Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Business acquisition contingent consideration

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, 2016	$	—
Contingent consideration resulting from acquisition of Viventia Bio Inc. as of acquisition date	46,200
Change in fair value of contingent consideration	(1,100		)
Ending balance, December 31, 2016	$	45,100

Summary of stock-based compensation expense

During the years ended December 31, 2016, 2015 and 2014, the Company recorded stock-based compensation expense, which was allocated as follows in the consolidated statements of operations and comprehensive income (loss) (in thousands):



	Year Ended December 31,
	2016		2015		2014
Research and development expense	$	1,455	$	1,032	$	1,069
General and administrative expense	2,558		1,497		1,363
	$	4,013	$	2,529	$	2,432

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, 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

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



Description	December 31, 2015		Active Markets (Level 1)		Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	$	36,079	$	36,079	$	—	$	—
Restricted cash	94		94		—		—
Total assets	$	36,173	$	36,173	$	—	$	—
Liabilities:
Warrant liability	$	115	$	—	$	—	$	115
Total liabilities	$	115	$	—	$	—	$	115

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

The following table sets forth a summary of changes in the fair value of the Company’s common stock warrant 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, 2016	$	115
Change in fair value of common stock warrants included in other income (expense)	(110		)
Ending balance, December 31, 2016	$	5

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 income (loss) per share for the periods indicated.



	Year ended December 31,
	2016	2015	2014
Stock options	650,109	—	—
Unvested restricted stock	—	—	—
Restricted stock units	—	—	—
Common stock warrants	—	—	—
	650,109	—	—

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

The following common stock equivalents were excluded from the calculation of diluted net income (loss) 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,
	2016	2015	2014
Stock options	1,374,359	1,803,574	1,438,528
Unvested restricted stock	22,150	41,657	125,027
Restricted stock units	3,333	150,932	—
Common stock warrants	926,840	926,840	899,340
	2,326,682	2,923,003	2,462,895