Prometheus Biosciences (RXDX) 10-Q 12 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 08, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Registrant Name	PROMETHEUS BIOSCIENCES, INC.
Entity Central Index Key	0001718852
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Small Business	true
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		38,939,220
Entity File Number	001-40187
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-4282653
Entity Address, Address Line One	9410 Carroll Park Drive
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	684-1300
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	RXDX
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false

Unaudited Condensed Consolidate

Unaudited Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 279,116	$ 54,201
Accounts receivable	679	1,086
Prepaid expenses and other current assets	7,313	2,169
Total current assets	287,108	57,456
Equipment, net	1,362	447
Deferred financing costs		1,730
Other assets	468
Total assets	288,938	59,633
Current liabilities
Accounts payable	1,663	958
Accrued compensation	3,311	2,722
Accrued expenses and other current liabilities	6,083	2,894
Amounts due to Nestlé, current—related party		5,675
Payable to PLI	475	1,130
Deferred revenue	3,561	1,876
Total current liabilities	15,093	15,255
Long-term debt, net		7,399
Deferred revenue, non-current	11,745	4,597
Preferred stock purchase right liability		3,900
Total liabilities	26,838	31,151
Commitments and contingencies (Note 9)
Convertible preferred stock—$0.0001 par value; No shares and 254,983,985 shares authorized at September 30, 2021 and December 31, 2020, respectively; No shares and 160,864,434 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively; liquidation preferences of $0 and $130,487 at September 30, 2021 and December 31, 2020, respectively		126,023
Stockholders’ equity (deficit):
Preferred stock—$0.0001 par value; 40,000,000 shares and no shares authorized at September 30, 2021 and December 31, 2020, respectively; No shares issued and outstanding at September 30, 2021 and December 31, 2020
Common stock—$0.0001 par value; 400,000,000 shares and 325,000,000 shares authorized as of September 30, 2021 and December 31, 2020, respectively; 38,907,081 shares and 1,768,325 shares issued at September 30, 2021 and December 31, 2020, respectively; 38,884,536 shares and 1,713,622 shares outstanding at September 30, 2021 and December 31, 2020, respectively;	4
Additional paid-in capital	421,519	1,605
Accumulated deficit	(159,423)	(99,146)
Total stockholders’ equity (deficit)	262,100	(97,541)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 288,938	$ 59,633

Unaudited Condensed Consolida_2

Unaudited Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	0	254,983,985
Convertible preferred stock, shares issued	0	160,864,434
Convertible preferred stock, shares outstanding	0	160,864,434
Convertible preferred stock, liquidation preference	$ 0	$ 130,487,000
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	325,000,000
Common stock, shares issued	38,907,081	1,768,325
Common stock, shares outstanding	38,884,536	1,713,622

Unaudited Condensed Consolida_3

Unaudited Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Collaboration revenue	$ 1,006	$ 359	$ 2,092	$ 766
Operating expenses:
Research and development	17,551	4,652	38,863	13,840
General and administrative	10,248	3,173	21,088	7,370
Total operating expense	27,799	7,825	59,951	21,210
Loss from operations	(26,793)	(7,466)	(57,859)	(20,444)
Other income (expense), net:
Interest income	27	3	82	8
Interest expense	(13)	(364)	(861)	(1,493)
Loss on early extinguishment of debt	(554)		(554)
Change in fair value of preferred stock purchase right liability			(980)
Change in fair value of preferred stock warrant liability		1	(105)	(2)
Total other income (expense), net	(540)	(360)	(2,418)	(1,487)
Loss from continuing operations	(27,333)	(7,826)	(60,277)	(21,931)
Income (loss) from discontinued operations		879		(6,584)
Net loss	$ (27,333)	$ (6,947)	$ (60,277)	$ (28,515)
Net loss per share, basic and diluted:
Continuing operations	$ (0.70)	$ (5.13)	$ (2.09)	$ (15.21)
Discontinued operations		0.58		(4.57)
Net loss per share, basic and diluted	$ (0.70)	$ (4.55)	$ (2.09)	$ (19.78)
Weighted average shares outstanding, basic and diluted	38,848,412	1,526,122	28,778,814	1,441,516

Unaudited Condensed Consolida_4

Unaudited Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series D-2 Convertible Preferred Stock	Convertible Preferred Stock	Series C Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning Balance at Dec. 31, 2019	$ (36,968)					$ 483	$ (37,451)
Temporary Equity, Balance, shares at Dec. 31, 2019			58,145,867
Temporary Equity, Balance at Dec. 31, 2019			$ 43,740
Balance, shares at Dec. 31, 2019					1,351,380
Issuance of convertible preferred stock for cash, net of issuance costs				$ 28,001
Issuance of convertible preferred stock for cash, net of issuance costs, shares				28,063,500
Convertible preferred stock issuance costs				$ (62)
Vesting of common shares issued to founders, shares					18,281
Issuance of common stock upon exercise of stock options	12					12
Issuance of common stock upon exercise of stock options, shares					23,750
Vesting of early exercised stock options	3					3
Vesting of early exercised stock options, shares					8,800
Stock-based compensation	147					147
Net loss	(13,128)						(13,128)
Ending Balance at Mar. 31, 2020	(49,934)					645	(50,579)
Temporary Equity, Balance, shares at Mar. 31, 2020			86,209,367
Temporary Equity, Balance at Mar. 31, 2020			$ 71,741
Balance, shares at Mar. 31, 2020					1,402,211
Beginning Balance at Dec. 31, 2019	(36,968)					483	(37,451)
Temporary Equity, Balance, shares at Dec. 31, 2019			58,145,867
Temporary Equity, Balance at Dec. 31, 2019			$ 43,740
Balance, shares at Dec. 31, 2019					1,351,380
Net loss	(28,515)
Ending Balance at Sep. 30, 2020	(64,785)					1,181	(65,966)
Temporary Equity, Balance, shares at Sep. 30, 2020			94,709,367
Temporary Equity, Balance at Sep. 30, 2020			$ 80,229
Balance, shares at Sep. 30, 2020					1,650,631
Beginning Balance at Mar. 31, 2020	(49,934)					645	(50,579)
Temporary Equity, Balance, shares at Mar. 31, 2020			86,209,367
Temporary Equity, Balance at Mar. 31, 2020			$ 71,741
Balance, shares at Mar. 31, 2020					1,402,211
Issuance of Series C convertible preferred stock upon release of escrow of acquisition-related contingent consideration				$ 3,500
Issuance of Series C convertible preferred stock upon release of escrow of acquisition-related contingent consideration, shares				3,500,000
Issuance of Series C convertible preferred stock for deferred purchase price				$ 5,000
Issuance of Series C convertible preferred stock for deferred purchase price, shares				5,000,000
Convertible preferred stock issuance costs				$ (12)
Vesting of common shares issued to founders, shares					18,281
Issuance of common stock upon exercise of stock options	48					48
Issuance of common stock upon exercise of stock options, shares					51,666
Vesting of early exercised stock options	3					3
Vesting of early exercised stock options, shares					8,609
Stock-based compensation	164					164
Net loss	(8,440)						(8,440)
Ending Balance at Jun. 30, 2020	(58,159)					860	(59,019)
Temporary Equity, Balance, shares at Jun. 30, 2020			94,709,367
Temporary Equity, Balance at Jun. 30, 2020			$ 80,229
Balance, shares at Jun. 30, 2020					1,480,767
Vesting of common shares issued to founders, shares					12,188
Issuance of common stock in exchange / consulting services	112					112
Issuance of common stock in exchange / consulting services, shares					36,200
Issuance of common stock upon exercise of stock options	4					4
Issuance of common stock upon exercise of stock options, shares					1,200
Vesting of common shares issued for licensing rights	1					1
Vesting of common shares issued for licensing rights, shares					111,667
Vesting of early exercised stock options	2					2
Vesting of early exercised stock options, shares					8,609
Stock-based compensation	202					202
Net loss	(6,947)						(6,947)
Ending Balance at Sep. 30, 2020	(64,785)					1,181	(65,966)
Temporary Equity, Balance, shares at Sep. 30, 2020			94,709,367
Temporary Equity, Balance at Sep. 30, 2020			$ 80,229
Balance, shares at Sep. 30, 2020					1,650,631
Beginning Balance at Dec. 31, 2020	$ (97,541)					1,605	(99,146)
Temporary Equity, Balance, shares at Dec. 31, 2020	160,864,434		160,864,434
Temporary Equity, Balance at Dec. 31, 2020	$ 126,023		$ 126,023
Balance, shares at Dec. 31, 2020	1,713,622				1,713,622
Issuance of convertible preferred stock for cash, net of issuance costs		$ 73,763
Issuance of convertible preferred stock for cash, net of issuance costs, shares		86,775,740
Convertible preferred stock issuance costs		$ (94)
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price		$ 6,144
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price		7,219,560
Reclassification of convertible preferred stock purchase right liability			$ 4,880
Conversion of convertible preferred stock into common stock at initial public offering	$ 210,810				$ 3	210,807
Temporary Equity, Conversion of convertible preferred stock into common stock at initial public offering, shares			(254,859,734)
Temporary Equity, Conversion of convertible preferred stock into common stock at initial public offering			$ (210,810)
Conversion of convertible preferred stock into common stock at initial public offering, shares					25,485,955
Issuance of shares of common stock in initial public offering for cash, net of issuance costs	199,838				$ 1	199,837
Issuance of shares of common stock in initial public offering for cash, net of issuance costs, shares					11,500,000
Reclassification of convertible preferred stock warrants	169					169
Issuance of common stock in exchange / consulting services	3					3
Issuance of common stock in exchange / consulting services, shares					500
Issuance costs related to initial public offering					$ 18,662
Issuance of common stock upon exercise of stock options	64					64
Issuance of common stock upon exercise of stock options, shares					56,645
Vesting of early exercised stock options	9					9
Vesting of early exercised stock options, shares					12,981
Stock-based compensation	792					792
Net loss	(13,945)						(13,945)
Ending Balance at Mar. 31, 2021	300,199				$ 4	413,286	(113,091)
Balance, shares at Mar. 31, 2021					38,769,703
Beginning Balance at Dec. 31, 2020	$ (97,541)					1,605	(99,146)
Temporary Equity, Balance, shares at Dec. 31, 2020	160,864,434		160,864,434
Temporary Equity, Balance at Dec. 31, 2020	$ 126,023		$ 126,023
Balance, shares at Dec. 31, 2020	1,713,622				1,713,622
Issuance of common stock upon exercise of stock options, shares	124,201
Net loss	$ (60,277)
Ending Balance at Sep. 30, 2021	$ 262,100				$ 4	421,519	(159,423)
Temporary Equity, Balance, shares at Sep. 30, 2021	0
Balance, shares at Sep. 30, 2021	38,884,536				38,884,536
Beginning Balance at Mar. 31, 2021	$ 300,199				$ 4	413,286	(113,091)
Balance, shares at Mar. 31, 2021					38,769,703
Issuance costs related to initial public offering	(46)					(46)
Issuance of common stock upon exercise of stock options	62					62
Issuance of common stock upon exercise of stock options, shares					54,561
Vesting of early exercised stock options	9					9
Vesting of early exercised stock options, shares					10,803
Stock-based compensation	1,203					1,203
Net loss	(18,999)						(18,999)
Ending Balance at Jun. 30, 2021	282,428				$ 4	414,514	(132,090)
Balance, shares at Jun. 30, 2021					38,835,067
Issuance of common stock in exchange / consulting services	715					715
Issuance of common stock in exchange / consulting services, shares					28,100
Issuance of common stock upon exercise of stock options	33					33
Issuance of common stock upon exercise of stock options, shares					12,995
Vesting of early exercised stock options	7					7
Vesting of early exercised stock options, shares					8,374
Stock-based compensation	6,250					6,250
Net loss	(27,333)						(27,333)
Ending Balance at Sep. 30, 2021	$ 262,100				$ 4	$ 421,519	$ (159,423)
Temporary Equity, Balance, shares at Sep. 30, 2021	0
Balance, shares at Sep. 30, 2021	38,884,536				38,884,536

