Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of Liabilities Measured at Fair Value on Recurring Basis

Liabilities measured at fair value on a recurring basis are as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		(Level 1)		(Level 2)		(Level 3)
At December 31, 2018
Preferred stock warrant liability	$	674	$	—	$	—	$	674

Schedule of Reconciliation of Warrant Liability Measured at Fair Value Using Level 3 Significant Unobservable Inputs

The following table provides a reconciliation of the preferred stock warrant liability measured at fair value using Level 3 significant unobservable inputs (in thousands):

	Preferred Stock Warrant Liability
Balance at December 31, 2018	$	674
Change in fair value		1,268
Reclassification of preferred stock warrant    liability to equity		(1,942	)
Balance at December 31, 2019	$	—

Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share Would Be Anti-dilutive

Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares; in thousands):

	December 31,
	2019		2018
Redeemable convertible preferred stock		—		8,148
Warrants to purchase convertible preferred stock		—		372
Warrants to purchase common stock		841		—
Common stock options		1,958		504
Common stock subject to repurchase		35		100
		2,834		9,124

Preferred Stock Warrants

Schedule of Assumptions Used to Determine Fair Value

The assumptions used in the Black-Scholes option pricing model to determine the fair value of the preferred stock warrant liability as of December 31, 2018 were as follows:

Fair value of underlying preferred stock	$	0.29
Risk-free interest rate	2.4% — 2.7%
Expected volatility	75.3% — 76.4%
Expected term (in years)	3.7 — 4.0
Expected dividend yield	—%