ORIC Pharmaceuticals (ORIC) S-1 10 Nov 20 IPO registration Financial data

Cover

Cover	9 Months Ended
	Sep. 30, 2020
Cover [Abstract]
Document Type	S-1
Amendment Flag	false
Entity Registrant Name	ORIC PHARMACEUTICALS, INC.
Entity Central Index Key	0001796280
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 62,031	$ 89,159	$ 42,636
Marketable securities	124,579
Prepaid expenses and other current assets	2,448	840	1,088
Total current assets	189,058	89,999	43,724
Property and equipment, net	1,893	2,241	2,514
Deferred offering costs		1,343
Other assets	711	1,853
Other assets, excluding deferred offering costs		510	496
Total assets	191,662	94,093	46,734
Current liabilities:
Accounts payable	1,598	152	446
Accrued other liabilities	5,330	5,202	2,150
Total current liabilities	6,928	5,354	2,596
Deferred rent-long term	359	765	1,251
Other liabilities-long term			47
Total liabilities	7,287	6,119	3,894
Commitments and contingencies (See Note 9,10)
Stockholders' equity (deficit):
Common stock	3
Additional paid-in capital	322,535	2,606	1,381
Accumulated deficit	(138,134)	(92,690)	(65,807)
Accumulated other comprehensive loss	(29)
Total stockholders' equity (deficit)	184,375	(90,084)	(64,426)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 191,662	94,093	46,734
Series A Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock		15,431	15,431
Series B Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock		53,906	53,906
Series C Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock		53,172	$ 37,929
Series D Convertible Preferred Stock
Convertible preferred stock:
Convertible preferred stock		$ 55,549

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Apr. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Convertible preferred stock, par value				$ 0.0001
Convertible preferred stock, authorized				20,348,788
Convertible preferred stock, issued				19,278,606
Convertible preferred stock, outstanding		0		19,278,606
Common stock, par value	$ 0.0001			$ 0.0001				$ 0.0001
Common stock, shares authorized	1,000,000,000			26,750,000				20,250,000
Common stock, shares, issued	30,545,165			1,984,222				1,802,134
Common stock, shares, outstanding	30,545,165			1,984,222				1,802,134
Pro Forma
Common stock, shares, issued				21,262,828				21,262,828
Common stock, shares, outstanding				21,262,828				21,262,828
Series A Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001			$ 0.0001				$ 0.0001
Convertible preferred stock, authorized	0			3,862,500				3,862,500
Convertible preferred stock, issued	0			3,862,500				3,862,500
Convertible preferred stock, outstanding	0		3,862,500	3,862,500	3,862,500	3,862,500	3,862,500	3,862,500	3,862,500
Aggregate liquidation preference	$ 0			$ 15,450				$ 15,450
Series A Convertible Preferred Stock | Pro Forma
Convertible preferred stock, issued				0				0
Convertible preferred stock, outstanding				0				0
Series B Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001			$ 0.0001				$ 0.0001
Convertible preferred stock, authorized	0			6,750,000				6,750,000
Convertible preferred stock, issued	0			6,749,999				6,749,999
Convertible preferred stock, outstanding	0		6,749,999	6,749,999	6,749,999	6,749,999	6,749,999	6,749,999	6,749,999
Aggregate liquidation preference	$ 0			$ 54,000				$ 54,000
Series B Convertible Preferred Stock | Pro Forma
Convertible preferred stock, issued				0				0
Convertible preferred stock, outstanding				0				0
Series C Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001			$ 0.0001				$ 0.0001
Convertible preferred stock, authorized	0			4,448,788				5,000,000
Convertible preferred stock, issued	0			4,448,780				3,177,271
Convertible preferred stock, outstanding	0		4,448,780	4,448,780	4,448,780	4,448,780	4,448,780	3,177,271
Aggregate liquidation preference	$ 0			$ 53,385				$ 38,127
Series C Convertible Preferred Stock | Pro Forma
Convertible preferred stock, issued				0				0
Convertible preferred stock, outstanding				0				0
Series D Convertible Preferred Stock
Convertible preferred stock, par value	$ 0.0001			$ 0.0001				$ 0.0001
Convertible preferred stock, authorized	0			5,287,500				0
Convertible preferred stock, issued	0			4,217,327				0
Convertible preferred stock, outstanding	0		4,217,327	4,217,327	4,217,327	3,777,564		0
Aggregate liquidation preference	$ 0			$ 55,669				$ 0
Series D Convertible Preferred Stock | Pro Forma
Convertible preferred stock, issued				0				0
Convertible preferred stock, outstanding				0				0

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Operating expenses:
Research and development	$ 8,831	$ 5,632	$ 23,808	$ 15,884	$ 22,844	$ 19,026
Acquired in-process research and development	12,971		12,971
General and administrative	3,800	1,465	9,125	3,914	5,725	3,345
Total operating expenses	25,602	7,097	45,904	19,798	28,569	22,371
Loss from operations	(25,602)	(7,097)	(45,904)	(19,798)	(28,569)	(22,371)
Other income:
Interest income, net	10	476	276	1,054	1,397	775
Other income	44	72	184	215	289	233
Total other income	54	548	460	1,269	1,686	1,008
Net loss	(25,548)	(6,549)	(45,444)	(18,529)	$ (26,883)	$ (21,363)
Other comprehensive loss:
Unrealized loss on available-for-salesecurities	(29)		(29)
Comprehensive loss	$ (25,577)	$ (6,549)	$ (45,473)	$ (18,529)
Net loss per share, basic and diluted	$ (0.84)	$ (3.36)	$ (2.52)	$ (9.87)	$ (14.15)	$ (12.32)
Weighted-average shares outstanding, basic and diluted	30,314,904	1,946,439	18,022,068	1,876,687	1,899,348	1,734,115

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C Convertible Preferred Stock	Series D Convertible Preferred Stock	Common Stock	Common StockInitial Public Offering	Additional Paid-in Capital	Additional Paid-in CapitalInitial Public Offering	Accumulated Deficit	AOCI Attributable to Parent [Member]
Beginning Balance at Dec. 31, 2017			$ 15,431	$ 53,906
Beginning Balance (in shares) at Dec. 31, 2017			3,862,500	6,749,999
Issuance of preferred stock, net of issuance costs					$ 37,929
Issuance of preferred stock, net of issuance costs (in shares)					3,177,271
Ending Balance at Dec. 31, 2018			$ 15,431	$ 53,906	$ 37,929
Ending Balance (in shares) at Dec. 31, 2018			3,862,500	6,749,999	3,177,271	0
Beginning Balance at Dec. 31, 2017	$ (43,611)								$ 833		$ (44,444)
Beginning Balance (in shares) at Dec. 31, 2017							1,672,087
Exercise of stock options	79								79
Exercise of stock options, shares							130,047
Stock-based compensation expense	469								469
Net loss	(21,363)										(21,363)
Ending Balance at Dec. 31, 2018	$ (64,426)								1,381		(65,807)
Ending Balance (in shares) at Dec. 31, 2018	1,802,134						1,802,134
Issuance of preferred stock, net of issuance costs					$ 15,243
Issuance of preferred stock, net of issuance costs (in shares)					1,271,509
Ending Balance at Mar. 31, 2019			$ 15,431	$ 53,906	$ 53,172
Ending Balance (in shares) at Mar. 31, 2019			3,862,500	6,749,999	4,448,780
Exercise of common stock options and vesting of early exercised common stock options	$ 21								21
Exercise of common stock options and vesting of early exercised common stock options (in shares)							26,159
Stock-based compensation expense	191								191
Net loss	(6,015)										(6,015)
Ending Balance at Mar. 31, 2019	$ (70,229)								1,593		(71,822)
Ending Balance (in shares) at Mar. 31, 2019							1,828,293
Beginning Balance at Dec. 31, 2018			$ 15,431	$ 53,906	$ 37,929
Beginning Balance (in shares) at Dec. 31, 2018			3,862,500	6,749,999	3,177,271	0
Issuance of preferred stock, net of issuance costs					$ 15,243	$ 55,549
Issuance of preferred stock, net of issuance costs (in shares)					1,271,509	4,217,327
Ending Balance at Dec. 31, 2019			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Ending Balance (in shares) at Dec. 31, 2019	19,278,606		3,862,500	6,749,999	4,448,780	4,217,327
Beginning Balance at Dec. 31, 2018	$ (64,426)								1,381		(65,807)
Beginning Balance (in shares) at Dec. 31, 2018	1,802,134						1,802,134
Exercise of stock options	$ 131								131
Exercise of stock options, shares	182,105						182,088
Stock-based compensation expense	$ 1,094								1,094
Net loss	(26,883)										(26,883)
Ending Balance at Dec. 31, 2019	$ (90,084)								2,606		(92,690)
Ending Balance (in shares) at Dec. 31, 2019	1,984,222						1,984,222
Beginning Balance at Mar. 31, 2019			$ 15,431	$ 53,906	$ 53,172
Beginning Balance (in shares) at Mar. 31, 2019			3,862,500	6,749,999	4,448,780
Issuance of preferred stock, net of issuance costs						$ 49,864
Issuance of preferred stock, net of issuance costs (in shares)						3,777,564
Ending Balance at Jun. 30, 2019			$ 15,431	$ 53,906	$ 53,172	$ 49,864
Ending Balance (in shares) at Jun. 30, 2019			3,862,500	6,749,999	4,448,780	3,777,564
Beginning Balance at Mar. 31, 2019	$ (70,229)								1,593		(71,822)
Beginning Balance (in shares) at Mar. 31, 2019							1,828,293
Exercise of common stock options and vesting of early exercised common stock options	59								59
Exercise of common stock options and vesting of early exercised common stock options (in shares)							111,884
Stock-based compensation expense	190								190
Net loss	(5,965)										(5,965)
Ending Balance at Jun. 30, 2019	(75,945)								1,842		(77,787)
Ending Balance (in shares) at Jun. 30, 2019							1,940,177
Issuance of preferred stock, net of issuance costs						$ 5,685
Issuance of preferred stock, net of issuance costs (in shares)						439,763
Ending Balance at Sep. 30, 2019			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Ending Balance (in shares) at Sep. 30, 2019			3,862,500	6,749,999	4,448,780	4,217,327
Exercise of common stock options and vesting of early exercised common stock options	14								14
Exercise of common stock options and vesting of early exercised common stock options (in shares)							15,789
Stock-based compensation expense	271								271
Net loss	(6,549)										(6,549)
Ending Balance at Sep. 30, 2019	$ (82,209)								2,127		(84,336)
Ending Balance (in shares) at Sep. 30, 2019							1,955,966
Beginning Balance at Dec. 31, 2019			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Beginning Balance (in shares) at Dec. 31, 2019	19,278,606		3,862,500	6,749,999	4,448,780	4,217,327
Ending Balance at Mar. 31, 2020			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Ending Balance (in shares) at Mar. 31, 2020			3,862,500	6,749,999	4,448,780	4,217,327
Beginning Balance at Dec. 31, 2019	$ (90,084)								2,606		(92,690)
Beginning Balance (in shares) at Dec. 31, 2019	1,984,222						1,984,222
Exercise of common stock options and vesting of early exercised common stock options	$ 12								12
Exercise of common stock options and vesting of early exercised common stock options (in shares)							13,433
Stock-based compensation expense	527								527
Net loss	(8,872)										(8,872)
Ending Balance at Mar. 31, 2020	$ (98,417)								3,145		(101,562)
Ending Balance (in shares) at Mar. 31, 2020							1,997,655
Beginning Balance at Dec. 31, 2019			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Beginning Balance (in shares) at Dec. 31, 2019	19,278,606		3,862,500	6,749,999	4,448,780	4,217,327
Ending Balance (in shares) at Sep. 30, 2020			0	0	0	0
Beginning Balance at Dec. 31, 2019	$ (90,084)								2,606		(92,690)
Beginning Balance (in shares) at Dec. 31, 2019	1,984,222						1,984,222
Exercise of stock options, shares	69,102
Ending Balance at Sep. 30, 2020	$ 184,375						$ 3		322,535		(138,134)	$ (29)
Ending Balance (in shares) at Sep. 30, 2020	30,545,165						30,545,165
Beginning Balance at Mar. 31, 2020			$ 15,431	$ 53,906	$ 53,172	$ 55,549
Conversion to Common Stock			$ (15,431)	$ (53,906)	$ (53,172)	$ (55,549)
Beginning Balance (in shares) at Mar. 31, 2020			3,862,500	6,749,999	4,448,780	4,217,327
Conversion to Common Stock (in shares)			(3,862,500)	(6,749,999)	(4,448,780)	(4,217,327)
Beginning Balance at Mar. 31, 2020	$ (98,417)								3,145		(101,562)
Beginning Balance (in shares) at Mar. 31, 2020							1,997,655
Exercise of common stock options and vesting of early exercised common stock options	39								39
Exercise of common stock options and vesting of early exercised common stock options (in shares)							23,200
Stock-based compensation expense	1,381								1,381
Initial public offering of common stock		$ 138,000						$ 1		$ 137,999
Initial public offering of common stock (in shares)								8,625,000
Issuance costs associated with initial public offering	(12,790)								(12,790)
Conversion to Common Stock	178,058						$ 2		178,056
Conversion to Common Stock (in shares)							19,278,606
Net loss	(11,024)										(11,024)
Ending Balance at Jun. 30, 2020	195,247						$ 3		307,830		(112,586)
Ending Balance (in shares) at Jun. 30, 2020							29,924,461
Ending Balance (in shares) at Sep. 30, 2020			0	0	0	0
Exercise of common stock options and vesting of early exercised common stock options	53								53
Exercise of common stock options and vesting of early exercised common stock options (in shares)							32,469
Stock-based compensation expense	1,681								1,681
Issuance of common stock related to acquisition	12,971								12,971
Issuance of common stock related to acquisition (in shares)							588,235
Other comprehensive loss	(29)											(29)
Net loss	(25,548)										(25,548)
Ending Balance at Sep. 30, 2020	$ 184,375						$ 3		$ 322,535		$ (138,134)	$ (29)
Ending Balance (in shares) at Sep. 30, 2020	30,545,165						30,545,165

