Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019			2018			2017
Numerator:
Net loss attributable to common stockholders	$	(70,279	)	$	(98,942	)	$	(89,380	)
Denominator:
Weighted average common shares outstanding, basic and diluted		56,649,220			40,743,492			40,449,410
Net loss per share attributable to common stockholders, basic and diluted	$	(1.24	)	$	(2.43	)	$	(2.21	)

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,
	2019		2018		2017
Stock options to purchase common stock		8,310,683		7,561,719		6,125,692
Unvested restricted stock units		130,000		226,900		356,778
Shares issuable under employee stock purchase plan		89,821		49,495		—
		8,530,504		7,838,114		6,482,470