Compensation and Other Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

The following table summarizes the Company’s stock option activity for the year ended December 31, 2018:

	Number of shares			Weighted Average Exercise Price PerShare		Weighted Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at beginning of year		1,622,065		$	24.54
Granted		305,708			27.09
Exercised		(68,093	)		5.39
Forfeited, expired or cancelled		(234,934	)		43.46
Outstanding at end of period		1,624,746		$	23.09		7.5	$	8,104
Exercisable at end of period		1,102,036		$	26.01		7.0	$	6,089

Unvested RSU Activity

Unvested RSU activity for the year ended December 31, 2018 is summarized below:

				Weighted-
Restricted Stock Units:	Number of			Average Grant-
	Shares			Date Fair Value
Unvested balance at January 1, 2018		18,480		$	18.00
Vested		(18,047	)		18.27
Unvested balance at December 31, 2018		433		$	7.01

Weighted Average Assumptions

The fair value of stock options granted during the years ended December 31, 2018 and 2017, was estimated based on the following weighted average assumptions for:

	Year Ended December 31,
	2018			2017
Dividend yield		0	%		0	%
Expected volatility		101	%		100	%
Risk-free interest rate		2.72	%		1.90	%
Expected term	5.60 years			5.55 years

Stock-based Compensation Expense

The following table shows total stock-based compensation expense for stock options, RSUs and ESPP in the consolidated statements of operations and comprehensive (loss) income (in thousands):

	Year Ended December 31,
	2018		2017
Research and development	$	369	$	876
General and administrative		3,533		6,425
Total stock-based compensation expense	$	3,902	$	7,301