0001564590-21-028030 | 10-Q | XBRL Viewer

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020 USD ($)
General and Administrative
Summary of Significant Accounting Policies [Line Items]
Related party transaction, costs incurred	$ 327,000

Net Loss Per Share Attributable to Common Stockholders (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Schedule of Basic and Diluted Net Loss Per Common Share

Basic and diluted net loss per common share is calculated as follows (in thousands except share and per share amounts):

	Three Months Ended March 31,
	2021			2020
Net loss	$	(11,449	)	$	(7,794	)
Cumulative dividends on convertible preferred stock		—			(1,299	)
Net loss attributable to common stockholders	$	(11,449	)	$	(9,093	)
Net loss per common share—basic and diluted	$	(0.54	)	$	(6.61	)
Weighted-average number of shares used in computing net loss per common share—basic and diluted		21,020,378			1,375,177

Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:

	As of March 31,
	2021		2020
Convertible preferred stock		—		117,809,883
Stock options to purchase common stock		2,651,635		2,092,479
Restricted stock units		80,000		—
Warrants to purchase common stock		27,759		27,759

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands):

	March 31, 2021
	Level 1		Level 2		Level 3		Total
Current assets:
Cash equivalents:
Money market funds	$	9,810		—		—	$	9,810
Total cash equivalents		9,810		—		—		9,810
Short-term investments:
Corporate debt securities		—		9,034		—		9,034
Commercial paper		—		64,044		—		64,044
U.S. Treasury notes		—		2,021		—		2,021
Total short-term investments		—		75,099		—		75,099
Total assets measured at fair value	$	9,810	$	75,099	$	—	$	84,909

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Current assets:
Cash equivalents:
Money market funds	$	15,677	$	—	$	—	$	15,677
Corporate debt securities		—		2,500		—		2,500
Commercial paper		—		13,499		—		13,499
Total cash equivalents		15,677		15,999		—		31,676
Short-term investments:
Corporate debt securities		—		11,588		—		11,588
Commercial paper		—		50,027		—		50,027
Total short-term investments		—		61,615		—		61,615
Total assets measured at fair value	$	15,677	$	77,614	$	—	$	93,291

Summary of Company's Financial Assets Measured at Fair Value

The following tables present information as to cost, unrealized gains and losses and fair value determination of the Company’s financial assets measured at fair value on a recurring basis (in thousands):

	March 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
Current assets:
Cash equivalents:
Money market funds	$	9,810	$	—	$	—		$	9,810
Total cash equivalents		9,810		—		—			9,810
Short-term investments:
Corporate debt securities		9,037		—		(3	)		9,034
Commercial paper		64,041		5		(2	)		64,044
U.S. Treasury notes		2,021		—		—			2,021
Total short-term investments		75,099		5		(5	)		75,099
Total assets measured at fair value	$	84,909	$	5	$	(5	)	$	84,909

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
Current assets:
Cash equivalents:
Money market funds	$	15,677	$	—	$	—		$	15,677
Corporate debt securities		2,502		—		(2	)		2,500
Commercial paper		13,498		1		—			13,499
Total cash equivalents		31,677		1		(2	)		31,676
Short-term investments:
Corporate debt securities		11,588		1		(1	)		11,588
Commercial paper		50,030		2		(5	)		50,027
Total short-term investments		61,618		3		(6	)		61,615
Total assets measured at fair value	$	93,295	$	4	$	(8	)	$	93,291

Net Loss Per Share Attributable to Common Stockholders - Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		117,809,883
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	2,651,635	2,092,479
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	80,000
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	27,759	27,759

Income Taxes	3 Months Ended
Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The Company did not record a provision or benefit for income taxes during the three months ended March 31, 2021 and 2020. As of March 31, 2021 and 2020, respectively, the Company continues to maintain a full valuation allowance against all of its deferred tax assets in light of its history of cumulative net losses.

Income Taxes

3 Months Ended

Mar. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

8. Income Taxes

The Company did not record a provision or benefit for income taxes during the three months ended March 31, 2021 and 2020. As of March 31, 2021 and 2020, respectively, the Company continues to maintain a full valuation allowance against all of its deferred tax assets in light of its history of cumulative net losses.

