0001564590-21-044018 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2021	Aug. 09, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-39370
Entity Registrant Name	Nkarta, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4515206
Entity Address, Address Line One	6000 Shoreline Court
Entity Address, Address Line Two	Suite 102
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	582-4923
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	NKTX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		32,906,550
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001787400

CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 24,421	$ 96,692
Short-term investments, available-for-sale	255,382	218,221
Prepaid expenses and other current assets	4,132	3,922
Total current assets	283,935	318,835
Restricted cash	452	413
Property and equipment, net	11,350	9,350
Operating lease right-of-use assets	12,050	8,505
Other long-term assets	1,324	547
Total assets	309,111	337,650
Current liabilities
Accounts payable	2,161	1,176
Operating lease liabilities, current portion	2,287	1,402
Accrued and other current liabilities	5,808	6,253
Total current liabilities	10,256	8,831
Operating lease liabilities, net of current portion	10,408	7,517
Other long-term liabilities	65	82
Total liabilities	20,729	16,430
Commitments and contingencies (Note 7)
Stockholders’ equity
Preferred stock
Common stock	3	3
Additional paid-in capital	447,302	439,235
Accumulated other comprehensive income	6	3
Accumulated deficit	(158,929)	(118,021)
Total stockholders’ equity	288,382	321,220
Total liabilities and stockholders’ equity	$ 309,111	$ 337,650

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses
Research and development	$ 15,957	$ 7,862	$ 29,496	$ 15,122
General and administrative	5,677	2,493	11,618	4,642
Total operating expenses	21,634	10,355	41,114	19,764
Loss from operations	(21,634)	(10,355)	(41,114)	(19,764)
Other income (expense), net:
Change in fair value of preferred stock purchase right liability		(40,741)		(40,163)
Interest income	104	27	214	152
Other income (expense), net	(5)	4	(8)	4
Total other income (expense), net	99	(40,710)	206	(40,007)
Net loss	(21,535)	(51,065)	(40,908)	(59,771)
Comprehensive loss:
Net loss	(21,535)	(51,065)	(40,908)	(59,771)
Other comprehensive gain (loss)	(28)	4	3	3
Comprehensive loss	$ (21,563)	$ (51,061)	$ (40,905)	$ (59,768)
Net loss per share, basic and diluted	$ (0.66)	$ (30.06)	$ (1.25)	$ (36.13)
Weighted average shares used to compute net loss per share, basic and diluted	32,827,365	1,698,560	32,783,730	1,654,304

CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Income) Loss	Accumulated Deficit	Convertible Preferred Stock
Beginning Balance at Dec. 31, 2019	$ (25,482)	$ 1	$ 1,179	$ (2)	$ (26,660)
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019						27,283,973
Temporary Equity, Beginning Balance at Dec. 31, 2019						$ 59,815
Beginning Balance, Shares at Dec. 31, 2019		1,600,601
Vesting of shares of common stock subject to repurchase	14		14
Vesting of shares of common stock subject to repurchase, Shares		17,494
Issuance of common stock upon exercise of stock option, net of repurchase	1		1
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		2,871
Share-based compensation expense	482		482
Unrealized gain (loss) on short-term investments	(1)			(1)
Net loss	(8,706)				(8,706)
Ending Balance at Mar. 31, 2020	(33,692)	$ 1	1,676	(3)	(35,366)
Temporary Equity, Ending Balance, Shares at Mar. 31, 2020						27,283,973
Temporary Equity, Ending Balance at Mar. 31, 2020						$ 59,815
Ending Balance, Shares at Mar. 31, 2020		1,620,966
Beginning Balance at Dec. 31, 2019	(25,482)	$ 1	1,179	(2)	(26,660)
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019						27,283,973
Temporary Equity, Beginning Balance at Dec. 31, 2019						$ 59,815
Beginning Balance, Shares at Dec. 31, 2019		1,600,601
Net loss	(59,771)
Ending Balance at Jun. 30, 2020	(83,890)	$ 1	2,539	1	(86,431)
Temporary Equity, Ending Balance, Shares at Jun. 30, 2020						27,283,973
Temporary Equity, Ending Balance at Jun. 30, 2020						$ 59,815
Ending Balance, Shares at Jun. 30, 2020		1,750,501
Beginning Balance at Mar. 31, 2020	(33,692)	$ 1	1,676	(3)	(35,366)
Temporary Equity, Beginning Balance, Shares at Mar. 31, 2020						27,283,973
Temporary Equity, Beginning Balance at Mar. 31, 2020						$ 59,815
Beginning Balance, Shares at Mar. 31, 2020		1,620,966
Vesting of shares of common stock subject to repurchase	12		12
Vesting of shares of common stock subject to repurchase, Shares		19,110
Issuance of common stock upon exercise of stock option, net of repurchase	285		285
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		110,425
Share-based compensation expense	566		566
Unrealized gain (loss) on short-term investments	4			4
Net loss	(51,065)				(51,065)
Ending Balance at Jun. 30, 2020	(83,890)	$ 1	2,539	1	(86,431)
Temporary Equity, Ending Balance, Shares at Jun. 30, 2020						27,283,973
Temporary Equity, Ending Balance at Jun. 30, 2020						$ 59,815
Ending Balance, Shares at Jun. 30, 2020		1,750,501
Beginning Balance at Dec. 31, 2020	321,220	$ 3	439,235	3	(118,021)
Beginning Balance, Shares at Dec. 31, 2020		32,627,963
Vesting of shares of common stock subject to repurchase	9		9
Vesting of shares of common stock subject to repurchase, Shares		15,802
Issuance of common stock upon exercise of stock option, net of repurchase	756		756
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		154,489
Share-based compensation expense	3,347		3,347
Unrealized gain (loss) on short-term investments	31			31
Net loss	(19,373)				(19,373)
Ending Balance at Mar. 31, 2021	305,990	$ 3	443,347	34	(137,394)
Ending Balance, Shares at Mar. 31, 2021		32,798,254
Beginning Balance at Dec. 31, 2020	$ 321,220	$ 3	439,235	3	(118,021)
Beginning Balance, Shares at Dec. 31, 2020		32,627,963
Issuance of common stock upon exercise of stock option, net of repurchase, Shares	194,354
Net loss	$ (40,908)
Ending Balance at Jun. 30, 2021	288,382	$ 3	447,302	6	(158,929)
Ending Balance, Shares at Jun. 30, 2021		32,852,861
Beginning Balance at Mar. 31, 2021	305,990	$ 3	443,347	34	(137,394)
Beginning Balance, Shares at Mar. 31, 2021		32,798,254
Vesting of shares of common stock subject to repurchase	9		9
Vesting of shares of common stock subject to repurchase, Shares		15,575
Issuance of common stock upon exercise of stock option, net of repurchase	256		256
Issuance of common stock upon exercise of stock option, net of repurchase, Shares		39,032
Share-based compensation expense	3,690		3,690
Unrealized gain (loss) on short-term investments	(28)			(28)
Net loss	(21,535)				(21,535)
Ending Balance at Jun. 30, 2021	$ 288,382	$ 3	$ 447,302	$ 6	$ (158,929)
Ending Balance, Shares at Jun. 30, 2021		32,852,861

