Convertible Preferred Stock and Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2020

Convertible Preferred Stock And Stockholders Equity [Abstract]

Summary of Authorized, Issued, Outstanding and Preferences of Convertible Preferred Stock

The authorized, issued, outstanding and preferences of the Company’s Series A Convertible Preferred Stock and Series A-2 Convertible Preferred Stock as of June 30, 2020 and December 31, 2019 were as follows (dollar amounts in thousands):

	June 30, 2020
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		47,132,862		66,908		67,400		6,307,084
		95,982,862		95,982,862	$	111,565	$	116,250		12,843,940

	December 31, 2019
Description	Preferred stock authorized		Preferred stock issued and outstanding		Carrying value		Liquidation preference		Common stock issuable upon conversion
Series A Convertible Preferred Stock		48,850,000		48,850,000	$	44,657	$	48,850		6,536,856
Series A-2 Convertible Preferred Stock		47,132,862		23,566,431		33,270		33,700		3,153,537
		95,982,862		72,416,431	$	77,927	$	82,550		9,690,393

Summary of Stock Option Activity Under 2017 Plan

The following table summarizes stock option activity under the 2017 Plan since December 31, 2018:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding at December 31, 2018		822,557		$	1.05		8.43	$	678
Granted		1,009,125			2.02
Exercised		(69,615	)		1.04
Forfeited		(126,640	)		1.51
Outstanding at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Granted		608,185			2.77
Exercised		(140,073	)		1.11
Forfeited		(20,321	)		1.95
Outstanding at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641
Exercisable at December 31, 2019		521,327		$	1.15		7.91	$	452
Vested and expected to vest at December 31, 2019		1,635,427		$	1.64		8.81	$	668
Exercisable at June 30, 2020		544,379		$	1.29		7.62	$	806
Vested and expected to vest at June 30, 2020		2,083,218		$	1.98		8.81	$	1,641

Summary of Assumptions Used to Value Stock Options Granted to Employees using Black-Scholes Option-Pricing

For purposes of calculating stock-based compensation, the Company estimates the fair value of stock options using the Black-Scholes option-pricing model. This model incorporates various assumptions, including the expected volatility, expected term, and interest rates. The underlying assumptions used to value stock options granted to employees using the Black-Scholes option-pricing were as follows:

	Three Months Ended June 30.		Six Months Ended June 30,
	2020	2019	2020	2019
Risk-free interest rate range	0.46%	1.84%	0.46%	1.84% to 2.51%
Dividend yield	0%	0%	0%	0%
Expected term of options (years)	6.78	6.78	6.78	6.78
Volatility rate range	99.85%	85.02%	99.85%	85.02%

Summary of Total Compensation Cost Recognized in Statements of Operations

The total compensation cost recognized in the statements of operations associated with all the stock-based compensation awards granted by the Company is as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Research and development	$	62	$	26	$	127	$	53
General and administrative		58		14		122		28
Total	$	120	$	40	$	249	$	81