- Definition

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

+ References + Details

Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2021 (remaining nine months)	$ 462
2022	403
2023	205
Total future minimum lease payments	$ 1,070

Commitments and Contingencies

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

5. Commitments and Contingencies

The Company enters into contracts in the normal course of business with contract research organizations, or CROs, for clinical trials and contract manufacturing organizations, or CMOs, for clinical supply manufacturing and with vendors for equipment, preclinical research studies, research supplies and other services and products for operating purposes. As of March 31, 2021, these commitments were approximately $3.1 million due within three to 12 months. These contracts generally provide for termination on notice of 60 to 90 days. During the three months ended March 31, 2021, the Company terminated several contracts with its equipment vendors and CMOs. The termination of these contracts resulted in the cancelation of commitments totaling $3.7 million that were disclosed as of December 31, 2020. From this amount, the Company recognized $2.2 million in expenses in the Company’s statement of operations for the write-off of $1.3 million in equipment deposits and $900,000 in other commitments and cancellation fees. As of March 31, 2021, $561,000 in unpaid cancellation and other related costs are classified as accrued research and development on the balance sheet.

Operating Lease Agreements

The Company leases a facility in Redwood City, California, under an operating lease with a term through August 2021 and in Baltimore, Maryland, under an operating lease with a term through June 2023. Rent expense for the three months ended March 31, 2021 and 2020 was $189,000 and $176,000, respectively. Future minimum lease payments under the Company’s non–cancelable operating leases as of March 31, 2021 were as follows (in thousands):

Year ended December 31:
2021 (remaining nine months)	$	462
2022		403
2023		205
Total future minimum lease payments	$	1,070

Guarantees and Indemnifications

In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of March 31, 2021, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.

Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021 USD ($) Employee shares	Dec. 31, 2020 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized stock-based compensation expenses related to outstanding unvested stock awards \| $	$ 13.4
Total unrecognized stock-based compensation expenses related to outstanding unvested stock awards weighted-average term of recognition	3 years 3 months 18 days
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock additional aggregate number of shares reserved	1,048,963
Common stock shares reserved for future issuance	2,762,909
2020 Equity Incentive Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, Shares issued during the period		80,000
Weighted average grant date fair value \| $ / shares		$ 16.50
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested	0
Share-based compensation arrangement by share-based payment award, equity instruments other than options, forfeited	0
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares reserved for future issuance	210,000
Number of employee stock purchase plan \| Employee	0

Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net loss	$ (11,449)	$ (7,794)
Cumulative dividends on convertible preferred stock		(1,299)
Net loss attributable to common stockholders	$ (11,449)	$ (9,093)
Net loss per common share—basic and diluted	$ (0.54)	$ (6.61)
Weighted-average number of shares used in computing net loss per common share—basic and diluted	21,020,378	1,375,177

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22595-107794

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669625-108580

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22595-107794

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1448-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1377-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

+ Details

Balance Sheet Components - Schedule of Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other Liabilities Current [Abstract]
Salaries and benefits	$ 1,281	$ 2,302
Professional services	450	425
Deferred rent	19	27
Other	475	374
Total other current liabilities	$ 2,225	$ 3,128

Balance Sheet Components

3 Months Ended

Mar. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

4. Balance Sheet Components

Other Current Liabilities

Other current liabilities consisted of the following (in thousands):

	March 31, 2021		December 31, 2020
Salaries and benefits	$	1,281	$	2,302
Professional services		450		425
Deferred rent		19		27
Other		475		374
Total other current liabilities	$	2,225	$	3,128

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands					3 Months Ended
	Oct. 22, 2020 shares	Sep. 29, 2020 USD ($) $ / shares shares	Sep. 24, 2020 shares	Sep. 18, 2020	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse stock split				0.111039552
Reverse stock split, description					On September 18, 2020, the Company effected a 9.0058:1 reverse stock split of its issued and outstanding common stock. Upon the effectiveness of the reverse stock split, (i) all shares of outstanding common stock were adjusted; (ii) the conversion prices of the convertible preferred stock were adjusted; (iii) the number of shares of common stock for which each outstanding option and warrant to purchase common stock is exercisable were adjusted; and (iv) the exercise price of each outstanding option and warrant to purchase common stock was adjusted. All of the outstanding common stock share numbers (including shares of common stock subject to the Company’s options, warrants and as-converted for the outstanding convertible preferred stock), share prices, exercise prices and per share amounts contained in the condensed financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock were not adjusted as a result of the reverse stock split.
Accumulated deficit \| $					$ 144,816	$ 133,367
Initial Public Offering \| Common Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock upon initial public offering, net of issuance costs, Shares		6,468,750
Shares issued and sold, price per share \| $ / shares		$ 16.00
Number of shares purchased in additional pursuant to underwriters' option	843,750
Net proceeds from shares issued \| $		$ 92,000
Conversion of convertible preferred stock into common stock upon initial public offering			117,809,883
Outstanding redeemable convertible preferred stock converted to common stock			13,085,913

