Annual report pursuant to Section 13 and 15(d)

Stock Plans and Stock-Based Compensation (Tables)

Stock Plans and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

The following table summarizes stock option activity:


	Shares Subject to Outstanding Options			Weighted- Average Exercise Price of Options		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2014		991,010		$	6.09		8.91	$	4,559
Options granted		845,703			9.00
Options exercised		—			0
Options forfeited		(15,631	)		4.75
Options expired		(16,999	)		12.31

Outstanding as of December 31, 2015		1,804,083			7.41		8.24	$	—
Options granted		646,667			1.28
Options exercised		—			0
Options forfeited		(14,319	)		4.50
Options expired		(42,043	)		25.01

Outstanding as of December 31, 2016		2,394,388		$	5.46		7.75	$	349

Vested and expected to vest as of December 31, 2016		2,351,745		$	5.50		7.73	$	331

Exercisable as of December 31, 2016		1,310,883		$	6.15		7.18	$	3

Summary of Stock-Based Compensation Expense, Net of Estimated Forfeitures

Stock-based compensation expense, net of estimated forfeitures, included in the statements of operations and comprehensive loss is as follows (in thousands):


	Year Ended December 31,
	2016		2015
Research and development	$	995	$	844
General and administrative		1,478		1,643

Total stock-based compensation expense	$	2,473	$	2,487

Estimated Weighted-Average Grant Date Fair Value

The following table presents the weighted-average assumptions the Company used in the Black-Scholes option-pricing model to derive the grant date fair values of stock options and performance-based stock options along with the resulting estimated weighted-average grant date fair values per share:


	Year Ended December 31,
	2016			2015
Expected term
Options		6.1 yrs			6.1 yrs
Performance options		5.1 yrs			—
Expected volatility
Options		80	%		78	%
Performance options		85	%		—
Risk-free interest rate
Options		1.57	%		1.65	%
Performance options		1.56	%		—
Expected dividend yield
Options		—			—
Performance options		—			—
Weighted-average grant date fair value per share
Options	$	0.89		$	6.13
Performance options	$	1.20			—

Performance Option [Member]

Summary of Stock Option Activity

The following table summarizes performance option activity:


	Shares Subject to Outstanding Options		Weighted- Average Exercise Price of Options
Outstanding as of December 31, 2015		—	$	—
Options granted		327,000		1.82

Outstanding as of December 31, 2016		327,000	$	1.82