Unaudited Condensed Consolida_5

Unaudited Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Stock issuance costs	$ (46)
Common Stock
Stock issuance costs		$ 18,662
Series D-2 Convertible Preferred Stock
Temporary stock, issuance costs		$ 94
Series C Convertible Preferred Stock
Temporary stock, issuance costs			$ 12	$ 62

Unaudited Condensed Consolida_6

Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net loss	$ (60,277)	$ (28,515)
Loss from continuing operations	(60,277)	(21,931)
Loss from discontinued operations, net of income taxes		(6,584)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	173	79
Stock-based compensation expenses	8,245	440
Loss on early extinguishment of debt	554
Change in fair value of preferred stock purchase right liability	980
Change in fair value of preferred stock warrant liability	105	2
Common stock issued in exchange for services	718	113
Noncash interest expense	553	1,075
Changes in operating assets and liabilities:
Accounts receivable	407	(589)
Prepaid expenses and other current assets	(5,144)	(1,075)
Other assets	(468)	212
Accounts payable	618	(1,210)
Accrued compensation	589	1,082
Accrued expenses and other current liabilities	3,441	655
Payments made to PLI		(2,967)
Payable to PLI	(655)
Deferred revenue	8,833	2,603
Net cash used in operating activities – continuing operations	(41,328)	(21,511)
Net cash used in operating activities – discontinued operations		(1,190)
Net cash used in operating activities	(41,328)	(22,701)
Cash flows from investing activities
Purchase of property and equipment	(946)	(225)
Net cash used in investing activities – continuing operations	(946)	(225)
Net cash used in investing activities – discontinued operations		(1,485)
Net cash used in investing activities	(946)	(1,710)
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs	73,749	27,986
Proceeds from issuance of long-term debt, net of issuance costs		7,338
Repayment of debt	(7,963)
Proceeds from sale of common stock in initial public offering	218,500
Payment of financing costs	(17,256)	(1,014)
Proceeds from issuance of common stock upon stock option exercises	159	61
Net cash provided by financing activities	267,189	34,371
Net increase in cash and cash equivalents	224,915	9,960
Cash and cash equivalents at beginning of period – continuing operations	54,201	4,450
Cash and cash equivalents at beginning of period – discontinued operations		3,921
Cash and cash equivalents cash at end of period	279,116	18,331
Cash and cash equivalents at end of period – discontinued operations		1,246
Cash and cash equivalents at end of period – continuing operations	279,116	17,085
Supplemental schedule of non-cash investing and financing activities
Conversion of convertible preferred stock into common stock upon completion of initial public offering	210,810
Reclassification of warrant liability to equity due to conversion from preferred stock warrant to common stock warrant upon completion of initial public offering	169
Acquisition-related consideration held in escrow		(3,500)
Vesting of unvested issued common stock	24	10
Costs incurred, but not paid, in connection with capital expenditures included in accounts payable	145	100
Series D Convertible Preferred Stock
Supplemental schedule of non-cash investing and financing activities
Reclassification of preferred stock purchase right liability to equity due to issuance of Series D convertible preferred stock	4,880
Series D-2 Convertible Preferred Stock
Supplemental schedule of non-cash investing and financing activities
Issuance of Series D-2 convertible preferred stock for the settlement of deferred purchase price	$ 6,144
Series C Convertible Preferred Stock
Supplemental schedule of non-cash investing and financing activities
Issuance of Series C convertible preferred stock for deferred purchase price		$ 5,000

Organization

Organization	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Organization	1. Organization Prometheus Biosciences, Inc. (the Company) was incorporated in the state of Delaware on October 26, 2016 under the name Precision IBD, Inc. and is headquartered in San Diego, California. The Company changed its name to Prometheus Biosciences, Inc. on October 1, 2019. The Company’s business is focused on the discovery, development and commercialization of novel therapeutic and companion diagnostic products for the treatment of immune-mediated diseases, starting first with inflammatory bowel disease (IBD). In June 2019, the Company acquired Prometheus Laboratories, Inc. (PLI) and the related intangible assets used by PLI. PLI was wholly owned by Nestlé Health Science US Holdings, Inc. and the related intangible assets were owned by Societé Des Produits Nestlé S.A (together, Nestlé) (see Note 6). PLI markets and conducts several laboratory developed tests useful to gastroenterologists in monitoring their IBD patients’ disease state and informing their therapeutic decisions. On December 31, 2020, the Company completed the spinoff of PLI by making an in-kind distribution of 100% of its interest in PLI to the Company’s stockholders of record on December 30, 2020 (see Note 6). Reverse Stock Split On March 5, 2021, the Company effected a one-for-ten Initial Public Offering On March 16, 2021, the Company completed its initial public offering (IPO) with the sale of 11,500,000 shares of common stock, which included the exercise in full by the underwriters of their option to purchase 1,500,000 additional shares, at an initial public offering price of $19.00 per share and received gross proceeds of $218.5 million, which resulted in net proceeds to the Company of approximately $199.8 million, after deducting underwriting discounts and commissions of approximately $15.3 million and offering-related transaction costs of approximately $3.4 million. In addition, in connection with the completion of the IPO, all outstanding shares of convertible preferred stock were converted into 25,485,955 shares of the Company’s common stock; outstanding warrants to purchase 148,848 shares of convertible preferred stock were converted into warrants to purchase 14,884 shares of the Company’s common stock; and 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. Liquidity The Company has incurred net losses since inception, experienced negative cash flows from operations, and as of September 30, 2021, has an accumulated deficit of $159.4 million The Company will be required to raise additional capital, however, there can be no assurance as to whether additional financing will be available on terms acceptable to the Company, if at all. If sufficient funds on acceptable terms are not available when needed, it would have a negative impact on the Company’s financial condition and could force the Company to delay, limit, reduce, or terminate product development or future commercialization efforts or grant rights to develop and market product candidates or testing products that the Company would otherwise plan to develop.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed consolidated financial statements and accompanying notes. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may materially differ from these estimates and assumptions. On December 31, 2020, the Company completed the spinoff of PLI. The results of operations for the three and nine months ended September 30, 2021 have been presented as discontinued operations in the accompanying condensed consolidated financial statements in accordance with Accounting Standards Codification (ASC) 205-20, Presentation of Financial Statements—Discontinued Operations consolidated financial statements relates to continuing operations (see Note 6 for additional information on discontinued operations). On an ongoing basis, management evaluates its estimates, primarily related to revenue recognition, stock-based compensation, accrued research and development costs, and for periods prior to its IPO, the fair value of common stock, the fair value of the convertible preferred stock, and the fair value of the preferred stock purchase right liability. These estimates are based on historical data and experience, as well as various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Estimates relating to the valuation of stock require the selection of appropriate valuation methodologies and models, and significant judgment in evaluating ranges of assumptions and financial inputs. Unaudited Interim Financial Information The unaudited financial statements at September 30, 2021, and for the three and nine months ended September 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (SEC), and with GAAP applicable to interim financial statements. These unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, consisting of only normal recurring accruals, which in the opinion of management are necessary to present fairly the Company’s financial position as of the interim date and results of operations for the interim periods presented. Interim results are not necessarily indicative of results for a full year or future periods. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ materially from those estimates. These unaudited financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2020, included in the Prospectus dated March 11, 2021 filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended, with the SEC on March 12, 2021. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and until December 31, 2020, the date at which the spinoff was completed, its wholly-owned subsidiary, PLI, and have been prepared in conformity with GAAP. All intercompany accounts and transactions have been eliminated in consolidation. Segment Reporting The Company’s Chief Executive Officer, who is considered to be the chief operating decision maker (CODM), reviews financial information presented on a consolidated basis, accompanied by information about operating segments for purposes of making operating decisions and assessing financial performance. Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the CODM in deciding how to allocate resources and in assessing performance. Prior to the spinoff of PLI in December 2020, the Company determined its operating segments to be the therapeutics and diagnostic services businesses. The therapeutics business derives substantially all of its revenue from collaboration agreements and devotes all of its efforts to development of product candidates and companion diagnostics in the IBD space. The diagnostic services business, which is recorded as discontinued operations, derived its revenue from diagnostic services in the IBD space generated from the conduct of laboratory developed tests. Since the spinoff, the Company has operated solely within the therapeutics segment. The Company operates solely in the United States. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. The cash and cash equivalents balance at September 30, 2021 and December 31, 2020 represents cash in readily available checking and money market accounts. Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash, cash equivalents, and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Deferred Financing Costs At December 31, 2020, f inancing costs, consisting of legal, accounting, printer and filing fees related to the Company’s IPO, totaled $1.7 million. Upon the completion of the IPO in March 2021, all of these expenses were offset against the proceeds from the IPO. Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers To date, all of the Company’s collaboration revenue has been derived from its collaboration agreement with Millennium Pharmaceuticals, Inc., a subsidiary of Takeda Pharmaceutical Company Limited (collectively, Takeda) and its collaboration agreement with Dr. Falk Pharma GmbH as described in Note 5. The terms of these arrangements include the following types of payments to the Company: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for research and development services provided by the Company; and royalties on net sales of licensed products. At the initiation of an agreement, the Company analyzes whether each unit of account results in a contract with a customer under ASC 606 or in an arrangement with a collaborator subject to guidance under ASC 808, Collaborative Arrangements The Company considers a variety of factors in determining the appropriate estimates and assumptions under these arrangements, such as whether the elements are distinct performance obligations, whether there are observable stand-alone prices, and whether any licenses are functional or symbolic. The Company evaluates each performance obligation to determine if it can be satisfied and recognized as revenue at a point in time or over time. Typically, license fees, non-refundable upfront fees, and funding of research activities are considered fixed, while milestone payments are identified as variable consideration which must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. The Company estimates the amount of variable consideration using the most likely amount, as milestone payments typically only have two possible outcomes. The Company recognizes revenue for sales-based royalty promised in exchange for the license of intellectual property only when the subsequent sale occurs. The Company may allocate transaction price using a number of methods including estimating standalone selling price of performance obligations and using the residual approach when the standalone selling price of the license is highly variable or uncertain, and observable standalone selling prices exist for the other goods or services promised in the contract. The Company receives payments from its collaborators based on terms established in each contract. Upfront payments and other payments may require deferral of revenue recognition to a future period until the Company is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the payment by the customer is akin to a deposit for research and development services. Research and Development and Clinical Trial Accruals Research and development costs are charged to expense as incurred. Research and development expenses include certain payroll and personnel expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In addition, clinical study and trial materials are manufactured by contract manufacturing organizations. In accruing for these services, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Stock-Based Compensation The Company expenses stock-based compensation to employees and non-employees over the requisite service period (usually the vesting period) on a straight-line basis, net of actual forfeitures during the period, based on the estimated grant-date fair value of the awards. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, and the assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. Valuation of Common Stock Prior to the IPO, given the absence of a public trading market for the Company’s common stock, its board of directors exercised their judgment and considered a number of objective and subjective factors to determine the best estimate of the fair value of the Company’s common stock, such as: contemporaneous valuations performed by independent third-party specialists, its stage of development, including the status of its research and development efforts of its product candidates, the material risks related to its businesses and industry, its results of operations before discontinued operations and financial position, including its levels of capital resources, the prices at which its sold shares of its convertible preferred stock, the rights, preferences and privileges of its convertible preferred stock relative to those of its common stock, the conditions in the biotechnology industry and the economy in general, the stock price performance and volatility of comparable life sciences public companies, as well as recently completed mergers and acquisitions of peer companies, the likelihood of achieving a liquidity event for the holders of its common stock or convertible preferred stock, such as an IPO or a sale of the Company given prevailing market conditions, trends and developments in its industry, external market conditions affecting the life sciences and biotechnology sectors, and the lack of liquidity of its common stock, among other factors. After the completion of the IPO, the fair value of each share of common stock is based on the closing price of the Company’s common stock as reported by Nasdaq. Preferred Stock Purchase Right Liabilities From time to time, the Company enters into convertible preferred stock financings where, in addition to the initial closing, investors agree to buy, and the Company agrees to sell, additional shares of that convertible preferred stock at a fixed price in the event that certain conditions are met or agreed upon milestones are achieved. The Company evaluates this purchase right and assesses whether it meets the definition of a freestanding instrument and, if so, determines the fair value of the purchase right liability and records it on the balance sheet with the remainder of the proceeds raised allocated to convertible preferred stock. The preferred stock purchase right liability is revalued at each reporting period with changes in the fair value of the liability recorded as change in fair value of preferred stock purchase right liability in the statements of operations. Upon the issuance of the shares of Series D-2 convertible preferred stock in January 2021, the no longer required liability accounting and the then fair value of the was reclassified into stockholders’ equity. The Company performed the final remeasurement of the preferred stock purchase right liability Net Loss Per Share Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. The Company has excluded 26,641 and 36,591 weighted-average shares subject to repurchase or forfeiture from the weighted-average number of common shares outstanding for the three and nine months ended September 30, 2021, respectively, and 140,136 and 179,917 weighted-average shares subject to repurchase or forfeiture from the weighted-average number of common shares outstanding for the three and nine months ended September 30, 2020, respectively. Dilutive common stock equivalents are comprised of convertible preferred stock and options outstanding under the Company’s stock option plan. Basic and diluted net loss attributable to common holders per share is presented in conformity with the two- class method required for participating securities as the convertible preferred stock are considered participating securities. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Accordingly, for the three and nine months ended September 30, 2021 and 2020, there is no difference in the number of shares used to calculate basic and diluted shares outstanding. Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): September 30, 2021 2020 Convertible preferred stock outstanding — 9,470,926 Common stock options issued and outstanding 5,392,052 2,020,559 Warrants to purchase common stock 14,884 — Warrants to purchase convertible preferred stock outstanding — 11,250 ESPP shares pending issuance 24,279 — Total 5,431,215 11,502,735 Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial position or results of operations upon adoption. In April 2012, the Jump-Start Our Business Startups Act (the JOBS Act) was signed into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company may elect to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than when public companies must adopt the standards. The Company has elected to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for emerging growth companies, which are the dates included below. Adoption of New Accounting Standards In February 2016, the FASB issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842) Leases (Topic 840) The Company made accounting policy elections to exclude leases with terms of 12 months or less from the recognition requirements and to not separate lease and non-lease components. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses: Measurement of credit Losses on Financial Instruments (ASU 2016-13) based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for sale debt securities. The Company early adopted this standard on January 1, 2021 by applying the modified retrospective approach and determined there was no cumulative-effect transition adjustment required to the opening balance of accumulated deficit for the recognition of additional credit losses upon adoption of this standard based on its outstanding accounts receivable, the composition and credit quality of its short-term investments, and current economic conditions as of that date. In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other options (Subtopic 470-20) and Derivative and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40).