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 10,589	$ 33,418
Short-term investments	75,099	61,615
Prepaid expenses and other current assets	3,133	4,207
Total current assets	88,821	99,240
Property and equipment, net	2,002	1,946
Prepaid expenses and other non-current assets	29	608
Total assets	90,852	101,794
Current liabilities:
Accounts payable	1,956	2,513
Accrued research and development	2,097	1,356
Other current liabilities	2,225	3,128
Total current liabilities	6,278	6,997
Deferred rent, long term portion	12	11
Total liabilities	6,290	7,008
Commitments and contingencies (Note 5)
Stockholders’ Equity:
Preferred stock
Common stock	2	2
Additional paid-in capital	229,376	228,155
Accumulated deficit	(144,816)	(133,367)
Accumulated other comprehensive loss		(4)
Total stockholders’ equity	84,562	94,786
Total liabilities and stockholders’ equity	$ 90,852	$ 101,794

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Provision or benefit for income taxes	$ 0	$ 0

- Definition

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

+ References + Details

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-Based Compensation Expense Recognized for Options and RSUs Granted

Stock-based compensation expense recognized for options and RSUs granted was as follows (in thousands):

	Three Months Ended March 31,
	2021		2020
Research and development	$	257	$	75
General and administrative		872		151
Total stock-based compensation expense	$	1,129	$	226

Condensed Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Convertible Preferred Stock
Beginning Balance at Dec. 31, 2019	$ (102,954)		$ 2,879	$ (105,836)	$ 3
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2019						117,809,883
Temporary Equity, Beginning Balance at Dec. 31, 2019						$ 131,363
Beginning Balance, Shares at Dec. 31, 2019		1,371,467
Stock issued on exercise of stock options	11		11
Stock issued on exercise of stock options, Shares		5,446
Stock-based compensation expense	226		226
Net loss	(7,794)			(7,794)
Unrealized gain (loss) on available-for-sale securities, net of tax	(3)				(3)
Ending Balance at Mar. 31, 2020	(110,514)		3,116	(113,630)
Temporary Equity, Ending Balance, Shares at Mar. 31, 2020						117,809,883
Temporary Equity, Ending Balance at Mar. 31, 2020						$ 131,363
Ending Balance, Shares at Mar. 31, 2020		1,376,913
Beginning Balance at Dec. 31, 2020	94,786	$ 2	228,155	(133,367)	(4)
Beginning Balance, Shares at Dec. 31, 2020		20,979,265
Stock issued on exercise of stock options	92		92
Stock issued on exercise of stock options, Shares		76,679
Stock-based compensation expense	1,129		1,129
Net loss	(11,449)			(11,449)
Unrealized gain (loss) on available-for-sale securities, net of tax	4				$ 4
Ending Balance at Mar. 31, 2021	$ 84,562	$ 2	$ 229,376	$ (144,816)
Ending Balance, Shares at Mar. 31, 2021		21,055,944

- Definition

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

+ References

+ Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References + Details

Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended
Condensed Statements of Operations - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 6,448	$ 6,085
General and administrative	5,040	1,711
Total operating expenses	11,488	7,796
Loss from operations	(11,488)	(7,796)
Interest income	39	108
Change in fair value of preferred stock tranche obligation		(106)
Net loss	(11,449)	(7,794)
Cumulative dividends on convertible preferred stock		(1,299)
Net loss attributable to common stockholders	$ (11,449)	$ (9,093)
Net loss per common share—basic and diluted	$ (0.54)	$ (6.61)
Weighted-average number of shares outstanding used in computing net loss per common share—basic and diluted	21,020,378	1,375,177

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2021	May 10, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Trading Symbol	GRAY
Entity Registrant Name	GRAYBUG VISION, INC.
Entity Central Index Key	0001534133
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		21,055,944
Entity File Number	001-39538
Entity Tax Identification Number	45-2120079
Entity Address, Address Line One	275 Shoreline Drive
Entity Address, Address Line Two	Suite 450
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94065
City Area Code	650
Local Phone Number	487-2800
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Stock-Based Compensation

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

2020 Equity Incentive Plan

In August 2020, the Company’s board of directors and stockholders adopted the Company’s 2020 Equity Incentive Plan, or the 2020 Plan, that became effective in connection with the IPO, and serves as the successor to the Company’s 2015 Stock Incentive Plan, or the 2015 Plan. The Company’s 2020 Plan authorizes the award of stock options, restricted stock units, or RSUs, restricted stock awards, or RSAs, stock appreciation rights, or SARs, performance awards and stock bonus awards. In March 2021, the Company increased the aggregate number of shares reserved for issuance by an additional 1,048,963 shares pursuant to the 2020 Plan. As of March 31, 2021, there were 2,762,909 shares available for issuance under the 2020 Plan.

