series C Convertible Preferred Stock
Debt Instrument [Line Items]
Conversion of convertible notes payable to preferred stock	4,576,342

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	Dec. 18, 2020	Dec. 31, 2020
Commitments and Contingencies [Line Items]
Operating lease, description		Currently, the Company is only party to non-cancellable office and laboratory space operating leases and a short-term office lease. Under the relevant guidance, the Company recognizes operating lease right-of-use (ROU) assets and liabilities based on the present value of the future minimum lease payments over the lease term at the commencement date, using the Company’s assumed incremental borrowing rate of 5.5%, and amortizes the ROU assets and liabilities over the lease term. Lease expense for operating leases is recognized on a straight-line basis over the lease term. The Company’s short-term lease is not subject to recognition of an ROU asset or liability or straight-line lease expense requirements.
Incremental borrowing rate		5.50%
Weighted-average remaining term of operating leases		9 months 18 days
Loss contingencies accrued		$ 0
Lease Term through November 2017 \| Office and Laboratory Space
Commitments and Contingencies [Line Items]
Operating lease, term of contract, description		In March 2014, the Company entered into a non-cancellable operating lease for office and laboratory space with a lease term through November 2017.
Lease Term through December 2021 \| Office and Laboratory Space
Commitments and Contingencies [Line Items]
Operating lease, term of contract, description		In July 2017, the Company entered into an amendment to this lease to extend the lease term through December 2021.
New Lease \| Office and Laboratory Space
Commitments and Contingencies [Line Items]
Operating lease, lease not yet commenced, description	On December 18, 2020, the Company entered into an amendment to the non-cancellable operating lease for its new headquarters location (as amended, the New Lease), which increased the square footage by adding adjacent space and extended the projected commencement date to November 1, 2021. Additionally, the non-cancellable temporary operating lease was amended (as amended, the Temporary Lease) to accommodate the projected commencement date of the New Lease.	On June 1, 2020, the Company entered into a second amendment to its existing operating lease (as amended, the 2014 Lease) and entered into a new non-cancellable temporary operating lease in connection with a newly executed non-cancellable operating lease for its new headquarters location, with a projected commencement date of July 1, 2021.
Operating lease, lease not yet commenced, lease payment under new lease	$ 14,700,000
Operating lease, lease not yet commenced, term of contract	5 years
Operating lease, lease not yet commenced, renewal term	5 years
Lessee, operating lease, lease not yet commenced, existence of option to extend [true false]	true
Operating lease, lease not yet commenced, initial monthly base rent	$ 251,000
Operating lease, lease not yet commenced, monthly base rent for last year lease	282,000
Letter of credit	$ 251,000
Temporary Lease \| Office and Laboratory Space
Commitments and Contingencies [Line Items]
Operating lease expiration period, description	The lease term under both the 2014 Lease and the Temporary Lease ends 15 days after the commencement date of the New Lease in November 2021.
Operating lease lease expiration period	15 days

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of ROU Assets and Liabilities Related to 2014 Lease and Temporary Lease (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
ROU assets (included in other assets)	$ 454
Operating lease, right-of-use asset, statement of financial position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Lease liabilities, current portion (included in accounts payable and accrued liabilities)	$ 0
Operating lease, liability, current, statement of financial position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Lease liabilities, net of current portion	$ 938	$ 393
Total lease liabilities	$ 938

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Maturities of Lease Liabilities due under 2014 Lease and Temporary Lease (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
2021	$ 17
2022	135
2023	208
2024	214
2025	220
2026	188
Total lease payments	982
Less imputed interest	(44)
Total lease liabilities	938
Less lease liabilities, current portion	0
Lease liabilities, net of current portion	$ 938	$ 393

Commitments and Contingencies_4

Commitments and Contingencies - Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in Measurement of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Cash paid included in operating cash flows	$ 163	$ 382

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Rent Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Operating leases	$ 453	$ 302	$ 302
Short-term lease	36	6
Total rent expense	$ 489	$ 308	$ 302