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	3. The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The carrying amounts of cash and cash equivalents, prepaid and other assets, accounts payable and accrued liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on the borrowing rates currently available to the Company for loans with similar terms, which is considered a Level 2 input, the Company believes that the fair value of long-term debt approximates its carrying value. The Company’s financial instruments that are carried at fair value consist of Level 3 liabilities. There were no transfers within the hierarchy during the three and nine months ended September 30, 2021 and 2020. At December 31, 2020, Level 3 liabilities that were measured at fair value on a recurring basis consisted of warrants to purchase shares of convertible preferred stock and a preferred stock purchase right liability. The Company had no Level 3 liabilities at September 30, 2021 as the liabilities for the warrants to purchase shares of convertible preferred stock and the preferred stock purchase right was remeasured and reclassified to stockholders’ equity upon the closing of the Company’s IPO in March 2021 and the issuance of shares of Series D-2 convertible preferred stock in January 2021, respectively. Convertible Preferred Stock Warrant Liability The convertible preferred stock warrant liability was recorded at fair value utilizing the Black-Scholes option pricing model using significant unobservable inputs consistent with the inputs used for the Company’s stock-based compensation expense adjusted for the preferred stock warrants’ expected term and the fair value of the underlying preferred stock. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the convertible preferred stock warrant liability at the date of the IPO and December 31, 2020 were as follows: IPO Date December 31, 2020 Fair value of underlying preferred stock $ 1.90 $ 0.83 Risk-free interest rate 1.70 % 1.70 % Expected volatility 70.00 % 70.00 % Expected term (in years) 9.0 9.2 Expected dividend yield —% —% Preferred Stock Purchase Right Liability At December 31, 2020, the preferred stock purchase right liability was determined using a valuation model that considered: (i) the risk-free rate commensurate with the expected milestone timing of 0.09%; (ii) the probability of the Series D-2 tranche of 80.0%; (iii) volatility of 80.0%; (iv) consideration received for the Series D-1 preferred stock; (v) the number of shares to be issued to satisfy the preferred stock purchase right and at what price; and (vi) certain implied and provided assumptions needed to calibrate the Series D-1 value and the Series D-2 purchase right. Upon the issuance of the shares of Series D-2 convertible preferred stock in January 2021, the liability was remeasured and as a result of closing the sale of shares of Series D-2 convertible preferred stock, a charge of $1.0 million was recorded in the statement of operations for the nine months ended September 30, 2021. Activity of Liabilities Using Fair Value Level 3 Measurements The following table summarizes the activity of the financial instruments valued using Level 3 inputs (in thousands): Convertible Preferred Stock Warrant Liability Series D Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 64 $ 3,900 Change in fair value 105 980 Conversion/Settlement during 2021 (169 ) (4,880 ) Balance at September 30, 2021 $ — $ —

Balance Sheet Details

Balance Sheet Details	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	4. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): September 30, 2021 December 31, 2020 Prepaid research and development 5,761 1,894 Other prepaid expenses 1,552 275 Total $ 7,313 $ 2,169 Equipment, Net Equipment, net, consist of the following (in thousands): September 30, 2021 December 31, 2020 Laboratory equipment $ 1,660 $ 572 Office equipment and furniture 24 24 1,684 596 Less accumulated depreciation (322 ) (149 ) Total $ 1,362 $ 447 Depreciation expense related to property and equipment was $0.1 million and $29,000 for the three months ended September 30, 2021 and 2020, respectively, and $0.2 million and $0.1 million for the nine months ended September 30, 2021 and 2020, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): September 30, 2021 December 31, 2020 Accrued research and development $ 5,490 $ 1,940 Accrued legal expenses 70 490 Unvested early exercise liability 42 67 Accrued other 481 397 Total $ 6,083 $ 2,894

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	5. Collaboration and License Agreements Cedars-Sinai Medical Center In September 2017, the Company entered into an Exclusive License Agreement with Cedars-Sinai Medical Center (Cedars-Sinai), a related party, as amended and restated (the Cedars-Sinai Agreement). Under the terms of the Cedars-Sinai Agreement, Cedars-Sinai granted the Company an exclusive, worldwide, royalty bearing license with respect to certain patent rights, information and materials related to therapeutic targets and companion diagnostic products, in each case to conduct research, develop, and commercialize therapeutic and diagnostic products for human use. The licensed technology includes information and materials arising out of Cedars-Sinai’s database and biobank, as well as exclusive access to this database and biobank, which is an integral part of the Company’s Prometheus360 platform. In August 2021, the Company and Cedars-Sinai amended and restated the Cedars-Sinai Agreement to, among other things, add a joint steering committee and cover new intellectual property. As consideration for the license rights, in September 2017 the Company issued (i) 257,500 shares of fully vested common stock, and (ii) 335,000 shares of unvested restricted common stock, all of which is vested as of December 31, 2020. The fair value of all of the shares were measured at the date of issuance. Additionally, the Company is obligated to pay Cedars-Sinai low- to mid-single digit percentage royalties on net sales of products covered under the Cedars-Sinai Agreement. In 2017, the Company and Cedars-Sinai also entered into Research agreements, under which the parties can provide research services to each other at pricing specified in individual statements of work. During the three and nine months ended September 30, 2021 and 2020, no services were provided under the agreements. Collaboration Agreement with Millennium Pharmaceuticals, Inc., a subsidiary of Takeda Pharmaceutical Company Limited In March 2019, the Company entered into a Companion Diagnostics Development and Collaboration Agreement (the Takeda Agreement) with Millennium Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda, pursuant to which the Company agreed to develop a companion diagnostic product for certain drug targets selected by Takeda, and Takeda agreed to develop and commercialize any therapeutic clinical candidates that it develops directed against any selected drug targets for the treatment of IBD (Takeda Drugs). In consideration of the rights granted to Takeda under the Takeda Agreement, the Company received a one-time upfront payment of $1.5 million and is eligible to receive, for any targets selected by Takeda, future development and regulatory milestone payments of up to $47.9 million, commercial milestone payments of up to $25.0 million, sales milestone payments of up to $75.0 million, and low-single digit percentage royalties on net sales of all Takeda Drugs, subject to the terms and conditions set forth in the Takeda Agreement. At inception and through September 30, 2021, the Company has identified one performance obligation per each target for all the deliverables under the agreement since the delivered elements are not distinct within the context of the contract. Accordingly, the Company will recognize revenue for the transaction price in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses over the four-year million for the nine months ended September 30, 2021 and 2020 , respectively, and had deferred revenue of $ million, $ 1.7 million as of September 30, 2021 and December 31, 2020 , respectively. The Company expects to recognize $ million of the deferred revenue balance during the remainder of 2021 . Dr. Falk Pharma GmbH Collaboration Agreement In July 2020, the Company entered into a Co-Development and Manufacturing Agreement (the Falk Agreement) with Dr. Falk Pharma GMBH (Falk), pursuant to which the parties agreed to co-develop and commercialize, exclusively in their respective territories, therapeutic product candidates targeting members of the TNF super family for the treatment of UC and CD under the Company’s PR600 program. Under the Falk Agreement, the Company is responsible for regulatory approvals and commercialization of any products in the United States and the rest of the world, other than the Falk territory. Falk is responsible for regulatory approvals and commercialization of any products in the European Union, United Kingdom, Switzerland, the countries of the European Economic Area (excluding Malta and the Republic of Cyprus), Australia and New Zealand (Falk territory). In consideration of the rights granted to Falk under the Falk Agreement, the Company received a one-time upfront payment of $2.5 million upon execution of the Falk Agreement in July 2020, and has received two subsequent preclinical development milestone payments of $2.5 million and $10.0 million. The first development milestone payment was paid when the underlying development plan was finalized in December 2020. The second development milestone payment was paid upon selection of a clinical candidate for the Company’s PR600 program in June 2021. The Company remains eligible to receive an additional preclinical development milestone payment of $5.0 million and low-single to low-double digit percentage royalties on net sales of all products incorporating antibodies covered by the agreement in the Falk territory, subject to the terms of the Falk Agreement. The Company agreed to pay Falk a low-single digit royalty on net sales for such products in the Company’s territory. Falk agreed to fund 25% of the Company’s third-party development costs set forth in the development plan. At inception and through September 30, 2021, the Company has identified one performance obligation for all the deliverables under the Falk Agreement. Accordingly, the Company is recognizing revenue for the transaction price allocated to the performance obligation in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses over the seven year period over which it expects to satisfy its performance obligation. The Company included the upfront payment and all milestone payments in the transaction price as it was deemed not probable of significant reversal at the inception of the agreement. In connection with the Falk Agreement, the Company recognized revenue of $0.2 million and $0.2 million for the three and nine months ended September 30, 2020, respectively, $0.9 million and $1.8 million for the three and nine months ended September 30, 2021, respectively, and had deferred revenue of $14.1 million and $4.8 million as of September 30, 2021 and December 31, 2020, respectively. This deferred revenue balance is expected to be recognized proportionally as expenses are incurred over the estimated seven-year A reconciliation of deferred revenue related to the Takeda Agreement and the Falk Agreement for the nine months ended September 30, 2021 is as follows (in thousands): Takeda Agreement Falk Agreement Total Balance at December 31, 2020 $ 1,710 $ 4,763 $ 6,473 Amounts received in 2021 (150 ) 11,075 10,925 Revenue recognized in 2021 (324 ) (1,768 ) (2,092 ) Balance at September 30, 2021 $ 1,236 $ 14,070 $ 15,306