2020 Employee Stock Purchase Plan

In August 2020 the Company’s board of directors and stockholders adopted the Company’s 2020 Employee Stock Purchase Plan, or the ESPP, that became effective in connection with the IPO, in order to enable eligible employees to purchase shares of the Company’s common stock with accumulated payroll deductions. As of March 31, 2021, there were 210,000 shares available for issuance under the ESPP. There have been no employee withholdings for the purchase of shares under the plan as of March 31, 2021.

Restricted Stock Units

During the year ended December 31, 2020, the Company issued 80,000 RSUs under the 2020 Plan. The weighted-average grant-date fair value per share of the RSUs was $16.50. As of March 31, 2021, none of the RSUs had vested or forfeited.

Stock-Based Compensation Expense

Stock-based compensation expense recognized for options and RSUs granted was as follows (in thousands):

	Three Months Ended March 31,
	2021		2020
Research and development	$	257	$	75
General and administrative		872		151
Total stock-based compensation expense	$	1,129	$	226

As of March 31, 2021, the total unrecognized stock-based compensation expense related to outstanding unvested stock awards that are expected to vest was $13.4 million, which the Company expects to recognize over an estimated weighted-average term of 3.3 years.

Preferred Stock Tranche Obligation - Additional Information (Details) - Series C Convertible Preferred Stock - USD ($)	1 Months Ended	2 Months Ended	3 Months Ended
	Jul. 31, 2019	Aug. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Temporary Equity [Line Items]
Convertible preferred stock authorized to sell	61,773,000
Convertible preferred stock, price per share	$ 1.4693
Convertible preferred stock, shares issued		37,432,787
Gross proceeds from issue of convertible preferred stock		$ 55,000,000
Convertible preferred stock, price per share	$ 1.4693
Loss on change in fair value of preferred stock tranche obligation				$ 106,000
Current Liability
Temporary Equity [Line Items]
Fair value of preferred stock tranche obligation			$ 2,200,000
Maximum
Temporary Equity [Line Items]
Convertible preferred stock option to purchase additional shares	17,014,902		17,014,902
Convertible preferred stock option to purchase additional shares after notified, period	30 days

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements contained in this Quarterly Report on Form 10-Q have been prepared in accordance with the rules and regulations of the U.S. Securities and Exchange Commission, or SEC, and, therefore, certain information and disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, have been omitted. In the opinion of management, the information reflects all adjustments necessary to make the results of operations for the interim periods a fair statement of such operations. All such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for the full year. The condensed balance sheet at December 31, 2020 has been derived from the audited financial statements at that date, but does not include all information and footnotes required by GAAP for complete financial statements. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements included in the Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on March 5, 2021.
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting periods. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to accrued research and development expenses, other long-lived assets, stock-based compensation and the valuation of deferred tax assets. The Company bases its estimates using historical experience, Company forecasts and future plans, current economic conditions, and information from third-party professionals that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities and recorded amounts of expenses that are not readily apparent from other sources, and adjusts those estimates and assumptions when facts and circumstances dictate.
Related Party Transactions	Related Party Transactions In August 2019, the Company engaged a consulting firm managed by the then-acting chief financial officer of the Company for professional services related to finance and other administrative functions. For the three months ended March 31, 2020, the costs incurred under this arrangement totaled $327,000. These costs were recorded as general and administrative expense in the accompanying condensed statements of operations. The Company terminated its relationship with this entity in September 2020.

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Other-than-temporary impairment losses	$ 0	$ 0
Fair value assets, level 1 to level 2 transfers, amount	0
Fair value assets, level 2 to level 1 transfers, amount	0
Fair value assets, transfers into level 3	0
Fair value liabilities, level 1 to Level 2 transfers amount	0
Fair value liabilities, level 2 to Level 1 transfers amount	0
Fair value liabilities, transfers into level 3	$ 0

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments

Future minimum lease payments under the Company’s non–cancelable operating leases as of March 31, 2021 were as follows (in thousands):

Year ended December 31:
2021 (remaining nine months)	$	462
2022		403
2023		205
Total future minimum lease payments	$	1,070