CONDENSED STATEMENT OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net loss		$ (40,908)	$ (59,771)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense		7,037	1,048
Depreciation and amortization		667	281
Accretion and amortization of premiums and discounts on investments, net		1,576	(32)
Non-cash lease expense		231	178
Change in fair value of preferred stock purchase right liability	$ 40,741		40,163
Changes in operating assets and liabilities:
Prepaid expenses and other assets		(987)	(368)
Accounts payable and accrued and other liabilities		285	(27)
Net cash used in operating activities		(32,099)	(18,528)
Cash flows from investing activities
Purchases of property and equipment		(2,411)	(4,812)
Purchases of short-term investments		(86,234)	(3,577)
Maturities of short-term investments		47,500	16,100
Net cash provided by (used in) investing activities		(41,145)	7,711
Cash flows from financing activities
Proceeds from stock option exercises		1,012	287
Proceeds from early exercise of stock options			12
Liability to related party			10,245
Payments of deferred offering costs			(2,440)
Net cash provided by financing activities		1,012	8,104
Net decrease in cash and cash equivalents		(72,232)	(2,713)
Cash, cash equivalents, and restricted cash beginning of period		97,105	20,875
Cash, cash equivalents, and restricted cash end of period	18,162	24,873	18,162
Reconciliation of cash, cash equivalents and restricted cash to the balance sheet:
Cash and cash equivalents	17,749	24,421	17,749
Restricted cash	413	452	413
Total cash, cash equivalents and restricted cash	$ 18,162	$ 24,873	$ 18,162

Organization and Description of Business

6 Months Ended

Jun. 30, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Description of Business

1. Organization and Description of Business

Description of the Business

Nkarta, Inc. (“Nkarta” or the “Company”) was incorporated in the State of Delaware in July 2015. The Company is a biopharmaceutical company developing engineered natural killer (“NK”) cells to treat cancer. The Company is focused on leveraging the natural potent power of NK cells to identify and kill abnormal cells and recruit adaptive immune effectors to generate responses that are specific and durable. Nkarta is combining its NK expansion platform technology with proprietary cell engineering technologies to generate an abundant supply of NK cells, engineer enhanced NK cell recognition of tumor targets, and improve persistence for sustained activity in the body for the treatment of cancer. Nkarta’s goal is to develop off-the-shelf NK cell therapy product candidates to improve outcomes for patients. The Company’s operations are based in South San Francisco, California and it operates in one segment.

Liquidity and Management Plans

The accompanying unaudited condensed financial statements have been prepared assuming that the Company will continue as a going concern. However, since inception, the Company has devoted substantially all of its efforts to organizing and staffing, business planning, raising capital, conducting preclinical studies and initiating clinical studies, and has not realized substantial revenues from its planned principal 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 its research and development activities. As of June 30, 2021, the Company had an accumulated deficit of $158.9 million and cash, cash equivalents, restricted cash and short-term investments of $280.3 million.

Management plans to continue to incur substantial costs in order to conduct research and development activities and additional capital will be needed to undertake these activities. The Company intends to raise such capital through debt or equity financings or other arrangements to fund operations. Management believes that the Company’s current cash, cash equivalents, restricted cash and short-term investments will provide sufficient funds to enable the Company to meet its obligations for at least twelve months from the filing date of this report.

Basis of Presentation and Significant Accounting Policies

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Basis of Presentation and Significant Accounting Policies

2. Basis of Presentation and Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed financial statements as of June 30, 2021 and for the three and six months ended June 30, 2021 and 2020 have been prepared in accordance with U.S. generally accepted accounting principle (“U.S. GAAP”) for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows.

The results for the three and six months ended June 30, 2021 are not necessarily indicative of the results expected for the full year or any subsequent interim period. The condensed balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2020, contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed by the Company with the Securities and Exchange Commission (the “SEC”) on March 25, 2021.