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Series C Convertible Preferred Stock
Preferred stock, issuance costs	$ 121	$ 213	$ 15	$ 198
Series D Convertible Preferred Stock
Preferred stock, issuance costs			$ 120

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (45,444)	$ (18,529)	$ (26,883)	$ (21,363)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	736	758	1,028	903
Stock-based compensation expense	3,589	652	1,094	469
Non-cash stock consideration, acquisition	12,971
Loss on fixed asset disposal		7	8	15
Amortization of discount on investments, net	33
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,599)	223	234	(297)
Accounts payable and accrued other liabilities	2,271	504	986	(410)
Net cash used in operating activities	(27,443)	(16,385)	(23,533)	(20,683)
Cash flows from investing activities:
Acquisitions of property and equipment	(256)	(712)	(768)	(525)
Purchases of marketable securities	(124,640)
Proceeds from notes receivable	193			17
Net cash used in investing activities	(124,703)	(712)	(768)	(508)
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to initial public offering, gross	138,000
Issuance costs associated with initial public offering	(12,692)
Payment of deferred financing costs	(394)		(99)
Proceeds from issuance of preferred stock		70,927	70,792	37,929
Issuance costs associated with preferred stock		(136)
Proceeds from stock option exercises	104	94	131	79
Net cash provided by financing activities	125,018	70,885	70,824	38,008
Net (decrease) increase in cash and cash equivalents	(27,128)	53,788	46,523	16,817
Cash and cash equivalents, beginning of period	89,159	42,636	42,636	25,819
Cash and cash equivalents, end of period	62,031	96,424	89,159	$ 42,636
Supplemental disclosure of non-cash investing and financing activities:
Conversion of preferred stock to common stock	178,058
Amounts accrued for purchase of property and equipment	$ 132	11
Unpaid deferred financing costs		$ 240	$ 1,244

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Description of the Business ORIC Pharmaceuticals, Inc. (ORIC or the Company) is a clinical-stage biopharmaceutical company dedicated to improving patients’ lives by O vercoming R esistance I n C ancer Since inception, the Company has devoted its primary efforts to raising capital, internal research and development activities and business development efforts and has incurred significant operating losses and negative cash flows from operations. In August 2020, the Company licensed from Mirati Therapeutics, Inc. development and commercialization rights to an allosteric inhibitor program directed towards the polycomb repressive complex 2 (PRC2) and in October 2020, the Company licensed from Voronoi, Inc. development and commercialization rights to a brain penetrant, orally bioavailable, irreversible inhibitor designed to selectively target epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) with high potency against exon 20 insertion mutations. As of September 30, 2020, the Company had an accumulated deficit of $138.1 million. Through September 30, 2020, all of the Company’s financial support has been provided primarily from the sale of convertible preferred stock and proceeds from the issuance of common stock. As the Company continues its expansion, it may seek additional financing and/or strategic investments, however, there can be no assurance that any additional financing or strategic investments will be available to the Company on acceptable terms, if at all. If events or circumstances occur such that the Company does not obtain additional funding, it will most likely be required to reduce its plans and/or certain discretionary spending, which could have a material adverse effect on the Company’s ability to achieve its intended business objectives. The accompanying financial statements do not include any adjustments that might be necessary if it were unable to continue as a going concern. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date of the issuance of these unaudited interim financial statements. Initial Public Offering and Related Transaction On April 28, 2020, the Company completed an initial public offering (IPO) selling 8,625,000 shares of common stock, which includes the full exercise by the underwriters of their option to purchase up to 1,125,000 additional shares, at a price of $16.00 per share resulting in gross proceeds of $138.0 million. After deducting underwriting discounts and commissions and other offering expenses related to the IPO of $12.8 million, the net proceeds to the Company from the transaction were $125.2 million. In connection with the IPO, all shares of convertible preferred stock outstanding at the time of the IPO converted into 19,278,606 shares of common stock. On April 21, 2020, the Company amended its certificate of incorporation to effect a one-for-four	(1) Organization and basis of presentation (a) Organization and nature of operations ORIC Pharmaceuticals, Inc. (“ORIC” or the “Company”) was incorporated Delaware in August 2014 and is headquartered in South San Francisco, California. The Company is a clinical-stage biopharmaceutical company dedicated to improving patients’ lives by Overcoming Resistance In Cancer Since inception, the Company has devoted its primary effort to raising capital and research and development activities and has incurred losses and negative cash flows from operations. The Company had an accumulated deficit of $92.7 million and cash and cash equivalents of $89.2 million at December 31, 2019. From its inception through December 31, 2019, all of the Company’s financial support has been provided primarily from the sale of its convertible preferred stock. As the Company continues its expansion, it may seek additional financing and/or strategic investments, however, there can be no assurance that any additional financing or strategic investments will be available to the Company on acceptable terms, if at all. If events or circumstances occur such that the Company does not obtain additional funding, it will most likely be required to reduce its plans and/or certain discretionary spending, which could have a material adverse effect on the Company’s ability to achieve its intended business objectives. The accompanying financial statements do not include any adjustments that might be necessary if it were unable to continue as a going concern. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date these financial statements were available to be issued. (b) Basis of presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP).

