Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Summary of Fair Value of Company's Warrant Liability

The following table rolls forward the fair value of the Company’s warrant liability, the fair value of which is determined by Level 3 inputs for the year ended December 31, 2016 (in thousands):

Fair value at January 1, 2016	$	—
Issuance of warrants on May 13, 2016		9,344
Change in fair value		(4,751	)
Fair value at December 31, 2016	$	4,593

Summary of Cash, Cash Equivalents and Marketable Securities

Below is a summary of cash, cash equivalents and marketable securities at December 31, 2016 and December 31, 2015:

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2016
Cash and cash equivalents:
Cash and money market funds	$	14,091	$	—	$	—		$	14,091
Corporate debt securities		1,005		—		—			1,005
Total cash and cash equivalents		15,096		—		—			15,096
Marketable securities:
Corporate debt securities due within 1 year		8,246		6		—			8,252
Total marketable securities		8,246		6		—			8,252
Total cash, cash equivalents and marketable securities	$	23,342	$	6	$	—		$	23,348
December 31, 2015:
Cash and cash equivalents:
Cash and money market funds	$	21,822	$	—	$	—		$	21,822
Corporate debt securities		4,812		—		—			4,812
Total cash and cash equivalents		26,634		—		—			26,634
Marketable securities:
Corporate debt securities due within 1 year	$	6,504	$	—	$	(3	)	$	6,501
Government agency securities due within 1 year		1,000		—		—			1,000
Total marketable securities		7,504		—		(3	)		7,501
Total cash, cash equivalents and marketable securities	$	34,138	$	—	$	(3	)	$	34,135

Summary of Assets And Liabilities Measured at Fair Value on Recurring Basis

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at December 31, 2016 and December 31, 2015:

	Fair Value Measurements as of December 31, 2016
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial assets carried at fair value:
Cash and money market funds	$	14,091	$	—	$	—	$	14,091
Corporate debt securities		—		1,005		—		1,005
Total cash and cash equivalents	$	14,091	$	1,005	$	—	$	15,096
Marketable securities:
Corporate debt securities due within 1 year		—	$	8,252		—	$	8,252
Total marketable securities	$	—	$	8,252	$	—	$	8,252
Total cash, cash equivalents and marketable securities	$	14,091	$	9,257	$	—	$	23,348
Financial liabilities carried at fair value:
Warrant liability	$	—	$	—	$	4,593	$	4,593
Total warrant liability	$	—	$	—	$	4,593	$	4,593

	Fair Value Measurements as of December 31, 2015
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial assets carried at fair value:
Cash and money market funds	$	21,822	$	—	$	—	$	21,822
Corporate debt securities		—		4,812				4,812
Total cash and cash equivalents	$	21,822	$	4,812	$	—	$	26,634
Marketable securities:
Corporate debt securities due within 1 year	$	—	$	6,501	$	—	$	6,501
Government agency securities due within 1 year		—		1,000		—		1,000
Total marketable securities	$	—	$	7,501	$	—	$	7,501
Total cash, cash equivalents and marketable securities	$	21,822	$	12,313	$	—	$	34,135

Summary of Outstanding Securities Not Included in Computation of Diluted Net Loss Per Common Share

The following table summarizes outstanding securities not included in the computation of diluted net loss per common share as their inclusion would be anti-dilutive for the years ended December 31, 2016, 2015 and 2014, respectively:

	Years Ended December 31,
	2016		2015		2014
Outstanding stock options		4,858,678		4,796,005		5,817,313
Outstanding warrants		19,453,295		608,696		608,696
Unvested restricted stock	—			42,750		477,600
Total		24,311,973		5,447,451		6,903,609

Stock-Based Compensation Expense

During the years ended December 31, 2016, 2015 and 2014, the Company recorded the following stock-based compensation expense:

	Years Ended December 31,
	2016		2015		2014
	(in thousands)
Research and development	$	293	$	298	$	899
General and administrative		706		765		1,909
Restructuring		—		69		—
Total stock-based compensation expense	$	999	$	1,132	$	2,808