Stockholders' Equity (Deficit_2

Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($)	Jun. 16, 2020	Apr. 01, 2019	Jun. 30, 2020	Jan. 31, 2020	Nov. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized	400,000,000					400,000,000	52,042,000
Preferred stock undesignated shares authorized	40,000,000					40,000,000	0
Common stock par value per share	$ 0.0001					$ 0.0001	$ 0.0001
Preferred stock par value per share	$ 0.0001					$ 0.0001	$ 0.0001
Reclassified accumulated deficit from predecessor deficit to additional paid in capital		$ 44,100,000
Convertible preferred stock, issued						0	37,267,000
Proceeds from issuance of Series C convertible preferred stock, net of issuance costs						$ 2,200,000	$ 72,623,000	$ 0
Issuance costs						$ 24,026,000	$ 0	0
Shares of common stock initially reserved for issuance						6,936,000	20,951,000
Total intrinsic value of options exercised						$ 500,000	$ 7,000	$ 0
Weighted-average grant date fair value of options granted						$ 11.63	$ 3.46	$ 0.30
Stock options exercised were unvested						69,359	194,729
Expected dividend yield						0.00%	0.00%	0.00%
Time-based Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost						$ 27,200,000
Weighted-average period of unrecognized compensation cost						3 years 2 months 12 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period						4 years
Expected term (in years)						6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period						2 years
Expected term (in years)						5 years 4 months 24 days	2 years	2 years
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units initially reserved for issuance									2,127,013
Increased to number of shares reserved under plan									4,771,615
2013 Equity Incentive Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period						10 years
2020 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock initially reserved for issuance			3,900,000
Percentage of shares of common stock outstanding on final day of immediately preceding calendar year			5.00%
Number of remaining shares available for issuance						2,851,824
2020 Incentive Award Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period						10 years
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock initially reserved for issuance			325,000
Participant maximum contribution as percentage of eligible compensation			15.00%
Percentage of purchase price of shares of lower of fair market value			85.00%
Shares issued under ESPP						28,979
Expected term (in years)						6 months
Expected dividend yield						0.00%
Unrecognized compensation cost						$ 200,000
Weighted-average period of unrecognized compensation cost						6 months
Employee Stock Purchase Plan \| Accounts Payable and Accrued Liabilities
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding liability						$ 35,000
Series A Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred unit converted into convertible preferred stock		1
Series B Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred unit converted into convertible preferred stock		1
Series C Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Convertible preferred stock, issued				537,232	17,915,525
Stock issued price per share				$ 4.2812	$ 4.2812
Proceeds from issuance of Series C convertible preferred stock, net of issuance costs				$ 2,200,000	$ 72,600,000
Issuance costs				$ 100,000	$ 4,100,000
Series C Convertible Preferred Stock \| Convertible Notes
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion of convertible note payable to preferred stock					6,893,036
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common unit converted into common stock		1
Outstanding shares of convertible preferred stock converted into common stock						17,921,000
Shares issued under ESPP						29,000
IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of stock number of shares issued in transaction	16,560,000
Sale of stock, price per share	$ 18
Proceeds from the IPO, net of underwriting discounts, commissions and offering costs	$ 274,100,000
Outstanding shares of convertible preferred stock converted into common stock	17,921,069
IPO \| Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized	400,000,000
Outstanding shares of convertible preferred stock converted into common stock			17,921,069

Stockholders' Equity (Deficit_3

Stockholders' Equity (Deficit) - Summary of Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Shares Authorized	0	38,055,000
Shares Issued and Outstanding		37,267,000
Liquidation Preference		$ 138,970
Carrying Value		$ 134,720
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		4,367,000
Shares Issued and Outstanding		4,350,000
Per Share Original Issue Price and Conversion Price		$ 2.2615
Liquidation Preference		$ 9,838
Carrying Value		$ 9,773
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		8,108,000
Shares Issued and Outstanding		8,108,000
Per Share Original Issue Price and Conversion Price		$ 2.8269
Liquidation Preference		$ 22,922
Carrying Value		$ 22,814
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		25,580,000
Shares Issued and Outstanding		24,809,000
Per Share Original Issue Price and Conversion Price		$ 4.2812
Liquidation Preference		$ 106,210
Carrying Value		$ 102,133

Stockholders' Equity (Deficit_4

Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Number
Outstanding at December 31, 2019 \| shares	1,667
Granted \| shares	2,291
Exercised \| shares	(119)
Forfeited \| shares	(51)
Outstanding at December 31, 2020 \| shares	3,788
Exercisable at December 31, 2020 \| shares	556
Weighted-Average Exercise Price
Outstanding at December 31, 2019 \| $ / shares	$ 1.08
Granted \| $ / shares	14.24
Exercised \| $ / shares	0.45
Forfeited \| $ / shares	1.24
Outstanding at December 31, 2020 \| $ / shares	9.06
Exercisable at December 31, 2020 \| $ / shares	$ 1.24
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding, Weighted- Average Remaining Contractual Term (in years)	9 years 1 month 6 days
Exercisable, Weighted- Average Remaining Contractual Term (in years)	8 years 3 months 18 days
Outstanding, Aggregate Intrinsic Value \| $	$ 65,082
Exercisable, Aggregate Intrinsic Value \| $	$ 13,491