Fair Value Measurements - Summary of Company 's Financial Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total cash equivalents, Aggregate Fair Value	$ 9,810	$ 31,676
Total short-term investments, Aggregate Fair Value	75,099	61,615
Total asset measured at fair value, Aggregate Fair Value	84,909	93,291
Fair Value, Recurring
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total cash equivalents, Amortized Cost	9,810	31,677
Total cash equivalents, Unrealized Gains		1
Total cash equivalents, Unrealized Losses		(2)
Total cash equivalents, Aggregate Fair Value	9,810	31,676
Total short-term investments, Amortized Cost	75,099	61,618
Total short-term investments, Unrealized Gains	5	3
Total short-term investments, Unrealized Losses	(5)	(6)
Total short-term investments, Aggregate Fair Value	75,099	61,615
Total asset measured at fair value, Amortized Cost	84,909	93,295
Total asset measured at fair value, Unrealized Gains	5	4
Total asset measured at fair value, Unrealized Losses	(5)	(8)
Total asset measured at fair value, Aggregate Fair Value	84,909	93,291
Fair Value, Recurring \| Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total cash equivalents, Amortized Cost	9,810	15,677
Total cash equivalents, Aggregate Fair Value	9,810	15,677
Fair Value, Recurring \| Corporate Debt Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total cash equivalents, Amortized Cost		2,502
Total cash equivalents, Unrealized Losses		(2)
Total cash equivalents, Aggregate Fair Value		2,500
Total short-term investments, Amortized Cost	9,037	11,588
Total short-term investments, Unrealized Gains		1
Total short-term investments, Unrealized Losses	(3)	(1)
Total short-term investments, Aggregate Fair Value	9,034	11,588
Fair Value, Recurring \| Commercial Paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total cash equivalents, Amortized Cost		13,498
Total cash equivalents, Unrealized Gains		1
Total cash equivalents, Aggregate Fair Value		13,499
Total short-term investments, Amortized Cost	64,041	50,030
Total short-term investments, Unrealized Gains	5	2
Total short-term investments, Unrealized Losses	(2)	(5)
Total short-term investments, Aggregate Fair Value	64,044	$ 50,027
Fair Value, Recurring \| U.S. Treasury Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total short-term investments, Amortized Cost	2,021
Total short-term investments, Aggregate Fair Value	$ 2,021

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net loss	$ (11,449)	$ (7,794)
Unrealized gain (loss) on available-for-sale securities, net of tax	4	(3)
Comprehensive loss	$ (11,445)	$ (7,797)

- Definition

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

+ References

+ Details

Organization

3 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

1. Organization

Graybug Vision, Inc., the Company or Graybug, is a clinical-stage biopharmaceutical company developing medicines for the treatment of diseases of the retina and optic nerve. The Company presently devotes substantially all of its resources to conducting research and development and raising capital. The Company was founded in May 2011 and maintains facilities in Redwood City, California and Baltimore, Maryland.

The Company is subject to risks common to clinical stage companies in the biopharmaceutical industry, including dependence on the clinical success of its product candidates, ability to obtain regulatory approvals of its product candidates, compliance with regulatory requirements, the need for substantial additional financing and protection of its proprietary technology.

Initial Public Offering

On September 29, 2020, the Company completed its initial public offering, or IPO, and issued and sold an aggregate of 6,468,750 shares of common stock (inclusive of 843,750 shares issued and sold pursuant to the exercise of the underwriters’ option to purchase additional shares on October 22, 2020) at a price of $16.00 per share for net proceeds of $92.0 million, after deducting underwriting discounts, commissions and offering expenses. Prior to the completion of the IPO, all 117,809,883 shares of convertible preferred stock then outstanding were converted into 13,085,913 shares of common stock.

Reverse Stock Split

On September 18, 2020, the Company effected a 9.0058:1 reverse stock split of its issued and outstanding common stock. Upon the effectiveness of the reverse stock split, (i) all shares of outstanding common stock were adjusted; (ii) the conversion prices of the convertible preferred stock were adjusted; (iii) the number of shares of common stock for which each outstanding option and warrant to purchase common stock is exercisable were adjusted; and (iv) the exercise price of each outstanding option and warrant to purchase common stock was adjusted. All of the outstanding common stock share numbers (including shares of common stock subject to the Company’s options, warrants and as-converted for the outstanding convertible preferred stock), share prices, exercise prices and per share amounts contained in the condensed financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock were not adjusted as a result of the reverse stock split.

