13. Stock Award Plans

On May 23, 2013, the Company adopted the 2013 Equity Incentive Plan (the “2013 Plan”) as the successor to and continuation of the 2004 Equity Incentive Plan (the “2004 Plan”). The 2013 Plan consists of 4.3 million additional shares and the number of unallocated shares remaining available for grant for new awards under the 2004 Plan. The 2013 Plan provides for the granting of stock awards including stock options and restricted stock units, to employees, directors and consultants. No additional awards will be granted under the 2004 Plan or under the 2004 Non-Employee Directors’ Stock Option Plan (the “NED Plan”) as all future awards will be made out of the 2013 Plan.

The following table summarizes information about the Company’s stock-based award plans as of December 31, 2017:

	Outstanding Options		Outstanding Restricted Stock Units		Shares Available for Future Issuance
2004 Equity Incentive Plan		1,231,740		—		—
2013 Equity Incentive Plan		5,795,035		1,135,216		1,509,343
2004 Non-Employee Directors’ Stock Option Plan		62,665		—		—
Total		7,089,440		1,135,216		1,509,343

In March 2004, the Company’s board of directors approved the Employee Stock Purchase Plan (“ESPP”), which became effective upon the closing of the Company’s initial public offering. Initially, the aggregate number of shares that could be sold under the ESPP was 400,000 shares of common stock. On January 1 of each year, for a period of ten years beginning January 1, 2005, the share reserve automatically increased by the lesser of: 140,000 shares, 1% of the total number of shares of common stock outstanding on that date, or an amount as may be determined by the board of directors. However, under no event can the annual increase cause the total number of shares reserved under the ESPP to exceed 10% of the total number of shares of capital stock outstanding on December 31 of the prior year. As of December 31, 2017, 246,205 shares were available for issuance under the ESPP. For the years ended December 31, 2017, 2016 and 2015, the Company sold 199,578, 104,758 and 64,245 shares, respectively, of its common stock to employees participating in the ESPP. The ESPP purchase of 136,660 shares for the year ended December 31, 2017 was initiated prior to year-end but did not settle until January 3, 2018. As a result, the shares sold are reflected in the ESPP share reserves but are excluded from common stock outstanding as of December 31, 2017.

The Company’s board of directors determines eligibility, vesting schedules and criteria and exercise prices for stock awards granted under the 2013 Plan. Options and restricted stock unit awards under the 2013 Plan expire not more than ten years from the date of the grant and are exercisable upon vesting. Stock options that vest over time generally vest over four years. Current time-based vesting stock option grants vest and become exercisable at the rate of 25% after one year and ratably on a monthly basis over a period of 36 months thereafter. Restricted stock units with time-based vesting generally vest at a rate of 25% per year over four years with consideration satisfied by service to the Company. The Company also issues stock awards with performance conditions.

Share-based payment transactions are recognized as compensation cost based on the fair value of the instrument on the date of grant. The Company accounts for non-employee stock-based compensation expense based on the estimated fair value of the options, which is determined using the Black-Scholes option valuation model and amortizes such expense on a straight-line basis over the service period for time-based awards and over the expected dates of achievement for performance-based awards. These awards are subject to re-measurement until service is complete. As of December 31, 2017, there were options to purchase 23,047 shares of common stock outstanding to consultants.

During the years ended December 31, 2017, 2016 and 2015, the Company recorded stock-based compensation expense of $4.8 million, $5.1 million and $8.7 million, respectively.

Total stock-based compensation expense recognized in the accompanying consolidated statements of operations is as follows (in thousands):

	Year Ended December 31,
	2017		2016		2015
Employee-related	$	4,847	$	5,135	$	8,407
Consultant-related		—		—		318
Total	$	4,847	$	5,135	$	8,725

Total stock-based compensation expense recognized in the accompanying consolidated statements of operations is included in the following categories (in thousands):

	Year Ended December 31,
	2017		2016		2015
Cost of goods sold	$	460	$	695	$	—
Research and development		1,010		1,309		3,029
Selling, general and administrative		3,377		3,131		5,696
Total	$	4,847	$	5,135	$	8,725

The Company uses the Black-Scholes option valuation model to estimate the grant date fair value of employee stock options. The expected term of an option granted is based on combining historical exercise data with expected weighted time outstanding. Expected weighted time outstanding is calculated by assuming the settlement of outstanding awards is at the midpoint between the remaining weighted average vesting date and the expiration date.