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	2. Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC) on Form 10-Q Rule 10-01 S-X. COVID-19, of COVID-19, stay-at-home COVID-19 stay-at-home work-from-home from COVID-19 The accompanying unaudited financial statements should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2019, which are included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b)(4) on April 24, 2020 under the Securities Act of 1933, as amended (the Securities Act). In the third quarter of 2020, the Company began reporting deferred offering costs within its other assets on its balance sheets. To conform to current presentation, the Company included $1.3 million of deferred financing costs at December 31, 2019 in other assets. This reclassification had no effect on the Company’s total assets, net loss or stockholders’ equity (deficit) as previously reported. Use of Estimates The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially from these estimates. Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash and cash equivalents and marketable securities that are recorded on its balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits its exposure. The Company has not experienced any losses since inception. The carrying amounts of cash and cash equivalents and marketable securities, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of 90 days or less at the time of purchase that are readily convertible into cash as cash equivalents. These investments may include money market funds, securities issued by U.S. Government agencies, corporate debt securities and commercial paper. Marketable Securities Investments with maturities at the date of acquisition of more than 90 days are considered marketable securities. The Company has classified its investment holdings as available-for-sale, available-for-sale held-to-maturity Available-for-sale Research and Development Expenses and Accrued Research and Development Expenses The Company is required to estimate its expenses resulting from its obligations under contracts with vendors, consultants, contract research organizations (CRO), and contract manufacturing organizations (CMO) in connection with conducting research and development activities. The financial terms of these contracts vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. Research and development costs are expensed in the period in which they are incurred. External costs consist primarily of payments to outside CROs, CMOs, clinical trial sites and central laboratories in connection with the Company’s discovery and preclinical activities, process development, clinical manufacturing and clinical development activities. External expenses are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers or its estimate of the level of service that has been performed at each reporting date. The Company allocates external costs by program, clinical or preclinical. Internal costs consist primary of employee-related costs, laboratory supplies, facilities, depreciation and costs related to compliance with regulatory requirements. The Company does not allocate internal costs by program because these costs are deployed across multiple programs and, as such, are not separately classified. License Fees Acquisitions of technology licenses are charged to acquired in-process Deferred Offering Costs The Company capitalizes costs that are directly associated with equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the offering. Should an in-process Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts). Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator Net loss $ (25,548 ) $ (6,549 ) $ (45,444 ) $ (18,529 ) Denominator Weighted average shares outstanding used in computing net loss per share, basic and diluted 30,314,904 1,946,439 18,022,068 1,876,687 Net loss per share, basic and diluted $ (0.84 ) $ (3.36 ) $ (2.52 ) $ (9.87 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: As of September 30, 2020 2019 Options to purchase common stock 3,959,693 2,251,594 Convertible preferred stock — 19,278,606 Total 3,959,693 21,530,200 Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) under its accounting standard codifications (ASC) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below. In December 2019, the FASB issued ASU No 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 2019-12 2019-12 New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) right-of-use No. 2020-05, No. 2016-02 No. 2018-10, Codification Improvements to Topic 842, Leases No. 2018-11, Leases (Topic 842): Targeted Improvements No. 2018-11 right-of-use In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses Topic 326 Measurement of Credit Losses on Financial Instruments 2016-13 2016-13 available-for-sale 326-30, Losses—Available-for-Sale	(2) Summary of significant accounting policies (a) Use of estimates The preparation of the Company’s financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. Accounting estimates and management judgments reflected in the financial statements include: normal recurring accruals; valuation of deferred tax assets, including valuation allowances; fair value of common stock and preferred stock; stock-based compensation; and useful lives of long-lived assets. 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. (b) Concentration of credit risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash deposits. 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. The Company has not experienced any losses on deposits since inception. (c) Fair value of financial instruments 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. The carrying amounts of cash, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items. (d) Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents primarily represent funds invested in readily available checking and money market accounts. As of December 31, 2018 and 2019, the Company had cash balances deposited at major financial institutions. (e) Prepaid expenses Any expenses paid prior to the related services rendered are recorded as prepaid expenses. Such prepaid expenses are reconciled and expensed in the period the expense is incurred. If the expense is for a service covering multiple periods, it is expensed from the date the services begin and over the period of the service rendered (or contract service period if services rendered dates are not defined). Prepaid expenses include subscriptions, licenses, research and development contracts and insurance. (f) Property and equipment Property and equipment, which consist of lab equipment, leasehold improvements, computer hardware and software, and furniture and fixtures which are stated at historical cost. Depreciation is recognized on a straight-line basis over the estimated useful lives of the related assets, which are generally three to seven years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimate useful life of the asset. The Company recorded $0.9 million and $1.0 million of depreciation expense for each of the years ended December 31, 2018 and 2019, respectively. (g) Impairment of property and equipment The Company accounts for the impairment of long-lived assets by reviewing these assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If circumstances require a long-lived asset or asset group to be tested for possible impairment, the Company first compares undiscounted cash flows expected to be generated by that asset or asset group to its carrying value. If the carrying value of the long-lived asset or asset group is not recoverable on an undiscounted-cash-flow basis, an impairment is recognized to the extent that the carrying value exceeds its fair value. The Company did not recognize impairment losses for the years ended December 31, 2018 and 2019. (h) Deferred rent Deferred rent consists of the difference between cash payments and the recognition of rent expense on a straight-line basis for the office facilities over the terms of the leases. The Company’s leased office facilities provide for fixed increases in minimum annual rent payments. The total amount of rent payments due over the lease term are being charged to rent expense ratably over the life of the leases. (i) Accrued research and development expenses The Company is required to estimate its expenses resulting from its obligations under contracts with vendors, consultants and contract research organizations, in connection with conducting research and development activities. The financial terms of these contracts vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. The Company reflects research and development expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of the preclinical study or clinical trial as measured by the timing of various aspects of the study or related activities. The Company determines accrual estimates through review of the underlying contracts along with discussions with research and other key personnel as to the progress of studies or trials, or other services being conducted. During the course of a study or trial, the Company adjusts its rate of expense recognition if actual results differ from its estimates. (j) Research and development expenses Research and development costs are expensed in the periods in which they are incurred. External costs consist primarily payments to outside consultants, CROs, CMOs, clinical trial sites and central laboratories in connection with the Company’s discovery and preclinical activities, process development, manufacturing and clinical development activities. External expenses are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers or our estimate of the level of service that has been performed at each reporting date. The Company allocates external costs by the stage of program, clinical or preclinical. Internal costs consist primary of employee-related costs, laboratory supplies, facilities, depreciation and costs related to compliance with regulatory requirements. The Company does not allocate internal costs by stage of program because these costs are deployed across multiple programs and, as such, are not separately classified. Research and development expenses amounted to $19.0 million and $22.8 million during the years ended December 31, 2018 and 2019, respectively. (k) Commitments and contingencies The Company recognizes a liability with regard to loss contingencies when it believes it is probable a liability has occurred, and the amount can be reasonably estimated. If some amount within a range of loss appears at the time to be a better estimate than any other amount within the range, the Company accrues that amount. When no amount within the range is a better estimate than any other amount the Company accrues the minimum amount in the range. The Company has not recorded any such liabilities as of December 31, 2018 and 2019. (l) Income taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning As of December 31, 2018 and 2019, the Company maintained valuation allowances against its deferred tax assets as the Company concluded it had not met the “more likely than not” to be realized threshold. Changes in the valuation allowance when they are recognized in the provision for income taxes would result in a change in the estimated annual effective tax rate. (m) Stock-based compensation Stock-based compensation expense represents the cost of the grant date fair value of employee, officer, director and non-employee The fair value of stock options is estimated using a Black-Scholes Merton valuation model on the date of grant. This method requires certain assumptions be used as inputs, such as the fair value of the underlying common stock, a risk-free interest rate, expected volatility of the Company’s common stock, expected term of the option before exercise and expected dividend yield. Options granted have a maximum contractual term of ten years. The risk-free interest rates used are based on the U.S. Treasury yield in effect at the time of grant for zero-coupon (n) Common stock valuation Due to the absence of an active market for the Company’s common stock, the Company utilized methodologies, approaches and assumptions consistent with the American Institute of Certified Public Accountants Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation (o) Deferred offering costs The Company capitalizes costs that are directly associated with in-process in-process (p) Comprehensive loss Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner (q) Net loss per share and unaudited pro forma net loss per share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, the convertible preferred stock and common stock options are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts). Year ended December 31, 2018 2019 Numerator Net loss attributable to common stockholders $ (21,363 ) $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,734,115 1,899,348 Net loss per share, basic and diluted $ (12.32 ) $ (14.15 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: Year ended December 31, 2018 2019 Options to purchase common stock 1,854,886 2,683,441 Convertible preferred stock 13,789,770 19,278,606 Total 15,644,656 21,962,047 Unaudited pro forma net loss per share Unaudited pro forma basic and diluted net loss per share is calculated to give effect to the one-for-one as-converted The following table sets forth the computation of the basic and diluted unaudited pro forma net loss per share (in thousands, except share and per share amounts): Year ended December 31, 2019 Numerator Net loss $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,899,348 Adjust: Assumed weighted-average effect of conversion of convertible preferred stock 17,241,861 Weighted-average shares outstanding used in computing pro forma net loss per share, basic and diluted 19,141,209 Pro forma net loss per share, basic and diluted $ (1.40 ) Unaudited Pro Forma Stockholders’ Equity The unaudited pro forma stockholders’ equity as of December 31, 2019 gives effect to the automatic conversion of all outstanding shares of the Company’s convertible preferred stock into an aggregate of 19,278,606 shares of common stock which will occur immediately prior to the completion of this offering, resulting in an aggregate of 21,262,828 outstanding shares of the Company’s common stock (which excludes 29,579 shares issued upon the early exercise of certain options, which are subject to a right of repurchase by the Company). (r) Recently issued accounting standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-employee No. 2018-07 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02), (Topic 840) right-of-use 2016-02 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates 2019-10”), one-year 2016-02 right-of-use

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	4. Property and Equipment, net Property and equipment, net consisted of the following (in thousands): September 30, 2020 December 31, 2019 Lab equipment $ 4,088 $ 3,748 Leasehold improvements 1,710 1,710 Computer hardware and software 206 158 Furniture and fixtures 140 140 Total property and equipment, gross 6,144 5,756 Less accumulated depreciation (4,251 ) (3,515 ) Total property and equipment, net $ 1,893 $ 2,241	(3) Property and equipment, net Property and equipment, net consisted of the following (in thousands): December 31, 2018 2019 Lab equipment $ 3,166 $ 3,748 Leasehold improvements 1,710 1,710 Computer hardware and software 144 158 Furniture and fixtures 72 140 Total property and equipment, gross 5,092 5,756 Less accumulated depreciation (2,578 ) (3,515 ) Total property and equipment, net $ 2,514 $ 2,241

Accrued Liabilities

Accrued Liabilities	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Accrued Liabilities	5. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued compensation $ 2,229 $ 1,883 Accrued clinical development costs 1,391 484 Accrued professional fees 657 338 Deferred rent—short-term 535 495 Accrued manufacturing costs 278 479 Other accruals 240 279 Accrued deferred financing costs — 1,244 Total accrued liabilities $ 5,330 $ 5,202	(4) Accrued other liabilities Accrued other liabilities consisted of the following (in thousands): December 31, 2018 2019 Accrued compensation $ 917 $ 1,883 Accrued deferred financing costs — 1,244 Deferred rent—short term 438 495 Accrued clinical development costs 149 484 Accrued manufacturing costs 173 479 Accrued professional fees 105 175 Accrued legal fees 16 163 Share purchase liabilities 115 39 Other accruals 238 240 Total accrued other liabilities $ 2,150 $ 5,202

Fair Value Measurements

Fair Value Measurements	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements 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: Observable inputs such as quoted prices in active markets; Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s interest receivable, included in prepaid expenses and other current assets, accounts payable and accrued liabilities are generally considered to be representative of their fair value because of the short term nature of these instruments. The Company’s investments, which may include money market funds and available-for-sale Following are the major categories of assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurement at End of Period Using: Fair Value Quoted Market (Level 1) Significant (Level 2) Significant (Level 3) Total At September 30, 2020 Money market funds(1) $ 62,031 $ 62,031 $ — $ — $ 62,031 U.S. treasury securities 124,579 124,579 — — 124,579 Total $ 186,610 $ 186,610 $ — $ — 186,610 At December 31, 2019 Money market funds(1) $ 88,159 $ 88,159 $ — $ — $ 88,159 (1) Included in cash and cash equivalents in accompanying balance sheets. No transfers between levels occurred during either of the reporting periods presented.	(5) Fair Value Measurements 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: Observable inputs such as quoted prices in active markets; Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. At December 31, 2018 and 2019, the carrying amounts of the Company’s financial instruments, which include cash, accounts payable and accrued expenses, approximate fair value because of their short maturities. Included in cash and cash equivalents at December 31, 2018 and 2019 are money market funds with a carrying value and fair value of $42.6 million and $88.1 million, respectively, based upon a Level 1 fair value assessment. As of December 31, 2018 and 2019, the Company did not hold any Level 2 or Level 3 financial assets.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	(6) Stockholders’ equity Under its Amended and Restated Articles of Incorporation dated June 3, 2019, the Company had a total of 47,098,788 shares of capital stock authorized for issuance, consisting of 26,750,000 shares of common stock, par value of $0.0001 per share, and 20,348,788 shares of convertible preferred stock, par value of $0.0001 per share. Shares of authorized convertible preferred stock are designated as 3,862,500 shares of Series A convertible preferred stock, 6,750,000 shares of Series B convertible preferred stock, 4,448,788 shares of Series C convertible preferred stock and 5,287,500 shares of Series D convertible preferred stock. (a) Series A convertible preferred stock In 2014 and 2015, the Company issued 3,862,500 shares of Series A convertible preferred stock in a private offering in exchange for net proceeds of $15.4 million. The purchase price for the Series A convertible preferred stock was $4.00 per share. (b) Series B convertible preferred stock In 2015 and 2016, the Company issued 6,749,999 shares of Series B convertible preferred stock in a private offering in exchange for net proceeds of $53.9 million. The purchase price for the Series B convertible preferred stock was $8.00 per share. (c) Series C convertible preferred stock In 2018 and 2019, the Company issued 4,448,780 shares of Series C convertible preferred stock in a private offering in exchange for net proceeds of $53.2 million. The purchase price for the Series C convertible preferred stock was $12.00 per share. (d) Series D convertible preferred stock In 2019, the Company issued 4,217,327 shares of Series D convertible preferred stock in a private offering for net proceeds of $55.5 million. The purchase price for the Series D convertible stock was $13.20 per share. (e) Common stock As of December 31, 2018 and 2019, of the authorized 20,250,000 and 26,750,000 shares of common stock, 1,802,134 and 1,984,222 shares were issued and outstanding, respectively. The fair value of the Company’s common stock was $1.60 and $9.16 as of December 31, 2018, and 2019, respectively, and was determined in part on third-party valuations. The voting, dividend, and liquidation rights of the holders of the common stock are subject to, and qualified by, the rights, powers, and preferences of the holders of the convertible preferred stock. The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders. Common stock reserved for future issuance consisted of the following: Year ended December 31, 2018 2019 Convertible preferred stock 13,789,770 19,278,606 Common stock options granted and outstanding 1,854,886 2,683,441 Common stock reserved for future option grants 271,490 203,696 Total common stock reserved for future issuance 15,916,146 22,165,743 The Series A, Series B, Series C and Series D convertible preferred stock has been classified as temporary equity in the accompanying balance sheets given that a majority of the Company’s Board of Directors seats are held by convertible preferred stock holders and could cause certain events to occur that are outside of the Company’s control whereby the Company could be obligated to redeem the convertible preferred stock. The Company has not adjusted the carrying values of the convertible preferred stock to the respective liquidation preferences of such shares as the instruments are currently not redeemable and the Company believes it is not probable that the instruments will become redeemable at this point in time. Adjustments to increase the carrying values to the respective liquidation preferences will be made if and when it becomes probable that an event would occur obligating the Company to pay such amounts. The Company’s convertible preferred stock has the following characteristics: (1) Dividends Holders of the Series A, Series B, Series C and Series D convertible preferred stock, in preference to any distributions to the holders of common stock, shall be entitled to receive dividends at an annual rate of $0.32 per share for the Series A convertible preferred stock holders, $0.64 per share for the Series B convertible preferred stock holders, $0.96 per share for the Series C convertible preferred stock and $1.056 per share for the Series D convertible preferred stock holders. Such dividends shall be payable only when and if declared by the Company’s Board of Directors and shall not be cumulative. No such dividends have been declared or paid through December 31, 2019. (2) Liquidation The holders of the Series A, Series B, Series C and Series D convertible preferred stock are entitled to receive liquidation preferences at the Series A, Series B, Series C and Series D original issue prices of $4.00, $8.00, $12.00, and $13.20, respectively, plus all accrued and declared but unpaid dividends. Liquidation payments to the holders of the Series A, Series B, Series C and Series D convertible preferred stock have priority and are made in preference to any payments to the holders of common stock. After full payment of the liquidation preference to the holders of the Series A, Series B, Series C and Series D convertible preferred stock, the remaining assets, if any, will be distributed ratably to the holders of the common stock. (3) Conversion rights The shares of Series A, Series B, Series C and Series D convertible preferred stock are convertible into an equal number of shares of common stock, at the option of the holder, subject to certain anti-dilution adjustments. The conversion rate for the convertible preferred stock is determined by dividing the original issue price, as adjusted for stock splits, by the conversion price. The conversion price is initially the original issue prices, but is subject to adjustment for dividends, stock splits, and other distributions. The conversion rate at December 31, 2019 for the Series A, Series B, Series C and Series D convertible preferred stock is 1:1. Each share of Series A, Series B, Series C and Series D convertible preferred stock are automatically converted into common stock at the then effective conversion rate (a) at any time upon the affirmative election of the holders of at least a majority of the outstanding shares of the Series A, Series B, Series C and Series D convertible preferred stock or (b) immediately upon the closing of a firmly underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, as amended, covering the offer and sale of common stock for the account of the Company in which (i) the public offering price represents a pre-money (4) Redemption rights The holders of Series A, Series B, Series C and Series D convertible preferred stock do not have any redemption rights. (5) Voting The holder of each share of Series A, Series B, Series C and Series D convertible preferred stock are entitled to one vote for each share of common stock into which it would convert and to vote as one class with the common stockholders on all matters.

