The Company’s 2006 Stock Incentive Plan (“the 2006 Plan”) was adopted by the Company’s board of directors in May 2006, amended by its board of directors in September 2006, approved by its stockholders in September 2006 and became effective in October 2006, upon the closing of the Company’s initial public offering. The Company originally reserved for issuance 750 shares of common stock under the 2006 Plan. In addition, the Plan contained an “evergreen” provision, which allowed for an annual increase in the number of shares available for issuance under the Plan on the first day of each fiscal year during the period beginning on the first day of fiscal year 2007 and ending on the second day of fiscal year 2010. Under the evergreen provision, the Company registered an additional 2,673 shares of common stock to be issued under the 2006 Plan.

On June 10, 2010, stockholders of the Company approved an amendment to the 2006 Plan to increase by 3,000 shares the number of shares of common stock reserved for issuance under the 2006 Plan from 3,423 shares to 6,423 shares.

On June 5, 2012, stockholders of the Company approved an amendment to the 2006 Plan to increase by 7,000 shares the number of shares of common stock reserved for issuance under the 2006 Plan from 6,423 shares to 13,423 shares.

The 2006 Plan provided for the grant of incentive stock options, nonstatutory stock options, restricted stock, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s officers, employees, consultants, advisors and directors, and those of any subsidiaries, were eligible to receive awards under the 2006 Plan. The Company’s board of directors administered the 2006 Plan.

Upon the approval of the 2015 Plan by stockholders, the 2006 Plan terminated, and all then outstanding awards under the 2006 Plan remained in effect, but no additional awards will be made under the 2006 Plan. However, the terms of the 2006 Plan will continue to apply to awards previously granted under the 2006 Plan.

The 2015 Plan allows for the issuance

6,900

new shares of common stock plus up to

1,894

shares of common stock that remained available for issuance under the previously approved

2006

Plan immediately prior to the effectiveness of the

2015

Plan, all of which shares rolled over and became available for issuance under the

2015

Plan upon its effectiveness. Solely to the extent that any of the

8,727

shares of common stock subject to awards that were issued and outstanding under the

2006

Plan immediately prior to the effectiveness of the

2015

Plan expire, terminate, are surrendered,

cancelled

or forfeited, such shares also will become available for the future grant of awards under the

2015

Plan. In

May 2018

, the Company’s stockholders approved an amendment and restatement of the

2015

Plan which included an

8,200

increase to the number of shares of common stock that may be issued pursuant to the

2015

Plan.

All of the foregoing share numbers are subject, in the case of incentive stock options, to any limitations under the Internal Revenue Code of 1986, as amended (the “Code”), and are also subject to adjustment upon stock splits, stock dividends, and other specified events. Certain sub-limitations apply to the shares available for issuance under the 2015 Plan. The 2015 Plan allows for the issuance of incentive stock options intended to qualify under Section 422 of the Code, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The maximum number of shares with respect to which awards may be granted to any participant under the 2015 Plan may not exceed 1,500 shares per fiscal year (subject to adjustment upon stock splits, stock dividends, and other specified events). The maximum value of shares subject to awards granted in any fiscal year to any individual non-employee director, together with the amount of any cash payments made to such non-employee director during such fiscal year, shall not exceed $625.

The 2015 Plan is administered by the Company’s Board of Directors. The Company’s officers, employees, consultants, advisors and directors are eligible to receive awards under the 2015 Plan; however, incentive stock options may only be granted to employees.

Options granted under the Company’s 2006 Plan and the 2015 Plan (the “Plans”), are exercisable for a period determined by the Company, but in no event longer than ten years from the date of the grant. Options generally vest over four years.