COVID-19 Pandemic

The COVID-19 pandemic has caused disruptions in the global economy and has affected and may continue to affect the Company’s business and operations. The extent of the impact of the COVID-19 pandemic on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the outbreak, the development and spread of more contagious and/or vaccine-resistant variants, the effectiveness of actions taken in the United States and other countries to contain, vaccinate against, and treat the disease, and its impact on the Company’s current and planned preclinical studies and clinical trials, employees and vendors, all of which are uncertain and cannot be predicted. The extent to which the COVID-19 pandemic may

impact the Company’s financial condition or results of operations is uncertain. 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 continues to evaluate the impact of the CARES Act on its financial position, results of operations and cash flows. The Company currently does not expect to apply for loans or grants under the CARES Act.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to preclinical studies, fair value of assets and liabilities, share-based compensation and income taxes. Management bases its estimates on historical experience, knowledge of current events and actions it may undertake in the future that management believes to be reasonable under the circumstances. Actual results may differ from these estimates and assumptions.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares plus the potential dilutive effects of potential dilutive securities outstanding during the period. Potential dilutive securities are excluded from diluted earnings or loss per share if the effect of such inclusion is antidilutive. The Company’s potentially dilutive securities, which include convertible preferred stock prior to the conversion of such shares to common stock, unvested common stock, and outstanding stock options under the Company’s equity incentive plan, have been excluded from the computation of diluted net loss per share as they would be anti-dilutive to the net loss per share. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position.

Recent Accounting Pronouncements

Income Taxes. In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in Topic 740 related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new guidance also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates. This standard is effective for fiscal years beginning after December 15, 2020, with early adoption permitted. The Company adopted this standard in the first quarter of 2021 using the prospective method, and the adoption did not have a material impact on the Company’s financial statements.

There were no other significant updates to the recently issued accounting standards other than as disclosed herewith for the six months ended June 30, 2021. Although there are several other new accounting pronouncements issued or proposed by the FASB, the Company does not believe any of those accounting pronouncements have had or will have a material impact on its financial position or operating results.

Net Loss Per Share

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Net Loss Per Share

3. Net Loss Per Share

The following tables summarize the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss	$	(21,535	)	$	(51,065	)	$	(40,908	)	$	(59,771	)
Denominator:
Weighted average common shares outstanding		32,879,406			1,815,833			32,843,343			1,775,961
Less: weighted average unvested common stock issued upon early exercise of common stock options		(52,041	)		(117,273	)		(59,613	)		(121,657	)
Weighted average shares used to compute net loss per share, basic and diluted		32,827,365			1,698,560			32,783,730			1,654,304
Net loss per share, basic and diluted	$	(0.66	)	$	(30.06	)	$	(1.25	)	$	(36.13	)

The following table summarizes the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive:

	As of June 30,
	2021		2020
Common stock options		4,293,442		2,424,747
Unvested common stock upon early exercise of common stock options		46,849		124,888
Convertible preferred stock		—		7,374,034
		4,340,291		9,923,669

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

4. Fair Value of Financial Instruments

The following tables summarize the fair value of the Company’s financial instruments (in thousands):

			Fair Value Measurements Using
	June 30, 2021		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents:
Money market funds	$	21,331	$	21,331	$	—	$	—
Short-term investments:
Corporate debt securities	$	89,989	$	—	$	89,989		—
Commercial paper		44,981		—		44,981		—
U.S. Government securities		120,412		—		120,412		—
Total short-term investments		255,382		—		255,382		—
Total	$	276,713	$	21,331	$	255,382	$	—

			Fair Value Measurements Using
	December 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents:
Money market funds	$	94,631	$	94,631	$	—	$	—
Short-term investments:
Corporate debt securities	$	48,614	$	—	$	48,614		—
Commercial paper		63,445		—		63,445		—
U.S. Government securities		106,162		—		106,162		—
Total short-term investments		218,221		—		218,221		—
Total	$	312,852	$	94,631	$	218,221	$	—

Cash Equivalents and Short-Term Investments

Financial assets measured at fair value on a recurring basis consist of the Company’s cash equivalents and short-term investments. Cash equivalents consisted of money market funds and short-term investments consisted of commercial paper, U.S. Government securities and corporate bonds. The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, and bids and/or offers.

Investments are classified as Level 1 within the fair value hierarchy if their quoted prices are available in active markets for identical securities. Investments in money market funds of $21.3 million and $94.6 million as of June 30, 2021 and December 31, 2020, respectively, were classified as Level 1 instruments and were included in cash and cash equivalents.

Investments in marketable securities are valued using Level 2 inputs. Level 2 securities are initially valued at the transaction price and subsequently valued and reported upon utilizing inputs other than quoted prices that are observable either directly or indirectly, such as quotes from third-party pricing vendors. Fair values determined by Level 2 inputs, which utilize data points that are observable such as quoted prices, interest rates and yield curves, require the exercise of judgment and use of estimates, that if changed, could significantly affect the Company’s financial position and results of operations. The marketable securities of $255.4 million and $218.2 million as of June 30, 2021 and December 31, 2020, respectively, were classified as Level 2 instruments and were included in short-term investments. Accrued interest receivable related to short-term investments was $1.4 million and $1.1 million as of June 30, 2021 and December 31, 2020, respectively, and included as part of prepaid expenses and other current assets in the condensed balance sheets.

The following tables summarize the Company’s short-term investments accounted for as available-for-sale securities as of June 30, 2021 and December 31, 2020 (in thousands):

		June 30, 2021
	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
Corporate debt securities	1 year or less	$	90,000	$	(14	)	$	3	$	89,989
Commercial paper	1 year or less		44,981		—			—		44,981
U.S. Government securities	1 year or less		120,395					17		120,412
Total		$	255,376	$	(14	)	$	20	$	255,382

		December 31, 2020
	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
Corporate debt securities	1 year or less	$	48,616	$	(6	)	$	4	$	48,614
Commercial paper	1 year or less		63,445		—			—		63,445
U.S. Government securities	1 year or less		106,157		(7	)		12	$	106,162
Total		$	218,218	$	(13	)	$	16	$	218,221

The Company has classified all of its available-for-sale investment securities as current assets on the condensed balance sheets based on the highly liquid nature of these investment securities and because these investment securities are considered available for use in current operations.