Equity Incentive Plans and Stoc

Equity Incentive Plans and Stock-Based Compensation	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans and Stock-Based Compensation	9. Equity Incentive Plans and Stock-Based Compensation Equity Incentive Plans In February 2020, the Company’s Board of Directors adopted, and its stockholders approved, the 2020 Equity Incentive Plan (the 2020 Plan), which became effective in April 2020 in connection with the Company’s IPO. Upon adoption of the 2020 Plan, the Company restricted the grant of future equity awards under its 2014 Equity Incentive Plan, as amended and restated (the 2014 Plan). The 2020 Plan provides for the grants of stock options and other equity-based awards to employees, non-employee Stock options granted under the 2020 Plan and the 2014 Plan become exercisable at various dates as determined by the Company’s Board of Directors or its authorized committee and will expire no more than ten years from their date of grant. Stock options generally vest over a four-year term. The exercise price of each option is determined by the Company’s Board of Directors, although generally options have an exercise price equal to the fair market value of the Company’s stock on the date of the option grant. In the case of incentive stock options, the exercise price shall not be less than 100% of the fair market value of the Company’s common stock at the time the option is granted. For holders of more than 10% of the Company’s total combined voting power of all classes of stock, incentive stock options may not be granted at less than 110% of the fair market value of the Company’s common stock at the date of grant and for a term not to exceed five years. As of September 30, 2020, there were 1,514,840 shares available for future issuance under the 2020 Plan. As of December 31, 2019, there were 203,696 shares available for future issuance under the 2014 Plan. The following table summarizes the option activity for the nine months ended September 30, 2020: Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 2,683,441 $ 3.75 Granted 1,449,509 16.90 Exercised (69,102 ) 1.62 Forfeited and cancelled (104,155 ) 7.39 Outstanding at September 30, 2020 3,959,693 $ 8.52 8.7 $ 65,531 Exercisable at September 30, 2020 1,060,901 $ 2.60 8.0 $ 23,797 Certain stock options granted under the Company’s 2014 Plan provided option holders the ability to early exercise their stock options prior to vesting. The shares of common stock granted from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees paid-in Employee Stock Purchase Plan In February 2020, the Company’s Board of Directors adopted, and its stockholders approved, the 2020 Employee Stock Purchase Plan (ESPP). The ESPP became effective in connection with the Company’s IPO however no offering period or purchase period under the ESPP will begin unless and until otherwise determined by the Company’s Board of Directors. A total of 290,000 shares of common stock were reserved for future issuance under the ESPP. Further, the number of shares of common stock available for issuance under the ESPP will automatically increase on the first day of each fiscal year following the fiscal year in which the first offering period under the ESPP commences in an amount equal to the lessor of (1) 500,000 shares, (2) 1% of the outstanding shares of the Company’s common stock on the last day of the immediately preceding fiscal year, or (3) such other amount as determined by the Company’s Board of Directors. As of September 30, 2020, no shares had been issued pursuant to the ESPP and there were no active offering periods or purchase periods. Stock-Based Compensation Expense Stock options are valued using the Black-Scholes Merton option pricing model on the date of grant. This option pricing model involves a number of estimates, including the expected lives of the stock options, the Company’s anticipated stock volatility and interest rates. Stock-based compensation expense is recognized using the ratable straight-line method over the vesting period. Forfeitures are recognized as they occur. The Company determines the assumptions used in the option pricing model in the following manner: • Expected term. • Expected volatility • Risk-free interest rate. • Expected dividend yield. Prior to the Company’s IPO, the fair value of the Company’s common stock underlying the stock options was determined by the Board of Directors with assistance from management and, in part, on input from an independent third-party valuation firm. The Board of Directors determined the fair value of common stock by considering a number of objective and subjective factors, including valuations of comparable companies, sales of convertible preferred stock, operating and financial performance, the lack of liquidity of the Company’s common stock and the general and industry-specific economic outlook. Subsequent to the Company’s IPO, the fair value of the Company’s common stock is determined based on its closing market price. The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes Merton option pricing model with the following weighted-average assumptions. Nine Months Ended September 30, 2020 2019 Stock price $ 16.00 - $35.92 $ 1.60 - $6.44 Risk-free interest rate 3.17% - 4.45% 1.39% - 2.58% Expected volatility 88.01% - 95.11% 100.52% - 104.15% Expected term (in years) 5.50 - 6.08 6.08 Expected dividend yield 0% 0% The Company recognized stock-based compensation expense of $1.7 million and $0.3 million for the three months ended September 30, 2020 and 2019, respectively, and $3.6 million and $0.7 million for the nine months ended September 30, 2020 and 2019, respectively. No stock-based compensation expense has been recognized as of September 30, 2020, pursuant to the Company’s ESPP. The total unrecognized compensation expense related to outstanding unvested stock-based awards as of September 30, 2020 and 2019 was $20.4 million and $5.5 million, respectively, which is expected to be recognized over a weighted-average remaining service period of 2.91 years for 2020 and 3.16 years for 2019. The table below summarizes the total stock-based compensation expense included in the Company’s statements of operations for stock options for the periods presented (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Research and development $ 592 $ 116 $ 1,406 $ 233 General and administrative 1,089 155 2,183 419 Total stock-based compensation expense $ 1,681 $ 271 $ 3,589 $ 652	(7) Stock-based compensation In October 2014, the Company approved the 2014 Equity Incentive Plan (the “2014 Plan”). The 2014 Plan provides for the issuance of 4,008,850 shares of common stock to officers, directors, employees, non-employee non-statutory The options that are granted from the 2014 Plan are exercisable at various dates as determined upon grant and will expire no more than ten years from their date of grant, or in the case of certain non-statutory The following table summarizes the option activity: Options Weighted- Weighted- Aggregate Outstanding at January 1, 2019 1,854,886 $ 1.48 9.2 Granted 1,169,000 6.56 9.7 Exercised (182,105 ) 0.72 5.3 Cancelled (158,340 ) 1.76 8.0 Outstanding at December 31, 2019 2,683,441 $ 3.75 9.0 $ 14,591 Exercisable at December 31, 2019 825,671 $ 1.96 8.5 $ 5,948 All exercisable options are vested and all outstanding options are vested or expected to vest. The aggregate intrinsic value of stock options exercisable during the year December 31, 2019 was $5.9 million. Certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees paid-in The fair value of stock options was estimated using the Black-Scholes Merton option pricing model with the following assumptions: Year ended December 31, 2018 2019 Stock price $ 1.60 $ 1.60 – $9.16 Risk-free interest rate 2.7% – 3.0% 1.4% – 2.6% Expected volatility 93% – 98% 77% – 104% Expected term (in years) 6.01 – 6.1 6.1 Expected dividend yield 0% 0% The Company recognized stock-based compensation expense of $0.5 million and $1.1 million for the years ended December 31, 2018 and 2019, respectively. The total unrecognized compensation expense related to outstanding unvested stock-based awards as of December 31, 2018 and 2019 was $2.3 million and $6.9 million, respectively, which is expected to be recognized over a weighted-average remaining service period of 3.4 years for both years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	(8) Income taxes Significant components of the Company’s provision for income taxes and income taxes computed using the U.S. federal statutory corporate tax rate were as follows (in thousands): Year ended December 31, 2018 2019 Statutory rate $ (4,487 ) $ (5,647 ) State tax (1,465 ) (2,351 ) Other permanent items (15 ) 17 Research and development credit (663 ) (692 ) Change in valuation allowance 6,536 8,673 Impact of Tax Cuts and Jobs Act — — Stock-based compensation 94 — Provisions for income taxes $ — $ — Significant components of the Company’s deferred taxes were as follows (in thousands): December 31, 2018 2019 Deferred tax assets: Net operating loss carryforward $ 17,353 $ 24,380 Research and development credits 2,147 3,319 Deferred rent 491 353 Accruals and other 255 771 Gross deferred tax assets 20,246 28,823 Less valuation allowance (19,910 ) (28,583 ) Total deferred tax assets 336 240 Deferred tax liabilities: Fixed assets (336 ) (240 ) Net deferred tax assets $ — $ — A valuation allowance of $28.6 million at December 31, 2019 has been recognized to offset the net deferred tax assets as realization of such assets is uncertain. The valuation allowance increased by $8.7 million during the year ended December 31, 2019. As of December 31, 2019, the Company had available net operating loss (NOL) carryforwards of $86.6 million. Of the $86.6 million of NOL carryforwards, $41.5 million begin to expire in 2034 and $45.1 million do not expire. The Company also has available California NOL carryforwards of approximately $88.6 million as of December 31, 2019, which begin to expire in 2034. Pursuant to Sections 382 and 383 of the Internal Revenue Code (“IRC”), annual use of the Company’s NOL and credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. Since the Company’s formation, the Company has raised capital through the issuance of capital stock, which on its own or combined with the purchasing stockholders’ subsequent disposition of those shares, may have resulted in such an ownership change, or could result in an ownership change in the future. Upon the occurrence of an ownership change under Section 382 as outlined above, utilization of the Company’s NOL and research and development credit carryforwards are subject to an annual limitation, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax-exempt The Company recognizes liabilities for uncertain tax positions based in a two-step The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands): December 31, 2018 2019 Beginning balance $ 347 $ 557 Increases (decreases) related to prior year tax positions — — Increases related to current year tax positions 210 226 Ending balance $ 557 $ 783 As of December 31, 2019, the Company had gross unrecognized tax benefits of $0.8 million, none of which would affect the effective tax rate if recognized. The Company does not anticipate any significant changes in its unrecognized tax benefits over the next 12 months. The Company’s policy is to recognize the interest expense and/or penalties related to income tax matters as a component of income tax expense. The Company had no accrual for interest or penalties on its balance sheets at December 31, 2019 and has not recognized interest and/or penalties in its statement of operations for the year ended December 31, 2019. The Company is subject to taxation in the United States and California. The Company is not currently under examination by any taxing authorities. Due to the carryover of tax attributes, the statute of limitations is currently open for tax years since inception.