	2018
	Options			Weighted Average Exercise Price
Outstanding at January 1, 2018		12,160		$	6.37
Granted		6,592			3.03
Exercised		(764	)		2.69
Forfeited		(1,564	)		4.24
Cancelled		(1,474	)		8.08
Outstanding at December 31, 2018		14,950		$	5.14
Options exercisable at December 31, 2018		8,396		$	6.50
Options vested and expected to vest at December 31, 2018		14,194		$	5.23

	Options Outstanding						Options Vested
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Vested		Weighted Average Exercise Price
$0.00 – $2.00		—		—	$	—		—	$	—
$2.01 – $4.00		8,287		7.2		3.05		2,805		3.07
$4.01 – $6.00		1,816		7.5		4.12		1,040		4.12
$6.01 – $8.00		2,746		5.1		7.47		2,497		7.47
$8.01 – $10.00		944		3.9		8.71		916		8.72
$10.01 –$12.00		84		6.2		10.41		65		10.42
$12.01 – $14.00		1,073		5.3		13.41		1,073		13.41
		14,950		6.5	$	5.14		8,396	$	6.50

As of December 31, 2018, the intrinsic value of the options outstanding was $0. The intrinsic value for stock options is calculated based on the difference between the exercise prices of the underlying awards and the quoted stock price of the Company’s common stock as of the reporting date.

The weighted-average, grant-date fair value of options granted during the years ended December 31, 2018, 2017 and 2016 was $2.09, $2.91 and $5.56, respectively. The weighted-average, grant-date fair value of options vested at December 31, 2018, 2017 and 2016 was $4.80, $4.92 and $4.67, respectively.

Under the provisions of ASC 718, stock-based compensation cost is based on the fair value of the portion of stock-based awards that is ultimately expected to vest during the period. The Company utilizes the Black-Scholes option pricing model for determining the estimated fair value for stock-based awards. The Black-Scholes model requires the use of assumptions which determine the fair value of the stock-based awards. Determining the fair value of stock-based awards at the grant date requires judgment, including estimating the expected term of stock options, the expected volatility of stock and expected dividends. The Company also estimates forfeitures at the grant date and recognizes compensation costs for only those awards that are expected to vest. Judgment is required in estimating the number of stock-based awards that are expected to be forfeited. The Company bases its estimate of the expected term on historical data for similar stock option grants, and calculates volatility based on actual volatility for the expected term of the option.

For the Years Ended December 31,

2018

2017

2016

Expected term of option

6.0 years

6.0 – 6.25 years

Expected volatility

79% – 81%

82% – 83%

81% – 84%

Risk free interest rate

2.55 – 2.98%

2.04 – 2.27%

1.15 – 2.09%

Expected dividend yield

Total compensation expense recorded in the accompanying statements of comprehensive loss associated with option grants made to employees for the years ended December 31, 2018, 2017 and 2016 was $9,077, $10,479 and $10,900, respectively. Total compensation expense recorded in the accompanying statements of comprehensive loss associated with option grants made to consultants for the years ended December 31, 2018, 2017 and 2016 was $251, $0 and $5, respectively.

As of December 31, 2018, the total compensation cost related to options not yet recognized in the financial statements is approximately $10,795, net of estimated forfeitures, and the weighted average period over which it is expected to be recognized is 2.8 years.

The Company established the 2006 ESPP

effective December 1, 2006. Eligible employees can purchase common stock pursuant to payroll deductions at a price equal to 85% of the lower of the fair market value of the common stock at the beginning or end of each six-month offering period. The Company originally reserved for issuance 250 shares of common stock under the 2006 ESPP. On June 10, 2010, stockholders of the Company approved an amendment to the 2006 ESPP to increase by 250 shares the number of shares of common stock reserved for issuance under the 2006 ESPP from 250 shares to 500 shares. On June 2, 2015, stockholders of the Company approved an amendment to the 2006 ESPP to increase by 1,700 shares the number of shares of common stock reserved for issuance under the 2006 ESPP from 500 to 2,200 shares.

The Company measures the fair value of issuances under the

2006

ESPP

using the Black-

Scholes

option pricing model at the end of each reporting period. The compensation cost for the

2006

ESPP

consists of the

% of the grant date stock price discount and the fair value of the option features.

The Company recorded compensation cost related to the 2006 ESPP of $52, $94 and $100 for the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, there were 1,533 shares available for future issuance under the 2006 ESPP.

For the Years Ended December 31,

2018

2017

2016

Expected term of option

6 months

Expected volatility

47% – 60%

58% – 73%

55% – 66%

Risk free interest rate

1.30 – 2.1%

0.05 – 1.3%

0.05 – 0.06%

Expected dividend yield