Fair Value of Financial Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring Basis

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

	Fair Value Measurements as of December 31, 2019 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents—money market funds	$	23,638	$	39,999	$	—	$	63,637
	$	23,638	$	39,999	$	—	$	63,637

Liabilities: none

	Fair Value Measurements as of December 31, 2018 Using:
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents—money market fund	$	—	$	8,134	$	—	$	8,134
	$	—	$	8,134	$	—	$	8,134
Liabilities:
Preferred stock warrant liability	$	—	$	—	$	4,947	$	4,947
Derivative liability	—		—		201		201
	$	—	$	—	$	5,148	$	5,148

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation

The following table provides a roll-forward of the aggregate fair values of the Company’s warrant liability and derivative liability, for which fair values are determined using Level 3 inputs:

(in thousands)	Preferred Stock Warrant Liability		Derivative Liability
Balance as of December 31, 2017	$	1,245	$	94
Issuance of warrants to purchase shares of Series B convertible preferred stock	304		—
Initial fair value of derivative liability in connection with the Hercules Loan Agreement	—		18
Change in fair value	3,398		89
Balance as of December 31, 2018	4,947		201
Change in fair value	288		(183)
Conversion of convertible preferred stock warrant into common stock warrant in connection with Merger	(5,235)		—
Balance at December 31, 2019	$	—	$	18