Commitments and contingencies

Commitments and contingencies	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Operating Leases Rent expense is recorded on a straight-line basis over the term of the respective lease. Total rent expense for the South San Francisco and San Diego locations was $0.3 million and $1.0 million for the three months and nine months ended September 30, 2020 and 2019, respectively. Future minimum lease payments under non-cancelable Operating Leases 2020 remaining three months $ 478 2021 1,871 2022 686 Total minimum lease payments $ 3,035 Litigation From time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no threatened litigation or litigation pending that could have, individually or in the aggregate, a material adverse effect on the Company’s financial position, results of operations or cash flows.	(9) Commitments and contingencies Operating lease The Company leases certain office and lab space in South San Francisco, California under a non-cancelable In March 2019, the Company entered into a lease agreement for office space in San Diego, California under a non-cancelable 13-month Rent expense is recorded on a straight-line basis over the term of the respective lease. Total rent expense for both locations was $1.3 million for both years ended December 31, 2018 and 2019. The future minimum lease payments required under non-cancelable Year ending December 31, 2020 $ 1,892 2021 1,871 2022 686 2023 — 2024 — Total minimum lease payments $ 4,449 Litigation The Company, from time to time, is involved in legal proceedings, regulatory actions, claims and litigation arising in the ordinary course of business. Currently, the Company is not a defendant in any lawsuit.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefit Plan	(10) Employee benefit plan The Company has a defined-contribution 401(k) plan for employees. Employees are eligible to participate in the plan beginning on the first day of the month following date of hire. Under the terms of the plan, employees may make voluntary contributions as a percentage of compensation and the Company has the option to make a discretionary match as determined by the Company’s Board of Directors, within prescribed limits. There were no employer contributions to the plan during the years ended December 31, 2018 or 2019.

Subsequent Events

Subsequent Events	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events On October 19, 2020, the Company entered into the Voronoi License Agreement with Voronoi. The Voronoi License Agreement gives the Company access to Voronoi’s preclinical stage epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) exon 20 insertion mutation program, including a lead product candidate now designated as ORIC-114. know-how, The Company’s financial obligations under the Voronoi License Agreement included an upfront payment comprised of a $5.0 million cash payment and the issuance to Voronoi of 283,259 shares of the Company’s common stock issued pursuant to a stock issuance agreement (Stock Agreement) entered into between the parties on October 19, 2020. The number of shares issued pursuant to the Stock Agreement was based on a price of $28.24 per share, representing a premium of 25% to the 30-day The Company is also obligated to make milestone payments to Voronoi upon the achievement of certain events. Upon the achievement of certain development and regulatory milestones with respect to the first licensed product, the Company is obligated to pay Voronoi up to a maximum of $111.0 million. Upon the achievement of certain commercial milestones with respect to the first licensed product, the Company is obligated to pay Voronoi up to a maximum of $225.0 million. If the Company pursues a second licensed product, the Company would pay Voronoi up to an additional $272.0 million in success-based milestones. In addition, the Company is obligated to pay royalties on net sales of licensed products in the ORIC Territory. Unless earlier terminated, the Voronoi License Agreement will continue in effect until the expiration of all royalty payment obligations. Following the expiration of the Voronoi License Agreement, the Company will retain its licenses under the intellectual property Voronoi licensed to it on a royalty-free basis. The Company and Voronoi may each terminate the Voronoi License Agreement if the other party materially breaches the terms of such agreement, subject to specified notice and cure provisions, or enters into bankruptcy or insolvency proceedings. Voronoi may also terminate the agreement if the Company discontinues development of licensed products for a specified period of time. The Company also has the right to terminate the Voronoi License Agreement without cause by providing prior notice to Voronoi. If Voronoi terminates the Voronoi License Agreement for cause, or if the Company terminates the Voronoi License Agreement without cause, then the Company is obligated to grant a nonexclusive license to Voronoi under certain of the Company’s patents and know-how	(11) Subsequent Events Reverse Stock Split On April 21, 2020, the Company filed an Amended and Restated Certificate of Incorporation effecting a 1-for-4

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2020
Text Block [Abstract]
License Agreements	3. License Agreements On August 3, 2020, the Company entered into a license agreement (Mirati License Agreement) with Mirati Therapeutics, Inc (Mirati). Under the Mirati License Agreement, Mirati granted the Company a worldwide, exclusive, sublicensable, royalty-free license under Mirati’s rights to certain patents and patent applications directed to certain small molecule compounds that bind to and inhibit PRC2 and certain related know-how, Unless earlier terminated, the Mirati License Agreement will continue in effect on a country-by-country product-by-licensed The Company’s financial obligations under the Mirati License Agreement was comprised of an upfront payment of 588,235 shares of ORIC common stock, valued at approximately $13.0 million based upon the closing price of the Company’s common stock on the acquisition date. The number of shares was based on a price of $34.00 per share, representing a premium of 10% to the 60-day volume-weighted The Company recorded the transaction as an asset purchase as management concluded that all of the value received was related to a single identifiable asset. Further, as the asset was in early development at the time the license was acquired, the Company concluded that there was no alternative future use for the asset and recorded a charge at the closing of the transaction for the full $13.0 million value assigned to the shares issued. This non-cash in-process On October 19, 2020, the Company entered into a license agreement with Voronoi, Inc. (Voronoi). See Note 11 for further discussion.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	6. Marketable Securities The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. In accordance with the Company’s investment policy, it has invested funds in marketable securities as of September 30, 2020. The Company had no marketable securities at December 31, 2019. The cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value U.S. treasury securities $ 124,608 $ — $ (29 ) $ 124,579 Total $ 124,608 $ — $ (29 ) $ 124,579 The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. At September 30, 2020, there were 13 securities in unrealized loss positions. These securities have not been in a continuous loss position for more than 12 months. Further, the Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell these investments before recovery of their amortized cost basis which may be at maturity. As such, the Company has classified these losses as temporary in nature. None of the Company’s available-for-sale

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2020
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	8. Convertible Preferred Stock Prior to its conversion to common stock in connection with the Company’s IPO in April 2020, the Company’s convertible preferred stock was classified as temporary equity on the Company’s balance sheets in accordance with authoritative guidance. Convertible preferred stock authorized and issued and its principal terms as of December 31, 2019 consisted of the following (in thousands, except share and per share amounts): As of December 31, 2019 Shares Authorized Shares Issued and Outstanding Issue Issue Price per Share Dividend Annual Rate per Share Aggregate Liquidation Preference Series A 3,862,500 3,862,500 2014 - 2015 $ 4.00 $ 0.32 $ 15,450 Series B 6,750,000 6,749,999 2015 - 2016 $ 8.00 $ 0.64 $ 54,000 Series C 4,448,788 4,448,780 2018 - 2019 $ 12.00 $ 0.96 $ 53,385 Series D 5,287,500 4,217,327 2019 $ 13.20 $ 1.056 $ 55,669 Total 20,348,788 19,278,606 In connection with the Company’s IPO in April 2020, all outstanding shares of the convertible preferred stock converted into 19,278,606 shares of common stock and the related carrying value was reclassified to common stock and additional paid-in