The Company considers whether unrealized losses have resulted from a credit loss or other factors. The unrealized losses on the Company’s available-for-sale securities as of June 30, 2021 and December 31, 2020 were caused by fluctuations in market value and interest rates as a result of the economic environment and not credit risk. The Company concluded that an allowance for credit losses was unnecessary as of June 30, 2021 and that there were no impairments as of December 31, 2020. It is neither management’s intention to sell nor is it more likely than not that the Company will be required to sell these investments prior to recovery of their cost basis or recovery of fair value. Unrealized gains and losses are included in accumulated other comprehensive income.

There was no realized gain or loss on available-for-sale securities in the periods presented. The Company uses the specific identification method to determine the cost basis of investments sold.

- Definition

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

+ References + Details

Balance Sheet Components

6 Months Ended

Jun. 30, 2021

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

5. Balance Sheet Components

Prepaid Expenses and Other Current Assets

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

	June 30, 2021		December 31, 2020
Prepaid expenses	$	2,420	$	2,586
Other current assets		1,712		1,336
Total prepaid expenses and other current assets	$	4,132	$	3,922

Property and Equipment, Net

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

	June 30, 2021			December 31, 2020
Leasehold improvements	$	3,413		$	1,984
Furniture and fixtures		523			322
Research equipment		8,051			4,892
Computers and software		124			124
Construction in progress		1,337			3,459
Total property and equipment		13,448			10,781
Less accumulated depreciation and amortization		(2,098	)		(1,431	)
Total property and equipment, net	$	11,350		$	9,350

Depreciation and amortization expense were $0.4 million and $0.7 million for the three and six months ended June 30, 2021, respectively, and $0.1 million and $0.3 million for the three and six months ended June 30, 2020, respectively.

Accrued and Other Current Liabilities

Accrued other current liabilities are comprised of the following (in thousands):

	June 30, 2021		December 31, 2020
Accrued compensation	$	3,422	$	3,534
Accrued research and development costs		1,297		1,675
Accrued property and equipment		156		117
Other accrued and current liabilities		933		927
Total accrued and other liabilities	$	5,808	$	6,253

Leases

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Leases

6. Leases

The Company has operating leases for its corporate office, laboratory space, manufacturing facility, and dedicated space in a vivarium in South San Francisco, California. Rent expense, which is recognized on a straight-line basis over the term of each lease, was $0.7 million and $1.2 million for the three and six months ended June 30, 2021, respectively, and $0.5 million and $0.9 million for the three and six months ended June 30, 2020, respectively. The total cash paid for operating leases included in the operating cash flows was $0.6 million and $1.0 million for the three and six months ended June 30, 2021, respectively, and $0.4 million and $0.8 million for the three and six months ended June 20, 2020, respectively. The weighted-average remaining lease term was 7.2 years for the corporate office and laboratory space leases as of June 30, 2021. The weighted-average discount rate was 9.2% as of June 30, 2021.

In May 2020, the Company signed an amendment to its office and laboratory facilities lease. The amended lease provides for an eight-year non-cancelable lease of additional office and laboratory space in the same building. The lease for additional office and laboratory space provides for abatement of rent during the first three months of the lease and contains rent escalations during the term of the lease. The lease for this additional space commenced in January 2021 and expires in January 2029. The lease amendment also includes an extension of the lease term for the existing office and laboratory space beginning on May 1, 2020 and expiring in January 2029. The lease agreement includes an option to extend the lease for an additional seven-year term.

In January 2021, the Company signed a third amendment to its corporate office and laboratory facilities lease which provides for lease of additional space in the same building. The lease of this additional space commenced in April 2021 and expires in March 2024. The other terms of the existing lease remain unchanged.

In July 2021, the Company entered into a new lease for corporate office, manufacturing and laboratory space located in South San Francisco, California. See Note 11, “Subsequent Events” for additional information.

Maturities of operating lease liabilities under existing operating leases as of June 30, 2021 were as follows (in thousands):

Year ending December 31,	Amount
2021 (remaining six months)	$	1,201
2022		2,288
2023		2,285
2024		2,184
2025		2,200
2026 and thereafter		7,322
Total future minimum lease payments		17,480
Less imputed interest		(4,785	)
Present value of net minimum lease payments	$	12,695
Operating lease liabilities:
Current		2,287
Non-current		10,408
Total lease liability	$	12,695

Commitments and Contingencies

6 Months Ended

Jun. 30, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments & Contingencies

Guarantee Agreement

The Company has agreements whereby it indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification period is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited; however, the Company has a director and officer insurance policy that limits its exposure and enables the Company to recover a portion of any future amounts under certain circumstances and subject to deductibles and exclusions. The Company had no liabilities recorded for these agreements as of June 30, 2021 and December 31, 2020.

Letters of Credit

As of June 30, 2021, the Company has a $0.5 million letter of credit agreement with a financial institution that is used as collateral for the Company’s corporate headquarters’ operating lease. The letter of credit automatically renews annually without amendment unless cancelled by the financial institutions within 30 days of the annual expiration date.

CRISPR Collaboration Agreement

6 Months Ended

Jun. 30, 2021

Collaboration Agreement [Abstract]

CRISPR Collaboration Agreement

8. CRISPR Collaboration Agreement

On May 5, 2021, the Company entered into a research collaboration agreement (the “CRISPR Agreement”) with CRISPR Therapeutics (“CRISPR”) to co-develop and co-commercialize an engineered CAR-NK product candidate targeting the CD70 tumor antigen and a second novel NK plus T cell (“NK+T”) product candidate. In addition, the Company will receive a license from CRISPR for up to five CRISPR-Cas9 gene editing targets that can be engineered into an unlimited number of its own NK cell products. CRISPR also has an option to co-develop and co-commercialize a future CAR-NK program.