Going Concern Considerations

The Company incurred losses from operations and had negative cash flows from operating activities for the three months ended March 31, 2021, and the Company’s accumulated deficit at March 31, 2021 was $144.8 million. The Company’s current operating plan indicates it will continue to incur losses from operations and generate negative cash flows from operating activities, given ongoing expenditures related to extensive research and development and the Company’s lack of revenue-generating activities at this point in the Company’s life cycle. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Based upon the Company’s current operating plan, the Company believes its existing cash, cash equivalents and short-term investments will enable the Company to fund its operating expenses and capital expenditure requirements in excess of 12 months from the issuance date of these financial statements. The Company bases this estimate on assumptions that may prove to be wrong, and it could utilize the available capital resources sooner than it currently expects. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations and ultimately achieve profitable operations. The Company bases the sufficiency of its existing cash, cash equivalents and short-term investments to fund its operations on the current period re-forecast of the Company’s projected cash burn rate following the Company’s decision to pause its Phase 3 clinical trial for GB-102.

In March 2021, the Company determined not to proceed with the significant investment required to initiate two Phase 3 clinical trials for GB-102 in late 2021. As a result, management now believes that the Company’s current cash, cash equivalents and short-term investments are adequate to meet its needs for the next 12 months from issuance, and the Company will seek to raise additional funds in order to further advance its research and development programs, operate its business and meet its obligations as they come due. The Company is pursuing financing alternatives, similar to what the Company has previously executed, which include equity financing. Such sources of capital may not, however, be available to the Company in the necessary time frame, in the amounts that the Company requires, on terms that are acceptable to the Company, or at all. If the Company is unable to raise the necessary funds when needed or reduce spending on currently planned activities, it may not be able to continue the development of its products or the Company could be required to delay, scale back, or eliminate some or all of its research and development programs and other operations and will materially harm its business, financial position and results of operations.

COVID-19 Pandemic

The impact of the worldwide spread of a novel strain of coronavirus (“COVID-19”) has been unprecedented and unpredictable, but based on the Company’s current assessment, the Company does not expect any material impact on its long-term strategic plans, operations and its liquidity due to the worldwide spread of COVID-19. However, the Company is continuing to assess the effect on its operations by monitoring the spread of COVID-19 and the actions implemented to combat the virus throughout the world and its assessment of the impact of COVID-19 may change.

Preferred Stock Tranche Obligation

3 Months Ended

Mar. 31, 2021

Temporary Equity Disclosure [Abstract]

Preferred Stock Tranche Obligation

6. Preferred Stock Tranche Obligation

In July 2019, the Company authorized the sale of up to 61,773,000 shares of its Series C Convertible Preferred Stock, or Series C, at a price of $1.4693 per share, or Series C Financing. In July and August 2019, the Company issued 37,432,787 shares of Series C for aggregate gross proceeds of $55.0 million. In connection with this financing, certain purchasers of the Series C had the option to purchase up to an additional 17,014,902 shares of Series C at a price per share of $1.4693 for a period of up to 30 days after the Company notified them of the three-month readout from the Phase 2a clinical trial of GB-102 in patients with macular edema secondary to diabetic macular edema and retinal vein occlusion, or the Preferred Stock Tranche Obligation. The Company concluded that the Preferred Stock Tranche Obligation met the definition of a freestanding financial instrument, as the rights were legally detachable and separately exercisable from the Series C. Therefore, the Company allocated the proceeds received from the issuance of shares under the Series C Preferred Stock Purchase Agreement between the Preferred Stock Tranche Obligation and the Series C. The fair value of the Preferred Stock Tranche Obligation of $2.2 million on issuance was allocated from the $55.0 million proceeds of the Series C Financing and classified as a current liability on the balance sheet as the Series C would become redeemable upon a deemed liquidation event, the occurrence of which was not within the Company’s control. The Preferred Stock Tranche Obligation was remeasured at fair value at each reporting period using an option pricing valuation methodology. For the three months ended March 31, 2020, the Company recognized a loss on change in fair value of preferred stock tranche obligation of $106,000.

In September 2020, the board of directors and the Series C investors amended the Series C stock purchase agreement such that the Preferred Stock Tranche Obligation was no longer exercisable and expired upon the effectiveness of the Company’s IPO registration statement. As a result, the liability for the Preferred Stock Tranche Obligation was permanently eliminated as of September 24, 2020. Due to the low probability of the Preferred Stock Tranche Obligation being settled, the fair value immediately prior to the IPO was immaterial.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed financial statements contained in this Quarterly Report on Form 10-Q have been prepared in accordance with the rules and regulations of the U.S. Securities and Exchange Commission, or SEC, and, therefore, certain information and disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, have been omitted.

In the opinion of management, the information reflects all adjustments necessary to make the results of operations for the interim periods a fair statement of such operations. All such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for the full year. The condensed balance sheet at December 31, 2020 has been derived from the audited financial statements at that date, but does not include all information and footnotes required by GAAP for complete financial statements. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements included in the Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on March 5, 2021.