The expected volatility assumption is based on an assessment of the historical volatility, with consideration of implied volatility, derived from an analysis of historical trade activity. The Company has selected risk-free interest rates based on U.S. Treasury securities with an equivalent expected term in effect on the date the options were granted. Additionally, the Company uses historical data and management judgment to estimate stock option exercise behavior and employee turnover rates to estimate the number of stock option awards that will eventually vest. The Company calculated the fair value of employee stock options granted during the years ended December 31, 2017, 2016 and 2015 using the following assumptions:

	Year Ended December 31,
	2017		2016		2015
Risk-free interest rate	1.83% — 2.13%		1.18% — 1.80%		1.61% —1.86%
Expected lives	5.41 — 5.78 years		5.13 — 5.82 years		5.79 — 5.86 years
Volatility	83.32% — 90.39%		77.57% — 82.75%		69.76% — 71.84%
Dividends		—		—		—

The following table summarizes information about stock options outstanding:

	Number of Shares			Weighted Average Exercise Price per Share		Aggregate Intrinsic Value ($000)
Outstanding at January 1, 2017		5,530,256		$	16.10
Granted		3,335,385			1.60
Exercised		(5,300	)		4.55
Forfeited		(598,204	)		3.17
Expired		(1,172,697	)		22.21
Outstanding at December 31, 2017		7,089,440		$	9.33	$	2,484
Vested and expected to vest at December 31, 2017		6,735,675		$	9.70	$	2,262
Exercisable at December 31, 2017		2,813,227		$	19.52	$	61

The weighted average grant date fair value of the stock options granted during the years ended December 31, 2017, 2016 and 2015 was $1.19, $3.05 and $12.80 per option, respectively. The total intrinsic value of options exercised during the year ended December 31, 2017 was de minimis. The total intrinsic value of options exercised during the years ended December 31, 2016 and 2015 was $0.1 million and $6.2 million, respectively. Intrinsic value is measured using the fair market value at the date of exercise for options exercised or at December 31 for outstanding options, less the applicable exercise price.

Cash received from the exercise of options during the years ended December 31, 2017, 2016 and 2015 was approximately $0.02 million, $0.5 million and $3.3 million, respectively. The weighted-average remaining contractual terms for options outstanding, vested and expected to vest and exercisable at December 31, 2017 was 6.87 years, 6.75 years and 3.57 years, respectively.

A summary of restricted stock unit activity for the year ended December 31, 2017 is presented below:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Outstanding at January 1, 2017		737,966		$	8.40
Granted		669,091			1.36
Vested		(192,361	)		10.02
Forfeited		(79,480	)		5.89
Outstanding at December 31, 2017		1,135,216		$	4.08

The total restricted stock units expected to vest as of December 31, 2017 was 939,240 with a weighted average grant date fair value of $4.28 per share. The total intrinsic value of restricted stock units expected to vest as of December 31, 2017 was $2.2 million. Intrinsic value of restricted stock units expected to vest is measured using the closing share price at December 31, 2017.

Total intrinsic value of restricted stock units vested during the years ended December 31, 2017, 2016 and 2015 was $0.4 million, $0.6 million and $5.2 million, respectively. Intrinsic value of restricted stock units vested is measured using the closing share price on the day prior to the vest date. The total grant date fair value of restricted stock units vested during the years ended December 31, 2017, 2016 and 2015 was $1.9 million, $2.6 million and $5.5 million, respectively.

As of December 31, 2017, there was $2.9 million and $3.2 million of unrecognized compensation expense related to options and restricted stock units with performance conditions, respectively, which is expected to be recognized over the weighted average vesting period of 2.3 years. The Company evaluates stock awards with performance conditions as to the probability that the performance conditions will be met and uses that information to estimate the date at which those performance conditions will be met in order to properly recognize stock-based compensation expense over the requisite service period.

As of December 31, 2017 and 2016, the Company recognized $0.9 million and $0.3 million of compensation costs related to the performance-based stock options, respectively. As of December 31, 2017, there was $3.5 million of unrecognized compensation costs related to performance-based stock options subject to performance conditions.

During the year ended December 31, 2015, there was $1.6 million of stock compensation expense related to certain executives who entered into severance agreements which resulted in a modification to the terms of their awards. The severance agreements generally allowed for the separated executives to continue to vest under their original award terms for a stated period of time without providing substantive services. There were no modifications in 2017 or 2016.