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Common Stock Valuation		(n) Common stock valuation Due to the absence of an active market for the Company’s common stock, the Company utilized methodologies, approaches and assumptions consistent with the American Institute of Certified Public Accountants Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes costs that are directly associated with equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the offering. Should an in-process	(o) Deferred offering costs The Company capitalizes costs that are directly associated with in-process in-process
Comprehensive Loss		(p) Comprehensive loss Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner
Net Loss Per Share	Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts). Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator Net loss $ (25,548 ) $ (6,549 ) $ (45,444 ) $ (18,529 ) Denominator Weighted average shares outstanding used in computing net loss per share, basic and diluted 30,314,904 1,946,439 18,022,068 1,876,687 Net loss per share, basic and diluted $ (0.84 ) $ (3.36 ) $ (2.52 ) $ (9.87 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: As of September 30, 2020 2019 Options to purchase common stock 3,959,693 2,251,594 Convertible preferred stock — 19,278,606 Total 3,959,693 21,530,200	(q) Net loss per share and unaudited pro forma net loss per share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, the convertible preferred stock and common stock options are considered to be potentially dilutive securities. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts). Year ended December 31, 2018 2019 Numerator Net loss attributable to common stockholders $ (21,363 ) $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,734,115 1,899,348 Net loss per share, basic and diluted $ (12.32 ) $ (14.15 ) The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: Year ended December 31, 2018 2019 Options to purchase common stock 1,854,886 2,683,441 Convertible preferred stock 13,789,770 19,278,606 Total 15,644,656 21,962,047 Unaudited pro forma net loss per share Unaudited pro forma basic and diluted net loss per share is calculated to give effect to the one-for-one as-converted The following table sets forth the computation of the basic and diluted unaudited pro forma net loss per share (in thousands, except share and per share amounts): Year ended December 31, 2019 Numerator Net loss $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,899,348 Adjust: Assumed weighted-average effect of conversion of convertible preferred stock 17,241,861 Weighted-average shares outstanding used in computing pro forma net loss per share, basic and diluted 19,141,209 Pro forma net loss per share, basic and diluted $ (1.40 ) Unaudited Pro Forma Stockholders’ Equity The unaudited pro forma stockholders’ equity as of December 31, 2019 gives effect to the automatic conversion of all outstanding shares of the Company’s convertible preferred stock into an aggregate of 19,278,606 shares of common stock which will occur immediately prior to the completion of this offering, resulting in an aggregate of 21,262,828 outstanding shares of the Company’s common stock (which excludes 29,579 shares issued upon the early exercise of certain options, which are subject to a right of repurchase by the Company).
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) under its accounting standard codifications (ASC) or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below. In December 2019, the FASB issued ASU No 2019-12 , Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 2019-12 2019-12	(r) Recently issued accounting standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-employee No. 2018-07 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) 2016-02), (Topic 840) right-of-use 2016-02 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates 2019-10”), one-year 2016-02 right-of-use
Basis of Presentation	Basis of Presentation The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States (GAAP) for interim financial information and with the instructions of the Securities and Exchange Commission (SEC) on Form 10-Q Rule 10-01 S-X. COVID-19, of COVID-19, stay-at-home COVID-19 stay-at-home work-from-home from COVID-19 The accompanying unaudited financial statements should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2019, which are included in the Company’s final prospectus filed with the SEC pursuant to Rule 424(b)(4) on April 24, 2020 under the Securities Act of 1933, as amended (the Securities Act). In the third quarter of 2020, the Company began reporting deferred offering costs within its other assets on its balance sheets. To conform to current presentation, the Company included $1.3 million of deferred financing costs at December 31, 2019 in other assets. This reclassification had no effect on the Company’s total assets, net loss or stockholders’ equity (deficit) as previously reported.
Use of Estimates	Use of Estimates The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying notes. These estimates and assumptions are based on current facts, historical experience and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results may differ materially from these estimates.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentration of credit risk, consist primarily of cash and cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash and cash equivalents and marketable securities that are recorded on its balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits its exposure. The Company has not experienced any losses since inception. The carrying amounts of cash and cash equivalents and marketable securities, prepaid expenses, accounts payable and accrued other liabilities are reasonable estimates of their fair value because of the short maturity of these items.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of 90 days or less at the time of purchase that are readily convertible into cash as cash equivalents. These investments may include money market funds, securities issued by U.S. Government agencies, corporate debt securities and commercial paper.
Marketable Securities	Marketable Securities Investments with maturities at the date of acquisition of more than 90 days are considered marketable securities. The Company has classified its investment holdings as available-for-sale, available-for-sale held-to-maturity Available-for-sale
Research and Development Expenses and Accrued Research and Development Expenses	Research and Development Expenses and Accrued Research and Development Expenses The Company is required to estimate its expenses resulting from its obligations under contracts with vendors, consultants, contract research organizations (CRO), and contract manufacturing organizations (CMO) in connection with conducting research and development activities. The financial terms of these contracts vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts. Research and development costs are expensed in the period in which they are incurred. External costs consist primarily of payments to outside CROs, CMOs, clinical trial sites and central laboratories in connection with the Company’s discovery and preclinical activities, process development, clinical manufacturing and clinical development activities. External expenses are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers or its estimate of the level of service that has been performed at each reporting date. The Company allocates external costs by program, clinical or preclinical. Internal costs consist primary of employee-related costs, laboratory supplies, facilities, depreciation and costs related to compliance with regulatory requirements. The Company does not allocate internal costs by program because these costs are deployed across multiple programs and, as such, are not separately classified.
License Fees	License Fees Acquisitions of technology licenses are charged to acquired in-process
New Accounting Pronouncements Not Yet Adopted	New Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) right-of-use No. 2020-05, No. 2016-02 No. 2018-10, Codification Improvements to Topic 842, Leases No. 2018-11, Leases (Topic 842): Targeted Improvements No. 2018-11 right-of-use In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses Topic 326 Measurement of Credit Losses on Financial Instruments 2016-13 2016-13 available-for-sale 326-30, Losses—Available-for-Sale

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share amounts). Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator Net loss $ (25,548 ) $ (6,549 ) $ (45,444 ) $ (18,529 ) Denominator Weighted average shares outstanding used in computing net loss per share, basic and diluted 30,314,904 1,946,439 18,022,068 1,876,687 Net loss per share, basic and diluted $ (0.84 ) $ (3.36 ) $ (2.52 ) $ (9.87 )	The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts). Year ended December 31, 2018 2019 Numerator Net loss attributable to common stockholders $ (21,363 ) $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,734,115 1,899,348 Net loss per share, basic and diluted $ (12.32 ) $ (14.15 )
Summary of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: As of September 30, 2020 2019 Options to purchase common stock 3,959,693 2,251,594 Convertible preferred stock — 19,278,606 Total 3,959,693 21,530,200
Pro Forma
Summary of Computation of Basic and Diluted Net Loss Per Share		The following table sets forth the computation of the basic and diluted unaudited pro forma net loss per share (in thousands, except share and per share amounts): Year ended December 31, 2019 Numerator Net loss $ (26,883 ) Denominator Weighted-average shares outstanding used in computing net loss per share, basic and diluted 1,899,348 Adjust: Assumed weighted-average effect of conversion of convertible preferred stock 17,241,861 Weighted-average shares outstanding used in computing pro forma net loss per share, basic and diluted 19,141,209 Pro forma net loss per share, basic and diluted $ (1.40 )

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, 2020 December 31, 2019 Accrued compensation $ 2,229 $ 1,883 Accrued clinical development costs 1,391 484 Accrued professional fees 657 338 Deferred rent—short-term 535 495 Accrued manufacturing costs 278 479 Other accruals 240 279 Accrued deferred financing costs — 1,244 Total accrued liabilities $ 5,330 $ 5,202	Accrued other liabilities consisted of the following (in thousands): December 31, 2018 2019 Accrued compensation $ 917 $ 1,883 Accrued deferred financing costs — 1,244 Deferred rent—short term 438 495 Accrued clinical development costs 149 484 Accrued manufacturing costs 173 479 Accrued professional fees 105 175 Accrued legal fees 16 163 Share purchase liabilities 115 39 Other accruals 238 240 Total accrued other liabilities $ 2,150 $ 5,202

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance consisted of the following: Year ended December 31, 2018 2019 Convertible preferred stock 13,789,770 19,278,606 Common stock options granted and outstanding 1,854,886 2,683,441 Common stock reserved for future option grants 271,490 203,696 Total common stock reserved for future issuance 15,916,146 22,165,743

Equity Incentive Plans and St_2

Equity Incentive Plans and Stock-Based Compensation (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Option Activity	The following table summarizes the option activity for the nine months ended September 30, 2020: Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 2,683,441 $ 3.75 Granted 1,449,509 16.90 Exercised (69,102 ) 1.62 Forfeited and cancelled (104,155 ) 7.39 Outstanding at September 30, 2020 3,959,693 $ 8.52 8.7 $ 65,531 Exercisable at September 30, 2020 1,060,901 $ 2.60 8.0 $ 23,797	The following table summarizes the option activity: Options Weighted- Weighted- Aggregate Outstanding at January 1, 2019 1,854,886 $ 1.48 9.2 Granted 1,169,000 6.56 9.7 Exercised (182,105 ) 0.72 5.3 Cancelled (158,340 ) 1.76 8.0 Outstanding at December 31, 2019 2,683,441 $ 3.75 9.0 $ 14,591 Exercisable at December 31, 2019 825,671 $ 1.96 8.5 $ 5,948
Summary of Fair Value of Stock Options Estimated Using Black-Scholes Merton Option Pricing Model Assumptions	The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes Merton option pricing model with the following weighted-average assumptions. Nine Months Ended September 30, 2020 2019 Stock price $ 16.00 - $35.92 $ 1.60 - $6.44 Risk-free interest rate 3.17% - 4.45% 1.39% - 2.58% Expected volatility 88.01% - 95.11% 100.52% - 104.15% Expected term (in years) 5.50 - 6.08 6.08 Expected dividend yield 0% 0%	The fair value of stock options was estimated using the Black-Scholes Merton option pricing model with the following assumptions: Year ended December 31, 2018 2019 Stock price $ 1.60 $ 1.60 – $9.16 Risk-free interest rate 2.7% – 3.0% 1.4% – 2.6% Expected volatility 93% – 98% 77% – 104% Expected term (in years) 6.01 – 6.1 6.1 Expected dividend yield 0% 0%
Summary of Total Stock-based Compensation Expense	The table below summarizes the total stock-based compensation expense included in the Company’s statements of operations for stock options for the periods presented (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Research and development $ 592 $ 116 $ 1,406 $ 233 General and administrative 1,089 155 2,183 419 Total stock-based compensation expense $ 1,681 $ 271 $ 3,589 $ 652

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Provision for Income Taxes and Income Taxes Computed	Significant components of the Company’s provision for income taxes and income taxes computed using the U.S. federal statutory corporate tax rate were as follows (in thousands): Year ended December 31, 2018 2019 Statutory rate $ (4,487 ) $ (5,647 ) State tax (1,465 ) (2,351 ) Other permanent items (15 ) 17 Research and development credit (663 ) (692 ) Change in valuation allowance 6,536 8,673 Impact of Tax Cuts and Jobs Act — — Stock-based compensation 94 — Provisions for income taxes $ — $ —
Significant Components of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred taxes were as follows (in thousands): December 31, 2018 2019 Deferred tax assets: Net operating loss carryforward $ 17,353 $ 24,380 Research and development credits 2,147 3,319 Deferred rent 491 353 Accruals and other 255 771 Gross deferred tax assets 20,246 28,823 Less valuation allowance (19,910 ) (28,583 ) Total deferred tax assets 336 240 Deferred tax liabilities: Fixed assets (336 ) (240 ) Net deferred tax assets $ — $ —
Summary of Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s gross unrecognized tax benefits (in thousands): December 31, 2018 2019 Beginning balance $ 347 $ 557 Increases (decreases) related to prior year tax positions — — Increases related to current year tax positions 210 226 Ending balance $ 557 $ 783

Commitments and contingencies (

Commitments and contingencies (Tables)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Future Minimum Lease Payments under Non-cancelable Operating Leases	Future minimum lease payments under non-cancelable Operating Leases 2020 remaining three months $ 478 2021 1,871 2022 686 Total minimum lease payments $ 3,035	The future minimum lease payments required under non-cancelable Year ending December 31, 2020 $ 1,892 2021 1,871 2022 686 2023 — 2024 — Total minimum lease payments $ 4,449

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): September 30, 2020 December 31, 2019 Lab equipment $ 4,088 $ 3,748 Leasehold improvements 1,710 1,710 Computer hardware and software 206 158 Furniture and fixtures 140 140 Total property and equipment, gross 6,144 5,756 Less accumulated depreciation (4,251 ) (3,515 ) Total property and equipment, net $ 1,893 $ 2,241

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Cost, Gross Unrealized Holding Gains, Gross Unrealized Holding Losses and Fair Value of Available for Sale Investments	The cost, gross unrealized holding gains, gross unrealized holding losses and fair value of available-for-sale September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value U.S. treasury securities $ 124,608 $ — $ (29 ) $ 124,579 Total $ 124,608 $ — $ (29 ) $ 124,579

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets Measured at Fair Value on Recurring Basis	Following are the major categories of assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in thousands): Fair Value Measurement at End of Period Using: Fair Value Quoted Market (Level 1) Significant (Level 2) Significant (Level 3) Total At September 30, 2020 Money market funds(1) $ 62,031 $ 62,031 $ — $ — $ 62,031 U.S. treasury securities 124,579 124,579 — — 124,579 Total $ 186,610 $ 186,610 $ — $ — 186,610 At December 31, 2019 Money market funds(1) $ 88,159 $ 88,159 $ — $ — $ 88,159 (1) Included in cash and cash equivalents in accompanying balance sheets.