Use of Estimates

The preparation of condensed financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and reported amounts of expenses during the reporting periods. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to accrued research and development expenses, other long-lived assets, stock-based compensation and the valuation of deferred tax assets.

The Company bases its estimates using historical experience, Company forecasts and future plans, current economic conditions, and information from third-party professionals that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities and recorded amounts of expenses that are not readily apparent from other sources, and adjusts those estimates and assumptions when facts and circumstances dictate.

Related Party Transactions

In August 2019, the Company engaged a consulting firm managed by the then-acting chief financial officer of the Company for professional services related to finance and other administrative functions. For the three months ended March 31, 2020, the costs incurred under this arrangement totaled $327,000. These costs were recorded as general and administrative expense in the accompanying condensed statements of operations. The Company terminated its relationship with this entity in September 2020.

Net Loss Per Share Attributable to Common Stockholders

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stockholders

9. Net Loss Per Share Attributable to Common Stockholders

Basic and diluted net loss per common share is calculated as follows (in thousands except share and per share amounts):

	Three Months Ended March 31,
	2021			2020
Net loss	$	(11,449	)	$	(7,794	)
Cumulative dividends on convertible preferred stock		—			(1,299	)
Net loss attributable to common stockholders	$	(11,449	)	$	(9,093	)
Net loss per common share—basic and diluted	$	(0.54	)	$	(6.61	)
Weighted-average number of shares used in computing net loss per common share—basic and diluted		21,020,378			1,375,177

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:

	As of March 31,
	2021		2020
Convertible preferred stock		—		117,809,883
Stock options to purchase common stock		2,651,635		2,092,479
Restricted stock units		80,000		—
Warrants to purchase common stock		27,759		27,759

Under the Series C Financing, up to 17,014,902 shares of convertible preferred stock could have been contingently issued upon achievement of certain development milestones. However, in September 2020, the board of directors and the Series C investors amended the Series C stock purchase agreement such that the Preferred Stock Tranche Obligation was no longer exercisable and expired upon the effectiveness of the Company’s IPO registration statement.

Fair Value Measurements

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines fair value based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels:

•

Level 1: Observable inputs such as unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date.

•

Level 2: Inputs (other than quoted prices included in Level 1) that are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active.

•

Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

	March 31, 2021
	Level 1		Level 2		Level 3		Total
Current assets:
Cash equivalents:
Money market funds	$	9,810		—		—	$	9,810
Total cash equivalents		9,810		—		—		9,810
Short-term investments:
Corporate debt securities		—		9,034		—		9,034
Commercial paper		—		64,044		—		64,044
U.S. Treasury notes		—		2,021		—		2,021
Total short-term investments		—		75,099		—		75,099
Total assets measured at fair value	$	9,810	$	75,099	$	—	$	84,909

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Current assets:
Cash equivalents:
Money market funds	$	15,677	$	—	$	—	$	15,677
Corporate debt securities		—		2,500		—		2,500
Commercial paper		—		13,499		—		13,499
Total cash equivalents		15,677		15,999		—		31,676
Short-term investments:
Corporate debt securities		—		11,588		—		11,588
Commercial paper		—		50,027		—		50,027
Total short-term investments		—		61,615		—		61,615
Total assets measured at fair value	$	15,677	$	77,614	$	—	$	93,291

	March 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
Current assets:
Cash equivalents:
Money market funds	$	9,810	$	—	$	—		$	9,810
Total cash equivalents		9,810		—		—			9,810
Short-term investments:
Corporate debt securities		9,037		—		(3	)		9,034
Commercial paper		64,041		5		(2	)		64,044
U.S. Treasury notes		2,021		—		—			2,021
Total short-term investments		75,099		5		(5	)		75,099
Total assets measured at fair value	$	84,909	$	5	$	(5	)	$	84,909

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
Current assets:
Cash equivalents:
Money market funds	$	15,677	$	—	$	—		$	15,677
Corporate debt securities		2,502		—		(2	)		2,500
Commercial paper		13,498		1		—			13,499
Total cash equivalents		31,677		1		(2	)		31,676
Short-term investments:
Corporate debt securities		11,588		1		(1	)		11,588
Commercial paper		50,030		2		(5	)		50,027
Total short-term investments		61,618		3		(6	)		61,615
Total assets measured at fair value	$	93,295	$	4	$	(8	)	$	93,291

Money market funds are highly liquid investments which are actively traded. The pricing information on the Company’s money market funds are based on quoted prices in active markets for identical securities. This approach results in the classification of these securities as Level 1 of the fair value hierarchy.

