Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Taxes

Schedule of loss before income taxes by jurisdiction

	Year Ended December 31,
	2015		2014		2013
U.S. operations	$	(11,823)	$	(8,517)	$	(5,236)
Foreign operations		(8,740)		—		—
Loss before income taxes	$	(20,563)	$	(8,517)	$	(5,236)

Reconciliation of statutory to effective rate

	Year Ended December 31,
	2015		2014		2013
Federal statutory income tax rate	(34.0)	%	(34.0)	%	(34.0)	%
State taxes, net of federal benefit	(3.8)		(6.6)		(6.6)
Foreign rate differential	6.0		—		—
Research and development tax credits	(1.5)		(1.0)		(1.6)
Change in deferred tax asset valuation allowance	33.3		41.6		42.2
Effective income tax rate	—	%	—	%	—	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

		December 31,
	2015		2014
Deferred tax assets:
Net operating loss carryforwards	$	5,750	$	5,606
Capitalized start up costs		4,401		—
Research and development tax credit carryforwards		500		203
Capitalized research and development expenses		611		620
Intangible asset		1,650		—
Stock‑based compensation expenses		373		11
Other		1		4
Total deferred tax assets		13,286		6,444
Deferred tax liabilities:
Other		—		—
Total deferred tax liabilities		—		—
Valuation allowance		(13,286)		(6,444)
Net deferred tax assets	$	—	$	—

Changes in deferred tax asset valuation allowance

		Year Ended December 31,
		2015		2014		2013
Valuation allowance at beginning of year	$	(6,444)	$	(2,899)	$	(690)
Decreases recorded as benefit to income tax provision		—		—		—
Increases recorded to income tax provision		(6,842)		(3,545)		(2,209)
Valuation allowance as of end of year	$	(13,286)	$	(6,444)	$	(2,899)

Schedule of Changes in Unrecognized Tax Benefits

	Year ended December 31,
	2015		2014		2013
Unrecognized tax benefits at beginning of year	$	—	$	—	$	—
Increases related to prior year tax provisions		(2,624)		—		—
Increases related to current year tax provisions		(1,776)		—		—
Unrecognized tax benefits as of end of year	$	(4,400)	$	—	$	—