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Temporary Equity Disclosure [Abstract]
Schedule of Convertible Preferred Stock Authorized and Issued and its Principal Terms	Convertible preferred stock authorized and issued and its principal terms as of December 31, 2019 consisted of the following (in thousands, except share and per share amounts): As of December 31, 2019 Shares Authorized Shares Issued and Outstanding Issue Issue Price per Share Dividend Annual Rate per Share Aggregate Liquidation Preference Series A 3,862,500 3,862,500 2014 - 2015 $ 4.00 $ 0.32 $ 15,450 Series B 6,750,000 6,749,999 2015 - 2016 $ 8.00 $ 0.64 $ 54,000 Series C 4,448,788 4,448,780 2018 - 2019 $ 12.00 $ 0.96 $ 53,385 Series D 5,287,500 4,217,327 2019 $ 13.20 $ 1.056 $ 55,669 Total 20,348,788 19,278,606

Description of the Business - A

Description of the Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	Apr. 28, 2020USD ($)$ / sharesshares	Apr. 21, 2020	Jun. 30, 2020shares	Sep. 30, 2020USD ($)$ / shares	Dec. 31, 2019USD ($)$ / shares	Sep. 30, 2019$ / shares	Dec. 31, 2018USD ($)$ / shares
Description Of Business [Line Items]
Accumulated deficit				$ 138,134	$ 92,690		$ 65,807
Cash and cash equivalents				62,031	$ 89,159		$ 42,636
Price per share of common stock | $ / shares							$ 1.60
Gross proceeds from IPO excluding underwriting discounts and commissions and other offering expenses				$ 138,000
Maximum
Description Of Business [Line Items]
Price per share of common stock | $ / shares				$ 35.92	$ 9.16	$ 6.44
Common Stock
Description Of Business [Line Items]
Gross proceeds from IPO excluding underwriting discounts and commissions and other offering expenses	$ 138,000
Underwriting discounts and commissions and other offering expenses	12,800
Net proceeds from IPO	$ 125,200
Reverse stock split		one-for-four
Reverse stock split ratio		0.25
Common Stock | Initial Public Offering
Description Of Business [Line Items]
Shares of common stock issued | shares	8,625,000		8,625,000
Price per share of common stock | $ / shares	$ 16
Convertible preferred stock outstanding converted into shares of common stock | shares	19,278,606
Common Stock | Option to Purchase Additional Shares | Maximum
Description Of Business [Line Items]
Shares of common stock issued | shares	1,125,000

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Liquid investments maturity period	90 days		3 months
Depreciation expense	$ 736,000	$ 758,000	$ 1,028,000	$ 903,000
Impairment of property and equipment			0	0
Research and development expense			$ 22,844,000	19,026,000
Options granted, maximum contractual term			10 years
Risk free interest rate description			The risk-free interest rates used are based on the U.S. Treasury yield in effect at the time of grant for zero-coupon U.S. treasury notes with maturities approximately equal to the expected term of the stock options.
Deferred offering costs			$ 0	$ 1,300,000
Common stock, shares, outstanding	30,545,165		1,984,222	1,802,134
Shares issued upon exercise of options			$ 131,000	$ 79,000
Deferred offering costs			$ 1,343,000
Pro Forma
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Common stock, shares, outstanding			21,262,828	21,262,828
Shares issued upon exercise of options			$ 29,579
Pro Forma | Convertible Preferred Stock
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Outstanding shares of convertible preferred stock converted into shares of common stock			19,278,606
Minimum
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets			3 years
Maximum
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets			7 years
ASU No 2019-12
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, early adoption	true
Change in accounting principle, accounting standards update, immaterial effect	true
Other Assets
Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Deferred offering costs			$ 1,300,000

Basis of Presentation and Sum_5

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Numerator
Net loss	$ (25,548)	$ (6,549)	$ (45,444)	$ (18,529)	$ (26,883)	$ (21,363)
Denominator
Weighted average shares outstanding used in computing net loss per share, basic and diluted	30,314,904	1,946,439	18,022,068	1,876,687	1,899,348	1,734,115
Net loss per share, basic and diluted	$ (0.84)	$ (3.36)	$ (2.52)	$ (9.87)	$ (14.15)	$ (12.32)

Basis of Presentation and Sum_6

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share	3,959,693	21,530,200	21,962,047	15,644,656
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share	3,959,693	2,251,594	2,683,441	1,854,886
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti dilutive securities excluded from computation of net loss per share		19,278,606	19,278,606	13,789,770

Basis of Presentation and Sum_7

Basis of Presentation and Summary of Significant Accounting Policies - Summary of Basic and Diluted Unaudited Pro Forma Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Numerator
Net loss	$ (25,548)	$ (6,549)	$ (45,444)	$ (18,529)	$ (26,883)	$ (21,363)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic and diluted	30,314,904	1,946,439	18,022,068	1,876,687	1,899,348	1,734,115
Adjust: Assumed weighted-average effect of conversion of convertible preferred stock					17,241,861
Weighted-average shares outstanding used in computing pro forma net loss per share, basic and diluted					19,141,209
Pro forma net loss per share, basic and diluted					$ (1.40)

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 6,144	$ 5,756	$ 5,092
Less accumulated depreciation	(4,251)	(3,515)	(2,578)
Total property and equipment, net	1,893	2,241	2,514
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,088	3,748	3,166
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,710	1,710	1,710
Computer Hardware and Software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	206	158	144
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 140	$ 140	$ 72

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 2,229	$ 1,883	$ 917
Accrued clinical development costs	1,391	484	149
Accrued professional fees	657	338
Accrued professional fees excluding legal fees		175	105
Accrued legal fees		163	16
Deferred rent-short-term	535	495	438
Accrued manufacturing costs	278	479	173
Other accruals		240	238
Other accruals	240	279
Accrued deferred financing costs		1,244
Share purchase liabilities		39	115
Total accrued liabilities	$ 5,330	$ 5,202	$ 2,150

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Line Items]
Cash and cash equivalents, at carrying value	$ 62,031,000	$ 89,159,000	$ 42,636,000
Transfer between level 1 to 2	0	0
Transfer between level 2 to 1	0	0
Transfer between level 2 to 3	0	0
Transfer between level 3 to 2	0	0
Transfer between level 1 to 3	0	0
Transfer between level 3 to 1	$ 0	0
Level 1 | Money Market Funds
Fair Value Disclosures [Line Items]
Cash and cash equivalents, at carrying value		88,100,000	42,600,000
Cash and cash equivalents, fair value		88,100,000	42,600,000
Level 2
Fair Value Disclosures [Line Items]
Assets, fair value disclosure		0	0
Level 3
Fair Value Disclosures [Line Items]
Assets, fair value disclosure		$ 0	$ 0

Stockholders' equity - Addition

Stockholders' equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2017
Class of Stock [Line Items]
Capital stock authorized	47,098,788
Common stock, shares authorized	26,750,000	20,250,000				1,000,000,000
Common stock, par value	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, authorized	20,348,788
Convertible preferred stock, par value	$ 0.0001
Convertible preferred stock, issued	19,278,606
Common stock, shares, issued	1,984,222	1,802,134				30,545,165
Common stock, shares, outstanding	1,984,222	1,802,134				30,545,165
Common stock, face value	$ 9.16	$ 1.60
Dividends declared or paid	$ 0
Convertible preferred stock, conversion ratio	The conversion rate at December 31, 2019 for the Series A, Series B, Series C and Series D convertible preferred stock is 1:1.
Convertible preferred stock redemption rights	The holders of Series A, Series B, Series C and Series D convertible preferred stock do not have any redemption rights.
Minimum
Class of Stock [Line Items]
Pre-money valuation of public offering price	$ 310,000,000
Gross cash proceeds from public offering	$ 40,000,000
Common Stock
Class of Stock [Line Items]
Common stock, shares, outstanding	1,984,222	1,802,134				30,545,165	29,924,461	1,997,655	1,955,966	1,940,177	1,828,293	1,672,087
Common stock voting right	Entitled to one vote for each share of common stock
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, authorized	3,862,500	3,862,500				0
Convertible preferred stock, par value	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, issued	3,862,500	3,862,500				0
Dividends, annual rate	$ 0.32
liquidation preferences, issue prices	$ 4
Series A Convertible Preferred Stock | Private Offering
Class of Stock [Line Items]
Convertible preferred stock, issued				3,862,500	3,862,500
Net proceeds of convertible preferred stock				$ 15,400,000	$ 15,400,000
Convertible preferred stock, purchase price				$ 4	$ 4
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, authorized	6,750,000	6,750,000				0
Convertible preferred stock, par value	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, issued	6,749,999	6,749,999				0
Dividends, annual rate	$ 0.64
liquidation preferences, issue prices	$ 8
Series B Convertible Preferred Stock | Private Offering
Class of Stock [Line Items]
Convertible preferred stock, issued			6,749,999	6,749,999
Net proceeds of convertible preferred stock			$ 53,900,000	$ 53,900,000
Convertible preferred stock, purchase price			$ 8	$ 8
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, authorized	4,448,788	5,000,000				0
Convertible preferred stock, par value	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, issued	4,448,780	3,177,271				0
Dividends, annual rate	$ 0.96
liquidation preferences, issue prices	$ 12
Series C Convertible Preferred Stock | Private Offering
Class of Stock [Line Items]
Convertible preferred stock, issued	4,448,780	4,448,780
Net proceeds of convertible preferred stock	$ 53,200,000	$ 53,200,000
Convertible preferred stock, purchase price	$ 12	$ 12
Series D Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, authorized	5,287,500	0				0
Convertible preferred stock, par value	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, issued	4,217,327	0				0
Dividends, annual rate	$ 1.056
liquidation preferences, issue prices	$ 13.20
Series D Convertible Preferred Stock | Private Offering
Class of Stock [Line Items]
Convertible preferred stock, issued	4,217,327
Net proceeds of convertible preferred stock	$ 55,500,000
Convertible preferred stock, purchase price	$ 13.20
Convertible Preferred Stock
Class of Stock [Line Items]
Common stock voting right	Entitled to one vote for each share of common stock

Stockholders' equity - Summary

Stockholders' equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Convertible preferred stock		19,278,606	13,789,770
Common stock options granted and outstanding	3,959,693	2,683,441	1,854,886
Common stock reserved for future option grants		203,696	271,490
Total common stock reserved for future issuance		22,165,743	15,916,146

Equity Incentive Plans and St_3

Equity Incentive Plans and Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2020	Oct. 31, 2014	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance							22,165,743	15,916,146
Aggregate intrinsic value of stock options exercisable			$ 23,797,000		$ 23,797,000		$ 5,948,000
Shares subject to repurchase			7,821		7,821		29,579	121,794
Stock-based compensation expense			$ 1,681,000	$ 271,000	$ 3,589,000	$ 652,000	$ 1,100,000	$ 500,000
Total unrecognized compensation expense related to outstanding unvested stock-based awards			20,400,000	$ 5,500,000	$ 20,400,000	$ 5,500,000	$ 6,900,000	$ 2,300,000
Total unrecognized compensation expense related to outstanding unvested stock-based awards expected to be recognized over weighted-average remaining service period					2 years 10 months 28 days	3 years 1 month 28 days	3 years 4 months 24 days
Number of common stock remained available for issuance							203,696	271,490
Expected dividend yield					0.00%	0.00%	0.00%	0.00%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Liabilities with shares issued with repurchase rights			$ 100,000		$ 100,000		$ 100,000	$ 100,000
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock initially reserved for issuance	2,656,500
Number of shares available for future issuance			1,514,840		1,514,840
Additional number of shares available for future issuance	2,656,500
Percentage of outstanding shares of common stock	5.00%
2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock initially reserved for issuance		4,008,850
Number of shares available for future issuance							203,696
Number of common stock remained available for issuance	241,653
2020 Plan and 2014 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
2020 Plan and 2014 Plan | Stock Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period		10 years
2020 Plan and 2014 Plan | Incentive Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price as a percentage of fair market value		100.00%
Minimum percentage required for holders of combined voting power to be eligible for incentive stock options		10.00%
Percentage of options may not be granted at less than fair market value of the common stock at the date of grant		110.00%
Maximum term of options may not be granted at less than fair market value of the common stock at the date of grant		5 years
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance	290,000
Additional number of shares available for future issuance	500,000
Percentage of outstanding shares of common stock	1.00%
Number of shares issued under ESPP					0

