6. STOCK‑BASED COMPENSATION

Equity Incentive Plans

In May 2012, we adopted the 2012 Equity Incentive Plan (the “2012 Plan”). The 2012 Plan provides for the grant of incentive stock options, nonstatutory stock options, RSAs, RSUs and Stock Appreciation Rights to employees, non-employee directors and consultants. As of December 31, 2018, total shares remaining available for issuance under the 2012 Plan were 5,134,462.

Employee Stock Purchase Plan

Under the 2004 Employee Stock Purchase Plan (the “ESPP”), our employees may purchase common stock through payroll deductions at a price equal to 85% of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. The ESPP provides for consecutive and overlapping offering periods of 24 months in duration, with each offering period composed of four consecutive six‑month purchase periods. The purchase periods end on either May 15 or November 15. ESPP contributions are limited to a maximum of 15% of an employee’s eligible compensation. The maximum number of shares that an employee may purchase in any purchase period is 2,500. An employee may not purchase shares with a value greater than $25,000 in any calendar year.

As of December 31, 2018, total shares remaining available for issuance under the ESPP were 194,051.

Performance‑Contingent RSAs and RSUs

Since 2011, the Compensation Committee of our Board of Directors (the “Compensation Committee”) has approved grants of performance‑contingent RSAs and RSUs to senior management and a non‑executive officer. Generally, these awards have dual triggers of vesting based upon the achievement of certain performance goals by a pre‑specified date, as well as a requirement for continued employment. Recognition of stock-based compensation expense begins when the performance goals are deemed probable of achievement.

Included in these performance-contingent RSAs is the remaining grant of 63,000 special long-term retention and incentive performance-contingent RSAs to senior management in 2011. The awards have dual triggers of vesting based upon the achievement of certain performance conditions over a six-year timeframe from 2011 through December 31, 2016 and require continued service to the Company. During the year ended December 31, 2016, we determined that the achievement of the requisite performance conditions was met. These awards were released in November 2017 upon vesting.

Market-Based RSAs and RSUs

2016 Market-Based RSAs and RSUs

On January 14, 2016, the Compensation Committee approved and granted 282,394 RSAs and 46,294 RSUs to senior management. These awards included a market condition based on Relative Total Shareholder Return (“TSR”) and a service condition that required continued employment collectively, the “Performance Measures”. The vesting percentages of these awards were calculated based on the two-year TSR with a catch-up provision opportunity measured on January 13, 2019 for RSAs and on September 30, 2018 for RSUs. Two-thirds of amounts earned at the end of year two would vest and be distributed on February 20, 2018, while the final one-third earned after two years as well as the catch-up amount earned would vest and be distributed on February 20, 2019 for RSAs and November 20, 2018 for RSUs. The actual payout of shares may range from a minimum of zero shares to a maximum of 328,688 shares granted upon the actual performance against the Performance Measures. The grant date fair value of these awards was determined using a Monte Carlo valuation model. The aggregate value of $2.0 million was to be recognized as compensation expense over the implied service period and would not be reversed if the market condition was not met.

In February 2018, the Compensation Committee certified the maximum achievement of the TSR as of the first measurement date, January 12, 2018. RSAs totaling 69,440 and RSUs totaling 30,862 representing two-thirds of the amounts were released on February 20, 2018. In connection with the separation of certain members of senior management from the Company in early February 2018, the Board of Directors agreed to accelerate the vesting and distribution of an aggregate of 118,821 RSAs to these members of senior management. The remaining 59,411 RSAs for these members of senior management were forfeited. As a net result of the vesting acceleration of the RSAs and the forfeiture of those unvested RSAs, an additional $0.7 million compensation expense was recognized in 2018.

In August and September 2018, the remaining 34,721 RSAs and 15,432 RSUs were forfeited due to the additional separation of senior management members, and $0.2 million of previously recognized compensation expense was reversed.

2017 Market-Based RSAs and RSUs

On January 17, 2017, the Compensation Committee approved and granted 353,508 RSAs and 53,360 RSUs to senior management. These awards included a market condition based on the TSR of Innoviva’s common stock as compared to the TSR of the Nasdaq Biotechnology Index (“Index”) and a service condition that required continued employment collectively, the “Performance Measures II.” The vesting percentages of these awards were calculated based on the two-year performance period with a catch-up provision opportunity measured on December 31, 2019 for RSAs and on September 30, 2019 for RSUs. Two-thirds of amounts earned at the end of year two would vest and be distributed on February 20, 2019, while the final one-third earned after two years as well as the catch-up amount earned would vest and be distributed on February 20, 2020 for RSAs and November 20, 2019 for RSUs. The actual payout of shares may range from a minimum of zero shares to a maximum of 406,868 shares granted upon the actual performance against the Performance Measures II. The grant date fair value of these awards was determined using a Monte Carlo valuation model. The aggregate value of $3.2 million was to be recognized as compensation expense over the implied service period and was subject to forfeiture.

In connection with the separation of certain members of senior management from the Company during 2018, all of the 2017 market-based RSAs and RSUs were forfeited and $1.3 million previously recognized compensation expense was reversed.

2018 Market-Based RSAs and RSUs

On March 2, 2018, the Compensation Committee approved and granted 111,668 RSAs and 49,630 RSUs to senior management. These awards included a market condition based on the TSR of Innoviva’s common stock over a three-year performance period from the date of grant for the RSAs and from the date of grant until September 30, 2020 for RSUs, and a service condition that required continued employment. The grant date fair value of these awards was determined using a Monte Carlo valuation model. The aggregate value of $1.7 million was to be recognized as compensation expense over the implied service period and would not be reversed if the market condition was not met, but with the exception of such person’s continued employment with the Company.