Discontinued Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2021
Discontinued Operations And Disposal Groups [Abstract]
Discontinued Operations	6. On June 30, 2019, the Company acquired 100% of the common stock of PLI and the related intangible assets used by PLI for total consideration of approximately $31.7 million, consisting of the issuance of 16.5 million shares of the Company’s Series C convertible preferred stock with a fair value of $16.5 million, the present value of $15.0 million in deferred cash payments due as follows: $5.0 million due on June 30, 2020 and $10.0 million due on June 30, 2021, and acquisition-related contingent consideration consisting of 3,500,000 shares of the of the Company’s Series C convertible preferred stock with a fair value of $3.5 million. The deferred cash payments totaling $15.0 million were not contingent upon any event and to reflect the interest component were discounted at 12%. In June 2020, $5.0 million of deferred cash payments were converted to 5,000,000 shares of Series C convertible preferred stock and in October 2020, $3.8 million of deferred cash payments were converted to 5,088,851 shares of Series D convertible preferred stock. In addition, in January 2021, $6.1 million of deferred cash payments were converted to 7,219,560 shares of Series D-2 shares of convertible preferred stock. As of September 30, 2021 and December 31, 2020, a total of $0 and $5.7 million, respectively, is recorded as Amounts due to Nestlé, current—related party in the accompanying condensed consolidated balance sheets. The acquisition-related contingent consideration stipulated certain revenue thresholds for the Anser ® test during the first calendar year following the acquisition. The shares were released from escrow on June 30, 2020 . In December 2020, in order to achieve the Company’s strategic objectives, the Company’s board of directors approved the spinoff of PLI by making an in-kind distribution of 100% of its interest in PLI to the Company’s stockholders of record on December 30, 2020. In connection with the spinoff, which was effected on December 31, 2020, the Company assigned PLI specific intellectual property to PLI; entered into a transition services agreement whereby the Company agreed to provide PLI with certain transition services including general and administrative, finance and clinical operations support; and entered into a sublease agreement under which the Company will continue to occupy approximately 40,000 square feet in the PLI facility for a term of one year, with an option to renew for an additional year. Post spinoff, the Company retained obligations under the Oxford Loan (see Note 7) and for the deferred cash payments to Nestlé. The major line items constituting the loss of PLI for the three and nine months ended September 30, 2020, which are reflected in the accompanying condensed consolidated statements of operations as discontinued operations, are as follows: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Diagnostic services revenue $ 9,569 $ 27,509 Operating expenses: Cost of diagnostic services revenue 3,064 9,800 Research and development 1,145 3,953 Sales and marketing 2,102 9,244 General and administrative 2,100 7,943 Restructuring — 2,274 Amortization of intangible assets 279 879 Total operating expenses 8,690 34,093 Income (loss) from discontinued operations $ 879 $ (6,584 ) Commitments and Contingencies At the acquisition date, PLI was involved with several legal proceedings and claims against it. All claims against PLI remained obligations of PLI and effective upon the spinoff, the Company has no remaining obligations with respect to these claims.

Long Term Debt

Long Term Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Long Term Debt	7. Long Term Debt In January 2020, the Company entered into a Loan and Security Agreement (the Loan Agreement) with Oxford Finance LLC and its affiliates (Oxford) (the Oxford Loan) which provided for total borrowings of up to $25.0 million, of which $7.5 million was drawn upon execution of the agreement. Interest accrued at an annual rate at the greater of (a) the 30-day U.S. LIBOR rate reported the last business day of the month that immediately precedes the month in which the interest will accrue, or (b) 2.01%, plus 5.98%, with a minimum annual rate of 7.99%. From March 1, 2020 through February 28, 2023, the Company was required to make interest only payments. Beginning March 1, 2023, in addition to interest payments, the monthly payments were to include an amount equal to the outstanding principal divided by 24 months. At maturity (or earlier prepayment), the Company was also required to make a final payment equal to 4.0% of the original principal amount borrowed and 3% of the future amount to be funded. The Oxford Loan was collateralized by a first priority security interest in substantially all of the Company’s current and future assets, other than its intellectual property, and contains customary conditions of borrowing, events of default and covenants, including covenants that restricted the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. Should an event of default occur, including the occurrence of a material adverse change, the Company could have been liable for immediate repayment of all obligations under the Oxford Loan. In December 2020, the Oxford Loan Agreement was amended to allow the PLI spinoff and to release PLI from all obligations pursuant to the Oxford Loan. In addition, warrants to purchase 112,500 shares of Series C convertible preferred stock were issued to Oxford in conjunction with the execution of the agreement at an exercise price of $1.00 per share. The warrants have a ten-year of $ 7.558 per share upon the completion of the IPO . The fair value of the warrant, the debt issuance costs and the final payment totaling approximately $ 0.6 million were amortized to interest expense using the effective interest method over the term of the debt. In July 2021, the Company voluntarily prepaid the aggregate outstanding principal balance of $7.5 million plus an additional $0.5 million consisting of the prepayment penalty, accrued interest, and final payment due under the terms of the Oxford Loan, and the Loan Agreement was terminated in accordance with its terms. All liens and security interests securing the Oxford Loan were released upon termination. The Company recognized a $0.6 million loss on extinguishment on the Company’s condensed consolidated statements of operations for the three and nine months ended September 30, 2021.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Stockholders' Equity (Deficit)	8. Amended Certificate of Incorporation In March 2021, the Company amended its Certificate of Incorporation to authorize 400,000,000 shares of common stock and 40,000,000 shares of preferred stock. Convertible Preferred Stock In connection with the completion of the Company’s IPO on March 16, 2021, all outstanding shares of convertible preferred stock were converted into 25,485,955 shares of the Company’s common stock and outstanding warrants to purchase 148,848 shares of convertible preferred stock were converted into warrants to purchase 14,884 shares of the Company’s common stock. As of December 31, 2020, 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. Series C Convertible Preferred Stock In March 2020, the Company sold 28,063,500 shares of Series C convertible preferred stock and received net cash proceeds totaling $28.0 million. Series D Convertible Preferred Stock In October 2020, the Company entered into a Series D convertible preferred stock purchase agreement (Series D SPA) under which it issued 61,066,216 shares of Series D-1 convertible preferred stock, for cash, at a price of $0.7558 per share, for net proceeds of $46.2 million (the Initial Series D Closing). In addition, 5,088,851 shares of Series D-1 convertible preferred stock were issued to Nestlé in satisfaction of a deferred purchase price obligation of $3.8 million. The Series D SPA contained provisions that potentially obligated the Company to issue an additional 94,007,051 shares of Series D-2 convertible preferred stock at $0.8510 per share in an additional closing, 7,231,311 of which was issuable to Nestlé for satisfaction of deferred purchase price obligations of $6.2 million, upon the approval by the Company’s board of directors, or at the option of the investors who participated in the Initial Series D Closing, or upon the achievement of certain milestones as defined in the Series D SPA, which purchase right terminates upon certain specified events, including an initial public offering of the Company, if any. The Company determined its obligation to issue additional shares of the Company’s Series D-2 convertible preferred stock in the Initial Series D Closing represented a freestanding financial instrument that required liability accounting. This freestanding preferred stock purchase right liability for the additional closing was recorded at fair value, with changes in fair value recognized in the statements of operations. As of the Initial Series D Closing, the estimated fair value of the preferred stock purchase right liability was $3.9 million. In January 2021, preferred stock purchase right liability was remeasured to fair value and the change in fair value of $1.0 million was recorded in the statement of operations for the three and nine months ended September 30, 2021. The liability was then reclassified to stockholders’ equity. The authorized, issued and outstanding shares of convertible preferred stock as of December 31, 2020 consisted of the following (in thousands, except share and per share amounts): Shares Authorized Shares Issued and Outstanding Per Share Original Issue Price Liquidation Value Carrying Value Series A 14,979,200 14,979,200 $ 0.50 $ 7,490 $ 7,391 Series B 26,666,667 26,666,667 0.75 20,000 19,901 Series C 53,176,000 53,063,500 1.00 53,064 52,937 Series D-1 66,155,067 66,155,067 0.76 49,933 45,794 Series D-2 94,007,051 — — — — Total 254,983,985 160,864,434 $ 130,487 $ 126,023 Equity Incentive Plans In 2017, the Company adopted the 2017 Equity Incentive Plan (the 2017 Plan), which as amended, had 5,524,354 shares of common stock reserved for issuance. Under the 2017 Plan, the Company could grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are employees, non-employee directors or consultants of the Company or its subsidiaries. The maximum term of the options granted under the 2017 Plan was no more than ten years. Grants generally vested at 25% one year from the vesting commencement date and ratably each month thereafter for a period of 36 months, subject to continuous service. The 2017 Plan allowed for the early exercise of all stock options granted if authorized by the board of directors at the time of grant. In February 2021, the board of directors adopted, and the Company’s stockholders approved, the 2021 Incentive Award Plan (the 2021 Plan), which became effective in connection with the IPO. Pursuant to the 2021 Plan, the Company ceased granting awards under the 2017 Plan. Under the 2021 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. The number of shares initially available for issuance under awards granted pursuant to the 2021 Plan is the sum of (1) 3,600,000 shares of common stock, plus (2) any shares subject to outstanding awards under the 2017 Plan as of the effective date of the 2021 Plan that become available for issuance under the 2021 Plan thereafter in accordance with its terms The Company’s stock option activity for the nine months ended September 30, 2021 is summarized in the