Under the terms of the CRISPR Agreement, the Company and CRISPR share equally all research and development costs and potential profits worldwide related to the CD70 CAR-NK product candidate, NK+T product candidate, and the potential future CAR-NK program (collectively, “Collaboration Products”). For the NK+T program, CRISPR is responsible for gene-editing activities and T cell related activities, and Nkarta is responsible for NK cell related activities. There were an insignificant amount of costs incurred pursuant to the CRISPR agreement in the quarter ended June 30, 2021. For each non-collaboration product candidate incorporating a gene editing target licensed from CRISPR, the Company would retain worldwide rights and may be required to make potential future payments based on the achievement of development and regulatory approval milestones totaling less than mid-twenty million dollars for each non-collaboration product, as well as tiered royalties up to the mid-single digits on net product sales of such product. As of June 30, 2021, the Company has not paid any amounts nor are any amounts owed under the agreement, and no milestones have been achieved.

Share-Based Compensation

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

9. Share-Based Compensation

Equity Incentive Plan

The Company’s 2020 Performance Incentive Plan (the “2020 Plan”) which was adopted by the Company’s board of directors in June 2020 and approved by the Company’s stockholders in July 2020, became effective upon the consummation of the Company’s initial public offering (“IPO”). Upon the effectiveness of the 2020 Plan, no further grants may be made under the Company’s 2015 Equity Incentive Plan (the “2015 Plan”). The Company’s 2020 Plan allows for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, stock bonuses, restricted stock, stock units and other forms of awards including cash awards to its officers, directors, employees, consultants and advisors.

A total of 4,295,638 shares of the Company’s common stock is authorized for issuance with respect to awards granted under the 2020 Plan. The share limit will automatically increase on the first trading day in January of each year (commencing in 2021) by an amount equal to the lesser of (1) 5% of the total number of outstanding shares of the Company’s common stock on the last trading day in December in the prior year, or (2) such lesser number as determined by the Company’s board of directors. Any shares subject to awards granted under the 2020 Plan or the 2015 Plan that are not paid, delivered or exercised before they expire or are canceled or terminated, or otherwise fail to vest, as well as shares used to pay the purchase or exercise price of such awards or related tax withholding obligations, will become available for new award grants under the 2020 Plan..

The following table summarizes the option activity under the 2020 Plan and 2015 Plan during the six months ended June 30, 2021:

	Number of shares			Weighted- average exercise price		Weighted- average remaining contractual term (in years)
Outstanding at December 31, 2020		3,640,715		$	11.00		9.0
Granted		862,847			48.74
Exercised		(194,354	)		5.21
Forfeited		(15,766	)		18.31
Outstanding at June 30, 2021		4,293,442		$	18.82		8.8
Exercisable at June 30, 2021		1,079,227		$	11.15		8.4
Vested and expected to vest at June 30, 2021		4,293,442		$	18.82		8.8

The weighted-average grant date fair value of stock option grants was $33.04 per share for the six months ended June 30, 2021.

Employee Stock Purchase Plan

The Company’s 2020 Employee Stock Purchase Plan (the “ESPP”), which was adopted by the Company’s board of directors in June 2020 and approved by the Company’s stockholders in July 2020, became effective upon the consummation of the IPO. A total of

622,652 shares of the Company’s common stock is initially available for issuance under the ESPP. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP provides for six-month offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. As of June 30, 2021, no shares had been issued under the ESPP, and the full number of shares authorized under the ESPP Plan was available for issuance purposes.

Liability for Early Exercise of Restricted Stock Options

Shares subject to repurchase by the Company were 46,849 shares and 77,393 shares, with the related liability of $0.1 million and $0.1 million recorded under other long-term liabilities in the condensed balance sheets as of June 30, 2021 and December 31, 2020, respectively.

Share-Based Compensation Expense

Share-based compensation expense for the three and six months ended June 30, 2021 and 2020 was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	1,744	$	229	$	3,314	$	424
General and administrative		1,946		337		3,723		624
Total share-based compensation	$	3,690	$	566	$	7,037	$	1,048

The total unrecognized compensation cost related to unvested share-based awards was $43.5 million, which is expected to be recognized over a weighted-average remaining service period of 3.22 years as of June 30, 2021.

Income Taxes

6 Months Ended

Jun. 30, 2021

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

There was no provision for income taxes recorded during the three and six months ended June 30, 2021 and 2020. The Company’s deferred tax assets continue to be fully offset by a valuation allowance.

- Definition

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

+ References + Details

Subsequent Events

6 Months Ended

Jun. 30, 2021

Subsequent Events [Abstract]

Subsequent Events

11. Subsequent Events

On July 9, 2021, the Company entered into a lease agreement for corporate office, manufacturing and laboratory space located in South San Francisco, California with an expiration date approximately twelve years after the lease commencement date. The Company will become responsible for paying rent on the lease commencement date. The Company’s monthly installment of base rent for the new premises will start at approximately $0.6 million commencing on the lease commencement date and will increase on an annual basis up to a maximum monthly base rent of approximately $0.8 million. The Company expects to pay base rent of approximately $98.8 million over the lease term. In addition to base rent, the Company is responsible for payment of direct expenses, which include operating, insurance and tax expenses. The lease also provides for certain tenant improvement allowances of up to approximately $25.2 million for tenant improvements and certain infrastructure upgrades in connection with the initial buildout of the premises, approximately $4.4 million of which, if utilized, would need to be repaid by the Company over the lease term. The Company is required to deliver a security deposit in the form of a letter of credit of $1.6 million to the Landlord in connection with the lease agreement.

Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements as of June 30, 2021 and for the three and six months ended June 30, 2021 and 2020 have been prepared in accordance with U.S. generally accepted accounting principle (“U.S. GAAP”) for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three and six months ended June 30, 2021 are not necessarily indicative of the results expected for the full year or any subsequent interim period. The condensed balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2020, contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed by the Company with the Securities and Exchange Commission (the “SEC”) on March 25, 2021.
COVID-19 Pandemic	COVID-19 Pandemic The COVID-19 pandemic has caused disruptions in the global economy and has affected and may continue to affect the Company’s business and operations. The extent of the impact of the COVID-19 pandemic on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the outbreak, the development and spread of more contagious and/or vaccine-resistant variants, the effectiveness of actions taken in the United States and other countries to contain, vaccinate against, and treat the disease, and its impact on the Company’s current and planned preclinical studies and clinical trials, employees and vendors, all of which are uncertain and cannot be predicted. The extent to which the COVID-19 pandemic may impact the Company’s financial condition or results of operations is uncertain. 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 continues to evaluate the impact of the CARES Act on its financial position, results of operations and cash flows. The Company currently does not expect to apply for loans or grants under the CARES Act.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the Company’s financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to preclinical studies, fair value of assets and liabilities, share-based compensation and income taxes. Management bases its estimates on historical experience, knowledge of current events and actions it may undertake in the future that management believes to be reasonable under the circumstances. Actual results may differ from these estimates and assumptions.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of common shares plus the potential dilutive effects of potential dilutive securities outstanding during the period. Potential dilutive securities are excluded from diluted earnings or loss per share if the effect of such inclusion is antidilutive. The Company’s potentially dilutive securities, which include convertible preferred stock prior to the conversion of such shares to common stock, unvested common stock, and outstanding stock options under the Company’s equity incentive plan, have been excluded from the computation of diluted net loss per share as they would be anti-dilutive to the net loss per share. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Income Taxes. In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-12—Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in Topic 740 related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new guidance also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates. This standard is effective for fiscal years beginning after December 15, 2020, with early adoption permitted. The Company adopted this standard in the first quarter of 2021 using the prospective method, and the adoption did not have a material impact on the Company’s financial statements. There were no other significant updates to the recently issued accounting standards other than as disclosed herewith for the six months ended June 30, 2021. Although there are several other new accounting pronouncements issued or proposed by the FASB, the Company does not believe any of those accounting pronouncements have had or will have a material impact on its financial position or operating results.

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss Per Share

The following tables summarize the computation of the basic and diluted net loss per share (in thousands except share and per share data):

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Numerator:
Net loss	$	(21,535	)	$	(51,065	)	$	(40,908	)	$	(59,771	)
Denominator:
Weighted average common shares outstanding		32,879,406			1,815,833			32,843,343			1,775,961
Less: weighted average unvested common stock issued upon early exercise of common stock options		(52,041	)		(117,273	)		(59,613	)		(121,657	)
Weighted average shares used to compute net loss per share, basic and diluted		32,827,365			1,698,560			32,783,730			1,654,304
Net loss per share, basic and diluted	$	(0.66	)	$	(30.06	)	$	(1.25	)	$	(36.13	)

Summarizes the Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share

The following table summarizes the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive:

	As of June 30,
	2021		2020
Common stock options		4,293,442		2,424,747
Unvested common stock upon early exercise of common stock options		46,849		124,888
Convertible preferred stock		—		7,374,034
		4,340,291		9,923,669

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2021

Summary of Fair Value of Financial Instrument

The following tables summarize the fair value of the Company’s financial instruments (in thousands):

			Fair Value Measurements Using
	June 30, 2021		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents:
Money market funds	$	21,331	$	21,331	$	—	$	—
Short-term investments:
Corporate debt securities	$	89,989	$	—	$	89,989		—
Commercial paper		44,981		—		44,981		—
U.S. Government securities		120,412		—		120,412		—
Total short-term investments		255,382		—		255,382		—
Total	$	276,713	$	21,331	$	255,382	$	—

			Fair Value Measurements Using
	December 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents:
Money market funds	$	94,631	$	94,631	$	—	$	—
Short-term investments:
Corporate debt securities	$	48,614	$	—	$	48,614		—
Commercial paper		63,445		—		63,445		—
U.S. Government securities		106,162		—		106,162		—
Total short-term investments		218,221		—		218,221		—
Total	$	312,852	$	94,631	$	218,221	$	—

Short-term investments

Schedule of Short-term Investments

The following tables summarize the Company’s short-term investments accounted for as available-for-sale securities as of June 30, 2021 and December 31, 2020 (in thousands):

		June 30, 2021
	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
Corporate debt securities	1 year or less	$	90,000	$	(14	)	$	3	$	89,989
Commercial paper	1 year or less		44,981		—			—		44,981
U.S. Government securities	1 year or less		120,395					17		120,412
Total		$	255,376	$	(14	)	$	20	$	255,382

		December 31, 2020
	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
Corporate debt securities	1 year or less	$	48,616	$	(6	)	$	4	$	48,614
Commercial paper	1 year or less		63,445		—			—		63,445
U.S. Government securities	1 year or less		106,157		(7	)		12	$	106,162
Total		$	218,218	$	(13	)	$	16	$	218,221

Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

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

	June 30, 2021		December 31, 2020
Prepaid expenses	$	2,420	$	2,586
Other current assets		1,712		1,336
Total prepaid expenses and other current assets	$	4,132	$	3,922

Schedule of Property and Equipment, Net

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

	June 30, 2021			December 31, 2020
Leasehold improvements	$	3,413		$	1,984
Furniture and fixtures		523			322
Research equipment		8,051			4,892
Computers and software		124			124
Construction in progress		1,337			3,459
Total property and equipment		13,448			10,781
Less accumulated depreciation and amortization		(2,098	)		(1,431	)
Total property and equipment, net	$	11,350		$	9,350

Schedule of Accrued Other Current Liabilities

Accrued other current liabilities are comprised of the following (in thousands):

	June 30, 2021		December 31, 2020
Accrued compensation	$	3,422	$	3,534
Accrued research and development costs		1,297		1,675
Accrued property and equipment		156		117
Other accrued and current liabilities		933		927
Total accrued and other liabilities	$	5,808	$	6,253

