Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Estimated Weighted Average Grant Date Fair Value per Share

The Company granted options and awards for 52,801 and 60,020 shares of common stock in the years ended December 31, 2015 and 2014, respectively. The fair values of the majority of employee stock options granted in the years ended December 31, 2015 and 2014 were estimated at the date of grant using the Black-Scholes model with the following assumptions and had the following estimated weighted average grant date fair value per share:

	Years Ended December 31,
	2015			2014
Expected term	5.8 years			5.9 years
Expected volatility		89	%		94	%
Risk-free interest rate		1.61	%		1.53	%
Expected dividend yield		0	%		0	%
Weighted-average grant date fair value per share	$	3.57		$	9.58

Summary of Stock Option Activities

A summary of ARCA’s stock option activities for the years ended December 31, 2015 and 2014, and related information as of December 31, 2015, is as follows:

	Options Outstanding
	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Options outstanding - December 31, 2013		120,433		$	25.72
Granted		32,644			12.64
Exercised		—			—
Forfeited and cancelled		(493	)		867.70
Options outstanding - December 31, 2014		152,584		$	20.20		8.25	$	—
Granted		21,492			4.92
Exercised		—			—
Forfeited and cancelled		(12,798	)		18.45
Options outstanding - December 31, 2015		161,278		$	18.30		6.97	$	—
Options exercisable - December 31, 2015		114,198		$	21.55		6.44	$	—
Options vested and expected to vest - December 31, 2015		161,102		$	18.31		6.97	$	—

Summary of RSU activity

A summary of RSU activity for the years ended December 31, 2015 and 2014 is presented below:

	Restricted Stock Units Outstanding
	Number of Shares			Weighted Average Grant Date Fair Value
RSUs outstanding - December 31, 2013		59,851		$	9.75
Granted		27,376			13.65
Vested and released		(19,953	)		9.75
Forfeited and cancelled	—			—
RSUs outstanding - December 31, 2014		67,274		$	11.33
Granted		31,309			4.77
Vested and released		(26,669	)		10.75
Forfeited and cancelled		(9,555	)		10.90
RSUs outstanding - December 31, 2015		62,359		$	8.36

Summary of Non-cash, Share-based Compensation Expense

For the years ended December 31, 2015 and 2014, the Company recognized the following non-cash, share-based compensation expense (in thousands):

	Years Ended
	December 31,
	2015		2014
Research and development	$	175	$	158
General and administrative	$	424	$	489
Total	$	599	$	647