following table: Number Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in Years) Weighted- Average Grant Date (Fair Value) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 2,930,246 $ 2.90 9.3 $ 2,290 Granted 2,632,621 $ 9.56 $ 5.93 Exercised (124,201 ) $ 1.29 Cancelled/forfeited (46,614 ) $ 6.43 Outstanding at September 30, 2021 5,392,052 $ 6.17 8.3 $ 95,010 Vested or expected to vest at September 30, 2021 5,392,052 $ 6.17 8.3 $ 95,010 Exercisable at September 30, 2021 1,141,561 $ 3.23 4.8 $ 23,385 The total intrinsic value of options exercised during the three months ended September 30, 2021 and 2020 was $0.3 million and $0, respectively. The total intrinsic value of options exercised during the nine months ended September 30, 2021 and 2020 was $1.7 million and $0.1 million, respectively. The total intrinsic value of options vested during the three months ended September 30, 2021 and 2020 was $8.8 million and $0.1 million, respectively. The total intrinsic value of options vested during the nine months ended September 30, 2021 and 2020 was $11.7 million and $0.2 million, respectively. The grant date fair value of stock options was determined using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Risk-free interest rate 1.0 – 1.1% 0.5% 0.6 – 1.1% 0.5 – 1.4% Expected volatility 73.0 – 74.2% 68.1% 73.0 – 95.2% 61.5 – 68.1% Expected term (in years) 5.8 – 6.1 6.1 5.8 – 6.1 6.1 Expected dividend yield —% —% —% —% Expected Term —The expected term of options granted represents the period of time that the options are expected to be outstanding. Due to the lack of historical exercise history, the expected term of the Company’s employee stock options has been determined utilizing the simplified method for awards that qualify as plain-vanilla options. Expected Volatility —The estimated volatility was based on the historical volatility of the common stock of a group of publicly traded companies deemed comparable to the Company. Risk-Free Interest Rate —The risk-free interest rate is the implied yield in effect at the time of the option grant based on U.S. Treasury securities with contract maturities similar to the expected term of the Company’s stock options. Dividend Rate —The Company has not paid any cash dividends on common stock since inception and does not anticipate paying any dividends in the foreseeable future. Consequently, an expected dividend yield of zero was used. Early Exercise Liability The unvested shares of the early-exercised options are held in escrow until the stock option becomes fully vested or until the employee’s termination, whichever occurs first. The right to repurchase these shares lapses over the four-year The following table summarizes the activity of the unvested common stock issued pursuant to an early exercise of stock option awards for the nine months ended September 30, 2021: Unvested at beginning of period 54,703 Vested or cancelled during the period (32,158 ) Unvested at end of period 22,545 Employee Stock Purchase Plan In February 2021, the Company’s board of directors approved the 2021 Employee Stock Purchase Plan (the ESPP), which became effective upon the pricing of the Company’s IPO on March 16, 2021. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. Initially, a total of 360,000 shares of common stock were reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be annually increased on the first day of each fiscal year during the term of the ESPP, beginning with the 2022 fiscal year, by an amount equal to the lessor of: (i) 1% of the total number of shares of common stock outstanding on December 31st of the preceding calendar year; or (ii) such other amount as the Company’s board of directors may determine. Stock compensation expense for the three and nine months ended September 30, 2021 related to the ESPP was $0.1 million and $0.3 million, respectively. As of September 30, 2021, the Company has not issued any shares under the ESPP. The Company had an outstanding liability of $0.4 million at September 30, 2021, which is included in accrued compensation on the condensed consolidated balance sheet, for employee contributions to the ESPP for shares pending issuance at the end of the offering period. The fair value of stock of the stock purchase right under the ESPP was determined using the Black-Scholes option pricing model with the following assumptions: Nine Months Ended September 30, 2021 Risk-free interest rate 0.03– 0.11% Expected volatility 71.6 – 80.9% Expected term (in years) 0.64 – 1.64 Expected dividend yield —% Stock-Based Compensation Expense The following table summarizes the components of stock-based compensation expense recognized in the accompanying statements of operations (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 534 $ 27 $ 972 $ 58 General and administrative 5,716 149 7,273 382 Discontinued operations — 26 — 73 Total stock-based compensation $ 6,250 $ 202 $ 8,245 $ 513 The total unrecognized compensation cost related to unvested stock-based awards as of September 30, 2021 was $17.7 million and is expected to be recognized over a weighted average period of 3.3 years. Stock Option Modification In August 2021, in connection with the passing of the Company’s former Chairman of the board of directors, the Company fully accelerated all of the former Chairman’s outstanding equity awards, which resulted in a charge of $4.6 million to stock-based compensation expense for the three months ended September 30, 2021.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Leases As a result of the PLI spinoff on December 31, 2020, the Company entered into a sublease agreement with PLI for approximately 40,000 square feet currently occupied in the PLI facility. The sublease agreement is for one year with an option to renew for an additional year. The monthly payment is $80,000 and total remaining payment obligations at September 30, 2021 and December 31, 2020 are $0.2 million and $1.0 million, respectively. In March 2021, the Company executed a non-cancellable lease agreement for office and laboratory space in San Diego, California. The lease has an initial term of ten years, following the commencement date with an option to extend the lease for an additional five-year In October 2021, the Company executed an amendment to the lease agreement to expand the leased premises. The amended lease extends the initial term of the original lease to 127 months following the commencement date of the expansion premises, with an option to extend the lease term for an additional five-year At September 30, 2021 , as the Company had not taken control of the space and the lease term had not yet commenced, no operating lease right-of-use assets or operating lease liabilities for the space has been recorded. The Company expects the lease to commence in 2022. Litigation From time to time, the Company may become involved in legal proceedings or be subject to claims arising in the ordinary course of its business. Regardless of outcome, legal proceedings or claims can have an adverse impact on the company because of defense and settlement costs, diversion of resources and other factors, and there can be no assurances that favorable outcomes will be obtained. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breech of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with officers and members of its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. At September 30, 2021, no claims exist under indemnification arrangements and accordingly, no amounts have been accrued in its condensed consolidated financial statements as of September 30, 2021.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	10. Related Party Transactions As discussed in Note 5, in September 2017, the Company entered into the Cedars-Sinai Agreement. As consideration for the license rights, the Company issued (i) 257,500 common stock shares at par value of $0.0001 per share, and (ii) 335,000 unvested restricted common stock shares at par value of $0.0001 per share. The parties also entered into additional license agreements as well as research agreements, under which the parties can provide research services to each other at pricing specified in the individual statements of work. During the three and nine months ended September 30, 2021 and 2020, no services were provided under the research agreements. During the three and nine months ended September 30, 2021, the Company incurred compensation related expenses for one employee who is an immediate family member of a former member of the Company’s board of directors. These expenses totaled $0.2 million and $0.5 million for the three and nine months ended September 30, 2021, respectively, which is included in in research and development expenses in the accompanying condensed consolidated statement of operations. During the three and nine months ended September 30, 2020, the Company incurred compensation related expenses for two employees, each of whom is an immediate family member of a different former member of the Company’s board of directors. These expenses totaled $0.1 million and $0.6 million for the three and nine months ended September 30, 2020, respectively, of which $0.2 million and $0.2 million are included in general and administrative expenses in the accompanying condensed consolidated statement of operations and $0.1 million and $0.4 million are included in research and development expenses, respectively. As of December 31, 2020, the Company has a $5.7 million liability recorded within Amounts due to Nestlé, current—related party in the condensed consolidated balance sheet. As disclosed in Notes 6 and 8, this amount relates to deferred consideration for the acquisition of PLI and was satisfied with the issuance of shares of Series D-2 convertible preferred stock in January 2021. The Company has an ongoing collaboration with Regents of the University of California, where a former member of its board of directors is employed. During the three and nine months ended September 30, 2021, the Company incurred $0.1 million and $0.3 million, respectively, in expense related to this collaboration that was recorded in research and development expenses in the accompanying condensed consolidated statement of operations for the three and nine months ended September 30, 2021. During the three and nine months ended September 30, 2020, the Company incurred $0.1 million and $0.2 million, respectively, in expense related to this collaboration that was recorded in Loss from discontinued operations in the accompanying condensed consolidated statements of operations for the three and nine months ended September 30, 2020. As a result of the PLI spinoff on December 31, 2020, the Company entered into a transition services agreement under which it assumed a $1.1 million liability related to the payout of PLI employee bonuses for the year ended December 31, 2020. This amount is included in the amount payable to PLI in the accompanying condensed consolidated balance sheets. Additionally, pursuant to this agreement, the Company is providing PLI certain transitional services, including general and administrative, finance and clinical operations support, and PLI is providing the Company with certain transitional services, including providing for the use of facilities under a sublease, in each case for specified monthly service fees. The initial term of the agreement is for one year, subject to earlier termination and extension thereafter. During the three and nine months ended September 30, 2021 , the Company paid PLI $ million and $ million, respectively, in accordance with the terms of this agreement.

