The Company has an Equity Compensation Plan (the “Plan”), which allows for grants in the form of incentive stock options, nonqualified stock options, stock units, stock awards, stock appreciation rights, and other stock-based awards. The Company also has a long-term incentive program (“LTIP”), pursuant to which the Company’s senior executives have been awarded stock options, restricted stock units (“RSUs”) and performance stock units (“PSUs”).

The following is a summary of stock option activity under the Plan as of and for the three months ended March 31, 2020:

					Weighted
			Weighted		Average
			Average		Remaining		Aggregate
	Number of		Exercise		Contractual		Intrinsic
	Shares		Price		Term (Years)		Value
Outstanding at December 31, 2019		13,861	$	2.41
Granted		—		—
Exercised		121		2.23
Cancelled/Forfeited		—		—
Outstanding at March 31, 2020		13,740		2.41		6.4	$	3,532
Exercisable at March 31, 2020		10,255	$	2.24		5.6	$	3,530

The following is a summary of PSU and RSU award activity under the Plan as of and for the three months ended March 31, 2020:

	Performance Stock Units					Restricted Stock Units
	Number of Shares			Weighted Average Grant Date Fair Value		Number of Shares		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2019		1,841		$	3.00		1,401	$	2.82
Granted		—			—		—		—
Incremental shares earned		77			—		—		—
Vested/settled		(388	)		3.11		—		—
Forfeited/expired		(351	)		3.13		—		—
Outstanding at March 31, 2020		1,179		$	3.01		1,401	$	2.82

The PSUs granted to senior executives under the LTIP are expressed as a target number of shares in the table above and may be earned based upon the Company’s achievement of certain corporate development goals, net revenue goals and total shareholder return (“TSR”) relative to the Nasdaq Biotechnology Index over the performance period, which is generally a three-year period. Depending on the outcome of the performance goals, a recipient may ultimately earn a number of shares greater or less than the target number of shares granted, ranging from 0% to 150%. The fair value of the TSR PSUs are expensed over the performance period and determined using a Monte Carlo simulation. The grant date fair value of PSUs that are not tied to market-based performance are expensed over the remaining performance period when it becomes probable that the related goal will be achieved.

The LTIP awards that vested during the three months ended March 31, 2020 and 2019 were net-share settled such that the Company withheld shares with a value equivalent to the employees’ tax obligations for applicable income and other employment taxes, and remitted cash to the appropriate taxing authorities. The Company withheld 170 and 127 shares during the three months ended March 31, 2020 and 2019, respectively, to satisfy tax obligations, which was determined based on the fair value of the shares on their vesting date equal to the Company’s closing stock price on such date. The Company paid $597 and $408 during the three months ended March 31, 2020 and 2019, respectively, to taxing authorities for the employees’ tax obligations, which is reflected as a cash outflow from financing activities within the consolidated statements of cash flows. Net-

share settlements have the effect of share repurchases by the Company as they reduce the number of shares that would have otherwise been issued as a result of the vesting.

In connection with Plan awards, the Company recognized share-based compensation expense for the three months ended March 31, 2020 and 2019 as follows:

	Three Months Ended
	March 31,
	2020		2019
Stock options	$	882	$	908
Restricted stock units		557		331
Performance stock units		539		127
Total share-based compensation expense	$	1,978	$	1,366