The fair value of short-term investments is determined from market pricing and other observable market inputs for similar securities obtained from various third-party data providers. The pricing services utilize industry-standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities; issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. This approach results in the classification of these securities as Level 2 of the fair value hierarchy.

As of March 31, 2021 and December 31, 2020, the contractual maturities of all available-for-sale investments were less than 12 months. The Company periodically reviews the available-for-sale investments for other-than-temporary impairment loss. All investments with unrealized losses have been in a loss position for less than 12 months. As a result, the Company did not recognize any other-than-temporary impairment losses as of March 31, 2021 and December 31, 2020.

There were no transfers between Levels 1, 2 or 3 for the periods presented.

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net loss	$ (11,449)	$ (7,794)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,129	226
Depreciation	118	93
Change in fair value of preferred stock tranche obligation		106
Accretion of premium and discounts on short-term investments	40	(16)
Changes in operating assets and liabilities:
Prepaid expenses and other current and non-current assets	1,654	201
Accounts payable	(508)	(380)
Accrued research and development	741	(1,425)
Other current and non-current liabilities	(989)	(1,722)
Net cash used in operating activities	(9,264)	(10,711)
Investing activities:
Purchases of property and equipment	(136)	(147)
Purchases of short-term investments	(21,521)
Maturity of short-term investments	8,000	17,000
Net cash (used in) provided by investing activities	(13,657)	16,853
Financing activities:
Proceeds from exercise of stock options	92	11
Payment of offering costs		(851)
Net cash provided by (used in) financing activities	92	(840)
Net (decrease) increase in cash and cash equivalents	(22,829)	5,302
Cash and cash equivalents at beginning of period	33,418	15,870
Cash and cash equivalents at end of period	10,589	21,172
Supplemental disclosure of noncash items:
Deferred offering costs included in accounts payable and other current liabilities		500
Property and equipment purchases included in accounts payable and other current liabilities	$ 87	$ 7

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Loss Contingencies [Line Items]
Contract termination commitment			$ 3,700,000
Commitment expenses recognized			$ 2,200,000
Rent expense	$ 189,000	$ 176,000
Redwood City, California
Loss Contingencies [Line Items]
Operating lease, term	2021-08
Baltimore, Maryland
Loss Contingencies [Line Items]
Operating lease, term	2023-06
Research and Development
Loss Contingencies [Line Items]
Contractual obligation	$ 3,100,000
Unpaid cancellation and other related costs	$ 561,000
Research and Development \| Minimum
Loss Contingencies [Line Items]
Contractual obligation term	3 months
Research and Development \| Maximum
Loss Contingencies [Line Items]
Contractual obligation term	12 months
Fixed Asset Purchase Agreements
Loss Contingencies [Line Items]
Write off of deposits	$ 1,300,000
Cancellation costs not yet been paid	$ 900,000

Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash equivalents	$ 9,810	$ 31,676
Short-term investments	75,099	61,615
Assets measured at fair value	84,909	93,291
Money Market Funds
Current assets:
Cash equivalents	9,810	15,677
Corporate Debt Securities
Current assets:
Cash equivalents		2,500
Short-term investments	9,034	11,588
Commercial Paper
Current assets:
Cash equivalents		13,499
Short-term investments	64,044	50,027
U.S. Treasury Notes
Current assets:
Short-term investments	2,021
Level 1
Current assets:
Cash equivalents	9,810	15,677
Assets measured at fair value	9,810	15,677
Level 1 \| Money Market Funds
Current assets:
Cash equivalents	9,810	15,677
Level 2
Current assets:
Cash equivalents		15,999
Short-term investments	75,099	61,615
Assets measured at fair value	75,099	77,614
Level 2 \| Corporate Debt Securities
Current assets:
Cash equivalents		2,500
Short-term investments	9,034	11,588
Level 2 \| Commercial Paper
Current assets:
Cash equivalents		13,499
Short-term investments	64,044	$ 50,027
Level 2 \| U.S. Treasury Notes
Current assets:
Short-term investments	$ 2,021

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Other Current Liabilities

Other current liabilities consisted of the following (in thousands):

	March 31, 2021		December 31, 2020
Salaries and benefits	$	1,281	$	2,302
Professional services		450		425
Deferred rent		19		27
Other		475		374
Total other current liabilities	$	2,225	$	3,128

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Recognized for Options and RSUs Granted (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,129	$ 226
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	257	75
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 872	$ 151

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Details) - shares	1 Months Ended	3 Months Ended
	Jul. 31, 2019	Mar. 31, 2021
Series C Convertible Preferred Stock \| Maximum
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Convertible preferred stock could have been issued	17,014,902	17,014,902