401(K) Plan

401(K) Plan	9 Months Ended
	Sep. 30, 2021
Compensation And Retirement Disclosure [Abstract]
401(K) Plan	1 1 . Effective January 1, 2018, the Company maintains a defined contribution 401(k) plan available to eligible employees. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under federal tax regulations. The Company, at its discretion, may make certain contributions to the 401(k) plan. Company contributions made during the three months ended September 30, 2021 and 2020 were $0.1 million and $0, respectively. Company contributions made during the nine months ended September 30, 2021 and 2020 were $0.2 million and $46,000, respectively.

COVID-19 Pandemic

COVID-19 Pandemic	9 Months Ended
	Sep. 30, 2021
Extraordinary And Unusual Items [Abstract]
COVID-19 Pandemic	12. The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the COVID-19 pandemic may impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed consolidated financial statements and accompanying notes. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may materially differ from these estimates and assumptions. On December 31, 2020, the Company completed the spinoff of PLI. The results of operations for the three and nine months ended September 30, 2021 have been presented as discontinued operations in the accompanying condensed consolidated financial statements in accordance with Accounting Standards Codification (ASC) 205-20, Presentation of Financial Statements—Discontinued Operations consolidated financial statements relates to continuing operations (see Note 6 for additional information on discontinued operations). On an ongoing basis, management evaluates its estimates, primarily related to revenue recognition, stock-based compensation, accrued research and development costs, and for periods prior to its IPO, the fair value of common stock, the fair value of the convertible preferred stock, and the fair value of the preferred stock purchase right liability. These estimates are based on historical data and experience, as well as various other factors that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Estimates relating to the valuation of stock require the selection of appropriate valuation methodologies and models, and significant judgment in evaluating ranges of assumptions and financial inputs.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The unaudited financial statements at September 30, 2021, and for the three and nine months ended September 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (SEC), and with GAAP applicable to interim financial statements. These unaudited financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, consisting of only normal recurring accruals, which in the opinion of management are necessary to present fairly the Company’s financial position as of the interim date and results of operations for the interim periods presented. Interim results are not necessarily indicative of results for a full year or future periods. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ materially from those estimates. These unaudited financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2020, included in the Prospectus dated March 11, 2021 filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended, with the SEC on March 12, 2021.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and until December 31, 2020, the date at which the spinoff was completed, its wholly-owned subsidiary, PLI, and have been prepared in conformity with GAAP. All intercompany accounts and transactions have been eliminated in consolidation.
Segment Reporting	Segment Reporting The Company’s Chief Executive Officer, who is considered to be the chief operating decision maker (CODM), reviews financial information presented on a consolidated basis, accompanied by information about operating segments for purposes of making operating decisions and assessing financial performance. Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the CODM in deciding how to allocate resources and in assessing performance. Prior to the spinoff of PLI in December 2020, the Company determined its operating segments to be the therapeutics and diagnostic services businesses. The therapeutics business derives substantially all of its revenue from collaboration agreements and devotes all of its efforts to development of product candidates and companion diagnostics in the IBD space. The diagnostic services business, which is recorded as discontinued operations, derived its revenue from diagnostic services in the IBD space generated from the conduct of laboratory developed tests. Since the spinoff, the Company has operated solely within the therapeutics segment. The Company operates solely in the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents. The cash and cash equivalents balance at September 30, 2021 and December 31, 2020 represents cash in readily available checking and money market accounts.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash, cash equivalents, and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held.
Deferred Financing Costs	Deferred Financing Costs At December 31, 2020, f inancing costs, consisting of legal, accounting, printer and filing fees related to the Company’s IPO, totaled $1.7 million. Upon the completion of the IPO in March 2021, all of these expenses were offset against the proceeds from the IPO.
Revenue Recognition	Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers To date, all of the Company’s collaboration revenue has been derived from its collaboration agreement with Millennium Pharmaceuticals, Inc., a subsidiary of Takeda Pharmaceutical Company Limited (collectively, Takeda) and its collaboration agreement with Dr. Falk Pharma GmbH as described in Note 5. The terms of these arrangements include the following types of payments to the Company: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for research and development services provided by the Company; and royalties on net sales of licensed products. At the initiation of an agreement, the Company analyzes whether each unit of account results in a contract with a customer under ASC 606 or in an arrangement with a collaborator subject to guidance under ASC 808, Collaborative Arrangements The Company considers a variety of factors in determining the appropriate estimates and assumptions under these arrangements, such as whether the elements are distinct performance obligations, whether there are observable stand-alone prices, and whether any licenses are functional or symbolic. The Company evaluates each performance obligation to determine if it can be satisfied and recognized as revenue at a point in time or over time. Typically, license fees, non-refundable upfront fees, and funding of research activities are considered fixed, while milestone payments are identified as variable consideration which must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. The Company estimates the amount of variable consideration using the most likely amount, as milestone payments typically only have two possible outcomes. The Company recognizes revenue for sales-based royalty promised in exchange for the license of intellectual property only when the subsequent sale occurs. The Company may allocate transaction price using a number of methods including estimating standalone selling price of performance obligations and using the residual approach when the standalone selling price of the license is highly variable or uncertain, and observable standalone selling prices exist for the other goods or services promised in the contract. The Company receives payments from its collaborators based on terms established in each contract. Upfront payments and other payments may require deferral of revenue recognition to a future period until the Company is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the payment by the customer is akin to a deposit for research and development services.
Research and Development and Clinical Trial Accruals	Research and Development and Clinical Trial Accruals Research and development costs are charged to expense as incurred. Research and development expenses include certain payroll and personnel expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In addition, clinical study and trial materials are manufactured by contract manufacturing organizations. In accruing for these services, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability.
Stock-Based Compensation	Stock-Based Compensation The Company expenses stock-based compensation to employees and non-employees over the requisite service period (usually the vesting period) on a straight-line basis, net of actual forfeitures during the period, based on the estimated grant-date fair value of the awards. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, and the assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment.
Valuation of Common Stock	Valuation of Common Stock Prior to the IPO, given the absence of a public trading market for the Company’s common stock, its board of directors exercised their judgment and considered a number of objective and subjective factors to determine the best estimate of the fair value of the Company’s common stock, such as: contemporaneous valuations performed by independent third-party specialists, its stage of development, including the status of its research and development efforts of its product candidates, the material risks related to its businesses and industry, its results of operations before discontinued operations and financial position, including its levels of capital resources, the prices at which its sold shares of its convertible preferred stock, the rights, preferences and privileges of its convertible preferred stock relative to those of its common stock, the conditions in the biotechnology industry and the economy in general, the stock price performance and volatility of comparable life sciences public companies, as well as recently completed mergers and acquisitions of peer companies, the likelihood of achieving a liquidity event for the holders of its common stock or convertible preferred stock, such as an IPO or a sale of the Company given prevailing market conditions, trends and developments in its industry, external market conditions affecting the life sciences and biotechnology sectors, and the lack of liquidity of its common stock, among other factors. After the completion of the IPO, the fair value of each share of common stock is based on the closing price of the Company’s common stock as reported by Nasdaq.
Preferred Stock Purchase Right Liabilities	Preferred Stock Purchase Right Liabilities From time to time, the Company enters into convertible preferred stock financings where, in addition to the initial closing, investors agree to buy, and the Company agrees to sell, additional shares of that convertible preferred stock at a fixed price in the event that certain conditions are met or agreed upon milestones are achieved. The Company evaluates this purchase right and assesses whether it meets the definition of a freestanding instrument and, if so, determines the fair value of the purchase right liability and records it on the balance sheet with the remainder of the proceeds raised allocated to convertible preferred stock. The preferred stock purchase right liability is revalued at each reporting period with changes in the fair value of the liability recorded as change in fair value of preferred stock purchase right liability in the statements of operations. Upon the issuance of the shares of Series D-2 convertible preferred stock in January 2021, the no longer required liability accounting and the then fair value of the was reclassified into stockholders’ equity. The Company performed the final remeasurement of the preferred stock purchase right liability
Net Loss Per Share	Net Loss Per Share Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. The Company has excluded 26,641 and 36,591 weighted-average shares subject to repurchase or forfeiture from the weighted-average number of common shares outstanding for the three and nine months ended September 30, 2021, respectively, and 140,136 and 179,917 weighted-average shares subject to repurchase or forfeiture from the weighted-average number of common shares outstanding for the three and nine months ended September 30, 2020, respectively. Dilutive common stock equivalents are comprised of convertible preferred stock and options outstanding under the Company’s stock option plan. Basic and diluted net loss attributable to common holders per share is presented in conformity with the two- class method required for participating securities as the convertible preferred stock are considered participating securities. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Accordingly, for the three and nine months ended September 30, 2021 and 2020, there is no difference in the number of shares used to calculate basic and diluted shares outstanding. Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): September 30, 2021 2020 Convertible preferred stock outstanding — 9,470,926 Common stock options issued and outstanding 5,392,052 2,020,559 Warrants to purchase common stock 14,884 — Warrants to purchase convertible preferred stock outstanding — 11,250 ESPP shares pending issuance 24,279 — Total 5,431,215 11,502,735
Recent Accounting Standards	Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial position or results of operations upon adoption. In April 2012, the Jump-Start Our Business Startups Act (the JOBS Act) was signed into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company may elect to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than when public companies must adopt the standards. The Company has elected to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for emerging growth companies, which are the dates included below. Adoption of New Accounting Standards In February 2016, the FASB issued Accounting Standards Update (ASU) 2016-02, Leases (Topic 842) Leases (Topic 840) The Company made accounting policy elections to exclude leases with terms of 12 months or less from the recognition requirements and to not separate lease and non-lease components. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses: Measurement of credit Losses on Financial Instruments (ASU 2016-13) based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for sale debt securities. The Company early adopted this standard on January 1, 2021 by applying the modified retrospective approach and determined there was no cumulative-effect transition adjustment required to the opening balance of accumulated deficit for the recognition of additional credit losses upon adoption of this standard based on its outstanding accounts receivable, the composition and credit quality of its short-term investments, and current economic conditions as of that date. In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other options (Subtopic 470-20) and Derivative and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40).

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss Per Share	Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): September 30, 2021 2020 Convertible preferred stock outstanding — 9,470,926 Common stock options issued and outstanding 5,392,052 2,020,559 Warrants to purchase common stock 14,884 — Warrants to purchase convertible preferred stock outstanding — 11,250 ESPP shares pending issuance 24,279 — Total 5,431,215 11,502,735

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Assumptions Used in Black-Scholes Option Pricing Model	The assumptions used in the Black-Scholes option pricing model to determine the fair value of the convertible preferred stock warrant liability at the date of the IPO and December 31, 2020 were as follows: IPO Date December 31, 2020 Fair value of underlying preferred stock $ 1.90 $ 0.83 Risk-free interest rate 1.70 % 1.70 % Expected volatility 70.00 % 70.00 % Expected term (in years) 9.0 9.2 Expected dividend yield —% —%
Summary of Activity of Financial Instruments	The following table summarizes the activity of the financial instruments valued using Level 3 inputs (in thousands): Convertible Preferred Stock Warrant Liability Series D Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 64 $ 3,900 Change in fair value 105 980 Conversion/Settlement during 2021 (169 ) (4,880 ) Balance at September 30, 2021 $ — $ —

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): September 30, 2021 December 31, 2020 Prepaid research and development 5,761 1,894 Other prepaid expenses 1,552 275 Total $ 7,313 $ 2,169
Schedule of Equipment, Net	Equipment, net, consist of the following (in thousands): September 30, 2021 December 31, 2020 Laboratory equipment $ 1,660 $ 572 Office equipment and furniture 24 24 1,684 596 Less accumulated depreciation (322 ) (149 ) Total $ 1,362 $ 447
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): September 30, 2021 December 31, 2020 Accrued research and development $ 5,490 $ 1,940 Accrued legal expenses 70 490 Unvested early exercise liability 42 67 Accrued other 481 397 Total $ 6,083 $ 2,894

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Reconciliation of Deferred Revenue	A reconciliation of deferred revenue related to the Takeda Agreement and the Falk Agreement for the nine months ended September 30, 2021 is as follows (in thousands): Takeda Agreement Falk Agreement Total Balance at December 31, 2020 $ 1,710 $ 4,763 $ 6,473 Amounts received in 2021 (150 ) 11,075 10,925 Revenue recognized in 2021 (324 ) (1,768 ) (2,092 ) Balance at September 30, 2021 $ 1,236 $ 14,070 $ 15,306

Discontinued Operations (Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2021
Discontinued Operations And Disposal Groups [Abstract]
Schedule of Consolidated Statements of Operations as Discontinued Operations	The major line items constituting the loss of PLI for the three and nine months ended September 30, 2020, which are reflected in the accompanying condensed consolidated statements of operations as discontinued operations, are as follows: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Diagnostic services revenue $ 9,569 $ 27,509 Operating expenses: Cost of diagnostic services revenue 3,064 9,800 Research and development 1,145 3,953 Sales and marketing 2,102 9,244 General and administrative 2,100 7,943 Restructuring — 2,274 Amortization of intangible assets 279 879 Total operating expenses 8,690 34,093 Income (loss) from discontinued operations $ 879 $ (6,584 )

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Summary of the Authorized, Issued and Outstanding Shares of Convertible Preferred Stock	The authorized, issued and outstanding shares of convertible preferred stock as of December 31, 2020 consisted of the following (in thousands, except share and per share amounts): Shares Authorized Shares Issued and Outstanding Per Share Original Issue Price Liquidation Value Carrying Value Series A 14,979,200 14,979,200 $ 0.50 $ 7,490 $ 7,391 Series B 26,666,667 26,666,667 0.75 20,000 19,901 Series C 53,176,000 53,063,500 1.00 53,064 52,937 Series D-1 66,155,067 66,155,067 0.76 49,933 45,794 Series D-2 94,007,051 — — — — Total 254,983,985 160,864,434 $ 130,487 $ 126,023
Summary of Stock Option Activity	The Company’s stock option activity for the nine months ended September 30, 2021 is summarized in the following table: Number Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in Years) Weighted- Average Grant Date (Fair Value) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 2,930,246 $ 2.90 9.3 $ 2,290 Granted 2,632,621 $ 9.56 $ 5.93 Exercised (124,201 ) $ 1.29 Cancelled/forfeited (46,614 ) $ 6.43 Outstanding at September 30, 2021 5,392,052 $ 6.17 8.3 $ 95,010 Vested or expected to vest at September 30, 2021 5,392,052 $ 6.17 8.3 $ 95,010 Exercisable at September 30, 2021 1,141,561 $ 3.23 4.8 $ 23,385
Summary of Grant Date Fair Value of Stock Options	The grant date fair value of stock options was determined using the Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Risk-free interest rate 1.0 – 1.1% 0.5% 0.6 – 1.1% 0.5 – 1.4% Expected volatility 73.0 – 74.2% 68.1% 73.0 – 95.2% 61.5 – 68.1% Expected term (in years) 5.8 – 6.1 6.1 5.8 – 6.1 6.1 Expected dividend yield —% —% —% —%
Summary of Activity Unvested Common Stock Issued Pursuant Early Exercise of Stock Options Awards	The following table summarizes the activity of the unvested common stock issued pursuant to an early exercise of stock option awards for the nine months ended September 30, 2021: Unvested at beginning of period 54,703 Vested or cancelled during the period (32,158 ) Unvested at end of period 22,545
Summary of Fair Value of Stock of the Stock Purchase Right Under ESPP	The fair value of stock of the stock purchase right under the ESPP was determined using the Black-Scholes option pricing model with the following assumptions: Nine Months Ended September 30, 2021 Risk-free interest rate 0.03– 0.11% Expected volatility 71.6 – 80.9% Expected term (in years) 0.64 – 1.64 Expected dividend yield —%
Summary of Stock-based Compensation Expense	The following table summarizes the components of stock-based compensation expense recognized in the accompanying statements of operations (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 534 $ 27 $ 972 $ 58 General and administrative 5,716 149 7,273 382 Discontinued operations — 26 — 73 Total stock-based compensation $ 6,250 $ 202 $ 8,245 $ 513

