Fair Value of Financial Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of December 31, 2018 and 2017:

	Fair Value Measurements as of December 31, 2018 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	126,047	$	—	$	—	$	126,047
Restricted cash		492		—		—		492
	$	126,539	$	—	$	—	$	126,539
	Fair Value Measurements as of December 31, 2017 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds	$	5,684	$	—	$	—	$	5,684
Restricted cash		24		—		—		24
	$	5,708	$	—	$	—	$	5,708
Liabilities:
Derivative liability	$	—	$	—	$	371	$	371
Warrant to purchase redeemable convertible preferred stock		—		—		35		35
	$	—	$	—	$	406	$	406

Warrants to Purchase Redeemable Convertible Preferred Stock [Member]

Summary of Changes in Fair Value Determined by Level 3 Inputs

The following table sets forth a summary of changes in the fair value of the Company’s preferred stock warrant liability for which fair value was determined by Level 3 inputs:

	Warrant Liability
Balance as of December 31, 2016	$	—
Initial fair value of warrant to purchase redeemable convertible preferred stock		18
Change in fair value		17
Balance as of December 31, 2017	$	35
Change in fair value		162
Conversion of preferred stock warrant to common stock warrant		(197	)
Balance as of December 31, 2018	$	—

Derivative Liabilities [Member]

Summary of Changes in Fair Value Determined by Level 3 Inputs

The following table sets forth a summary of changes in the fair value of the Company’s derivative liability for which fair value is determined by Level 3 inputs:

	Derivative Liability
Balance as of December 31, 2016	$	88
Change in fair value		283
Balance as of December 31, 2017		371
Change in fair value		1,629
Payment		(2,000	)
Balance as of December 31, 2018	$	—