Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2017

Basic and Diluted Net Loss per Share Attributable to Common Stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:

	Year Ended December 31,
	2017			2016			2015
Numerator:
Net loss attributable to common stockholders	$	(89,380	)	$	(91,579	)	$	(54,780	)
Denominator:
Weighted average common shares outstanding, basic and diluted		40,449,410			39,846,928			23,532,400
Net loss per share attributable to common stockholders, basic and diluted	$	(2.21	)	$	(2.30	)	$	(2.33	)

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Year Ended December 31,
	2017		2016		2015
Stock options to purchase common stock		6,125,692		5,069,133		5,026,246
Unvested restricted stock units		356,778		115,500		—
		6,482,470		5,184,633		5,026,246