Organization - Additional Infor

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands	Mar. 16, 2021USD ($)$ / sharesshares	Mar. 05, 2021	Mar. 31, 2021shares	Sep. 30, 2021USD ($)shares	Dec. 31, 2020USD ($)shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Date of incorporation				Oct. 26, 2016
Percentage of spinoff in kind distribution					100.00%
Description of reverse stock split				Company effected a one-for-ten reverse stock split of the Company’s common stock
Reverse stock split, conversion ratio		0.1
Proceeds from sale of common stock in initial public offering | $				$ 218,500
Common stock, shares authorized	400,000,000		400,000,000	400,000,000	325,000,000
Preferred stock, shares authorized	40,000,000		40,000,000	40,000,000	0
Accumulated deficit | $				$ 159,423	$ 99,146
Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Warrant to purchase of convertible preferred stock	148,848
Common Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock, shares			11,500,000
Conversion of convertible preferred stock into common stock at initial public offering, shares			25,485,955
Common Stock | Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of convertible preferred stock into common stock at initial public offering, shares	25,485,955
Common Stock | Convertible Preferred Stock Warrant Liability
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of convertible preferred stock into common stock at initial public offering, shares	14,884
IPO
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock, shares	11,500,000
Common stock price per share | $ / shares	$ 19
Gross proceeds from issuance initial public offering | $	$ 218,500
Proceeds from sale of common stock in initial public offering | $	199,800
Payments of underwriting discounts and commissions | $	15,300
Offering-related transaction costs | $	$ 3,400
Underwriters
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock, shares	1,500,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Deferred financing costs					$ 1.7
Weighted-average shares subject to repurchase or forfeiture	26,641	140,136	36,591	179,917
ASU 2016-02
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, early adoption	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021		Jan. 1, 2021
ASU 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, early adoption	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021		Jan. 1, 2021
ASU 2020-06
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, early adoption	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021		Jan. 1, 2021
Change in accounting principle, accounting standards update, immaterial effect	true		true
Series D-2 Convertible Preferred Stock
Summary Of Significant Accounting Policies [Line Items]
Change in fair value into other income (expense)			$ 1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	5,431,215	11,502,735
Convertible Preferred Stock Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		9,470,926
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	5,392,052	2,020,559
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	14,884
Warrants to Purchase Convertible Preferred Stock Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		11,250
ESPP Shares Pending Issuance
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	24,279

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transfers within Level 3 hierarchy	$ 0	$ 0	$ 0	$ 0
Level 3 liabilities	$ 0		0
Change in fair value			$ 1,000,000
Expected Risk-Free Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input					0.0009
Probability of Tranche
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input					0.800
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input					0.800

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Summary of Assumptions Used in Black-Scholes Option Pricing Model (Details)	Mar. 16, 2021$ / shares	Dec. 31, 2020$ / shares
Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value of underlying preferred stock	$ 1.90	$ 0.83
Expected Risk-Free Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input		0.0009
Expected Risk-Free Rate | Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0170	0.0170
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input		0.800
Expected Volatility | Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.7000	0.7000
Expected Term | Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	9 years	9 years 2 months 12 days

Fair Value Measurements and F_5

Fair Value Measurements and Fair Value of Financial Instruments - Summary of Activity of Financial Instruments (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Change in fair value	$ 1,000
Balance at September 30, 2021	0
Convertible Preferred Stock Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2020	64
Change in fair value	105
Conversion/Settlement during 2021	(169)
Balance at September 30, 2021	0
Series D Convertible Preferred Stock Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2020	3,900
Change in fair value	980
Conversion/Settlement during 2021	(4,880)
Balance at September 30, 2021	$ 0

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid research and development	$ 5,761	$ 1,894
Other prepaid expenses	1,552	275
Total	$ 7,313	$ 2,169

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule of Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Equipment, gross	$ 1,684	$ 596
Less accumulated depreciation	(322)	(149)
Total	1,362	447
Laboratory Equipment
Property Plant And Equipment [Line Items]
Equipment, gross	1,660	572
Office Equipment and Furniture
Property Plant And Equipment [Line Items]
Equipment, gross	$ 24	$ 24

Balance Sheet Details - Additio

Balance Sheet Details - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 100,000	$ 29,000	$ 200,000	$ 100,000

Balance Sheet Details - Sched_3

Balance Sheet Details - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued research and development	$ 5,490	$ 1,940
Accrued legal expenses	70	490
Unvested early exercise liability	42	67
Accrued other	481	397
Total	$ 6,083	$ 2,894

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Details)	1 Months Ended				3 Months Ended		9 Months Ended
	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)shares	Jul. 31, 2020USD ($)Milestone	Mar. 31, 2019USD ($)	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)shares	Sep. 30, 2020USD ($)	Sep. 30, 2017shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued | shares		1,768,325			38,907,081		38,907,081
Revenue recognized							$ 2,092,000
Deferred revenue		$ 6,473,000			$ 15,306,000		15,306,000
Cedars-Sinai Agreement | Cedars-Sinai | Vested Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued | shares									257,500
Cedars-Sinai Agreement | Cedars-Sinai | Unvested Restricted Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued | shares									335,000
Takeda Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized							324,000
Deferred revenue		1,710,000			1,236,000		1,236,000
Takeda Agreement | Takeda
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement, upfront payment received				$ 1,500,000
Revenue recognized					100,000	$ 200,000	300,000	$ 600,000
Deferred revenue		1,700,000			1,200,000		1,200,000
Takeda Agreement | Takeda | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development and regulatory milestone payments receivable				47,900,000
Commercial milestone payments receivable				25,000,000
Sales milestone payments receivable				$ 75,000,000
Falk Agreement | Falk
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized					900,000	$ 200,000	1,768,000	$ 200,000
Deferred revenue		4,763,000			$ 14,070,000		$ 14,070,000
Collaboration agreement, upfront payment received upon agreement execution			$ 2,500,000
Number of subsequent pre-clinical development milestone payments received | Milestone			2
Collaboration agreement, pre-clinical development milestone payment received upon finalization of development plan		$ 2,500,000
Collaboration agreement, pre-clinical development milestone payment received upon clinical candidate selected	$ 10,000,000
Collaboration agreement additional pre-clinical development milestone payment eligible to receive			$ 5,000,000
Funding percentage third-party development costs set forth in development plan			25.00%

Collaboration and License Agr_4

Collaboration and License Agreements - Additional Information (Details1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-10-01 $ in Millions	Sep. 30, 2021USD ($)
Takeda Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Revenue, remaining performance obligation expected to be recognized amount	$ 0.2
Takeda Agreement | Takeda
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	4 years
Falk Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	3 months
Revenue, remaining performance obligation expected to be recognized amount	$ 1
Falk Agreement | Falk
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	7 years

Collaboration and License Agr_5

Collaboration and License Agreements - Schedule of Reconciliation of Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Balance at December 31, 2020			$ 6,473
Amounts received in 2021			10,925
Revenue recognized in 2021			(2,092)
Balance at September 30, 2021	$ 15,306		15,306
Takeda Agreement
Disaggregation Of Revenue [Line Items]
Balance at December 31, 2020			1,710
Amounts received in 2021			(150)
Revenue recognized in 2021			(324)
Balance at September 30, 2021	1,236		1,236
Falk Agreement | Falk
Disaggregation Of Revenue [Line Items]
Balance at December 31, 2020			4,763
Amounts received in 2021			11,075
Revenue recognized in 2021	(900)	$ (200)	(1,768)	$ (200)
Balance at September 30, 2021	$ 14,070		$ 14,070

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Details) $ in Thousands	Jun. 30, 2019USD ($)shares	Jan. 31, 2021USD ($)shares	Oct. 31, 2020USD ($)shares	Jun. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)ft²	Sep. 30, 2021USD ($)	Jun. 30, 2021USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Amounts due to Nestlé, current—related party					$ 5,675
PLI | Spinoff
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Discontinued operation distribution of interest, percentage					100.00%
Area of Space Leased | ft²					40,000
Term of sublease					1 year
PLI
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Percentage of voting interest acquired	100.00%
Total consideration	$ 31,700
Business acquisition, deferred cash payment	15,000		$ 3,800	$ 5,000
Business acquisition, deferred cash payment due on June 30, 2020				$ 5,000
Business acquisition, deferred cash payment due on June 30, 2021							$ 10,000
Acquisition-related contingent consideration	$ 3,500
Percentage of discount rate on interest component	12.00%
Amounts due to Nestlé, current—related party					$ 5,700	$ 0
PLI | Series C Convertible Preferred Stock
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, number of shares issued | shares	16,500,000
Business acquisition, number of shares issued with fair value	$ 16,500
Acquisition-related contingent consideration shares | shares	3,500,000
Business acquisition deferred cash payment converted to shares of convertible preferred stock | shares				5,000,000
PLI | Series D Convertible Preferred Stock
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition deferred cash payment converted to shares of convertible preferred stock | shares			5,088,851
PLI | Series D-2 Convertible Preferred Stock
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business acquisition, number of shares issued | shares		7,219,560
Business acquisition, deferred cash payment		$ 6,100
Business acquisition deferred cash payment converted to shares of convertible preferred stock | shares		7,219,560

Discontinued Operations - Sched

Discontinued Operations - Schedule of Consolidated Statements of Operations as Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Operating expenses:
Income (loss) from discontinued operations	$ 879	$ (6,584)
PLI | Spinoff
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Diagnostic services revenue	9,569	27,509
Operating expenses:
Cost of diagnostic services revenue	3,064	9,800
Research and development	1,145	3,953
Sales and marketing	2,102	9,244
General and administrative	2,100	7,943
Restructuring		2,274
Amortization of intangible assets	279	879
Total operating expenses	8,690	34,093
Income (loss) from discontinued operations	$ 879	$ (6,584)

Long Term Debt - Additional Inf

Long Term Debt - Additional Information (Details) - USD ($)	Mar. 16, 2021	Jul. 31, 2021	Jan. 31, 2020	Sep. 30, 2021	Sep. 30, 2021
Debt Instrument [Line Items]
Loss on extinguishment of debt				$ (554,000)	$ (554,000)
Oxford Finance LLC
Debt Instrument [Line Items]
Long term debt, maximum borrowing amount			$ 25,000,000
Long term debt, amount drawn upon execution of agreement			$ 7,500,000
Interest rate			2.01%
Additional interest rate			5.98%
Debt instrument minimum annual interest rate			7.99%
Percentage of final payment equal to original principal amount borrowed			4.00%
Percentage of future amount to be funded			3.00%
Prepayment of outstanding principal balance		$ 7,500,000
Prepayment penalty, accrued interest and final payment		$ 500,000
Loss on extinguishment of debt				$ (600,000)	$ (600,000)
Oxford Finance LLC | Series C Convertible Preferred Stock
Debt Instrument [Line Items]
Warrant to purchase of convertible preferred stock			112,500
Exercise price of warrants	$ 7.558		$ 1
Warrants term			10 years
Conversion of convertible preferred stock into common stock at initial public offering, shares	14,884
Fair value of warrant, debt issuance cost and final payment			$ 600,000