In connection with the separation of the senior management members from the Company during 2018, all of the 2018 market-based RSAs and RSUs were forfeited.

Director Compensation Program

Our non-employee directors receive compensation for services provided as a director. Each member of our Board of Directors who is not an employee receives both cash and equity compensation for services as a director, member of a committee of the Board of Directors, lead independent director and chairman, as applicable. In October 2017, both the cash and equity components of the compensation program were amended, effective immediately (the “October 2017 Amendments”).

Each of our independent directors receives periodic automatic grants of equity awards under a program implemented under the 2012 Plan. These grants are non‑discretionary. Only our independent directors or affiliates of such directors are eligible to receive automatic grants under the 2012 Plan. Under the program, each individual who first became a non-employee director will, on the date such individual joins the Board of Directors, automatically be granted a one‑time grant of RSUs covering a number of shares of our common stock calculated as $125,000 ($250,000 prior to the October 2017 Amendments) divided by our common stock closing share price on the date of grant as reported on The Nasdaq Global Select Market, rounded down to the nearest whole share (the “Initial RSUs”), plus a one‑time grant of RSUs covering a number of shares of our common stock calculated as $225,000 ($250,000 prior to the October 2017 Amendments) divided by our common stock closing share price on the date of grant as reported on The Nasdaq Global Select Market, which would be pro-rated for the number of whole months remaining until the anniversary of the prior year’s stockholders’ meeting, rounded down to the nearest whole share (the “Pro Rata RSUs”). The Initial RSUs vest in two equal annual installments, while Pro Rata RSUs vest in a single installment at the sooner of the next annual stockholder meeting or the one-year grant anniversary, in each case subject to the non-employee director’s continuous service through the applicable vesting date.

Annually, upon his or her re‑election to the Board of Directors at the Annual Meeting of Stockholders, each non-employee director is automatically granted an RSU covering a number of shares of our common stock calculated as $225,000 ($250,000 prior to the October 2017 Amendments) divided by our common stock closing share price on the date of grant as reported on The Nasdaq Global Select Market, rounded down to the nearest whole share. These RSUs will vest at the sooner of the next annual stockholder meeting or the one-year anniversary of grant, subject to the non-employee director’s continuous service through the applicable vesting date. Following the amendment to our non-employee director compensation program, both the annual RSUs and Initial RSUs described above remained unchanged with the exception that the number of shares of our common stock subject to each award has been reduced.

These RSUs will vest in full upon the director’s death, the occurrence of a change in control or, with respect to awards made after the October 2017 Amendments, the director’s disability before the director’s service terminates. Director RSUs carry dividend equivalent rights to be credited with an amount equal to all cash dividends paid on the underlying shares of common stock while unvested. Dividend equivalents are subject to the same terms and conditions, including vesting, as the RSUs to which they attach and are paid in cash upon vesting.

Stock‑Based Compensation Expense

Stock‑based compensation expense is included in the consolidated statements of operations as follows:


	Year Ended December 31,
(In thousands)	2018		2017		2016
Research and development	$	—	$	697	$	632
General and administrative		3,233		9,136		7,665
Total stock-based compensation expense	$	3,233	$	9,833	$	8,297

Stock‑based compensation expense included in the consolidated statements of operations by award type is as follows:


	Year Ended December 31,
(In thousands)	2018		2017		2016
Stock options	$	305	$	593	$	632
RSUs		1,650		2,282		1,920
RSAs		1,920		4,497		3,492
Performance-based RSAs		—		242		1,293
Market-based RSUs (PSUs)		(224)		291		112
Market-based RSAs (PSAs)		(464)		1,855		693
ESPP		46		73		155
Total stock-based compensation expense	$	3,233	$	9,833	$	8,297

For the year ended December 31, 2018, $1.7 million of stock-based compensation was reversed for the forfeited market-based awards due to the separation of senior management members.

As of December 31, 2018, the unrecognized stock-based compensation cost and the estimated weighted-average amortization period were as follows:


	Unrecognized		Weighted-Average
	Compensation		Amortization
(In thousands)	Cost		Period (Years)
RSUs	$	682	0.6
RSAs		761	2.2
Total unrecognized compensation cost	$	1,443

Compensation Awards

The following table summarizes equity award activity under the 2012 Plan and prior plans and related information:


		Weighted-
		Average			Weighted-			Weighted-
		Exercise			Average			Average
	Number of	Price of		Number of	Fair Value		Number of	Fair Value
	outstanding	Outstanding		outstanding	per Share		outstanding	per Share
(In thousands, except per share data)	options	Options		RSUs and PSUs	at Grant		RSAs and PSAs	at Grant
Balance as of December 31, 2017	1,655	$	23.89	370	$	11.57	1,448	$	10.61
Granted	—		—	177		14.29	202		13.11
Exercised	(84)		12.22	—		—	—		—
Released RSUs/RSAs	—		—	(224)		13.33	(444)		12.49
Forfeited	(334)		26.43	(218)		10.07	(1,129)		10.00
Balance as of December 31, 2018	1,237		24.00	105		15.54	77		15.37

As of December 31, 2018, the aggregate intrinsic value of the options outstanding and options exercisable was $0.8 million.

The total intrinsic value of the options exercised was $0.4 million for the year ended December 31, 2018 and was not material in the years ended December 31, 2017 and 2016. The total estimated fair value of options vested was $0.8 million, $3.8 million and $4.7 million in the years ended December 31, 2018, 2017 and 2016, respectively.

The total estimated fair value of RSUs and PSUs vested was $2.6 million in the year ended December 31, 2018 and 2017, and $3.9 million in the year ended December 31, 2016.

The total estimated fair value of RSAs and PSAs vested was $7.6 million, $6.3 million and $14.7 million in the years ended December 31, 2018, 2017 and 2016, respectively.