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

In November 2018, the Company entered into a Series A-2 Convertible Preferred Stock Purchase Agreement, which was amended in March 2019 (as so amended, the “Series A-2 Agreement”) under which it agreed to issue up to 47,132,862 shares of Series A-2 Convertible Preferred Stock. Under the Series A-2 Agreement, the Company initially issued 7,482,515 shares at a price of $1.43 per share for net proceeds of $10.4 million in November 2018 and 16,083,916 shares at a price of $1.43 per share for net proceeds of $22.9 million in March 2019. The Series A-2 Agreement provided for a second tranche closing, pursuant to which the investors were required to purchase, and the Company to sell, an additional 23,566,431 shares of Series A-2 Convertible Preferred Stock at $1.43 per share upon the achievement of the defined milestone, or earlier upon board of directors and requisite stockholder approval to waive such requirement. In June 2020, the board of directors and requisite stockholders approved such waiver and the Company issued 23,566,431 shares of Series A-2 Convertible Preferred Stock at a price of $1.43 per share for net proceeds of $33.6 million.

There have been no dividends declared by the Company’s board of directors as of June 30, 2020.

In January 2017, the Company’s board of directors and stockholders adopted the 2017 Equity Incentive Plan, which was amended and restated in July 2017, (as so amended and restated, the “2017 Plan”), which allows for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and other stock awards.

For financial reporting purposes, the Company performed common stock valuations with the assistance of a third-party valuation specialist as of March 31, 2020, May 31, 2019, November 30, 2018, December 31, 2017 and April 30, 2017 to determine stock-based compensation expense for stock options.

As of June 30, 2020 and December 31, 2019, the maximum number of shares of common stock reserved for issuance under the 2017 Plan was 2,730,496. As of June 30, 2020 and December 31, 2019, 426,065 and 1,025,425 shares of common stock remain available for future issuance under the 2017 Plan, respectively.

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

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

During the six-month period ended June 30, 2019, the Company granted 681,950 options, at a weighted-average exercise price of $2.02. The weighted-average grant date fair values of options granted during each of the three and six months ended June 30, 2020 were $2.25 per share. The weighted-average grant date fair values of options granted during each of the three and six months ended June 30, 2019 were $1.50 per share. The aggregate intrinsic value of stock options exercised during each of the three and six months ended June 30, 2020 was $0.2 million. The aggregate intrinsic value of stock options exercised during each of the three and six months ended June 30, 2019 was $0.1 million.

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%

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

The total unrecognized compensation cost related to outstanding employee awards as of June 30, 2020 was $2.5 million, and is expected to be recognized over a weighted-average period of 2.8 years.