Stockholders' Equity (Deficit_2

Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($)	Mar. 16, 2021	Feb. 28, 2021	Jan. 31, 2021	Oct. 31, 2020	Mar. 31, 2020	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2017	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock, shares authorized	400,000,000					400,000,000	400,000,000		400,000,000			325,000,000
Preferred stock, shares authorized	40,000,000					40,000,000	40,000,000		40,000,000			0
Net cash proceeds from sale of convertible preferred stock									$ 73,749,000	$ 27,986,000
Total intrinsic value of options exercised						$ 300,000		$ 0	1,700,000	100,000
Total intrinsic value of options vested						8,800,000		100,000	$ 11,700,000	200,000
Unvested shares early exercised option right to repurchase shares vesting period									4 years
Early exercise liability						42,000			$ 42,000			$ 100,000
Stock compensation expense						6,250,000		$ 202,000	8,245,000	$ 513,000
Unrecognized compensation cost related to unvested stock-based awards						17,700,000			$ 17,700,000
Unrecognized compensation cost is expected to be recognized over a weighted average period									3 years 3 months 18 days
2021 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common stock reserved for issuance		360,000
Annually increase amount equal to lessor of percentage of shares of common stock outstanding on the final day of the immediately preceding calendar year		1.00%
Participants to purchase common stock through payroll deductions maximum percentage of eligible compensation		20.00%
Stock compensation expense						100,000			$ 300,000
Shares issued									0
Outstanding liability related to employee contributions for shares pending issuance						400,000			$ 400,000
Stock Option Modification
Class Of Stock [Line Items]
Stock compensation expense						$ 4,600,000
2017 Equity Incentive Plan
Class Of Stock [Line Items]
Common stock reserved for issuance											5,524,354
Maximum options granted period											10 years
Award subject to continuous service											36 months
2017 Equity Incentive Plan | Tranche One
Class Of Stock [Line Items]
Percentage of award vested											25.00%
Award vesting period											1 year
2021 Incentive Award Plan
Class Of Stock [Line Items]
Common stock, shares available for grant		3,600,000				3,074,775			3,074,775
Annually increase amount equal to lessor of percentage of shares of common stock outstanding on the final day of the immediately preceding calendar year		5.00%
Convertible Preferred Stock
Class Of Stock [Line Items]
Warrant to purchase of convertible preferred stock	148,848
Series C Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares sold					28,063,500
Net cash proceeds from sale of convertible preferred stock					$ 28,000,000
Series D-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares sold				61,066,216
Net cash proceeds from sale of convertible preferred stock				$ 46,200,000
Shares issued, price per share				$ 0.7558
Convertible preferred stock issued for deferred purchase price obligation, shares				5,088,851
Convertible preferred stock, shares issued for deferred purchase price obligation, value				$ 3,800,000
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price				5,088,851
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price				$ 3,800,000
Series D-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares sold			93,995,300	94,007,051			86,775,740
Shares issued, price per share				$ 0.8510
Convertible preferred stock issued for deferred purchase price obligation, shares			7,219,560	7,231,311			7,219,560
Convertible preferred stock, shares issued for deferred purchase price obligation, value			$ 6,100,000	$ 6,200,000			$ 6,144,000
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price			7,219,560	7,231,311			7,219,560
Issuance of Series D-2 convertible preferred stock for settlement of deferred purchase price			$ 6,100,000	$ 6,200,000			$ 6,144,000
Change in fair value of preferred stock purchase right liability						$ 1,000,000			$ 1,000,000
Series D Convertible Preferred Stock
Class Of Stock [Line Items]
Fair value of preferred stock purchase right liability				$ 3,900,000
Common Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock into common stock at initial public offering, shares							25,485,955
Common Stock | Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of convertible preferred stock into common stock at initial public offering, shares	25,485,955
Common Stock | Convertible Preferred Stock Warrant Liability
Class Of Stock [Line Items]
Conversion of convertible preferred stock into common stock at initial public offering, shares	14,884

Stockholders' Equity (Deficit_3

Stockholders' Equity (Deficit) - Summary of the Authorized, Issued and Outstanding Shares of Convertible Preferred Stock (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Temporary Equity [Line Items]
Shares Authorized	0	254,983,985
Shares Issued and Outstanding		160,864,434
Per Share Original Issue Price	$ 0.0001	$ 0.0001
Liquidation Value	$ 0	$ 130,487,000
Carrying Value		$ 126,023,000
Series A
Temporary Equity [Line Items]
Shares Authorized		14,979,200
Shares Issued and Outstanding		14,979,200
Per Share Original Issue Price		$ 0.50
Liquidation Value		$ 7,490,000
Carrying Value		$ 7,391,000
Series B
Temporary Equity [Line Items]
Shares Authorized		26,666,667
Shares Issued and Outstanding		26,666,667
Per Share Original Issue Price		$ 0.75
Liquidation Value		$ 20,000,000
Carrying Value		$ 19,901,000
Series C
Temporary Equity [Line Items]
Shares Authorized		53,176,000
Shares Issued and Outstanding		53,063,500
Per Share Original Issue Price		$ 1
Liquidation Value		$ 53,064,000
Carrying Value		$ 52,937,000
Series D-1
Temporary Equity [Line Items]
Shares Authorized		66,155,067
Shares Issued and Outstanding		66,155,067
Per Share Original Issue Price		$ 0.76
Liquidation Value		$ 49,933,000
Carrying Value		$ 45,794,000
Series D-2
Temporary Equity [Line Items]
Shares Authorized		94,007,051

Stockholders' Equity (Deficit_4

Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Equity [Abstract]
Number of shares, Outstanding at December 31, 2020 | shares	2,930,246
Number of shares, Granted | shares	2,632,621
Number of shares, Exercised | shares	(124,201)
Number of shares, Cancelled/forfeited | shares	(46,614)
Number of shares, Outstanding at September 30, 2021 | shares	5,392,052	2,930,246
Number of shares, Vested or expected to vest at September 30, 2021 | shares	5,392,052
Number of shares, Exercisable at September 30, 2021 | shares	1,141,561
Weighted Average Exercise Price, Outstanding at December 31, 2020	$ 2.90
Weighted Average Exercise Price, Granted	9.56
Weighted Average Exercise Price, Exercised	1.29
Weighted Average Exercise Price, Cancelled/forfeited	6.43
Weighted Average Exercise Price, Outstanding at September 30, 2021	6.17	$ 2.90
Weighted Average Exercise Price, Vested or expected to vest at September 30, 2021	6.17
Weighted Average Exercise Price, Exercisable at September 30, 2021	$ 3.23
Weighted Average Remaining Contractual Terms (in Years), Outstanding	8 years 3 months 18 days	9 years 3 months 18 days
Weighted Average Remaining Contractual Terms (in Years), Vested or excepted to vest at September 30, 2021	8 years 3 months 18 days
Weighted Average Remaining Contractual Terms (in Years), Exercisable at September 30, 2021	4 years 9 months 18 days
Weighted Average Grant Date (Fair Value), Granted	$ 5.93
Aggregate Intrinsic Value, Outstanding | $	$ 95,010	$ 2,290
Aggregate Intrinsic Value, Vested or excepted to vest at September 30, 2021 | $	95,010
Aggregate Intrinsic Value, Exercisable at September 30, 2021 | $	$ 23,385

Stockholders' Equity (Deficit_5

Stockholders' Equity (Deficit) - Summary of Grant Date Fair Value of Stock Options (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		0.50%
Risk-free interest rate, Minimum	1.00%		0.60%	0.50%
Risk-free interest rate, Maximum	1.10%		1.10%	1.40%
Expected volatility		68.10%
Expected volatility, Minimum	73.00%		73.00%	61.50%
Expected volatility, Maximum	74.20%		95.20%	68.10%
Expected term (in years)		6 years 1 month 6 days		6 years 1 month 6 days
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 18 days		5 years 9 months 18 days
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

Stockholders' Equity (Deficit_6

Stockholders' Equity (Deficit) - Summary of Activity Unvested Common Stock Issued Pursuant Early Exercise of Stock Options Awards (Details)	9 Months Ended
	Sep. 30, 2021shares
Equity [Abstract]
Unvested at beginning of period	54,703
Vested or cancelled during the period	(32,158)
Unvested at end of period	22,545

Stockholders' Equity (Deficit_7

Stockholders' Equity (Deficit) - Summary of Fair Value of Stock of the Stock Purchase Right Under ESPP (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		0.50%
Risk-free interest rate, Minimum	1.00%		0.60%	0.50%
Risk-free interest rate, Maximum	1.10%		1.10%	1.40%
Expected volatility		68.10%
Expected volatility, Minimum	73.00%		73.00%	61.50%
Expected volatility, Maximum	74.20%		95.20%	68.10%
Expected term (in years)		6 years 1 month 6 days		6 years 1 month 6 days
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, Minimum			0.03%
Risk-free interest rate, Maximum			0.11%
Expected volatility, Minimum			71.60%
Expected volatility, Maximum			80.90%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 18 days		5 years 9 months 18 days
Minimum [Member] | 2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			7 months 20 days
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
Maximum | 2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			1 year 7 months 20 days

Stockholders' Equity (Deficit_8

Stockholders' Equity (Deficit) - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 6,250	$ 202	$ 8,245	$ 513
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	534	27	972	58
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 5,716	149	$ 7,273	382
Discontinued Operations
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation		$ 26		$ 73

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	Dec. 31, 2020USD ($)ft²	Oct. 31, 2021USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)ft²
Commitments and Contingencies [Line Items]
Indemnification claims				$ 0
Accrued indemnification				0
Office and Laboratory Space, San Diego
Commitments and Contingencies [Line Items]
Initial lease term			10 years
Option to extend additional lease term			5 years
Approximate monthly rental payment proceeds from lease			$ 200,000
Tenant improvement allowance				900,000
Operating lease right-of-use asset				0
Operating lease liability				0
Office and Laboratory Space, San Diego | Maximum
Commitments and Contingencies [Line Items]
Tenant improvement allowance			$ 6,300,000
Subsequent Event | Lease Amendment
Commitments and Contingencies [Line Items]
Initial lease term		127 months
Option to extend additional lease term		5 years
Approximate monthly rental payment proceeds from lease		$ 200,000
Subsequent Event | Lease Amendment | Maximum
Commitments and Contingencies [Line Items]
Tenant improvement allowance		$ 6,300,000
PLI
Commitments and Contingencies [Line Items]
Area of Land | ft²	40,000				40,000
Sublease agreement term	1 year
Monthly payment	$ 80,000
Remaining payment obligations				$ 200,000	$ 1,000,000

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2021shares	Sep. 30, 2021USD ($)Employee$ / sharesshares	Sep. 30, 2020USD ($)Employee	Sep. 30, 2021USD ($)Employee$ / sharesshares	Sep. 30, 2020USD ($)Employee	Dec. 31, 2020USD ($)$ / sharesshares	Sep. 30, 2017$ / sharesshares
Related Party Transaction [Line Items]
Common stock, shares issued | shares		38,907,081		38,907,081		1,768,325
Common stock, par value | $ / shares		$ 0.0001		$ 0.0001		$ 0.0001
Number of employees | Employee		1	2	1	2
Compensation related expense			$ 100		$ 600
Amounts due to Nestlé, current—related party						$ 5,675
Payment for collaboration expense		$ 100	100	$ 300	200
PLI
Related Party Transaction [Line Items]
Amounts due to Nestlé, current—related party		0		0		5,700
PLI | Series D-2 Convertible Preferred Stock
Related Party Transaction [Line Items]
Business acquisition, number of shares issued | shares	7,219,560
General and Administrative
Related Party Transaction [Line Items]
Compensation related expense			200		200
Research and Development
Related Party Transaction [Line Items]
Compensation related expense		200	$ 100	500	$ 400
Nestle
Related Party Transaction [Line Items]
Amounts due to Nestlé, current—related party						5,700
Cedars-Sinai Agreement | Vested Common Stock | Cedars-Sinai
Related Party Transaction [Line Items]
Common stock, shares issued | shares							257,500
Common stock, par value | $ / shares							$ 0.0001
Cedars-Sinai Agreement | Unvested Restricted Common Stock | Cedars-Sinai
Related Party Transaction [Line Items]
Common stock, shares issued | shares							335,000
Unvested restricted common stock shares par value | $ / shares							$ 0.0001
Transition Services Agreement
Related Party Transaction [Line Items]
Payment for terms of agreement		$ 500		$ 2,700
Transition Services Agreement | PLI Spinoff
Related Party Transaction [Line Items]
Payout bonus liability						$ 1,100
Initial term of agreement						1 year

401(K) Plan - Additional Inform

401(K) Plan - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Company contribution to 401(k) plan	$ 100,000	$ 0	$ 200,000	$ 46,000