Leases (Tables)

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Schedule of Maturities of Operating Lease Liabilities

Maturities of operating lease liabilities under existing operating leases as of June 30, 2021 were as follows (in thousands):

Year ending December 31,	Amount
2021 (remaining six months)	$	1,201
2022		2,288
2023		2,285
2024		2,184
2025		2,200
2026 and thereafter		7,322
Total future minimum lease payments		17,480
Less imputed interest		(4,785	)
Present value of net minimum lease payments	$	12,695
Operating lease liabilities:
Current		2,287
Non-current		10,408
Total lease liability	$	12,695

Share-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes the option activity under the 2020 Plan and 2015 Plan during the six months ended June 30, 2021:

	Number of shares			Weighted- average exercise price		Weighted- average remaining contractual term (in years)
Outstanding at December 31, 2020		3,640,715		$	11.00		9.0
Granted		862,847			48.74
Exercised		(194,354	)		5.21
Forfeited		(15,766	)		18.31
Outstanding at June 30, 2021		4,293,442		$	18.82		8.8
Exercisable at June 30, 2021		1,079,227		$	11.15		8.4
Vested and expected to vest at June 30, 2021		4,293,442		$	18.82		8.8

Summary of Share-based Compensation Expense

Share-based compensation expense for the three and six months ended June 30, 2021 and 2020 was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	1,744	$	229	$	3,314	$	424
General and administrative		1,946		337		3,723		624
Total share-based compensation	$	3,690	$	566	$	7,037	$	1,048

Organization and Description of Business - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segments \| Segment	1
Accumulated deficit	$ 158,929	$ 118,021
Cash, cash equivalents restricted cash and short-term investments	$ 280,300

Basis of Presentation and Significant Accounting Polices - Additional Information (Details) - ASU 2019-12	Jun. 30, 2021
Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Mar. 31, 2021
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true

- Definition

Indicates (true false) whether accounting standards update was adopted.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 65
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (a)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 1
-Subparagraph (a)
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 65
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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- Definition

Date accounting standards update was adopted, in CCYY-MM-DD format.

+ References

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+ Details

Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (21,535)	$ (19,373)	$ (51,065)	$ (8,706)	$ (40,908)	$ (59,771)
Denominator:
Weighted average common shares outstanding	32,879,406		1,815,833		32,843,343	1,775,961
Less: weighted average unvested common stock issued upon early exercise of common stock options	(52,041)		(117,273)		(59,613)	(121,657)
Weighted average shares used to compute net loss per share, basic and diluted	32,827,365		1,698,560		32,783,730	1,654,304
Net loss per share, basic and diluted	$ (0.66)		$ (30.06)		$ (1.25)	$ (36.13)

- Definition

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

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+ Details

Net Loss Per Share - Summarizes the Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	4,340,291	9,923,669
Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	4,293,442	2,424,747
Unvested Common Stock Upon Early Exercise of Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	46,849	124,888
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		7,374,034

Fair Value of Financial Instruments - Summary of Fair Value of Financial Instrument (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Money market funds	$ 21,331	$ 94,631
Total short-term investments	255,382	218,221
Total	276,713	312,852
Commercial Paper
Assets:
Total short-term investments	44,981	63,445
Corporate Debt Securities
Assets:
Total short-term investments	89,989	48,614
U.S. Government Securities
Assets:
Total short-term investments	120,412	106,162
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Money market funds	21,331	94,631
Total	21,331	94,631
Significant Other Observable Inputs (Level 2)
Assets:
Total short-term investments	255,382	218,221
Total	255,382	218,221
Significant Other Observable Inputs (Level 2) \| Commercial Paper
Assets:
Total short-term investments	44,981	63,445
Significant Other Observable Inputs (Level 2) \| Corporate Debt Securities
Assets:
Total short-term investments	89,989	48,614
Significant Other Observable Inputs (Level 2) \| U.S. Government Securities
Assets:
Total short-term investments	$ 120,412	$ 106,162

Fair Value of Financial Instruments - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Impairments		$ 0
Realized gain or loss on available-for-sale securities	$ 0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money Market Funds
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Investments	21,300,000	94,600,000
Significant Other Observable Inputs (Level 2) \| Short-term investments
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Marketable securities	255,400,000	218,200,000
Accrued interest receivable	$ 1,400,000	$ 1,100,000

Fair Value of Financial Instruments - Schedule of Short-term Investments Accounted as Available-for-sale Securities (Details) - Short-term investments - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available for sale securities, Amortized Cost	$ 255,376	$ 218,218
Available for sale securities, Unrealized Losses	(14)	(13)
Available for sale securities, Unrealized Gains	20	16
Available for sale securities,Estimated Fair Value	255,382	218,221
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available for sale securities, Amortized Cost	44,981	63,445
Available for sale securities,Estimated Fair Value	$ 44,981	$ 63,445
Commercial Paper \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Maturity (in years)	1 year	1 year
U.S. Government Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available for sale securities, Amortized Cost	$ 120,395	$ 106,157
Available for sale securities, Unrealized Losses		(7)
Available for sale securities, Unrealized Gains	17	12
Available for sale securities,Estimated Fair Value	$ 120,412	$ 106,162
U.S. Government Securities \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Maturity (in years)	1 year	1 year
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available for sale securities, Amortized Cost	$ 90,000	$ 48,616
Available for sale securities, Unrealized Losses	(14)	(6)
Available for sale securities, Unrealized Gains	3	4
Available for sale securities,Estimated Fair Value	$ 89,989	$ 48,614
Corporate Debt Securities \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, Maturity (in years)	1 year	1 year

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Prepaid expenses	$ 2,420	$ 2,586
Other current assets	1,712	1,336
Total prepaid expenses and other current assets	$ 4,132	$ 3,922

Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 13,448	$ 10,781
Less accumulated depreciation and amortization	(2,098)	(1,431)
Total property and equipment, net	11,350	9,350
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	3,413	1,984
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	523	322
Research Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	8,051	4,892
Computers and Software
Property Plant And Equipment [Line Items]
Total property and equipment	124	124
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,337	$ 3,459

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 0.4	$ 0.1	$ 0.7	$ 0.3

Balance Sheet Components - Schedule of Accrued Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued compensation	$ 3,422	$ 3,534
Accrued research and development costs	1,297	1,675
Accrued property and equipment	156	117
Other accrued and current liabilities	933	927
Total accrued and other liabilities	$ 5,808	$ 6,253

Leases - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Jan. 31, 2021	May 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lessee Lease Description [Line Items]
Rent expense			$ 0.7	$ 0.5	$ 1.2	$ 0.9
Cash paid for operating leases			$ 0.6	$ 0.4	$ 1.0	$ 0.8
Weighted-average discount rate			9.20%		9.20%
Corporate Office and Laboratory Space
Lessee Lease Description [Line Items]
Weighted-average remaining lease term			7 years 2 months 12 days		7 years 2 months 12 days
Renewal term		7 years
Corporate Office and Laboratory Facilities
Lessee Lease Description [Line Items]
Lease term		8 years
Lease expiration year		2029
Operating lease, existence of option to extend		true
Lessee option to extend description					The lease amendment also includes an extension of the lease term for the existing office and laboratory space beginning on May 1, 2020 and expiring in January 2029. The lease agreement includes an option to extend the lease for an additional seven-year term
Corporate Office and Laboratory Facilities \| Third amendment
Lessee Lease Description [Line Items]
Lessee option to extend description					The lease of this additional space commenced in April 2021 and expires in March 2024. The other terms of the existing lease remain unchanged
Lease expiration month and year	2024-03

Leases - Schedule of Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
2021 (remaining six months)	$ 1,201
2022	2,288
2023	2,285
2024	2,184
2025	2,200
2026 and thereafter	7,322
Total future minimum lease payments	17,480
Less imputed interest	(4,785)
Present value of net minimum lease payments	12,695
Operating lease liabilities:
Operating lease liabilities, current portion	2,287	$ 1,402
Operating lease liabilities, net of current portion	10,408	$ 7,517
Total lease liability	$ 12,695

Commitments and Contingencies - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Liabilities recorded for agreements	$ 0	$ 0
Agreement with Financial Institution
Loss Contingencies [Line Items]
Letters of credit outstanding amount	$ 500,000
Letter of credit notice period by financial institution before annual expiration date	30 days

CRISPR Collaboration Agreement - Additional Information (Details) - Research Collaboration Agreement		6 Months Ended
	May 05, 2021 CRISPR-Cas9	Jun. 30, 2021 USD ($)
Development and Regulatory Approval Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential future payments		totaling less than mid-twenty million dollars
Amount paid under the agreement		$ 0
Amounts owed under the agreement.		$ 0
NK Cell Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of non-exclusive rights to gene editing targets \| CRISPR-Cas9	5

Share-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value of stock option	$ 33.04
Other long-term liabilities	$ 65	$ 82
Unrecognized compensation cost	$ 43,500
Unrecognized compensation cost, expected to be recognized over weighted average remaining service period	3 years 2 months 19 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares subject to repurchase	46,849	77,393
Other long-term liabilities	$ 100	$ 100
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock available for issuance	622,652
Maximum percentage of employee compensation eligible for plan	15.00%
Offering period	6 months
Commons stock purchase price as percentage of fair value	85.00%
Shares issued	0
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock authorized for issuance	4,295,638
Increase in share limit as percentage of outstanding shares of common stock on last trading day in prior year	5.00%

Share-Based Compensation - Summary of Stock Option Activity (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares, outstanding beginning balance \| shares	3,640,715
Number of shares, granted \| shares	862,847
Number of shares, exercised \| shares	(194,354)
Number of shares, forfeited \| shares	(15,766)
Number of shares, outstanding ending balance \| shares	4,293,442	3,640,715
Number of shares, exercisable \| shares	1,079,227
Number of shares, vested and expected to vest \| shares	4,293,442
Weighted-average exercise price, outstanding beginning balance \| $ / shares	$ 11.00
Weighted-average exercise price, granted \| $ / shares	48.74
Weighted-average exercise price, exercised \| $ / shares	5.21
Weighted-average exercise price, forfeited \| $ / shares	18.31
Weighted-average exercise price, outstanding ending balance \| $ / shares	18.82	$ 11.00
Weighted-average exercise price, exercisable \| $ / shares	11.15
Weighted-average exercise price, vested and expected to vest \| $ / shares	$ 18.82
Weighted-average remaining contractual term (in years), outstanding balance	8 years 9 months 18 days	9 years
Weighted-average remaining contractual term (in years), exercisable	8 years 4 months 24 days
Weighted-average remaining contractual term (in years), vested and expected to vest	8 years 9 months 18 days

Share-Based Compensation - Summary of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 3,690	$ 566	$ 7,037	$ 1,048
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	1,744	229	3,314	424
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 1,946	$ 337	$ 3,723	$ 624

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Subsequent Events - Additional Information (Details) - Subsequent Event	Jul. 09, 2021 USD ($)
Subsequent Event [Line Items]
Lessee, operating lease, term of contract	12 years
Monthly base rent	$ 600,000
Maximum monthly base rent after increase on annual basis	800,000
Expects to pay base rent over the lease term.	98,800,000
Cash received for tenant improvement allowances to be repaid	4,400,000
Maximum
Subsequent Event [Line Items]
Tenant improvement allowances yet to receive	25,200,000
Letter of Credit
Subsequent Event [Line Items]
Security deposit	$ 1,600,000