Our 2018 Equity Incentive Plan (the “2018 EIP”) is intended to be the successor to and continuation of the Dynavax Technologies Corporation 2011 Equity Incentive Plan (the “2011 EIP”). The aggregate number of shares of our common stock that may be issued under the 2018 EIP (subject to adjustment for certain changes in capitalization) is comprised of the sum of (i) 5,000,000 newly reserved shares of common stock, (ii) 140,250 unallocated shares of common stock remaining available for grant under the 2011 EIP as of May 31, 2018, and (iii) 7,477,619 shares subject to outstanding stock awards granted under the 2011 EIP and the Dynavax Technologies Corporation 2017 Inducement Award Plan that may become available from time to time as set forth in the 2018 EIP. The 2018 EIP provides for the issuance of up to 12,617,869 shares of our common stock to our employees and directors.

On May 28, 2020 and on May 30, 2019, our stockholders approved an amendment to 2018 Equity Incentive Plan (the “Amended 2018 EIP”) to, among other things, increase the aggregate number of shares of common stock authorized for issuance by 7,600,000 and 2,300,000, respectively. Under the Amended 2018 EIP, the aggregate number of shares of our common stock that may be issued to employees and directors (subject to adjustment for certain changes in capitalization) is 22,517,869.

Option activity under our stock-based compensation plans during the six months ended June 30, 2020 was as follows (in thousands except per share amounts):

	Shares Underlying Outstanding Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance at December 31, 2019		8,006		$	13.86
Options granted		1,574			5.36
Options exercised		(7	)		5.74
Options cancelled:
Options forfeited (unvested)		(226	)		7.43
Options expired (vested)		(151	)		16.88
Balance at June 30, 2020		9,196		$	12.52		4.36	$	13,445
Vested and expected to vest at June 30, 2020		8,932		$	12.72		4.30	$	12,626
Exercisable at June 30, 2020		5,151		$	17.29		2.92	$	1,168

Restricted stock unit activity under our stock-based compensation plans during the six months ended June 30, 2020 was as follows (in thousands except per share amounts):

	Number of Shares (in thousands)			Weighted-Average Grant-Date Fair Value Per Share
Non-vested as of December 31, 2019		1,784		$	9.16
Granted		1,166			5.29
Vested		(732	)		10.53
Forfeited		(138	)		7.62
Non-vested as of June 30, 2020		2,080		$	6.61

The aggregate intrinsic value of the restricted stock units outstanding as of June 30, 2020, based on our stock price on that date was $18.5 million. Fair value of restricted stock units is determined at the date of grant using our closing stock price.

As of June 30, 2020, approximately 138,000 shares underlying stock options and approximately 185,000 restricted stock unit awards with performance-based vesting criteria were outstanding.

Under our stock-based compensation plans, option awards generally vest over a three or four-year period contingent upon continuous service, and expire seven to ten years from the date of grant (or earlier upon termination of continuous service). The fair value-based measurement of each option is estimated on the date of grant using the Black-Scholes option valuation model.

The fair value-based measurements and weighted-average assumptions used in the calculations of these measurements are as follows:

	Stock Options						Stock Options						Employee Stock Purchase Plan
	Three Months Ended						Six Months Ended						Six Months Ended
	June 30,						June 30,						June 30,
	2020			2019			2020			2019			2020			2019
Weighted-average fair value per share	$	3.77		$	4.92		$	3.61		$	4.67		$	2.17		$	5.19
Risk-free interest rate		0.3	%		2.3	%		1.2	%		2.2	%		1.5	%		2.5	%
Expected life (in years)		4.5			4.5			4.5			4.5			1.2			1.2
Volatility		0.9			0.9			0.9			0.9			0.6			0.8

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2020		2019		2020			2019
Research and development	$	774	$	1,976	$	(799	)	$	4,156
Selling, general and administrative		2,491		2,470		4,933			5,550
Restructuring		-		4,122		-			4,122
Cost of sales - product		179		292		315			630
Inventory		644		489		1,417			1,061
Total	$	4,088	$	9,349	$	5,866		$	15,519

Compensation expense is based on awards ultimately expected to vest and reflects estimated forfeitures. Stock-based compensation for the six months ended June 30, 2020 included reversal of expenses related to cancellation of certain equity grants in the first quarter of 2020.

As of June 30, 2020, the total unrecognized compensation cost related to non-vested equity awards including all awards with time-based vesting amounted to $20.9 million, which is expected to be recognized over the remaining weighted-average vesting period of 1.7 years. Additionally, as of June 30, 2020, the total unrecognized compensation cost related to equity awards with performance-based vesting criteria amounted to $0.9 million.

The Amended and Restated 2014 Employee Stock Purchase Plan (the “Purchase Plan”) provides for the purchase of common stock by eligible employees and became effective on May 28, 2014. On May 31, 2018, our stockholders approved an amendment to the Purchase Plan to increase the aggregate number of shares of common stock authorized for issuance by 600,000 shares. The purchase price per share is the lesser of (i) 85% of the fair market value of the common stock on the commencement of the two-year offer period (generally, the sixteenth day in February or August) or (ii) 85% of the fair market value of the common stock on the exercise date, which is the last day of a purchase period (generally, the fifteenth day in February or August). For the six months ended June 30, 2020, employees have acquired 91,653 shares of our common stock under the Purchase Plan and 359,264 shares of our common stock remained available for future purchases under the Purchase Plan.