Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Schedule 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 as of March 31, 2020 and December 31, 2019, and indicates the fair value hierarchy of the valuation techniques utilized by the Company to determine such fair value (in thousands):  

			Fair Value Measurements at March 31, 2020
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents(1)	$	69,346	$	69,346	$	—	$	—
Commercial paper	17,363		—		17,363		—
U.S. Government-sponsored enterprise	20,318		—		20,318		—
U.S. Treasury securities	12,814		12,814		—		—
Corporate debt securities	35,228		—		35,228		—
Total assets	$	155,069	$	82,160	$	72,909	$	—
Liabilities
Common stock warrants	$	25,290	$	—	$	—	$	25,290
Total liabilities	$	25,290	$	—	$	—	$	25,290

			Fair Value Measurements at December 31, 2019
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents(1)	$	49,077	$	49,077	$	—	$	—
Commercial paper	24,157		—		24,157		—
U.S. Government-sponsored enterprise	33,099		—		33,099		—
U.S. Treasury securities	17,979		17,979		—		—
Corporate debt securities	50,048		—		50,048		—
Total assets	$	174,360	$	67,056	$	107,304	$	—
Liabilities
Common stock warrants	$	23,509	$	—	$	—	$	23,509
Total liabilities	$	23,509	$	—	$	—	$	23,509

(1)

Generally, cash equivalents include money market funds and investments with a maturity of three months or less from the date of purchase.

Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants

The assumptions used to estimate the fair values of the outstanding Series A warrants at March 31, 2020 and December 31, 2019 are presented below:

	March 31, 2020		December 31, 2019
Risk-free interest rate	0.3	%	1.6	%
Expected dividend yield	0.0	%	0.0	%
Expected volatility	74.9	%	77.2	%
Expected term (in years)	2.5		2.8

Summary of Changes in Fair Value of Total Level 3 Financial Assets

The following table presents a summary of changes in the fair value of the Company’s Level 3 financial liabilities for the three months ended March 31, 2020 and 2019:

	Three Months Ended March 31,
	2020			2019
Balance at beginning of the period	$	23,509		$	17,926
Loss recognized from the change in fair value of common stock warrants	1,922			12,746
Decrease in fair value from warrants exercised during the period	(141		)	(910		)
Balance at end of the period	$	25,290		$	29,762