Stockholders’ Equity

Shares Reserved for Future Issuance

The following shares of common stock were reserved for future issuance as of June 30, 2018:



Common stock options outstanding	14,815
RSUs outstanding	221
Common stock available for future grant under 2012 Equity Incentive Plan	624
Common stock available for future grant under 2015 Inducement Plan	42
Employee Stock Purchase Plan	1,918
Total common shares reserved for future issuance	17,620

The following table summarizes our stock option and RSU activity (together Stock Awards) under all equity incentive plans for the six months ended June 30, 2018 (shares in thousands):



	Number of options		Weighted average exercise price		Number of RSUs		Weighted average grant date fair value
Stock Awards outstanding at December 31, 2017	10,649		$	4.44	416		$	0.89
Granted	7,165		$	0.98	68		$	0.65
Exercised (options) or Vested (RSUs)	(4	)	$	0.38	(209	)	$	0.87
Canceled/forfeited/expired	(2,995	)	$	5.99	(54	)	$	0.89
Stock Awards outstanding at June 30, 2018	14,815		$	2.45	221		$	0.84

Stock-Based Compensation

The following table summarizes the weighted average assumptions used to estimate the fair value of stock options and performance stock awards granted to employees under our 2012 Equity Incentive Plan and 2015 Inducement Plan and the shares purchasable under our Employee Stock Purchase Plan during the periods presented:



	Three months ended June 30,				Six months ended June 30,
	2018		2017		2018		2017
Stock options
Risk-free interest rate	2.7	%	1.9	%	2.7	%	2.0	%
Volatility	87.6	%	89.5	%	87.7	%	89.4	%
Dividend yield	—		—		—		—
Expected term (years)	6.1		6.1		6.1		6.1
Performance stock options
Risk-free interest rate	—		—		2.7	%	2.1	%
Volatility	—		—		87.4	%	89.9	%
Dividend yield	—		—		—		—
Expected term (years)	0.0		0.0		5.7		5.6
Employee stock purchase plan shares
Risk-free interest rate	1.9	%	0.9	%	1.6	%	0.8	%
Volatility	86.3	%	111.5	%	87.7	%	113.8	%
Dividend yield	—		—		—		—
Expected term (years)	0.5		0.5		0.5		0.5

The following table summarizes the allocation of our stock-based compensation expense for all stock awards during the periods presented:



	Three months ended June 30,					Six months ended June 30,
	2018		2017			2018		2017
Research and development	$	769	$	650		$	1,255	$	1,758
Research and development-restructuring related adjustments	—		(1,399		)	—		(1,399		)
General and administrative	588		935			1,729		2,209
General and administrative-restructuring related adjustments	—		2,679			—		2,679
Total	$	1,357	$	2,865		$	2,984	$	5,247