SHARE BASED COMPENSATION

Restricted Shares

Service Based Restricted Stock Units

The following table summarizes the Company’s service based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested December 31, 2018	400,426		$	24.95
Granted	62,850		23.12
Vested	(24,769	)	20.88
Forfeited/canceled	(1,250	)	25.25
Unvested March 31, 2019	437,257		$	24.92

At March 31, 2019, unamortized stock compensation for service based restricted stock units was $8.3 million, with a weighted-average recognition period of 3.0 years.

Performance Based Restricted Stock Units

The following table summarizes the Company’s performance based restricted stock unit activity during the three months ended March 31, 2019:



	Number of Restricted Stock Units	Weighted Average Grant Date Fair Value
Unvested December 31, 2018	226,750	$	21.54
Granted	50,000	23.34
Vested	—	—
Forfeited/canceled	—	—
Unvested March 31, 2019	276,750	$	21.86

At March 31, 2019, unamortized stock compensation for performance based restricted stock units was $1.8 million, with a weighted-average recognition period of 1.2 years.

Stock Options

The following table summarizes stock option activity during the three months ended March 31, 2019:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650
Granted	440,700		23.20
Exercised	(23,727	)	12.81
Forfeited/canceled	(33,134	)	24.94
Outstanding at March 31, 2019	7,661,176		$	18.81	6.87	$	40,435

At March 31, 2019, unamortized stock compensation for stock options was $30.9 million, with a weighted-average recognition period of 2.8 years.

At March 31, 2019, outstanding options to purchase 5.0 million shares of common stock were exercisable with a weighted-average exercise price per share of $16.92.

Share Based Compensation

The following table sets forth total stock-based compensation for the three months ended March 31, 2019 and 2018 (in thousands):



	Three Months Ended March 31,
	2019		2018
Research and development	$	1,670	$	1,407
Selling, general & administrative	4,850		3,202
Total	$	6,520	$	4,609

Exercise of Warrants

The Company issued 168,612 shares of common stock upon the exercise of outstanding warrants during the three months ended March 31, 2018, for cash received by the Company in the amount of $0.6 million. As of March 31, 2019 and December 31, 2018, there were zero warrants exercisable for common shares outstanding.