Stockholders' Equity (Deficit_5

Stockholders' Equity (Deficit) - Schedule of Assumptions used in Black-Scholes Model to Determine Fair Value of Stock/Unit Option Grants and Shares Purchasable under ESPP (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, Minimum	0.30%	1.40%	2.40%
Risk-free interest rate, Maximum	1.50%	2.70%	2.90%
Expected volatility, Minimum	88.00%	84.00%	83.00%
Expected volatility, Maximum	92.00%	88.00%	84.00%
Expected dividend yield	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 4 months 24 days	2 years	2 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, Minimum	0.10%
Risk-free interest rate, Maximum	0.20%
Expected volatility, Minimum	75.00%
Expected volatility, Maximum	96.00%
Expected term (in years)	6 months
Expected dividend yield	0.00%

Stockholders' Equity (Deficit_6

Stockholders' Equity (Deficit) - Schedule of Allocated Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,310	$ 406	$ 60
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,895	84	26
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,415	$ 322	$ 34

Stockholders' Equity (Deficit_7

Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details) - shares shares in Thousands	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Common stock reserved for future issuance	6,936	20,951
Conversion of Convertible Preferred Stock
Class Of Stock [Line Items]
Common stock reserved for future issuance	0	17,666
Common Stock Options Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuance	3,788	1,667
Preferred and Common Stock Warrants Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuance	0	17
Equity Awards Available for Future Issuance under Equity Plans
Class Of Stock [Line Items]
Common stock reserved for future issuance	2,852	1,601
Common Stock Authorized under the ESPP
Class Of Stock [Line Items]
Common stock reserved for future issuance	296	0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
Income Taxes - Additional Information (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Income Taxes Disclosure [Line Items]
Provision for income taxes	$ 0	$ 0
Increase in the valuation allowance	13,500,000
Accruals for interest or penalties	0	0
Interest or penalties	0	$ 0
Federal
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards	$ 40,200,000
Net operating loss available to offset against current taxable income percentage	100.00%
Net operating loss available to offset against future taxable income percentage	80.00%
Federal and state tax credit carryforwards	$ 1,700,000
Tax credit expiration beginning year	2039
State
Income Taxes Disclosure [Line Items]
Net operating loss (NOL) carryforwards	$ 40,000,000
Net operating loss carryforwards, expiration beginning year	2039
Federal and state tax credit carryforwards	$ 1,000,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes Computed by Applying Statutory Federal Income Tax Rate (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at statutory rates	$ (9,315,000)	$ (5,194,000)
State income tax, net of federal benefit	(3,004,000)	(1,057,000)
Permanent items	1,000	14,000
Book income for pre-conversion period		527,000
Interest on convertible notes		445,000
Realized gain on conversion of convertible notes		958,000
Reserve for uncertain tax positions	398,000	140,000
Research and development tax credits	(1,639,000)	(584,000)
Deferred taxes recognized upon conversion		(3,076,000)
Valuation allowance	13,488,000	7,827,000
Other	71,000
Income tax expense (benefit)	$ 0	$ 0

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 11,277	$ 4,275
Research and development tax credits	1,855	438
Deferred revenue	4,443
Accrued expenses	153	179
Intangibles and fixed assets	2,483	2,721
Lease liability	263	265
Stock-based compensation	969	160
Total deferred tax assets	21,443	8,038
Less valuation allowance	(21,316)	(7,827)
Net deferred tax assets	127	211
Deferred tax liabilities:
Right-of-use asset	(127)	(211)
Total deferred tax liabilities	$ (127)	$ (211)

Income Taxes - Summarizes of Ac

Income Taxes - Summarizes of Activity Related to Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at the beginning of the year	$ 156
Increases related to current year positions	446	$ 156
Increases related to prior year positions	62
Other true up	7
Gross unrecognized tax benefits at the end of the year	$ 671	$ 156

Quarterly Financial Data (una_3

Quarterly Financial Data (unaudited) - Summary of Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenue	$ 2,142		$ 1,746		$ 1,541		$ 1,358		$ 1,445		$ 650		$ 224		$ 0		$ 6,787	$ 2,319	$ 379
Operating expenses	18,435		13,212		11,909		7,508		7,492		5,856		4,129		2,174		51,064	19,651	10,877
Other income (expense)	18		27		(188)		65		(4,354)		(1,462)		(1,211)		(375)		(78)	(7,402)	(718)
Net loss	$ (16,275)		$ (11,439)		$ (10,556)		$ (6,085)		$ (10,401)		$ (6,668)		$ (5,116)		$ (2,549)		$ (44,355)	$ (24,734)	$ (11,216)
Net loss per share/unit, basic and diluted	$ (0.43)	[1]	$ (0.31)	[1]	$ (1.23)	[1]	$ (2.14)	[1]	$ (3.75)	[1]	$ (2.43)	[1]	$ (1.89)	[1]	$ (0.97)	[1]	$ (2.05)	$ (9.12)	$ (4.53)

[1]	Net loss per share/unit is computed independently for each quarter and the full year based upon respective shares/units outstanding; therefore, the sum of the quarterly net loss per share/unit amounts may not equal the annual amounts reported.