The Company issued 500 and 67,625 shares of common stock upon exercise of stock options during the six months ended June 30, 2020 and 2019, respectively. The Company issued 423,113 and 346,045 shares of common stock upon vesting of RSUs during the six months ended June 30, 2020 and 2019, respectively.

The Company has 100,000,000 shares of stock authorized for issuance, all of which are common stock, par value $0.0001 per share.

In October 2011, the Company issued an anti-dilutive warrant to Alan Auerbach, the Company’s founder and chief executive officer. The warrant was issued to provide Mr. Auerbach with the right to maintain ownership of at least 20% of the Company’s common stock in the event that the Company raised capital through the sale of its securities in the future.

In connection with the closing of a public offering in October 2012, the exercise price and number of shares underlying the warrant issued to Mr. Auerbach were established and, accordingly, the final value of the warrant became fixed. Pursuant to the terms of the warrant, Mr. Auerbach may exercise the warrant to acquire 2,116,250 shares of the Company’s common stock at $16 per share until October 4, 2021.

The Company’s 2011 Incentive Award Plan, as amended, or the 2011 Plan, was adopted by the Company’s Board of Directors on September 15, 2011. Pursuant to the 2011 Plan, the Company may grant incentive stock options and nonqualified stock options, as well as other forms of equity-based compensation. Incentive stock options may be granted only to employees, while consultants, employees, officers and directors are eligible for the grant of nonqualified options under the 2011 Plan. The maximum term of stock options granted under the 2011 Plan is 10 years and the awards generally vest over a three-year period. The exercise price of incentive stock options granted under the 2011 Plan must be at least equal to the fair value of such shares on the date of grant. Through June 30, 2020, a total of 12,529,412 shares of the Company’s common stock had been reserved for issuance under the 2011 Plan.

All of the options awarded by the Company have been “plain vanilla options” as determined by the SEC Staff Accounting Bulletin 107, or Share Based Payment. As of June 30, 2020, 6,230,574 shares of the Company’s common stock are issuable upon the exercise of outstanding stock options and vesting of RSUs granted under the 2011 Plan and 2,122,539 shares of the Company’s common stock are available for future issuance under the 2011 Plan. The fair value of options granted to employees and nonemployees was estimated using the Black-Scholes Option Pricing Method (see Note 2) with the following weighted-average assumptions used during the six months ended June 30:

	2020			2019
Dividend yield		0.0	%		0.0	%
Expected volatility		102.7	%		99.9	%
Risk-free interest rate		1.0	%		2.5	%
Expected life in years		5.80			5.76

The Company’s 2017 Employment Inducement Incentive Award Plan, or the 2017 Plan, was adopted by the Company’s Board of Directors on April 27, 2017. Pursuant to the 2017 Plan, the Company may grant stock options and RSUs, as well as other forms of equity-based compensation to employees, as an inducement to join the Company. The maximum term of stock options granted under the 2017 Plan is 10 years and the awards generally vest over a three-year period. The exercise price of stock options granted under the 2017 Plan must be at least equal to the fair market value of such shares on the date of grant. As of June 30, 2020, a total of 2,000,000 shares of the Company’s common stock have been reserved for issuance under the 2017 Plan. As of June 30, 2020, 1,258,685 shares of the Company’s common stock are issuable upon the exercise of outstanding stock options and vesting of RSUs granted under the 2017 Plan and 538,182 shares of the Company’s common stock are available for future issuance under the 2017 Plan.

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
Stock-based compensation:
Options -
Selling, general, and administrative	$	963	$	1,952	$	1,883	$	4,938
Research and development		731		1,882		1,572		4,215
Restricted stock units -
Selling, general, and administrative		3,767		5,500		7,539		12,389
Research and development		5,169		6,106		8,543		12,036
Total stock-based compensation expense	$	10,630	$	15,440	$	19,537	$	33,578

Activity with respect to options granted under the 2011 Plan and 2017 Plan is summarized as follows:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		5,042,325		$	82.42		5.2	$	1,951
Granted		606,900		$	9.96		9.7
Forfeited		-		$	-
Exercised		(500	)	$	3.75			$	5
Expired		(476,087	)	$	92.81
Outstanding at June 30, 2020		5,172,638		$	72.97		5.5	$	3,723
Nonvested at June 30, 2020		944,433		$	13.49		9.4
Exercisable		4,228,205		$	86.25		4.6	$	2,329

At June 30, 2020, total estimated unrecognized employee compensation cost related to non-vested stock options granted prior to that date was approximately $8.7 million, which is expected to be recognized over a weighted-average period of 1.9 years. At June 30, 2020, the total estimated unrecognized employee compensation cost related to non-vested RSUs was approximately $30.6 million, which is expected to be recognized over a weighted-average period of 1.6 years. The weighted-average grant date fair value of options granted during the six months ended June 30, 2020 and 2019 was $7.86 and $21.82 per share, respectively. The weighted average grant date fair value of RSUs awarded during the six months ended June 30, 2020 and 2019 was $10.61 and $22.14 per share, respectively.

	Shares			Weighted Average Grant-Date Fair Value
Nonvested shares at December 31, 2019		439,194			19.38
Granted		606,900			7.86
Vested/Issued		(101,661	)		32.46
Forfeited		-			-
Nonvested shares at June 30, 2020		944,433		$	10.57

	Shares			Weighted Average Grant-Date Fair Value
Nonvested shares at December 31, 2019		1,991,125		$	27.63
Granted		1,051,303			10.61
Vested/Issued		(423,113	)		41.43
Forfeited		(302,694	)		26.42
Nonvested shares at June 30, 2020		2,316,621		$	17.55