Equity Incentive Plans and St_4

Equity Incentive Plans and Stock-Based Compensation - Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, Beginning Balance	2,683,441	1,854,886
Options, Granted	1,449,509	1,169,000
Options, Exercised	(69,102)	(182,105)
Options, Forfeited and cancelled	(104,155)	(158,340)
Options outstanding, Ending Balance	3,959,693	2,683,441	1,854,886
Options, Exercisable	1,060,901	825,671
Weighted Average Exercise Price, Options outstanding Beginning Balance	$ 3.75	$ 1.48
Weighted Average Exercise Price, Granted	16.90	6.56
Weighted Average Exercise Price, Exercised	1.62	0.72
Weighted Average Exercise Price, Forfeited and Cancelled	7.39	1.76
Weighted Average Exercise Price, Options outstanding Ending Balance	8.52	3.75	$ 1.48
Weighted Average Exercise Price, Exercisable	$ 2.60	$ 1.96
Weighted Average Remaining Contractual Term (in years), Granted		9 years 8 months 12 days
Weighted Average Remaining Contractual Term (in years), Exercised		5 years 3 months 18 days
Weighted Average Remaining Contractual Term (in years), Cancelled		8 years
Weighted Average Remaining Contractual Term (in years), Options outstanding	8 years 8 months 12 days	9 years	9 years 2 months 12 days
Weighted Average Remaining Contractual Term (in years), Exercisable	8 years	8 years 6 months
Aggregate Intrinsic Value, Options outstanding	$ 65,531	$ 14,591
Aggregate Intrinsic Value, Exercisable	$ 23,797	$ 5,948

Equity Incentive Plans and St_5

Equity Incentive Plans and Stock-Based Compensation - Summary of Fair Value of Stock Options Estimated Using Black-Scholes Merton Option Pricing Model Assumptions (Detail) - $ / shares	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock price				$ 1.60
Risk-free interest rate, minimum	3.17%	1.39%	1.40%	2.70%
Risk-free interest rate, maximum	4.45%	2.58%	2.60%	3.00%
Expected volatility, minimum	88.01%	100.52%	77.00%	93.00%
Expected volatility, maximum	95.11%	104.15%	104.00%	98.00%
Expected term (in years)		6 years 29 days	6 years 1 month 6 days
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock price	$ 16	$ 1.60	$ 1.60
Expected term (in years)	5 years 6 months			6 years 3 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock price	$ 35.92	$ 6.44	$ 9.16
Expected term (in years)	6 years 29 days			6 years 1 month 6 days

Income taxes - Schedule of Prov

Income taxes - Schedule of Provision for Income Taxes and Income Taxes Computed (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory rate	$ (5,647)	$ (4,487)
State tax	(2,351)	(1,465)
Other permanent items	17	(15)
Research and development credit	(692)	(663)
Change in valuation allowance	8,673	6,536
Impact of Tax Cuts and Jobs Act	0	0
Stock-based compensation		94
Provisions for income taxes	$ 0	$ 0

Income taxes - Significant Comp

Income taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforward	$ 24,380	$ 17,353
Research and development credits	3,319	2,147
Deferred rent	353	491
Accruals and other	771	255
Gross deferred tax assets	28,823	20,246
Less valuation allowance	(28,583)	(19,910)
Total deferred tax assets	240	336
Deferred tax liabilities:
Fixed assets	(240)	(336)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation allowance	$ (28,583,000)	$ (19,910,000)
Increase in valuation allowance	8,700,000
Net operating loss carryforwards	$ 86,600,000
Operating loss carryforwards, expiration	Dec. 31, 2034
Unrecognized tax benefits	$ 783,000	$ 557,000	$ 347,000
Accrual for interest or penalties	0
Begin to expire in 2034
Net operating loss carryforwards	41,500,000
Not expire
Net operating loss carryforwards	45,100,000
CALIFORNIA
Net operating loss carryforwards	$ 88,600,000
Operating loss carryforwards, expiration	Dec. 31, 2034

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Beginning balance	$ 557	$ 347
Increases (decreases) related to prior year tax positions	0	0
Increases related to current year tax positions	226	210
Ending balance	$ 783	$ 557

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
South San Francisco and San Diego Locations
Loss Contingencies [Line Items]
Total rent expense		$ 0.3	$ 0.3	$ 1	$ 1	$ 1.3	$ 1.3
South San Francisco, California
Loss Contingencies [Line Items]
Operating lease expiration date						May 31, 2022
Operating Lease, Term of Contract						5 years
Operating Lease, Renewal Term						5 years
San Diego, California
Loss Contingencies [Line Items]
Operating Lease, Term of Contract								13 months
Extend the lease term	May 2021

Commitment and Contingencies _2

Commitment and Contingencies - Summary of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
2020		$ 1,892
2020 remaining three months	$ 478
2021	1,871	1,871
2022	686	686
2023		0
2024		0
Total minimum lease payments	$ 3,035	$ 4,449

Employee benefit plans - Additi

Employee benefit plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Employer contributions	$ 0	$ 0

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	Oct. 19, 2020USD ($)Product$ / sharesshares	Apr. 21, 2020	Sep. 30, 2020shares	Aug. 03, 2020Product	Dec. 31, 2019shares	Dec. 31, 2018shares
Subsequent Event [Line Items]
Number of licensed products obliged to develop and commercialize | Product				1
Upfront payment shares issued | shares			30,545,165		1,984,222	1,802,134
Common Stock
Subsequent Event [Line Items]
Reverse stock split		one-for-four
Reverse stock split ratio		0.25
Subsequent Event
Subsequent Event [Line Items]
Number of licensed products obliged to develop and commercialize | Product	1
Subsequent Event | Voronoi Inc. | Development and Regulatory Milestone [Member]
Subsequent Event [Line Items]
License agreement, milestone payments maximum amount	$ 111,000,000
Subsequent Event | Voronoi Inc. | Commercial Milestone [Member]
Subsequent Event [Line Items]
License agreement, milestone payments maximum amount	225,000,000
Subsequent Event | Voronoi Inc. | Success Based Milestones [Member]
Subsequent Event [Line Items]
License agreement, additional milestone payment	272,000,000
Subsequent Event | Common Stock
Subsequent Event [Line Items]
Reverse stock split		One-for-four
Reverse stock split ratio		0.25
Subsequent Event | Common Stock | Voronoi Inc. | Private Placement
Subsequent Event [Line Items]
Upfront cash payment	$ 5
Upfront payment shares issued | shares	283,259
Issued price per share | $ / shares	$ 28.24
Premium percentage	25.00%

License Agreements - Additional

License Agreements - Additional Information (Detail) $ / shares in Units, $ in Thousands	Aug. 03, 2020USD ($)Product$ / sharesshares	Sep. 30, 2020USD ($)shares	Dec. 31, 2019shares	Dec. 31, 2018shares
License Agreements [Line Items]
Number of licensed products obliged to develop and commercialize | Product	1
Upfront payment shares issued | shares		30,545,165	1,984,222	1,802,134
Upfront payment value | $		$ 3
Mirati Therapeutics, Inc
License Agreements [Line Items]
Number of period the agreement in effect	10 years
Mirati Therapeutics, Inc | Private Placement | Common Stock
License Agreements [Line Items]
Upfront payment shares issued | shares	588,235
Upfront payment value | $	$ 13,000
Issue Price per Share | $ / shares	$ 34
Premium percentage	10.00%
Stock transfer restrictions period	18 months

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail)	Sep. 30, 2020Security	Dec. 31, 2019USD ($)
Investments Debt And Equity Securities [Abstract]
Marketable securities | $		$ 0
Number of securities in unrealized loss position | Security	13

Marketable Securities - Schedul

Marketable Securities - Schedule of Cost, Gross Unrealized Holding Gains, Gross Unrealized Holding Losses and Fair Value of Available for Sale Investments (Detail) $ in Thousands	Sep. 30, 2020USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 124,608
Unrealized Losses	(29)
Estimated Fair Value	124,579
U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	124,608
Unrealized Losses	(29)
Estimated Fair Value	$ 124,579

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	$ 186,610
Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	62,031	$ 88,159
U.S. Treasury Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	124,579
Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	186,610
Level 1 | Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	62,031	88,159
Level 1 | U.S. Treasury Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	124,579
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	186,610
Fair Value | Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	62,031	$ 88,159
Fair Value | U.S. Treasury Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets, Fair Value	$ 124,579

Convertible Preferred Stock - S

Convertible Preferred Stock - Schedule of Convertible Preferred Stock Authorized and Issued and its Principal Terms (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	Apr. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
Shares Authorized	20,348,788
Shares Issued	19,278,606
Shares Outstanding	19,278,606		0
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	3,862,500	0						3,862,500
Shares Issued	3,862,500	0						3,862,500
Shares Outstanding	3,862,500	0		3,862,500	3,862,500	3,862,500	3,862,500	3,862,500	3,862,500
Issue Price per Share	$ 4
Dividend Annual Rate per Share	$ 0.320
Aggregate liquidation preference	$ 15,450	$ 0						$ 15,450
Series A Convertible Preferred Stock | Minimum
Temporary Equity [Line Items]
Issue Period	2014
Series A Convertible Preferred Stock | Maximum
Temporary Equity [Line Items]
Issue Period	2015
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	6,750,000	0						6,750,000
Shares Issued	6,749,999	0						6,749,999
Shares Outstanding	6,749,999	0		6,749,999	6,749,999	6,749,999	6,749,999	6,749,999	6,749,999
Issue Price per Share	$ 8
Dividend Annual Rate per Share	$ 0.640
Aggregate liquidation preference	$ 54,000	$ 0						$ 54,000
Series B Convertible Preferred Stock | Minimum
Temporary Equity [Line Items]
Issue Period	2015
Series B Convertible Preferred Stock | Maximum
Temporary Equity [Line Items]
Issue Period	2016
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	4,448,788	0						5,000,000
Shares Issued	4,448,780	0						3,177,271
Shares Outstanding	4,448,780	0		4,448,780	4,448,780	4,448,780	4,448,780	3,177,271
Issue Price per Share	$ 12
Dividend Annual Rate per Share	$ 0.960
Aggregate liquidation preference	$ 53,385	$ 0						$ 38,127
Series C Convertible Preferred Stock | Minimum
Temporary Equity [Line Items]
Issue Period	2018
Series C Convertible Preferred Stock | Maximum
Temporary Equity [Line Items]
Issue Period	2019
Series D Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized	5,287,500	0						0
Shares Issued	4,217,327	0						0
Shares Outstanding	4,217,327	0		4,217,327	4,217,327	3,777,564		0
Issue Period	2019
Issue Price per Share	$ 13.20
Dividend Annual Rate per Share	$ 1.056
Aggregate liquidation preference	$ 55,669	$ 0						$ 0

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - shares	Apr. 30, 2020	Dec. 31, 2019
Temporary Equity Disclosure [Abstract]
Outstanding shares of convertible preferred stock converted into shares of common stock	19,278,606
Convertible preferred stock, outstanding	0	19,278,606

Equity Incentive Plans and St_6

Equity Incentive Plans and Stock-Based Compensation - Summary of Total Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,681	$ 271	$ 3,589	$ 652	$ 1,100	$ 500
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	592	116	1,406	233
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,089	$ 155	$ 2,183	$ 419