Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Summary of stock-based compensation expense

During the years ended December 31, 2017, 2016 and 2015, the Company recorded stock-based compensation expense, which was allocated as follows in the consolidated statements of operations and comprehensive (loss) income (in thousands):



	Year Ended December 31,
	2017		2016		2015
Research and development expense	$	404	$	1,455	$	1,032
General and administrative expense	977		2,558		1,497
	$	1,381	$	4,013	$	2,529

Summary of assets and liabilities measured at fair value on a recurring basis

The following table presents information about the Company’s financial assets and liabilities that have been measured at fair value, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value. The Company determines the fair value of the common stock warrants (See Note 11) and contingent consideration (See Note 3) using Level 3 inputs.

The following table summarizes the assets and liabilities measured at fair value on a recurring basis at December 31, 2017 (in thousands):



Description	December 31, 2017		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	14,680	$	14,680	$	—	$	—
Restricted cash	10		10		—		—
Total assets	$	14,690	$	14,690	$	—	$	—
Liabilities:
Contingent consideration	39,600		—		—		39,600
Total liabilities	$	39,600	$	—	$	—	$	39,600

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



Description	December 31, 2016		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	25,342	$	25,342	$	—	$	—
Restricted cash	10		10		—		—
Total assets	$	25,352	$	25,352	$	—	$	—
Liabilities:
Warrant liability	$	5	$	—	$	—	$	5
Contingent consideration	45,100		—		—		45,100
Total liabilities	$	45,105	$	—	$	—	$	45,105

Summary of changes in the fair value of the Company's common stock warrant liability

The following table sets forth a summary of changes in the fair value of the Company’s common stock warrant liability:



Beginning balance, January 1, 2017	$	5
Change in fair value of common stock warrants included in other income (expense)	(5		)
Ending balance, December 31, 2017	$	—

These warrants expired un-exercised in December 2017.

Business acquisition contingent consideration liability

The following table sets forth a summary of changes in the fair value of the Company's contingent consideration liability, which represented a recurring measurement classified within Level 3 of the fair value hierarchy, wherein fair value was estimated using significant unobservable inputs (in thousands):



Beginning balance, January 1, 2017	$	45,100
Provisional purchase price accounting adjustment (Note 3)	(14,600		)
Loss from change in fair value of contingent consideration	9,100
Ending balance, December 31, 2017	$	39,600

Summary of common stock equivalents using the treasury stock method

The following common stock equivalents, using the treasury-stock method, were included in the calculation of diluted net (loss) income per share for the periods indicated.



	Year ended December 31,
	2017	2016	2015
Stock options	—	650,109	—
	—	650,109	—

Summary of common stock equivalents excluded from calculation of diluted net (loss) income per share

The following common stock equivalents were excluded from the calculation of diluted net (loss) income per share for the periods indicated because including them would have had an anti-dilutive effect or the exercise prices were greater than the average market price of the common shares.



	Year ended December 31,
	2017	2016	2015
Stock options	2,695,796	1,374,359	1,803,574
Unvested restricted stock	4,430	22,150	41,657
Restricted stock units	—	3,333	150,932
Common stock warrants	10,055,000	926,840	926,840
	12,755,226	2,326,682	2,923,003